A MANUAL
OF
ELECTRO-METALLURGY:
INCLUDING
THE APPLICATION OF THE ART
TO
MANUFACTURING PROCESSES.
BY
JAMES NAPIER, F. C. S.
FOURTH AMERICAN,
FROM THE
FOURTH LONDON EDITION, REVISED AND ENLARGED.
ILLUSTRATED BY NUMEROUS ENGRAVINGS.
PHILADELPHIA:
HENRY  CAR EY BAIRD,
INDUSTRIAL PUBLISHER,
406 W\ilnut Street.








PUBLISHER'S NOTICE.
THE fact of this Treatise being reprinted from the
plates of BYRNE'S PRACTICAL METAL WORKER'S ASSISTANT
will sufficiently account for the numbering of the chapters, pages, and engravings appearing to be somewhat
irregular. It may here be as well to state that the present is an exact and faithful reprint of the Fourth London Edition.
PHILADELPHIA, Dec. 2, 1867.








PREFACE.
THE author of the following Treatise was engaged for several
years in the application of Electro-Metallurgy to the purposes of
manufacture. His operations were performed with solutions of
all the metals, and upon objects of every size and form. They
commenced when the art was young-when its practical applications were speculative-its advantages and disadvantages equally
unknown; when difficulties of all kinds, such as beset every
new art, had to be met, and considered, and overcome.
The course of his daily proceedings threw him into the way of
observations, much more extensive and much more diversified,
than could possibly have occurred to any amateur of the art.
Where large operations in an extensive business were concerned,
it was necessary to attend to details that some would have considered trifling, and to overcome obstacles that others might have
deemed insurmountable. Under the pressure of these circumstances, all means were employed to procure information. Innumerable electrotype processes were repeated as soon as they
were published, and original experiments were made in a variety
of forms, and frequently on an extensive scale, with a view to
the removal of particular difficulties, or to find the means of accomplishing certain desirable ends.
These proceedings and inquiries afforded numerous results, not
only useful in the manufacture in which the author was engaged,
but interesting to the man of science. And it is because bf their
general utility to all persons engaged in the multifarious processes
into which the art of Electro-Metallurgy has ramified, that he has
been induced to throw them into the form of the following Treatise.
While, however, he can state, that what is collected here is
derived from extensive personal experience, he by no means




Vi                       PREFACE.
ventures to assume that the work is free from deficiencies. He
has too frequently had to deplore the effects of his processes, and
to point out the desirableness of others of greater certainty and
economy.
Neither can the author presume that this work will be a stardard on the subject to which it relates. Arts and sciences, like
kingdoms and nations, have their several periods of rise, prevalence, and decadence; and nothing can be more unstable than
descriptions of an art like Electro-Metallurgy-an art that must
fluctuate with the course of experimental discovery, that has
rapidly attained a distinguished eminence, and that promises to
extend its utility still farther over regions now unthought of.
The superb specimens of its products, which were displayed to
the admiration of the world, at the GREAT EXHIBITION OF THE
INDUSTRY OF ALL NATIONS, prove at once the immense importance of Electro-Metallurgy, and how much may yet be expected
from one of the most ingenious of those modern applications of
science, which subject the powers of nature to the use and pleasure of civilized man.
GLASGOW, May, 1851.
NOTE TO THE THIRD EDITION.
The rapid sale of two editions of the Manual of Electro-Metallurgy has afforded great gratification to the author, and he has
embraced the present opportunity of revisal to include every approved novelty, so as to bring the work down to the present state
of knowledge on this most valuable art.
GLASGOW, February, 1857.




CONTENTS.
PAGCE
HISTORY OF THE ART OF ELECTRO-METALLURGY,.. 489
DESCRIPTION OF GALVANIC BATTERIES, AND THEIR RESPECTIVE
PECULIARITIES,                                      509
ELECTROTYPE PROCESSES,.                                 533
MISCELLANEOUS APPLICATIONS OF THE PROCESS OF COATING WITH
COPPER,                                             563
BRONZING,.. 572
DEPOSITION OF METALS UPON ONE ANOTHER,                  574
ELECTRO-PLATING,.                                      587
ELECTRO-GILDING,.                                       610
RESULTS OF EXPERIMENTS ON THE DEPOSITION OF OTHER METALS
AS COATINGS,                                        617
THEORETICAL OBSERVATIONS,                               628
INDEX,...633








MANUAL
ELECTRO-METALLURGY.
CHAPTER XXIV.
HISTORY OF THE ART OF ELECTRO-METALLURGY.
IN reviewing the rise and progress of any discovery in the arts
and sciences, particularly of one connected with the application of
chemistry to manufacturing purposes, there are two circumstances
which almost invariably demand especial notice. The first is, that
the discovery has been the result of accidental observation-a fact
eliminated during investigations undertaken for other purposesrather than the result of a direct endeavor to make the discovery.
The second is, that, after the discovery has been made known, it is
found that many previously published experiments exhibited results which bore more or less directly upon the subsequent discovery, and which are consequently sometimes cited to detract from
the merit of the discoverer, and the originality and value of his
discovery. The following historical sketch will show that these
observations directly apply to the discovery of the art of ElectroMetallurgy:VOLTA'S DIscovERY.-At the beginning of the year 1800, Professor Volta invented the Apparatus which has been named after
him, the Voltaic Pile. As originally constructed by Volta, it consisted of an equal number of round pieces of zinc, silver, and
paste-board-the zinc and silver pieces being each about the size
(489)




490      THE PRACTICAL METAL-WORKER'S ASSISTANT.
of a penny, and those of pasteboard a little smaller; the pasteboard pieces were soaked in a solution of common salt, and then
with the metals were piled in the following manner:-zinc, silver,
pasteboard; zinc, silver, pasteboard; and so on, in the same order,
till all the pieces, amounting to upwards of a hundred, were piled
upon each other, the uppermost plate being of silver, and, as
already stated, the undermost of zinc; these exterior plates, to
each of which a wire is attached, form the terminals or poles of
the pile. Fig. 540 shows the construction of the Pile.
Fig. 540
]'w|I1.... { C —Silver Plate.
A   \   /    _ (illllll!llllllllllllllllllll     z  z    Zinc  Plate.
/   W —Pasteboard between.
A   AA-The Wires in connection with
z         the Terminal Plates.
By this instrument all the phenomena of an ordinary battery can
be produced.
CHEMICAL DECOMPOSITIONS BY THE  PILE.-This discovery
placed in the hands of the philosopher an instrument by which he
could make such investigations as had never previously been conceived to be possible. Nicholson, for example, effected the decomposition of water and of several metallic salts: and observed, as a
general rule, that in the decomposition of the latter the metal of
the salt was reduced upon the zinc terminal of the pile.
FIRST BATTERY.-Cruikshanks, of Woolwich, with a view to
facilitate the construction of the pile, employed square plates of
copper and zinc, soldered together two and two; these were
cemented, by means of pitch, into a wooden trough, at the distance
of about a quarter of an inch from each other, and so arranged
that the zinc plates all faced one end of the trough, and the copper
plates the other end. The spaces or cells between every pair of
plates were filled with a solution of common salt, or a mixture of
acid and water, which produced the same effect as the moist cards
in the pile. The trough thus charged with its metals and solution
acted the same part as the Voltaic pile. This was the first of
those instruments now so well known as the "galvanic battery."
DECOMPOSITION BY THE BATTERY, AND ITS APPLICATION.Cruikshanks attached a silver wire to each terminal of his battery,




HISTORY OF ELECTRO-METALLURGY.              491
and the other ends of these wires he placed in a glass tube. When
this tube was filled with a solution of acetate of lead, and the
electric current was allowed to pass through it for some time, metallic lead was found deposited upon the wire attached to the zinc
terminal of the battery. Solutions of sulphate of copper, nitrate
of silver, and several other salts, were tried with similar results.
The metals, as Cruikshanks expressed it, were "revived," and that
so completely, as to suggest to him the application of the battery
to the analysis of minerals. While Cruikshanks, Nicholson, and
several other gentlemen in this country were making investigations and applications of voltaic electricity, upon the Continent,
Brugnatelli, Fourcroy, Vauquelin, and Thenard were making
similar investigations, and obtaining similar results.*
DEPOSITION OF METALS UPON  OTHERS.-Brugnatelli, in his
Annals of Chemistry, gives a long list of experiments on the decomposition of salts by the pile. He observed the transfer of the
elements of a decomposed compound from one pole to anotherthat silver, when deposited upon platinum, preserved all its metallic
brightness-and that, when copper or zinc were used in connection with the silver terminal, or positive pole, of the pile for decomposing salts, these metals were dissolved, and deposited upon the
negative pole. The researches of Fourcroy, Vauquelin, and Th6nard
gave the same results.
GILDING. —In 1805, Brugnatelli, in a letter to Van Mons, mentions, among other scientific facts, that "he had gilt in a complete
manner two large silver medals, by bringing them, by means of a
steel wire, into communication with the negative pole of a voltaic
pile, and keeping them one after the other immersed in ammoniuret
of gold newly made and well saturated."t
EARLY OPINIONS CONCERNING ELECTRO-DECOMPOSITION.-The
above few instances are selected from a host of a similar kind upon
electro-decomposition, to show that the fact of the deposition of
metals by an electric current was familiar to philosophers at this
early stage of the history of galvanism; that nevertheless, the.
phenomenon was never thought of further than as a curious
action of electricity when passing through a solution containing
metals; and that although these effects were produced again and
again, it was only to prove and enforce certain speculative views
respecting the electric fluid. As for example, Brugnatelli had
formed an idea that the electric fluid had some relations to an acid
which he called the electric acid, and he therefore viewed the decomposit;on of solutions, and the obtaining of the metal, which he
termed an electrate, as the result of the combination of this electric
acid with the metal of the solution. In one of his memoirs upon
this subject, he says-" Gold and platinum are not sensibly altered
by the electric matter which passes through them, though it often
* Wilkinson, Elements of Galvanism, vol. ii. 1804.
t Phil. Magazine, 1805.




492       THE PRACTICAL METAL-WORKER'S ASSISTANT.
happens that the electric current deposits on gold a stratum of zinc
copper, mercury, or silver, according to whichever of these metallic
bodies it traverses."* In the same paper it is several times stated
that gold and platina do not seem sensibly affected by the electric
acid. And, when he communicated the above experiment of gilding the two medals, his object was to show that he had now found
that the electric acid had also the power of acting upon gold; and
the publication of these results and observations excited no other
idea in the minds of philosophers of that period than that they
were mere scientific curiosities. The editor of the Philosophical
uiagazine appended the following note to the extract already
quoted:-" The result here detailed reminds me of one, somewhat
similar, which took place during some experiments performed
some years ago in the Askesian Rooms. Some gold leaf was put
loose upon a new piece of copper coin, which was then brought
into the circuit of the pile. A part of the gold was inflamed, and
other portions adhered to the surface of the copper, as completely
as if they had been attached by any common gilding process."t
HOW THESE RESULTS AFFECT THE DISCOVERY.-We have been
particular in thus noticing the observations of the first pioneers in
electro-chemistry, because these and similar facts of later date
have been brought prominently forward by writers upon electrometallurgy, with the apparent intention to detract from the merit
due to the discoverers of the new art; founding their objection on
the ground that the principle upon which the discovery is founded
is not new. "Electro-metallurgy," says Mr. Smee, "may be said to
have its origin in the discovery of the constant battery by Professor Daniell, for in that instrument the copper is continually
reduced upon the negative plate." And again, when speaking of
Daniells' battery, he says-" Mr. M. De la Rue experimented on its
properties, and found the copper plate also covered with a coating
of metallic copper, which is continually being deposited; and so
perfect is the sheet of copper thus formed, that being stripped off,
it has the counterparts of every scratch of the plate on which it is
deposited.":
Doubtless these experiments border very closely upon the discovery; but yet they have no more claim to serve as dates to its
origin than those we have been referring to. But if it be necessary that an originating experiment must have a resemblance to
that which it suggests-such as Daniell's battery; and the single
cell of electro-metallurgy-why omit to refer to Dr. Wollaston's
earlier experiments of 1801? He says-" If a piece of silver, in
connection with a more positivd metal, be put into a solution of
copper, the silver is coated over with the copper, which coating
will stand the operation of burnishing."~  But in our opinion none
* Brugnatelli, Annals of Chemistry, vol. xviii., and Wilkinson, vol. ii.
t Phil. Mag., 1805.
J Smee, Elements of Electro-Metallurgy, 2d Edition, 1843.
Philosophical Transactions, 1801.




HISTORY OF ELECTRO-METALLURGY.            493
of these results originated electro-metallurgy: the discovery of that
art, although it is an application of such results as we have described,
was as original on the part of the discoverers,.and as unconnected
with these results at the time it was made, as it would have been
had the earlier observations never been published. The discovery
seems to have been deduced from results which the discoverers
had obtained in their own experiments, not even while searching
for such a discovery but during investigations instituted for other
purposes.
USE OF OBSERVED FACTS.-It must not be supposed that we
depreciate the value of the published facts upon the decomposition
of salts, nor that we overlook their relation to the discovery which
followed; for the multiplication of facts, and the improvement of
instruments for experimenting, enlarge our knowledge of the principles to be investigated or applied; they facilitate inquiry, and
increase the number of observers. The circumstances connected
with the discovery of ELECTRO-METALLURGY-Of the application
of the decomposing force of an electro current passing through a
solution, will illustrate these observations.
SPENCER'S FIRST EXPERIMENTS.-Mr. Thomas Spencer, of Liverpool, states that, in 1837, while experimenting with a modification
of a Daniell's battery, he used a penny piece instead of a plain piece
of copper, as a pole. Copper was deposited from the solution upon
it, and on removing the wire which attached the penny to the zinc
plate he also pulled off a portion of the deposited copper, which he
found to be an exact counterpart or mould of a part of the head and
letters of the coin as smooth and sharp as the original. But this did
not suggest to him any useful application, until sometime after he
dropped, accidentally, a little varnish upon a slip of copper which he
was about to use in the same way as he had used the penyt piece.
On finding that no deposit of copper took place on the pAi s where
the varnish had dropped, he then conceived the idea of applying thin
principle to the arts, by coating a piece of copper with varnish or
wax, and cutting a design through the wax or varnish, leaving the
copper bare, and then depositing upon these parts, so that upon
removing the varnish the design would be left in rdlef.
JACOBI'S EXPERIMENTS. —While Mr. Spencer was following up
these ideas, the following paragraph appeared in the Athenaum foi
4th May, 1839:
"Galvanic Engraving in Relief.-While M. Daguerre and Mr. Fox
Talbot have been dipping their pencils in the solar spectrum, and
astonishing us with their inventions, it appears that Professor
Jacobi, at St. Petersburgh, has also made a discovery which promises to be of little less importance to the arts. Hie has found.
method-if we understand our informant rightly-of converting
any line, however fine, engraved on copper, into a relief, by galvanic process. The Emperor of Russia has placed at the Professor's disposal, funds to enable him to perfect his discovery."
In consequence of this announcement, Mr. Spencer, on the 8th




494      THE PRACTICAL METAL-WORKER S ASSISTANT.
of May, 1839, gave notice to the Liverpool Polytechnic Institution,
that he should make a communication to them of his process' for
effecting results similar to those of Professor Jacobi. But MI
Spencer appears to have changed his design of reading it to the
above Institution, in order to have it read at the meeting of the
British Association, which was to take place a short time after.
JORDAN'S EXPERIMENTS.-Meanwhile the announcement of the
Athenwum was quoted in the London AMechanics' Magazine for May
11th, 1839, which brought forth a letter from Mr. C.J. Jordan, a
book-printer, dated 22d May, 1839, and published on the 8th June
of the same year in the London Mechanics' Magazine. In this letter
Mr. Jordan describes his experiments upon the same subject, detailing the method of procuring electrotypes, and offering hints for
their application which have since been acted upon with considerable success. The following is a copy of Mr. Jordan's letter, which
was, no doubt, the first published description of the art in this
country:
"Engraving by Galvanism.
"Sir:-Observing in the last page of a recent Number of your
Magazine, a notice extracted from the Athenaeum, relative to a discovery of Professor Jacobi, its perusal occasioned the recollection
of some experiments performed about the commencement of last
summer, with the view of obtaining impressions from engraved
copper plates, by the aid of galvanism, which led me to infer some
analogy in principle with those of the Russian Professor, and may
probably give me the right to claim priority in its discovery and
application. These experiments were abandoned from the want of
that most important element in pursuits of this nature-time; the
writer's share of the said element being occupied in a manner more
imperative than pleasing. I regret, however, not having made it
the subject of an earlier communication, as this would have placed
my pretensions beyond doubt; but, inasmuch as the notice alluded
to is given from memory, and is undescriptive, while I may be
enabled to exhibit the modus operandi, my assertion may be at
least partially substantiated.
"It is well known to experimentalists on the chemical action of
voltaic electricity, that solutions of several metallic salts are decomposed by its agency, and the metal procured in a free state. Such
results are very conspicuous with copper salts, which metal may be
obtained from its sulphate (blue vitriol), by simply immersing the
poles of a galvanic battery in its solution, the positive wire becoming
gradually coated with copper. This phenomenon of metallic reduction is an essential feature in the action of sustaining batteries, the
effect, in this case, taking place on more extensive surfaces. But
the form of voltaic apparatus which exhibits this result in the most
interesting manner, and relates more immediately to the subject of
the present communication, may be thus described: —It consists of
a glass tube, closed at one extremity with a plug of plaster of Paris,




HISTO1aY OF ELECTRO-METALLURGY.           495
and nearly filled with a solution of sulphate of copper; this tube
and its contents are immersed in a solution of common salt. A plate
of copper is placed in the first solution, and is connected, by means
of a wire and solder, with a zinc plate which dips into the latter.
A slow electric action is thus established through the pores of the
plaster, which it is not necessary to mention here-the result of
which is the precipitation of minutely crystallized copper on the
plate of that metal, in a state of greater or less malleability according to the slowness or rapidity with which it is deposited. In
some experiments of this nature, on removing the copper thus
formed, I remarked that the surface in contact with the plate
equalled the latter in smoothness and polish, and mentioned this
fact to some individuals of my acquaintance. It occurred to
me, therefore, that if the surface of the plate was engraved, an
impression might be obtained. This was found to be the case;
for, on detaching the precipitated metal, the most delicate and
superficial markings, from the fine particles of powder used in
polishing, to the deeper touches of a needle or a graver, exhibited
their correspondent impressions in relief, with great fidelity. It
is, therefore, evident that this principle will admit of improvement,
and that casts and moulds may be obtained from any form of
copper.
"This rendered it probable that impressions may be obtained
from those other metals having an electro-negative relation to the
zinc plate of the battery. With this view, a common printingtype was substituted for the copper plate, and treated in the same
manner. This also was successful; the reduced copper coated that
portion of the type immersed in the solution.  This, when removed, was found to be a perfect matrix, and might be employed
for the purpose of casting, where time is not an object.
It appears, therefore, that this discovery may be turned to some
practical account. It may be taken advantage of in procuring
casts from various metals, as above alluded to; for instance, a
copper die may be formed from a cast of a coin or medal, in silver,
type metal, or lead, etc., which may be employed in striking impressions in soft metals. Casts may probably be obtained from a
plaster surface surrounding a plate of copper; tubes or any small
vessels may also be made by precipitating the metal around a wire,
or any kind of surface, to form the interior, which may be removed
mechanically, by the aid of an acid solvent, or by heat.
"C. J. JORDAN."
" To the Editor of the London Mechanics'.Magazine."
Clear and perspicuous as this letter is, it did not attract the
slightest notice. And a few weeks after, we find that its existence
was forgotten even by the editor of the magazine in which ift
appeared.
SPENCER'S FIRST PRINTED PAPER UPON ELECTROTYPE. -Mr,
Spencer's communication, referred to above, was, in consequence




496      THE PRACTICAL METAL-WVORKER'S ASSISTANT.
of some misunderstanding, not read at the meeting of the British
Association, but it was immediately afterwards read before the
Polytechnic Institution of Liverpool, at their meeting on the 13th
September, 1839, which was upwards of three months after the
publication of Mr. Jordan's letter in the London Mechanics'.iagyazine. Mr. Spencer's paper was accompanied with specimens both
of electrotypes and of printing from electrotypes. The publication of this paper acted like an electric shock upon society, and
men both of science and art became active competitors in this new
field of application; the one class anxious to bear away the honors
arising from some important improvement; the other, the profits
which might follow some novel application of the process to their
own or some other branch of manufacture. Indeed, thousands of
all classes and ages, who had never previously given science a
passing thought, became fascinated with the new art, and-the
process being simple and easy to perform —the amateurs soon became excellent electrotypists. With these combined efforts, it
need not be wondered at that in a very short time improvements
of great scientific interest were pointed out, and applications of the
greatest importance to the arts and manufactures of this country
were introduced. In consequence, some of our old and standard
manufactures, as we shall subsequently have occasion to notice at
some length, have already been revolutionized.
HISTORICAL ANOMALY. —During a period of nearly five years
-while the country was passing through an electrotyping mania
-Mr. Spencer held the undivided honor of being the first to
apply the deposition of metals to practical purposes in this coun.
try, but early in 1844, Mr. Henry Dircks, in a letter to the London
Mechanics' Magazine, revived Mr. Jordan's letter, and told us that
he was aware of its existence from the time of its first publication.
We cannot eulogise either the policy, or the love of scientifir
truth, which induced Mr. Direks to remain silent so long, and see
the claims of Mr. Jordan set aside by one whom he considered to
be a mere pretender to the merit of the discovery. Nor; after a
careful and impartial examination of all the details published on
the subject, can we agree to his condemnation of Mr. Spencer's
prior claims; as he, Mr. Spencer, upon the 8th of May, as already
noticed, stated to a public meeting of the Polytechnic Society of
Liverpool, that he had made a similar discovery previous to any
knowledge of either what Jordan or Jacobi had done, and which
was a publication as much as if printed in the Times or Athenteum,
and especially when followed by a detailed description of the discovery.
It is to be regretted that Mr. Jordan's diffidence, which in this
case was far from being commendable, prevented his setting the
public right upon this important matter. As a consequence, he
must now be content with a much smaller share of the honor of
the discovery than he might have enjoyed.
Crs reviewing the circumstances of this discovery, it strikes us




HISTORY OF ELECTRO-METALLURGY.             497
as being a remarkable instance of the unity of intellectual perception in reference to the general principles of Nature and their applications; for we believe that Professor Jacobi, Mr. Spencer, and
Mr. Jordan, viewed the subject of electro depositions in the same
light, and about the same time; and each, according to their several abilities, presented to the public the same discovery, independent of the other, excepting the announcement made by one having
hastened the publication of the observations of the others.
The following is Mr. Spencer's original paper on electro-metallurgy, which we give at length, trusting that its importance in connection with the history of the art, and the lucid description of its
practice, will serve as a sufficient apology for not abridging it:
"On Working in Metal by Voltaic Electricity, reprinted from the Paper Published by the Liverpool Polytechnic Society, and read at the
Meeting of September the 12th, 1839, Notice being given May the
8th: Henry Booth, Esq., President, in the Chair.
"In the paper that I have the honor to lay before the society, I
do not profess to have brought forward a perfect invention. My
only object is to point out a means by which, I hope, practical
men may be enabled to apply a great and universal principle of
Nature to the useful and ornamental purposes of life. In this I
may be considered sanguine-an error, I am aware, too often fallen
into by those who, like myself, imagine they have discovered a
useful application of an important principle; but however this
may fall out, I shall lay an account of its results, with specimens,
successful and unsuccessful, before the members and the publicpreviously stating, however, that all my first experiments were
made on a small scale-a method of procedure attended with many
advantages to the experimentalist himself, but having its disadvantage when laid before the public. In this first respect, perhaps,
the chemical experimenter has an advantage over the mechanical
one, as the success of his experiment, when tried on a small scale,
doubly guarantees it if conducted on a still larger scale: with
mechanical results I believe in most instances it is the reverse. But
when the chemist produces his microscopic proofs, the public
are generally slow to believe that such minute appearances should
warrant him in coming to any general conclusion.
"In the latter part of September, 1837, I was induced to make
some electro-chemical experiments, with single pairs of plates,
consisting of small pieces of zinc and equal-sized pieces of copper,
connected together with wires of the latter metal. It was intended
that the action should be slow: the fluids in which the metallic
electrodes were immersed were in consequence separated by thin
discs of plaster of Paris. In one cell thus formed was placed sul.
phate of copper in solution-in the other, a weak solution of
common salt. I need scarcely add that the copper electrode was
placed in the cupreous solution, the other being in that of the salt.
32




498      THE PRACTICAL METAL-WORKER S ASSISTANT.
I mention these experiments briefly-not because they are directly
connected with what I shall have to lay before the society, but
because, by a portion of their results, I was induced to come to
the conclusions I have done in the following paper. I was desirous that no action should take place on the wires by which the
electrodes were held together; and t-o attain this object I varnished
them with sealing-wax varnish: but, in one instance, I dropt a
portion on the copper electrode that was attached. I thought
nothing of this circumstance at the moment, but put the experiment in action.
" This operation was conducted in a glass vessel; I had consequently an opportunity of occasionally examining its progress from
the exterior. After the lapse of a few days, metallic crystals had
covered the copper electrode-with the exception of that portion
which had been spotted with the drops of varnish. I at once saw
that I had it in my power to guide the metallic deposition in any
shape or form I chose, by a corresponding application of varnish
or other non-metallic substance.
"I had been aware of what every one who uses a sustaining
galvanic battery with sulphate of copper in solution must knowthat the copper plates acquire a coating of copper from the action
of the battery; but I had never thought of applying it to a useful
purpose, except to multiply the plates of a species of battery,
which I did in 1836. My present attempt was with a piece of thin
copper plate, having about four inches of superfices, with an equal
sized piece of zinc, connected as before by a piece of copper wire.
I gave the copper a coating of soft cement, consisting of beeswax,
resin, and a red earth. It was compounded in the manner recommended by Dr. Faraday, in his work on Chemical Manipulation,
but with a larger proportion of wax. The plate received its coating while hot. When it was cold, I scratched the initials of my
name rudely on the plate, taking special care that the cement was
quite removed from the scratches, that the copper might be thoroughly exposed. This was put in action in a cylindrical glass
vessel, about half filled with a saturated solution of sulphate of
copper. I then took a common gas glass, similar to that used to
envelope an argand burner, and filled one end of it with plaster of
Paris, to the depth of three-quarters of an inch. Into this I put
water, adding a few crystals of sulphate of soda to excite action,
the plaster of Paris acting as a partition to separate the fluids, but,
at the same time, being sufficiently porous to allow the electro.
chemical action to permeate its substance.
"I now bent the wire in such a manner that the zinc end of the
arrangement should be in the saline solution, while the copper
end, when in its place, should be in the cupreous solution. The
gas glass, with the wire, was then placed in the vessel containing
the sulphate of copper.
"It was then suffered to remain at rest, when in a few hours I
perceived that action had commenced, and that the portion of the




HISTORY OF ELECTRO-METALLURGY.             499
copper rendered bare by the scratches had become gradually
coated with pure bright deposited metal, whilst all the surrounding portions were not at all acted on. I now saw my former observations realized; but whether the deposition so formed would
retain its hold on the plate, and whether it would be of sufficient
solidity or strength to bear working if applied to a useful purpose, became questions which I now determined to solve by experiment. It also became a question-should I be successful in these
two points-whether I should be able to produce lines sufficiently
in relief to print from. This latter appeared to depend entirely
on the nature of the cement or etching-ground I might use.
"This I endeavored to solve at once; and, I may state, it appeared at the time to be the main difficulty, as my impression then
was, that little less than one-eighth of an inch of relief would be
requisite to print from.
"I now procured a piece of copper, and gave it a coating of a
modification of the cement I have already mentioned, and having
covered it to about one-eighth of an inch in thickness, I took a steel
point and endeavored to draw lines in the form of net-work, that
should entirely penetrate the cement, and leave the surface of the
copper exposed. But in this I experienced much difficulty,.from
the thickness I deemed it necessary to use; more especially when
I came to draw the cross lines of the net-work. The cement being
soft, the lines were pushed as it were into each other, and when it
was made of harder texture, the intervening squares of the network chipped off the surface of the metallic plate. However
those that remained perfect I put in action as before.
"In the progress of this experiment I discovered that the solidity
of the metallic deposition depended entirely on the weakness or
intensity of the electro-chemical action, which I knew I had in my
power to regulate at pleasure, by the thickness of the intervening
wall of plaster of Paris, and by the coarseness or fineness of the
material. I made three similar experiments, altering the texture
and thickness of the plaster each time, by which I ascertained that
if the partitions were thin and coarse, the metallic depositions proceeded with great rapidity, but the crystals were friable and easily
separated; on the other hand, if I made them thicker and of a little
finer material, the action was slower, but the metallic deposition
was as solid and ductile as copper formed by the usual methods
-indeed, when the action was exceedingly slow, I have had a
metallic deposition apparently much harder than common sheet
copper, but more brittle.
"There was one most important and, to me, discouraging circum
stance attending these experiments, which was, that when I heated
the plates to get off the covering of cement, the meshes of copper
net-work occasionally came off with it. I at one time imagined this
difficulty inseparable, as it appeared that I had cleared the cement
entirely from the surface of the copper that I meant to have exposed; and I concluded that there must be difference in the mole




500      THE PRACTICAL METAL-WORKER S ASSISTANT.
cular arrangement of copper prepared by heat and that prepared
by voltaic action, which prevented their chemical combination.
However, I determined, should this prove so, to turn it to account
in another manner, which I shall relate in the second portion of
the paper.'I now occupied myself for a considerable period in making
experiments on this latter section of the subject.
"In one of them I found, on examination, that a portion of the
copper deposition, which I had been forming on the surface of a
coin, adhered so strongly that I was quite unable to get it offindeed, a chemical combination had apparently taken place. This
was only on one or two spots on the prominent parts of the coin.
I immediately recollected that, on the day I put the experiment in
action, I had been using nitric acid for another purpose, on the
table I was operating on, and that in all probability the coin might
have been laid down where a few drops of the acid had accidentally
fallen. Bearing this in view, I took a piece of copper, coated it
with cement, made a few scratches on its surface until,the copper
appeared, and immersed it for a short time in dilute nitric acid,
until I perceived, by an elimination of nitrous gas, that the exposed
portions were acted upon sufficiently to be slightly corroded. I
washed the copper in water, and put it in action as before described.
In forty-eight hours I examined it, and found the lines were entirely filled with copper, I applied heat, and then spirits of turpentine, to get off the cement, and, to my satisfaction, I found that the
voltaic copper had completely combined itself with the sheet on
which it was deposited.
" I then gave a plate a coating of cement to a considerable thickness, and sent it to an engraver; but when it was returned I found
the lines were cleared out so as to be wedge-shaped, or somewhat
in the form of a V, leaving a hair line of the copper exposed at
the bottom, and a broad space near the surface; and where the
turn of the letters took place, the top edges of the lines were
galled and rendered rugged by the action of the graver. This, of
course, was an important objection, which I have since been able to
remedy in some degree by an alteration in the shape of the graver,
which should be made of a shape more resembling a narrow parallelogram than those in common use: some engravers have many
of their tools so made. I did not put this plate in action, as I saw
that the lines, when in relief, would have been broad at the top
and narrow at the bottom. I took another plate, gave it a coating
of the wax, and had it written on with a mere point. I deposited
copper on the lines, and afterwards had it printed from.*' I now considered part of the difficulties removed: the principal one yet remaining was to find a cement or etching-ground,
the texture of which should be capable of being cut to the re* This plate was shown to friends, and also specimens of printing from it,
In 1838.




HISTORY OF ELECTRO-METALLURGY.            501
quired depth, without raising what is technically termed a burr,
and, at the same time, of sufficient toughness to adhere to the
plate, when reduced to a small isolated point, which would necessarily occur in the operation which wood-engravers term crosshatching.
"I have since learned, from practical engravers, that much less
relief is necessary to print from than I had deemed indispensable,
and that, on becoming more familiar with the cutting of the waxcement, they would be enabled to engrave in it with great facility
and precision.
"I tried a number of experiments with different combinations
of wax, resins, varnishes, earths, and metallic oxides, all with more
or less success. One combination that exceeded all others in its
texture was principally composed of beeswax, resin, and white
lead. This had nearly every requisite, so that I was enabled to
polish the surface of the plate with it until it was nearly as smooth.
as a plate of glass. With this compound I had two plates, five
inches by seven, coated over, and portions of maps cut on the
cement, which I had intended should have been printed off. I applied the same process to these as to the others, immersing them
into dilute nitric acid before putting them in action; indeed I suffered them to remain about ten minutes in the solution. I then put
them into the voltaic arrangement. The action proceeded slowly
and perfectly for a few days, when I removed them. I applied
heat as usual, to remove the cement, but all came away, as in a
former instance-the voltaic copper peeling off the plate with the
greatest facility. I was much puzzled at this unexpected result;
but, on cleaning the plate, I discovered a delicate trace of lead, exactly corresponding to the lines drawn on the cement previous to
the immersion in the dilute acid. The cause of this failure was
at once obvious: the carbonate of lead I had used to compound
the etching-ground had been decomposed by the dilute nitric acid
and the metallic lead thus reduced had deposited itself on the exposed portions of the copper plates, preventing the voltaic copper
from chemically combining with the sheet copper. I was now
with regret obliged to give up this compound, and to adopt another,
consisting of beeswax, common resin, and a small portion of
plaster of Paris. This seems to answer the purpose tolerably,
though I have no doubt, by an extended practice, a better may
still be obtained by a person practically acquainted with the etching-grounds in use among engravers.
" I now proceed to the second, and I believe the most satisfactory portion of the subject. Although I have placed these experiments last, some of them were made at the same time with the
others already described, and some of them before; but, to render
the subject more intelligible, I have placed them thus.
" The members of the society will recollect that, on the first
evening it met, I read a paper on the'production of metallic veins
in the crust of the earth,' and that among other specimens of cupre.




502      THE PRACTICAL METAL WORKEB'S ASSISTlx'v.l
ous crystallization which I produced on that occasion, I exhibited
three coins-one wholly covered with metallic crystals, the other
on one side only. It was used under the following circumstances.
When about to make the experiment, I had not a slip of copper
at hand to form the negative end of my arrangement, and, as a
good substitute, I took a penny and fastened it to one end of the
wire, and put it, in connection with a piece of zinc, in the apparatus
already described.
"Voltaic action took place, and the copper coin became covered
with a deposition of copper in a crystalline form. But, when
about to make another experiment, and being desirous of using
the piece of wire used in the first instance, I pulled it off the coin
to which it was attached. In doing this, a piece of the deposited
copper came off with it; on examining the under portion of which,
I found it contained an exact mould of a part of the head and
letters of the coin, as smooth and sharp in every respect as the
original on which it was deposited. I was much struck with this
at the time; but, on examination, the deposition metal was very
brittle. This, and the fact that it would require a metallic nucleus
to aggregate on, made me apprehensive that its future usefulness
would be materially abridged; but it was reserved for future experiment, and in consequence laid aside for a time, until my attention was recalled to the subject in a subsequent experiment, already
detailed, by the drops of varnish on a slip of copper. Finding in
that instance that the deposit would take the direction of any nonconducting material, and be, as it were, guided by it, I was induced
to give the previous branch of the subject a second trial, because
I had, in the first instance, supposed that the deposition would
only take place continuously, and not on isolated specks of a
metallic surface, as I now found it would; but the principal inducement to investigate the subject was the fact of finding that
deposited copper had much more tenacity than I at first imagined.
"Being aware of the apparent natural law which limits metallic
deposition by voltaic electricity, excepting in the presence of a
metallic body, I perceived that the uses of the process would, in
consequence, be extremely limited, except in the multiplication of
already engraved plates, as, whatever ornament it might produce,
it would only be done by adhering to the condition of a metallic
mould.
"I accordingly determined to make an experiment on a very
prominent copper medal. It was placed in a voltaic circuit, as
already described, and deposited a surface of copper on one of its
sides to about the thickness of a shilling. I then proceeded to get
the deposition off. In this I experienced some difficulty, but ultinlately succeeded. On examination with a lens, every line was as
perfect as the coin from which it was taken. I was then induced
to use the same piece again, and let it remain a much longer time
in action, that I might have a thicker and more substantial mould,
in order to test fairly the strength of the metal. It was accord



HISTORY OF ELECTRO-METALLURGY.             503
ingly put again in action, and let remain until it had acquired a
much thicker coating of the metallic deposition; but on attempting to remove it from the medal I found I was unable. It had,
apparently, completely adhered to it.
"I had often practised, with some degree of success, a method
of preventing the oxidation of polished steel, by slightly heating
it until it would melt fine beeswax; it was then wiped, apparently
completely off, but the pores or surface of the metal became impregnated with the wax.
"'I thought of this method, and applied it to a copper coin.
"I first heated it, applied wax, and then wiped it so completely
off, that the sharpness of the coin was not at all interfered with. I
proceeded as before, and deposited a thick coating of copper on
its surface. Being desirous to take it off, I applied the heat of a
spirit-lamp to the back, when a sharp crackling noise took place,
and I had the satisfaction of perceiving that the coin was completely loosened. In short, I had a most complete and perfect
copper mould of one side of a half-penny.
"I have since taken some impressions from the mould thus
taken, and, by adopting the above method with the wax, they are
separated with the greatest ease.
"By this experiment it would appear that the wax impregnates
the surface of the metal to an inconsiderable depth, and prevents
a chemical adhesion from taking place on the two surfaces; and I
can only account for the crackling noise, on separation, by supposing it probable that the molecular arrangement of the voltaic
metal is different from that subjected to percussion, and this difference causes an unequal degree of expansibility on the application
of heat.
"I became now of opinion, that this latter method might be
applied to engraving much better than the method described in
the first portion of this paper. Having found in a former experiment that copper in a voltaic circuit deposited itself on lead with
as much rapidity as on copper, I took a silver coin, and put it between two pieces of clean sheet-lead, and placed them under a
common screw-press. From the softness of the lead, I had a complete and sharp mould of both sides of the coin, without sustaining injury. I then took a piece of copper wire, soldered the lead
to one end, and the piece of zinc to the other, and put them into
the voltaic arrangement I have already described. I did not, in
this instance, wax the mould, as I felt assured that the deposited
copper would easily separate from the lead by the application of
heat, from the different expansibility of the two metals.
"In this result I was not disappointed. When the heat of a
spirit-lamp was applied for a few seconds to the lead, the copper
impression came easily off. So complete do I think this latter
portion of the subject, that I have no hesitation in asserting that
fac-similies of any coin or medal, no matter of what size, may
be readily taken, and as sharp as the original. To test further the




504      THE PRACTICAL METAL-WORKER'S ASSISTANT.
capabilities of this method, I took a piece of lead plate, and stamped
some letters of its surface to a depth sufficient to print from, when
in relief. I deposited the copper on it, and found it came easily
off, the letters being in relief.
"Finding from this experiment that the extreme softness of lead
allowed it to be impressed on by type metal, I caused a small portion of ornamental letter-press to be set up in type, and placing it
on a planed piece of sheet lead, it was subjected to the action of a
screw press.
"After considerable pressure, it was found that a perfectly sharp
mould of the whole had been obtained in the lead. A wire was
now soldered to it, and it was placed in an apparatus similar in
principle, but larger than the one already described. At the end
of eight days from this time, copper was deposited to one-eighth of
an inch in thickness; it was then removed from the apparatus, and
the rough edges of the deposited copper being filed off; it was subjected to heat, when the two metals began to loosen. The separation was completed by inserting a piece of wedge-shaped wood
between them.
"I had now the satisfaction of perceiving that I had by these
means obtained a most perfect specimen of stereotyping in copper,
which had only to be mounted on a wooden block to be ready to
print from.
" From the successful issue of this experiment, which was mainly
due to the susceptibility of the lead, I was induced to attempt to
copyr a wood engraving by a similar method, provided the wood
would bear the requisite pressure. Knowing that wood engravings are executed on the end of the block, I had better hopes of
succeeding, the wood being less likely to sustain injury.
"I accordingly procured a small wood block, and placed its engraved surface in contact with a piece of sheet lead made very clean,
and subjected it to pressure, as in the former instance. I had now,
as before, the gratification of perceiving that a perfect mould of the
little block had been obtained, and no injury done to the original.
Several wood engravings and copperplates were subjected to similar
treatment, and are now in process of being deposited on in the
apparatus before me.
"' I now come to the third and concluding portion of the experiments on this subject. The object being to deposit a metallic surface on a model of clay, wood, or other non-metallic body-as,
otherwise, I imagined the application of this principle would be
extremely limited. Many experiments were made to attain this
result, which I shall not detail, but content myself with describing
those which were ultimately most successful.
"I procured two models of an ornament, one made of clay, and
the other of plaster of Paris, soaked them for some time in linseedoil, took them out, and suffered them to dry-first getting the oil
clean off the surface. When dry, I gave them a thin coat of mastic
varnish. When the varnish was nearly dry, but not thoroughly so, I




HISTORY OF ELECTRO-METALLURGY.            505
sprinkled some bronze powder on that portion I wished to make a
mould of. This powder is principally composed of mercury and
sulphur, or it may be chemically termed a sulphuret of mercury.
There is a sort that acts much better, in which is a portion of gold.
I had, however, a complete metalliferous coating on the surface
of the model, by which I was enabled to deposit a surface of copper on it, by the voltaic method I have already described. I have
also gilt the surface of a clay model with gold leaf, and have been
successful in depositing copper on its surface. There is likewise
another, and as I trust it will prove, a simpler method of attaining
this object; but as I have not yet sufficiently tested it by experiment,
I shall take another opportunity of describing it."
[At the close of the paper, several specimens of coins, medals, and
copper plates, some of them in the act of formation by the voltaic
process, were exhibited by Mr. Spencer to the Society.]
PLUMBAGO AS A COATING.-Shortly after Mr. Spencer's paper
was published, several important improvements were introduced,
one or two of which we will refer to here, and will give the others
when detailing the processes to which the improvements were applied. The first was the use of plumbago or black lead, to give
the surface of non-metallic bodies a conducting property. This
was the discovery of Mr. Robert Murray, a gentleman of high attainments and unassuming manners, who communicated the process
to the members of the Royal Institution orally. The Society of
Arts afterwards awarded to Mr. Murray a silver medal, as an expression of their sense of the value of the discovery. Seldom was
reward more deserving, or a discovery more important to the pur.
poses to which it was to be applied, for this application at once
freed electro-metallurgy from every bond: it was no longer necessary to use either metallic moulds, or moulds having metal reduced
upon their surfaces by chemical means-which, according to the
processes then known, was both tedious and uncertain, and only
applicable to certain substances. Plumbago possessed all the requisite properties: it was convenient, plentiful, and cheap, easily
applied, and equally effective for every substance on which the
electrotypist desired to obtain a deposit, or which he could wish to
cover with metal, either for useful or ornamental purposes.
SEPARATE BATTERY.-The second improvement to be noticed is
one that must have followed the original discovery very soon, namely,
the application of a separate battery for the purposes of deposition.
This was suggested by Mr. Mason. Although those instances of
deposition of metals which have been referred to in the early history
of galvanism were effected by means of separate batteries, namely,
by placing the ends of the wires attached to the terminals of the
battery in the solution to be decomposed, still the discovery under




506      THE PRACTICAL METAL-WORKER S ASSISTANT.
consideration was made by means of what is termed the single cell.
It consisted in simply attaching by a wire the article upon which
a deposition was to be made to a piece of zinc, and immersing the
zinc in diluted acid, and the other article in a solution of the metal
to be deposited; the two liquids being separated by a porous partition, or diaphragm, such as moist bladder, or unglazed porcelain.
In this case, the whole electricity was expended within the cell, to
deposit the metal within or upon the mould. By Mr. Mason's discovery, the electricity generated in the cell could be made to do an
equivalent of work in a separate cell as well-making the original
arrangement the generating cell or battery to the second cell. In
this last cell was also a solution of a metal having in it a sheet of
similar metal attached to the copper of the first cell, and the mould
to be covered was attached to the zinc of the first cell. Fig. 541
is an illustration of Mason's improvement, which consisted in causing a medal, in the act of being deposited, to serve as part of a
battery for the deposition of another medal.
02, Outer vessel filled with sulphate of copper; o', another vessel, with P, a porous cell filled with dilute acid, in which is placed
z a zinc plate, which is connected by a wire with a medal m' in
the second vessel charged with sulFig. 541.        phate of copper. The medal, m, in
the first cell, is connected by a wire
to a piece of copper, c, in the second
cell: the electricity passes from the
zinc z to m, and by the wire to c,
then to in', and by the wire back to
the zinc z.. c i,             The use of a separate battery, however self-evident, was a valuable ad-. dition to the electro-metallurgist for
\02      A          ~many of his operations; although
-<i ~:    for some purposes the original single
cell is to be preferred.
LAWS OF DEPOSITION.-As might have been expected in the
excitement occasioned by the announcement of a new art, every
individual experimenter became so engrossed by his own investigations and their results, as to overlook the labors of others, and
at last to lay claim to the honor of originating all the discoveries
they announced; while the truth is, that nearly all the important
facts of electro-metallurgy appear to have occurred almost simultaneously to various experimenters. We shall quote one or two
instances of these absorbing claims, as it is important to rectify the
errors they contain, because no successful laborer, howeter humble,
in the field of science or art, should be overlooked by his fellowlaborer whose opportunities for research may be much more favor.
able.




HISTORY OF ELECTRO-METALLURGY.              5017
Extract from Smee's "Electro-JMetallurgy."
"The laws regulating the reduction of all metals in different
states were first given in this work as the result of my own discoveries. By these we can throw down gold, silver, platinum, palladium, copper, iron, and almost all other metals, in three states,
namely, as a black powder, as a crystalline deposit, or as a flexible
plate. These laws appear to me at once to raise the isolated facts
known as the electrotype into a science, and to add electro-metallurgy as an auxiliary to the noble arts of this country."
That Mr. Smee discovered the laws referred to we have not the
slightest doubt: they were published as laws in his book, and they
are commonly quoted as Mr. Smee's~ nevertheless, he was not the
first who discovered them; the same laws were pointed out by
Mr. Spencer, in his original paper just quoted, published eighteen
months previously to the appearance of Mr. Smee's work, as will
be seen from the following extracts:
Laws given by Smee.           Laws given by Spencer.
"Law I.-The metals are in-    "I discovered that the solidity
variably thrown down as a black  of the metallic deposition depowder, when the current of  pended entirely on the weakness
electricity is so strong, in rela-  or intensity of the electro-chemtion to the strength of the solu-  ical action, which I knew I had
tion, that hydrogen is evolved  in my power to regulate at
from the negative plate of the  pleasure, by the thickness of the
decomposition cell.            intervening wall of plaster of
Paris, and by the coarseness or
"Law  II.- Every metal is  fineness of the material. I made
thrown down in a crystalline  three similar experiments, alterstate, when there is no evolution  ing the texture and thickness
of gas from the negative plate, each time, by which I asceror no tendency thereto.        tained, that if the partitions were
thin and coarse, the metallic de"Law  III. - Metals are re-  position proceeded with great
duced in the reguline state, when  rapidity, but the crystals were
the quantity of electricity, in  friable and easily separated; on
relation to the strength of the  the other hand, if I made them
solution, is insufficient to cause thicker, and of a little finer mathe production of hydrogen in  terial, the action was slower, but
the negative plate of the decom- the metallic deposition was as
position trough, and yet the quan-  solid and ductile as copperformed
tity of electricity very nearly  by the usual methods. Indeed,
suffices to induce that phenom-  when the action was exceedingly
enon."                         slow, I have had a metallic depo
sition much harder than common
sheet copper, but more brittle."
The identity of these deductions or laws requires no comment;
and, comparing the circumstances of the one having nothing but




508      THE PRACTICAL METAL-WORKER'S ASSISTANT.
the rude apparatus of a new-born art suggested by himself, to that
of the other, enjoying the advantage of eighteen months improvements, Mr. Spencer is astonishingly correct, and his name should
be identified with the discovery of these laws. The claim of originality involved in the inference drawn by Mr. Smee, though formidable at first sight, is nevertheless, without foundation. Mr.
Smee says: "These laws appear to me at once to raise the isolated
facts known as the electrotype into a science, and to add electrometallurgy as an auxiliary to the noble arts of this country." Unfortunately for the validity of Mr. Smee's claim, patents were taken
out long previous, both in England and France, for the application of the electro-depositions to the arts. And Messrs. Elkington's
patent for silvering and gilding by this process-a patent which
has not yet been superseded-was not only published in full detail,
but was in extensive operation months before the publication of
Mr. Smee's book. Nevertheless, the publication of Mr. Smee's
book did good service to the art of electrotyping; and the invention of his battery has so identified his name with the science, that
it will go down to posterity as that of an active and successful
laborer in the field of electricity: to Mr. Smee we owe, moreover,
the very appropriate name for the art, Electro-metallurgy.
WORKS PUBLISHED ON ELECTRO-METALLURGY.-Besides many
interesting papers in journals and magazines, several separate works
were published on this art. Some months previously to the publication of Mr. Smee's work, Mr. Spencer had given the world "Instructions for the multiplication of works of art in metal by voltaic
electricity;" and shortly after Mr. Smee's work appeared, we had, in
rapid succession, Walker's Electrotype iManipulation, Sturgeon's Art
of Electrotyping, Shaw's Manual of Electro-metallurgy, etc., all showing much practical knowledge of the subject. Walker's Manipulation, from its practical nature and its concise form, became the
favorite of the amateur, and did more to popularize the art than all
the others put together; and although little pretensions were made
to originality, the author will not fail to have an honorable remembrance in the history of the art.
PATENTS TAKEN OUT FOR ELECTRO-METALLURGY.-The application of the art to useful purposes was so self-evident and so eagerly
sought after, that no less than ten patents were taken out for useful
applications, between the discovery of the art and the close of 1841;
and not a year has passed since, without adding patents for certain
improvements, and applications of Electro-metallurgy to some particular branch of manufacture, several of which will be noticed in
their proper places, as many of them, although based upon right
principles, were commercially speaking, entire failures.




DESCRIPTION OF GAtVANIC BATTERIES.          009
CHAPTER XXV.
DESCRIPTION OF GALVANIC BATTERIES, AND THEIR RESPECTIVE
PECULIARITIES.
NOMENCLATURE.-The terms that are employed to denote the
various parts of agalvanic battery, and of other electrotype arrangements, frequently puzzle the student, and lead him into difficulties.
Before we proceed to describe the various forms of the battery, we
shall, for this reason, give a preliminary account of the nomencla
ture of galvanism.
The two extremities of a battery have long been called Polesone of them the Positive, and the other the Negative, Pole. But
objections have been taken to the use of the terms negative, positive,
and pole, on the ground that such terms do not convey a correct
idea of the circumstances or of the effects produced. Before connecting the two metals or extremities of a battery, there is no electricity evolved, nor is there any electrical tension on any part of
the arrangement; and when the connection is formed the electricity
simply makes a circuit, it is therefore supposed that no particular
portion of that circuit can be said to be either negative or positive
to another portion.
PROPOSED TERMS.-Various terms have been suggested as substitutes for negative and positive, and also for pole. Dr. Faraday
has proposed the following: for pole, he substitutes electrode, which
signifies a way; for the negative pole, cathode, signifying downwards;
and for the positive pole, anode or upwards. To understand these
terms properly, we must suppose a battery lying upon the ground
with its copper (positive) end to the east, and the wire connecting
the ends of the battery bent into an arch similar to the course of
the sun; the electric current will thus flow up from the east end of
the battery, and descend into it at the west end. The fluid that is
decomposed by a current of electricity passing through it is termed
by Faraday an electrolyte; the elements liberated by this decomposition he terms ions, distinguishing those liberated at the cathode as
cations, which in sulphate of copper would be the metal, and those
liberated at the anode as anions, which would be the acid portion
of the sulphate of copper.
The late Professor Daniell, disapproving of the terms cathode
and anode, substitued platinode for the negative, and zincode for the
positive, pole. We think these terms are better adapted for electrometallurgy than cathode and anode, which have no direct reference to ordinary conditions; while zincode distinctily expresses
the substance dissolved, and platinode the element not acted upon.
Professor Graham adopts the terms zincous and chlorous poles, as
synonymous with zincode and platinode, or positive and negative.
Although the terms positive, negative, and pole, may not be the




510      THE PRACTICAL METAL-WORKER S ASSISTANT.
best, still, under all the conditions of electro-metallurgy, we deem
them as appropriate as any of the proposed substitutes, some of
which are based on supposed conditions which have not been
proved, and may be found incorrect.
When we shall have occasion to use the two terms pole and electrode, these will be used synonymously: positive and negative electrode are synonymous with positive and negative pole.
Electrolyte will be applied to a solution when undergoing decomposition by the electric current passing through it.
The positive electrode, or pole, is that metal in the electrolyte
which is being dissolved, or, if not capable of being dissolved, at
which the acid or solvent of the electrolyte is being liberated, as
when sulphate of copper forms the electrolyte, the sulphuric acid
is liberated. The negative electrode, or pole, is that metal or substance in the electrolyte upon which the metal is being deposited
by the influence of the electric current, such as a medal upon which
copper is being deposited in an electrotype process.
BATTERIES.
SINGLE PAIR OF PLATES.-If a piece of ordinary metallic zinc
be put into dilute sulphuric acid, it is speedily acted upon by the
acid, and hydrogen gas is at the same time evolved from its surface, having a disagreable smell arising from impurities contained
in the zinc or acid. If the zinc be taken out, and a little mercury
be rubbed over its surface, an amalgamation takes place between
the two metals: the plate becomes of a beautiful bright silver
appearance. If the zinc thus amalgamated be again put into the
dilute acid, there is no action, for the mercury retains the zinc with
sufficient force to protect it from the acid. If a piece of copper be
immersed along with the zinc, and the two metals be made to touch
each other, a particular influence is induced among the three elements, zinc, copper, and acid;. the acid again acts upon the zinc as
if no mercury was upon it, but the hydrogen is now seen to escape
from the surface of the copper; this action will go on as long as
the two rnWtals are kept in contact. Or if, instead of causing the
two metals to touch, a wire be attached to each, and their opposite
ends are placed in a little dilute acid in another vessel, the same
action will take place between the zinc and copper as when they
were in contact; but in this instance, the ends of the two wires
which dip into the vessel containing acid will undergo a change:
the one attached to the zinc will give off a quantity of hydrogen
gas, while the one attached to the copper, supposing it to be also
copper, will rapidly dissolve.
Figure 542. Represents the zinc and copper, placed in dilute
sulphuric acid, brought into contact; in this experiment, gas will
be seen escaping from the copper.
Figure 543. Zinc and copper, placed in dilute acid, and wires
attached, which, when connected, will exhibit the same effects as
in the first case.




DESCRIPTION OF GALVANIC BATTERIES           511
Figure 544. Shows the wires connected by means of a liquid,
such as acid and water, sulphate of copper, etc.
Figs. 542       543         544.
The copper and zinc, C and z, with the acid in the first vessel,
Figure 544, constitute a battery of one pair. The wine glass e, wi
acid, in which the wires are placed, is termed the decomposition
cell.
BEST KIND OF ZINC.-The zinc used for the battery should be
milled or rolled zinc, not thinner than 8th of an inch, otherwise the
waste will be very great; for amalgamated zinc, when it becomes
thin, is so tender and brittle, that the utmost care cannot preserve
it whole. The best thickness for the zincs, when their size is
upwards of four inches square, is Ith of an inch; but if under
this size, -th to 3-th of an inch is the proper thickness. Cast
plates of zinc should not be used, as they are negative to rolled
zinc, and give less electrical power: they are so porous that no
amalgamation will protect them from the action of the acid-producing "local action," as it is termed, which is not only a waste of
zinc and acid, but prevents, to a great extent, the production of the
quantity of electrical force which the surface of the zinc in use is
calculated to give.
AMALGAMATION OF THE ZINC PLATES.-The amalgamation of
zinc is a process exceedingly simple; nevertheless, if care be not
taken, a very great loss in mercury and zinc is soon effected.
A stoneware pan is best to use, and should be sufficiently capacious to allow the zinc plate to lie flat within it: a mixture of
eight parts water, and one part sulphuric acid, should be put into
the pan, sufficient in quantity to cover the zinc plate, which should
lie in it till the surface is perfectly bright. The pan is now raised
on the one side, and a little mercury put into the lower part, care
being taken that the zinc does not touch the mercury, to prevent
which is the object of raising the pan on one side. A little coarse
tow, tied to the end of a piece of wood, is dipped into the mercury,
which lifts small portions of the metal mechanically, which is then
rubbed with considerable pressure upon both sides of the zinc
plate, over which the mercury flows easily: the plate is then
washed, by dipping it into clean water, and is next made to stand
upon its edge in another pan, with two small pieces of wood under




512      THE PRACTICAL METAL-WORKER'S ASSISTANT.
it, so as to allow the mercury to drain from it. Instead of tow, an
old scratch brush is generally used in plating factories: this is a
brush made of fine brass wire, tied upon a piece of wood; but we
prefer tow, when carefully employed, as the brass wire amalgamates with the mercury, and causes a loss of that metal. After
the zincs have drained for a few hours, the process should be
repeated, only it is not necessary to allow the metal to lie in the
acid in the second process previous to rubbing in the mercury:
after draining a few hours the second time, amalgamation is completed. In the first process a plate, of a foot square, amalgamated
on both sides, will retain three ounces of mercury; but for the
second process, or any time after, the same size of plate will only
retain 11 ounces of mercury.
Zinc rapidly absorbs mercury, which permeates the whole metal.
If the mercury was in quantity, the zinc would dissolve in it;
hence the propriety of rubbing the mercury into the zinc, only in
small portion, for if allowed to imbibe as much as it is capable of
doing, it would not only be a loss of mercury, but the plate would
become exceedingly brittle. When too much mercury is used, a
portion of it will filter out from the plate by standing, but it carries
with it some zinc dissolved, which tends to deteriorate the quality
of the metal for the battery.
The zinc in the battery, after being used, should never be allowed
to lie in the acid when. the battery is not in use, but should be taken
out, and the surface carefully brushed with a hard hair brush, in
water, and then laid by in a safe place. The matter thus brushed
off; being an amalgam of zinc, is to be carefully collected, and kept
in dilute sulphuric acid, or in the waste acid from the batteries.
most of the zinc in this amalgam will dissolve out, so that a great
portion of the mercury may be recovered, or by placing these
brushings in a coarse cloth bag, and subjecting it to pressure in a
screiw-press, most of the mercury may by this means be recovered.
ECONOMY IN AMALGAMATION.-If the battery is to be used seldom, and only for a short period at a time, another method of
amalgamation may be adopted. The zinc plate, after lying in the
dilute acid till the surface is bright, may be rubbed over with a
solution of nitrate of mercury, which gives a very thin amalgamation; but this method is unsuitable if the battery is to be in use
for several hours together.
When a battery is being worked daily, it will be advisable to
repeat the amalgamation from time to time, otherwise local action
will begin, and the working power of the battery be weakened,
while the loss in zinc will be increased.
The following is the proportional rate which we have found on
the large scale under the most favorable circumstances. A new
zinc plate, amalgamated as described, working continuously24 hours, zinc lost 121 ounces-copper deposited 12 ounces;
48 hours, zinc lost 201 ounces-copper deposited 17 ounces'
60 hours, zinc lost 34 ounces-copper deposited 24- ounces.




DESCRIPTION OF GALVANIC BATTERIES.          513
From these and similar data we found that the most economical
way of using zincs is the following: after being in the battery
twenty-four hours, they are to be taken out, brushed, and laid
aside; after working other twenty-four hours, they are to be again
brushed and imnmediately re-amalgamated: if these directions are
attended to, i ounce of mercury will be sufficient for one foot
square of zinc, both sides.
The advantages of proper amalgamation will be made more evi
dent in the sequel. We have only to add here, in consequence of
an oft-expressed fear of the danger of working with quicksilver,
that no apprehension need be felt: the skin does not absorb it, and
there being no heat required in the operation that could convert
the mercury into Vapor, the only state in which it is dangerous, no
salivation can take place.
DISTANCE BETWEEN THE BATTERY PLATES.-TO return again
to the battery-cell. It will be found that if the two metals-the
zinc and copper in acid, Fig. 544-be put very close to each other,
the action will be much more rapid than when they are far apart.
It will also be found that, allowing the zinc and copper to be kept
at one distance, but the wires in the decomposition-cell to be put at
different distances, similar results will take place. When the wires
are close the action in the battery-cell will be more powerful than
when the two wires are put farther apart: these properties are ap
plicable to all batteries and decomposition-cells of every kind.
The following results will give an idea of the relations of these
several conditions:
1st. One pair of copper and zinc plates, measuring superficially
6 square inches, were immersed in a solution consisting of 1 acid
to 35 water: plates of copper of equal size to those of zinc and
copper were laid in the decomposition-cell, which was then filled
with a liquid of equal strength to that in the battery-cell; the
plates in the battery-cell and the decomposition-cell were then
placed one inch apart: in four hours
The zinc in the battery-cell lost by dissolving 101 grains;
The copper dissolved in decomposition-cell 10 grains.
2d. The battery-plates were put 12 inches apart, and the plates
in decomposition-cell 1 inch apart: in four hours
There were dissolved in the battery-cell, zinc 7 grains;
In decomposition-cell, copper 6 grains.
3d. The battery plates were placed 1 inch apart, and the plates
in decomposition-cell 12 inches apart: in four hours
The zinc in battery-cell lost 4~1 grains;
The copper in decomposition-cell lost 31 grains.
These results show the importance of attending to the condi
tions of the respective agents, and also, that distance in the decom
position-cell offers greater resistance than distance in the battery
cell.
DIFFERENT ELEMENTS OF BATTERIES.-Although our observa
tions have been made on zinc, copper, and dilute sulphuric acid in
33




514      TVE PRACTICAL METAL-WORKER'S ASSISTANT.
the battery-cell, still these are not the only essential elements in a
battery, as almost any two metals with a liquid similarly arranged
will produce an electric current; but the current will vary according to the nature of the metals employed, and the effects produced
upon them by the solution in which they are placed. If the exciting solution has the power of acting upon both metals, as when
zinc and copper are immersed in dilute nitric acid, the current of
electricity produced by the action of the acid upon the zinc will
be neutralized to an extent corresponding to the relative action of
the acid upon the copper. To have any effective electrical power,
it is necessary that one of the metals employed be capable of combining easily with one of the elements of the solution in which
they are placed, and forming a soluble salt, while the other does
not; and the power obtained under proper circumstances has an
intimate relation with these two properties in contrast. The metal
which undergoes solution is termed the positive metal, the other
the negative metal. Metals are not considered to possess any intrinsic negative or positive principle; their relations in this respect
are governed solely by the circumstances in which they may be
placed. For instance, if we connect a piece of copper and a piece
of iron, and immerse them in acidulated water, the iron is dissolved,
and is positive in relation to the copper; but if the same metals
are immersed in a solution of yellow hydro-sulphuret of potassium,
the copper is dissolved, and is positive relatively to the iron.
Hence, to obtain a galvanic battery, the conditions are simply to
provide two metals, and immerse them in a solution capable of
acting upon the one and not upon the other. The first table shows
the order in which the common metals stand to each other, in respect of their relative negative and positive properties, when immersed in water acidulated with sulphuric acid. The second table
is given by Gmelin as the relations of the metals, in water and sea
water, the most intensely negative metal standing highest, and the
metal which acts most positively standing lowest:
Platinum                     Platinum
Gold                         Gold
Antimony                     Silver
Silver                       Copper
Nickle                       Bismuth
Bismuth                      Antimony
Copper                       Iron
Lead                         Tin
Iron                         Lead
Tin                          Cadmium
Cadmium                      Zinc
Zinc
According to this arrangement, each metal is positive with
respect to all that stand before it, and the electrical conditions of




DESCRIPTION OF GALVANIC BATTERIES.          515
any Dair become the more contrasted the further apart they stand
in the scale. Thus, a battery composed of zinc and platinum is
nuch more powerful than one composed of zinc and copper; and
again, copper and iron make a very weak battery.
A battery may also be formed by having one metal and two
kinds of solutions, separated by a porous diaphragm. For example,
we may have strong nitric acid in one division, and dilute sulphuric
or muriatic acid in the other; and by putting into each a piece of
clean iron, a powerful current is obtained. These and several
other arrangements of solutions and metals, are expensive and
troublesome to keep in order, and are therefore never used for
practical purposes in the art of electro-metallurgy.
PROPERTIES OF METALS FIT FOR BATTERIES.-In looking to the
above table, it may be asked, "Since lead stands next to copper,
and is so much cheaper, why should it not be used instead?" The
reason is, that there are other properties which a metal, especially
that used as the negative element, ought to possess to fit it for use
in a voltaic arrangement; such as the power of freely conducting
an electric current, of keeping a bright surface, and not becoming
oxidized; none of which properties belong to lead. Could that
metal be kept from oxidizing, a very powerful current of electricity
might be obtained by using it with zinc; but its surface soon gets
coated with an oxide possessing none of the properties of the metal,
and hence the arrangement becomes zinc and oxide of lead, which
produces but a weak current of electricity. These remarks refer
to any metal that is subject to oxidization-an incident which is
often a source of annoyance to the electrotypist when using copper
plates.
Lead slightly amalgamated, and used as the negative metal with
zinc, produces a very constant current for a time.
Lead is also a very bad conductor of the electric current, which
renders it unsuitable for an element in the battery, the negative
metal being considered as only acting the part of a conductor: this
property materially affects the available power of an arrangement.
The following table shows the relative Conducting power of the
respective metals:
Silver...   120
Copper...   120
Gold..        80
Zinc...    40
Platinum..    24
Iron...    24
Tin...    20
Lead..        12
We have just stated that a battery composed of zinc and pla
tinum will be more powerful than one composed of zinc and conper, so far as regards their negative and positive tendencies; but




516      THE PRACTICAL METAL-WORKER'S ASSISTANT.
so much does the conducting power of the negative metal affect
the practical usefulness of a battery, that notwithstanding the fact
that platinum is much m)re negative than copper, there is so much
of the effective electricity expended in overcoming the resistance
which the inferior conductibility of the platinum offers to the progress of the current, that a battery of zinc and copper proves to be
a more effective and useful battery for electro-metallurgy than one
made of zinc and platinum. Hence also the reason that iron and
copper, or iron and any other metal, make but an indifferent battery
-iron being a bad conductor; while lead, which will be seen in
the table, stands lowest in this property, is therefore unfit for batteries.
In fitting up a voltaic arrangement with a negative metal that is
not a good condluctor, such as platinum, the closer it is placed to
the exciting liquid, in connection with another metal that is a good
conductor, the better; because the current obtained will be the
more effectual.
The following experiments will illustrate these remarks with a
few of the common metals used as negative electrodes. There
were, in each battery, six square inches of each metal exposed to the
action of the acid, which was sulphuric acid diluted with 25 parts
of water. The poles were of the same size, of copper, placed in
sulphate of copper; and the quantity of copper deposited was
taken as the data, each trial being of a different length of time:
FIRST, IN ACTION HALF AN HOUR.
BATTERY.                    DEPOSITED.
Tin and zinc.... 17 grains.
Copper and zinc... 18   "
Platinum and zinc...  -5   "
Platinized silver and zinc. 2-0   "
SECOND, IN ACTION TWO AND A-HALF HOURS.
Tin and zinc.... 5-9 grains.
Copper and zinc... 88   "
Platinum and zinc. 4-5   "
Platinized silver and zinc. 97   "
THIRD, IN ACTION SIXTEEN HOURS.
Tin and zinc.. - 64'5 grains.
Copper and zinc... 50-5   "
Platinum and zinc.. 43-0   "
Platinized silver and zinc. 67-3   "
From these few experiments it appears that tin and zinc, when
used for a long time, constitute a very effective battery. It is
very constant in its action, and thus suited for time. It stands
next to platinized silver.  The whole, in nineteen hours, gave
respectively



DESCRIPTION OF GALVANIC BATTERIES.          517
Platinized silver..    79' grains.
Tin....  72'1   "
Copper...  61'1   "
Platinum...  48-0   "
BABINGTON'S BATTERY. —If we look back to the description
given of the voltaic pile (page 489), and the improvement made upon
it by Cruikshanks, we perceive the relation they bear to the pieces
of copper and zinc mentioned in page 510; but the relation is more
apparent in Babington's improvement upon Cruikshank's battery.
When working with this battery, it was found that the energy of
Figs. 545            546.
the battery did not depend, as was supposed, upon the extent of
surface of the zinc and copper which were in contact, but upon
the extent of surface of these metals in contact with the liquid
with which the battery was excited; and that it was sufficient if
the zinc and copper touched each other in a single point; —provided that the plates were plunged into the liquid, and that the
copper plate should be exactly opposite to a zinc plate in the same
cell, a space between them. Hence, instead of soldering the zinc
and copper together, as Mr.
Cruikshanks did, it was                 Fig. 5 7.
enough to effect a communication by turning over a portion of the copper plate at
the top, and soldering it to
the upper extremity of the
zinc. Thus-c, the copper,
is' bent over to touch and be
soldered to the zinc plate z. 
For this arrangement, the
wooden trough was divided,
by plates of glass or varnished wood, into as many
cells as there were pairs of
zinc and copper. The cells
being filled with the acid, or
exciting solution, the metals
were then placed into them in such a manner that each pair of




518      THE PRACTICAL METAL-WORKER'S 4SSISTANT.
zinc and copper plates had a partition between. By this arrange.
ment the zinc of one pair faced the copper of the next pair in the
cell, as shown in Figures 546 and 547. The former represents the
plates immersed in the solution; the latter, the plates suspended on
a rack over the solution. This arrangement was termed Babington's Battery.
WOLLASTON'S BATTERY.-Although we have spoken of the
great value of amalgamated zinc for batteries, still at the period
when the arrangement just described was introduced, amalgamation was not known; and the zinc plates were, therefore, always
liable to be destroyed by the acid. It was, consequently, of importance that no zinc should be exposed to the action of the acid
that was not calculated to give electricity, as the energy of each
pair of plates depends upon the extent of surface of the two metals
exactly opposite to each other. It will be evident that in Babington's
arrangement only one side of the zinc was effective in giving electricity, while both sides were exposed to the action of the acid. To
obviate this defect, Dr.
Fig. 548.             Wollaston caused the copa a. a                      per plate to surround the
zinc, by which the whole
-t t1;   lll 1  1t 110) surface of the zinc exposed
to the acid was made effective in producing electricity, and thereby doubling
its quantity without further cost. The accompanying figure (Fig.
548) shows the manner in which this battery was originally constructed.
This improvement, if we except several modifications of construction for the facility of taking the plates asunder for cleaning,
etc., did all for this kind of battery that could be done.
MODIFICATION OF WOLLASTON'S BATTERY NOW IN USE.-Wollaston's battery is still generally used in large factories for depositing metals; and it is found by experience to be the most convenient
and economical of all the batteries yet contrived. The modification we have found to be very suitable, and practically useful, may
be thus described. In the arrangement represented above, when
amalgamated zincs are used, small quantities of amalgam fall from
the zinc plates upon the copper, which not only occasion local
action, but the mercury amalgamates with the copper, spreads over
it, and to a great extent lessens its efficiency; and as the copper
must be red hot to expel the mercury,
Fig. 549.   much loss of copper as well as mercury
is the result. To obviate this defect, the
copper is connected above the zinc and
Ca An       left open at bottom; as, for example, a
thin sheet of copper, of dimensions accord;ng with the size of the cells in the battery, is cut thus: This copper is bent in the middle at b, the ends a a dip into the cells, while




DESCRIPTION OF GALVANIC BATTERIES.          519
is bent over to connect with the zinc plate of the neighboring
cell, thus:
Figs. 550                551.
at  t
The zinc plates are placed between the bent copper a a. The following diagram of a battery of several pairs of plates will illustrate
these observations:
Fig. 552.
z zz z,  The zinc plates.
C C c, Copper plates.
PPP, Partitions of trough,
which are generally made       c   z  c   z        z  C
of thin wood.
ww, Wires from battery.
P 
The zinc and copper are connected together by a binding screw.
To construct this battery the zinc plates are put in first, being
made to slide in grooves, cut in the sides of the trough, the plates
standing in the centre of their respective cells: the copper plates
are put in, and the copper bands marked c are made fast to the
zincs by binding screws, care being taken that the parts where
they are connected are clean and bright, and that the copper and
zinc touch nowhere else. A battery of nine pairs of plates can
be fitted up and made ready for action in ten minutes.
In fitting up batteries of this sort, we are aware that sometimes
great care is taken that the partitions in the trough be perfectly
water-tight, and also formed of some non-conducting material, such
as glass, or of wood, either pitched or saturated with some non-conducting substance; but we have found in practice that these precautions are not required, the principal thing to attend to being,
that the metals should not be allowed to touch, except in their
proper connections.
DEFECTS OF COMMON ACID BATTERIES.-Although we have
spoken thus favorably of the principles upon which Wollaston's
battery is constructed, still as a philosophical instrument it is far
from being perfect: hence the many modifications of it which have
been recommended. Indeed, electro-chemists, since the time of
Volta, have been endeavoring to invent an instrument free from
the defects which attach to Wollaston'3-one capable of giving, at




t20      THE PRACTICAL METAL-WORKER'S ASSISTANT.
the same time, a constant and powerful current, abundant in quantity, and of great intensity. The success and results of these endeavors are so closely connected with the art of electro-metallurgy,
and the knowledge of them is so essential to a successful prosecution of the art, that we must not be sparing in our descriptive details.
In operating with a Wollaston's battery, or any other arrangement composed of similar elements, such as zinc, sulphuric or
muriatic acid, and copper, silver or platinum, it will be found that the
current of electricity obtained diminishes in quantity and strength
in proportion to the time of action. This is the result of various
causes:
1st. The hydrogen which is evolved at the surface of the negative metal in the battery, which we shall say is copper, adheres
with considerable force to the surface of the metal, and consequently
obstructs its superficial influence, so that the quantity of electricity
which the surface of the two metals is calculated to give is much
lessened.
2d. After the battery is in action a short time, a portion of the
sulphate or chloride of zinc, formed in the battery by the solution
of the zinc, becomes reduced upon the surface of the copper. This
reduction is supposed to be owing to the electrolyzation of the zinc
solution by the passage of electricity, but it is, more probably,
caused by a galvanic action upon the copper plate and the solution
in the battery. It generally begins at the lower edge of the copper
plate, and spreads upwards. This weakens the electric current,
both by inducing a galvanic action between the zinc and the copper. upon which it is deposited, and by its tendency to send a current of electricity in an opposite direction to the main current, thereby:neutralizing to a great extent the original power of the circle.
3d. When copper is used it becomes gradually covered over with
a thin, black, slimy coating of oxide and other impurities, which
materially affects the regularity and strength of the current: this
is a source of considerable annoyance in working, and necessitates
a regular cleaning of the coppers, which should be done immediately on being taken out of the battery, by brushing with a hard
hair brush in water; but when the battery has been long in action,
this mode of cleaning is insufficient: the plates will then require
to be rubbed over with a little dilute nitric acid, and then washed.
If the black coating be allowed to dry upon the coppers, they must
then be dipped into strong nitric acid till their surfaces are acted
upon; or they may be moistened with a little urine, then brought
to a dull red in the fire, and immediately plunged into water; but
in both cases there is a loss of copper. A small quantity of the
black matter, upon being tested, gave oxide of copper, with a trace
of iron, antimony, and lead, which are the general impurities of
sheet copper.
Max, Duke of Leuchtenberg,* has giving the following results
* Progress of General Science, vol; ii.




DESCRIPTION OF GALVANIC BATTERIES.            521
of an analysis of the black matter found upon the copper plate
forming the positive electrode in a copper solution.
Sand..                        1'90
Antimony.....   9'22
Tin....3350
Arsenic.....   740
Platinum....    044
Gold.....   098
Silver.....      4'45
Lead......   015
Copper.....   924
Iron....   030
Nickle.....    226
Cobalt.....    086
Vanadium.....    064
Sulphur.....   246
Selenium...                  1-27
Oxygen.....  24'8S.
99'9&
An analysis of this sort invests the subject with great interest.
We wish there had also been given an analysis of the copper that
was used as the electrode, and the quantity of black matter obtained,
and the quantity of copper dissolved to yield that product: for the
analysis indicates an amount and diversity of impurities in copper
that has never hitherto been thought of. Both the number and
the proportions are startling. However, it is a known fact, that
the more impure the copper is that is used for a pole, the black
matter is not only more easily, but more abundantly produced.
Another source of weakness to the electric current, and which
affects more or less all batteries of whatever construction, arises
from the action of the acid upon the zinc. The more freely this
action is allowed to proceed the more constant and powerful is the
battery. The acid in combining with the zinc forms a salt, which,
if it adhered to the surface of the plate, would soon stop further
action; but this salt being soluble in water, is dissolved from the
surface of the plate as soon as formed, allowing a new surface to
be exposed. But water can only dissolve a certain quantity of
the salt, and its power of dissolving decreases as it approaches to
the limit of saturation: hence there is a constant tendency to a
decrease of power in the battery, and if means be not taken to withdraw the salt of zinc formed, the battery will continue to decrease
in power, till at length it ceases to act. But long before the battery
ceases to act, the presence of sulphate of zinc manifests itself in
several ways, neutralizing the efficacy of the battery. The zinc
salt, as it dissolves from the plate, being heavier than the acid soiution, falls to the bottom; hence in a very short time the solution X




522      THE PRACTICAL METAL-WORKER'S ASSISTANT.
formed of strata of different densities, and this induces a galvanie
action between the lower and upper portions of the plates, both copper and zinc, and accounts for the deposition of zinc on the bottom
part of the plates, as above referred to. This local galvanic action
between the bottom and top parts of the zinc plate is sometimes so
great when the battery has been long in action, as to double the
thickness of the zinc plate at bottom, while the part near the surface
of the solution is nearly penetrated by the acid; and when a battery
is formed of a number of pairs, the terminal zincs are those most
affected, the one forming the negative terminal or pole more so
than the other. We have found a deposition of 61 ounces of zinc
upon the two lower inches of a plate terminal, which measured, in
the solution, six inches by five, the battery having been in operation but eighteen hours. When this occurs, the quantity of electricity circulating through the battery is very small. Although
this evil may not proceed to the extent of having quantities of
zinc deposited upon the bottom part of the plates, still the tendency
to deposition which every one who employs a battery must have
observed, as also the more rapid action of the acid on the upper
parts of the plates, shows that the action of the acid over the surface of the plate is very irregular, and consequently the quantity
of electricity must be irregular in the same degree, often producing in the battery an intermittent action.
Various means have been devised for removing the sulphate of
zinc, and adding corresponding quantities of new acid water; the
most simple and effective of which, according to our experience,
is to make the battery trough much deeper than is required for
the plates, which may be supported either by grooves in the side
of the trough, cut to the proper depth, or by a fillet of wood, or
perforated false bottom; so that the zinc salt when formed may
fall under the plates, and thus a much longer time elapse before
its presence produces any decidedly bad effect.
* There can be no doubt, we think, that some easy means will yet
be devised for carrying off the dense solution of sulphate of zinc,
before it rises to the plates, and for replacing it by acid water from
above,,thus giving to the battery a uniformity and steadiness of
action it does not at present possess. There have been many ingenious contrivances tried for this purpose by the amateur, but
we have seen none so simple and economical for manufacturing
purposes, as that referred to.
DANIELL'S BATTERY.-A few years ago, some of the disadvantages now detailed were to a great extent overcome by a very ingenious arrangement discovered by the late Professor Daniell.
The discovery consists in the separation of the zinc from the
copper by a porous diaphragm, such as bladder, unglazed porcelain, etc., and the use of two distinct fluids. The portion of the battery containing the zinc is charged with dilute acid as before, but
the portion containing the copper is filled with a solution of sulphate of copper. The action in this battery is similar to that




DESCRIPTION OF GALVANIC BATTERIES.            523
described in the ordinary battery; tile zinc is dissolved by the
acid, but the hydrogen, instead of being evolved at the copper
plate, combines with the acid of the sulphate of copper: metallic
copper is thus set at liberty upon, and combines with, the copper
plate of the battery, not only maintaining but improving its surface, during the evolution of a constant current of electricity.  From the constancy of the  Fig. 553.
current maintained the battery has been termed
the Constant Battery. The construction of a
single pair is described by Professor Daniell
in the following terms:
"A cell of this battery consists of a cylinder of copper 31 inches in diameter, which    I
experience has proved to afford the most advantages between the generating and conducting surfaces, but which may vary in height
according to the power which it is wished to obtain. A membranous tube, formed of the gullet of an ox, is hung in the centre
by a collar, and a circular copper plate, resting upon a rim, is
placed near the top of the cylinder, and in this is suspended, by a
wooden cross-bar, a cylindrical rod of amalgamated zinc, half an
inch in diameter; the cell is charged with eight parts of water, and
one of oil of vitriol, which has been saturated with sulphate of
copper, and portions of the solid salt are placed upon the upper
copper plate, which is perforated like a collander for the purpose
of keeping the solution always in a state of saturation. The internal tube is filled with the same acid mixture without the copper.
A tube of porous earthenware may be substituted for the membrane with great convenience, but probably with some little loss
of power.*
A number of such cells may be connected very readily, by attaching the zinc of the one to the copper of
the other, and (as shown in Fig. 554) thus
forming an intensity arrangement of
great power and constancy.
This arrangement of battery is eminently suited to all kinds of electrical
operations, and it may be borne in mind
that it was by operating with this battery the idea of electro-metallurgy first
occurred. In this battery we see that the evils arising from the
slow liberation of the hydrogen from the surface of the negative
metal, and the deposition of the zinc upon the copper, and also
the blackening of the surface of the copper, are all surmounted.
Nevertheless it is not used to any extent in the art of electrometallurgy, it being much less economical than the ordinary batteries, from the quantity of copper salt necessary to keep it in a work* Daniell's Chemical Philosophy, 2d edition, 1843, p. 504.




524      THE PRACTICAL METAL-WORKER'S ASSISTANT.
ing condition, and from the necessity of using porous diaphragms,
which speedily wear out. If the diaphragm is made of animal
membrane, the acid very soon destroys it; and although unglazed
porcelain lasts a little longer, the acid acts upon the alumina, so
that after a few days' working the diaphragm becomes too porous;
and if the zinc plate touches the porous vessel, a circumstance very
difficult to avoid, there is very soon formed in and upon the porous
surface a deposit of copper which speedily renders the cell useless,
besides producing a loss of copper. The saturation of the zinc
solution, already spoken of, not unfrequently produces the same
effects-the saturated portion of the bottom becomes reduced by
the local action, and thus often a minute point of metallic zinc
touches the cell, and forms a nucleus for a deposit of copper upon
the porous cell, which spreads over the surface very rapidly.
There are always pieces of amalgamated zinc, like fine scales, falling to the bottom of the cell, which also form nuclei for the deposition of copper upon the porous cell.
After the cells have been some time in use, if they are laid aside
and allowed to dry, they are very liable to break. Care should be
taken to keep them in clean water till the salts within the pores
are dissolved out; but if this precaution is taken they may be
preserved for a long time if only used occasionally.
The remarks upon the economy of the arrangement just described have reference to its use as an instrument, or separate battery, for the deposition of a metal in a separate cell (decomposition cell); but not to the arrangement known in electro-metallurgy
as the single cell process, which is simply a modification of one
pair of Daniell's arrangement; a description of which, with its
comparative economy, will be given in another part of this treatise.
Professor Daniell says that any depth of cell may be used according to the power required, but this cannot be done with equal
advantage, for a large surface of zinc in a cell is not the most
economical, when a great quantity of electricity is required.
GROVE's BATTERY.-Another battery, constructed upon the
same principle as Daniell's, but differing in the arrangement of the
metals, and the substances used to excite them, was invented by
Mr. Grove, and is known as Grove's Battery. In this arrangement, platinum is used instead of copper, and strong nitric acid instead of the sulphate of copper of Daniell's batFig. 555.    tery. One pair may be fitted up conveniently
in a tumbler or jelly-pot. A cylinder of. zinc is
placed inside the tumbler; within this cylinder is
placed a porous vessel, in which is a slip of platinum either in sheet or foil; the porous vessel
is filled with strong nitric acid, and the tumbler
with dilute sulphuric acid: a wire is next attached to each metal, and the battery is complete.
When a series of pairs is to be used, the form we have found most
convenient is to arrange the metals in the same manner as we have




DESCRIPTION OF GALVANIC BATTERIES.           525
described for Wollaston's trough (page 518). The zin3 is formed
in the same shape as shown by Fig. 555. The zinc is placed in the
cell of the trough, and the porous vessel which should be flat is
placed within the zinc, so that the platinum in it may be connected with the zinc of the neighboring pair, as represented in
figure 556.
zzz, Are the zinc plates of             Fig. 556.
the form of figure 555.
aaa, Porous cells filled with
nitric acid.
ccc, Plates  of platinum
united to the zinc at top by
binding screws.
PP, Are partitions. The divisions of the battery trough           e.
need not be water tight, but
merely such as will prevent the zincs from touching one another.
It will be seen that by this means any number of pairs may be
easily arranged. Care, however, must be taken, when fitting up
such an arrangement, that the platinum be kept closely connected
with the zinc by a large surface, otherwise the platinum will be
fused at the connections. A flat piece of wood, with a groove to
fit the zinc, is often made the means of keeping the two metals
together, but we prefer flat binding screws of brass, for if kept
clean they assist the connection, being good conductors.  The
fusion of the platinum connections, a practical and often expensive
annoyance, may, however, be completely prevented by coating
about half an inch of the end of the platinum, either with copper
or silver, which is easily effected by the electro-process: the coated
part is then connected with the zinc by any convenient means
without the risk of fusing.
Figure 557 represents a section of Mr. Grove's nitric acid battery, in a series of four pairs of zinc and platinum. The outer
thick line, A B C D, is an earthenware trough, which is divided
into four cells. The dotted lines represent four porous vessels, of
a size sufficient to contain about double the quantity of liquid that
is contained between the outer surfaces of the porous vessels and
the earthenware cells. The dark central lines are the plates of
amalgamated zinc; and the thinner lines, that bend round under
the porous cells, show the position of the platinum foil, which is
attached to the zinc plate by small screws.
This form of battery is also free from some of the objections to
the common battery, but it is seldom or never used in the ordinary
processes of electro-metallurgy. Its advantages over every other
known form of battery are, its great activity of action, and intensity or power of current-a circumstance not generally sought
after by electro-metallurgists. But if it were duly considered that
a battery consisting of three pairs of zinc and platinum is far
more effective than an ordinary battery of ten or twelve pairs




526      THE PRACTICAL METAL-WORKER'S ASSISTANT.
(although the elements of its construction are more expensive), it
would stand a fair chance of being adopted as the more economical
battery of the two.
Fig. 557.
8   E  ~     E      C
B     E      F~     E
The porous cells have not the objection of being closed up by
the deposition of metals upon or within them; but they are affected
by the acids, and by long working they become too porous, the
nitric acid passing through and causing rapid destruction of the,inc. It wants the constancy of Daniell's, its quantity declining:rapidly when long in action-one feature we have often experienced which we have not seen observed by other experimenters.
When working with a Grove's battery of from eight to twelve
pairs, the platinum being six inches by seven inches, after the battery was in action for four or five hours, during which it diminished in quantity gradually, all of a sudden it seemed to recover
its energy, giving a quantity and power not much less than it gave
in the first hour, and then declined again rapidly, but occasionally
renewing its vigor for short periods. We have thought it probable that this reaction may be caused by the formation of nitrate
of ammonia in the rapid decomposition of the nitric acid during
the first action of the battery, which, as it accumulates, may be
reacted upon.
The prevailing and permanent objection to the use of this
arrangement, not only for manufacturing purposes, but for many
experimental purposes, is this, that it emits nitrous fumes which
corrode every thing within their reach, and prove very disagreeable
to every person breathing them. For a small single pair of
Grove's battery it is very convenient to use a circular form, in
which case a little cylinder of wood, bored so that its sides be
about Ith of an inch thick, does well for a porous cell, and will
last a long time.
BUNSEN'S BATTERY is a modification of Groves' and much used
on the continent for electrical purDoses. Carbon is used instead




DESCRIPTION OF GALVANIC BATTERIES.             527
of the platinum, and for convenience it is generally made cylin 
drical. The mode of construction is to form a hollow cylinder by
coking pounded coal in an iron mould, then soaking the coke cylinder in a solution of sugar and calcining a second time, which
gives great compactness. The porous cell containing the zinc and
dilute acid is placed in this cylinder, and the whole put into a
glass or stoneware vessel charged with nitric acid; of course the
coke cylinder and zinc are connected, and thus the battery is completed.* Nitrous fumes are evolved from this battery also.
SMEE'S BATTERY.-Some of the defects in the common battery
of zinc and copper were much lessened by an ingenious contrivance
of Mlr. Alfred Smee. This gentleman had observed that if the
copper plate of the battery be roughened, either by corrosive acids
or by rubbing the surface with sand paper, its action was made
much more efficient, the rough surface evolving the hydrogen
much more freely. Taking advantage, therefore, of this principle, he covered platinum foil with a finely divided black powder
of platinum, deposited by electricity from a solution of that metal,
and used this in place of the copper in the ordinary battery. Instead of platinum foil, Mr. Smee soon after adopted silver foil,
which is much less expensive. The method of preparing these
plates is given by Mr. Smee as follows: —" The silver to be prepared for this should be of a thickness sufficient to carry the current of electricity, and should be roughened by brushing it over with
a little strong nitric acid, so that a frosted appearance is obtained.
It is then washed and placed in a vessel with dilute sulphuric acid,
to which a few drops of nitro-muriate of platinum has been added.
A porous tube is then placed into this vessel with a few drops of
dilute sulphuric acid; into this tube a piece of zinc is put, contact
being made between the zinc and silver; the platinum will, in a
few seconds, be thrown down upon the silver as a black metallic
powder. The operation is now completed, and the platinized
silver ready for use."t  A simple method, which obviates the use
of a battery is thus described: lay the silver between two pieces
of sand paper, and press it with a common smoothing iron, then
pull the silver out while under the pressure. The platinum solution is made very hot, and the silver dipped in it for some time,
which effects the coating.
The nitro-muriate of platinum is easily prepared: take one part
of nitric acid, and two parts of hydrochloric acid (muriatic acid);
mix together and add a little platinum, either as metal or sponge;
keep the whole at or near a boiling heat; the metal is then dissolved; forming the solution required.
* A more simple and less expensive modification of this arrangement, is to
put a solid bar of carbon or coke into a porous cell filled with nitric acid,
which is placed in a stone or glass jar filled with dilute sulphuric acid, having a cylinder of zinc surrounding the porous cell, leaving about one inch of
space between the porous cell and zinc, similar to a Daniell's, forming a mod.
ification of Grove's, having carbon instead of the platinum.
t Smee's Elements of Electro-Metallurgy, 2d edition, p. 24, 1843.




528      THE PRACTICAL METAL-WORKER'S ASSISTANT.
Several experiments have been tried with a view to substitute a
cheaper metal than silver to deposit the platinum upon, but not
with much success. Cheap metals have also been coated with
silver by the electro-process, and been used for depositing the platinum upon. The most successful is a composition metal made of
tin, lead, and a little antimony, rolled into sheet and plated by silver;
this was found very convenient, because it could be easily bent
into any required shape, and it keeps its place without the necessity of fixing in frames as required by thin silver; nevertheless,
for constant work these plates are found not to present any permanent advantage, and have been abandoned; besides, to give a
sufficient coating of silver, becomes as expensive as silver foil.
Mr. Smee, in constructing his battery, has been guided by the
expense of the silver, and therefore reverses the order of arrangement introduced by Wollaston, by surrounding the platinized silver
with the zinc. Fig. 558 represents a single cell of this form of battery. A, is the jar containing the solution. z z,
Fig. 558.    the two amalgamated zinc plates. s, the platinized
silver plate. The whole are suspended by a cross
bar of wood; and as it is essential to the proper
X'iiiiflhl'l'  working of the battery that the plates be always
=-_   15   parallel to one another, the wooden frame is gen~ —.\ erally extended round the edge of the thin silver
plate, though it is not so represented in the figure.
One of the clamps at the top of the wooden bar
~  is connected with the platinized silver plate, and
i' _!z   the other with a pair of zinc plates. Instead of
a glass or stoneware jar, small square troughs,
made of gutta percha, are often used for the
Smee's battery, as they suit admirably, and are
not liable to break.
When intensity of electricity is required, it is necessary to use a
number of such cells, which may be arranged in a wooden frame,
in the manner shown by Fig. 559, where a b represent the two
Fig. 559       poles of the battery, and c c the wires by
c         which the cells are connected with one
another.
A superior form of compound Smee's
_  battery, contrived by Acland, is represented in Fig. 560. In this apparatus
the plates are all connected to a frame
that can be elevated or depressed by
means of. an iron rod and rachet wheel, so that the plates may be
either partially or entirely immersed in the solution, or raised at
pleasure out of it. The connections are so contrived, that by a
slight alteration the battery is adapted to afford either quantity or
intensity of electric power. It is usually made to contain six cells,
any number of which can be used at once that a given process may
require. The exciting fluid is contained in an incorrodible stone



DESCRIPTION OF GALVANIC BATTERIES.          529
ware trough, placed in a mahogany box. A battery of this description, each silver plate of which measures 20 square inches, has
sufficient power, when decomposing water,'to disengage one cubic
inch of mixed gases in 50 seconds,,and will heat to redness 4 inches
of platinum wire.
Letter B in Fig. 560 represents an apparatus for showing the de
Fig. 560.
composition of water into oxygen and hydrogen gas by the voltaic
battery.
It will be observed in Smee's arrangement that there are two
surfaces of zinc, in every pair exposed to the acid, which do not
give off any electricity, but when long in use are much acted upon,
forming a consideration of some value toea manufacturer.
The silver used is very thin, and liable to crack when taken
from its frame, and therefore cannot be made into different constructions of battery in the same manner as we can do with copper. It is also liable to have zinc deposited upon its surface when
long in action.
There is we believe no arrangement of battery better known
and more used by amateur electrotypists than Smee's, and there
are probably none better adapted for small operations; but it has
not been introduced to any extent in the factory. When used in
series, the advantages it possesses over Wollaston's do not counterbalance the extra labor and expense attending its use, and many
who have tried it in the operations of the factory have for these
reasons given it up.
Numerous modifications of these different batteries have been
proposed from time to time, intended for different objects, but those
given embrace all that are used for electro-metallurgical purposes.
Owing to the apparent advantages of certain forms of battery, the
following may be referred to:
EARTH BATTERY.-The fact that when a piece of copper and a
34




530      THE PRACTICAL METAL-WORKER'S ASSISTANT.
piece of zinc are imbedded in the earth and connected by a wire,
there is a current of electricity obtained from them, in the same
way as if they were placed in any battery trough, instantly suggested the application of the earth, or what is termed an earth
battery, to the purposes of depositing. We need hardly say these
trials were without success. The electricity obtained in this way
is very weak, depending wholly upon the moisture of the earth,
and the arrangement forming therefore simply a water battery.
We have made electrotypes by this means, and also plated small
articles, but the action or deposition is very slow. We have obtained a greater amount of deposition in five minutes from one
square inch of zinc and copper placed in dilute sulphuric acid,
than from four feet of zinc and copper placed in the earth in the
space of an hour. An earth battery adapted to deposit from 150
to 200 punces of silver per day, would require acres of land.
In this as in all other forms of battery the deposit is in relation
to the zinc oxidated in the battery; there would therefore be no
economy in using the earth battery, and to lessen the amount of
surface required by an intensity arrangement, would not alter the
law, but rather add to the expense, as it would require upwards of
100 pairs in the earth to be equal to 3 or 4 pairs of Wollaston's
for the object of depositing; and would thus be adding to the cost
of depositing one hundred times the equivalent of zinc instead of
four times its equivalent.
MAGNETO-ELECTRIC MACHINE.-Several years ago, Mr. Woolrich, of Birmingham, patented a discovery for applying to the
deposition of metals the electricity obtained from magnetism or the
magneto-electric current, instead of voltaic electricity. We have
never had an opportunity of operating with Mr. Woolrich's machine, nor of seeing it in operation for the purpose of deposition.
We cannot speak of it from experience; but, from a statement
made at the meeting of the British Association in 1850, by Mr.
Elkington, of Birmingham, who is the proprietor of the patent,
and a gentleman of most extensive experience, it would seem that
he had up to that time never been induced to give up the ordinary
battery in favor of magnetism or any other suggested improve-ment. We understand however that this means of obtaining the
electricity for the purposes of electro-metallurgy has recently been
much improved, by forms of magnets, etc., patented by Mr. Millward,'and described by him as follows: "The first branch of the
improvement is carried into effect by the employment of an electromagnet formed by a current of electricity produced from a
magneto-electric machine, instead of that generated in a voltaic
-battery; and such an electro-magnet may be very advantageously
used for magnetizing large bars of steel, or for producing very
powerful magnets. Any of the known forms of magneto-electric
machines will serve thus to convert a bar of steel to an electromnagnet, but the patentee prefers to use one composed of four,.eight, or any other number of permanent magnets, having double




DESCRIPTION OF GALVANIC BATTERIES.         538
the number of armatures, and coiled with strong wire of about 60
feet in length. The machine about to be described has been found
to answer well in practice. In this machine the steel magnets are
composed of eight plates of a U form, weighing about 30 lbs.
each plate, and there are eight such compound magnets, all the
north poles of which are arranged on one side of the machine,
and the south poles on the other side, although this precise arrangement is not essential, and may be varied. The armatures are
of soft iron, weighing about 15 lbs., and are coiled about with 60
feet of copper wire of No. 4 gauge, and insulated in the usual
manner. The armatures revolve in a brass wheel, and are caused
to pass as near to the poles of the magnets as practicable, the commutator or break acting on the whole eight magnets at the same
instant, so that the current of electricity shall always pass in one
direction, and the surface of the whole of the 64 plates be in combination at the same time. The bar of soft iron used as the
electro-magnet with this machine weighs about 500 lbs., and is
coiled with bundles of about 30 copper wires of No. 16 gauge,
and about 60 feet in length (the bundles are formed by binding a
series of uncovered wires together into one covered strand or
bundle), and the power of the electro-magnet will depend upon the
power of the permanent magnets used in the machine, both as tc
the weight it will support from a keeper, and as to its capability
of rendering bars of steel permanently magnetic by contact therewith. It will therefore be evident that by having two sets of the
permanent magnets, and changing them in such machine, their
supporting power may be increased by continued charges or passes
from the electro-magnet thus produced. In one form of electromagnetic machine represented and described under the second
head of the invention, the steel bars or permanent magnets are
eight in number (these bars may be of cast or soft iron, but when
soft iron is employed, bars of steel permanently magnetized will
have to be used in conjunction with them), of a U form, and arranged aroufid a circle with their poles pointing towards the centre.
Each arm of each of the magnets has attached to it straight bars
of steel, also rendered permanently magnetic (of which any desired
number, and of any length or size, may be employed, according to
the strength of magnet required), which are so placed as to be out
of the influence of the armatures when the latter are revolving.
The poles of the U-shaped magnets are, on the contrary, as nearly
as possible in contact with the armatures which revolve within thecircle formed by them, either between the poles or in front of them.
Instead of the bars which form the circle being of steel and magnetized, they may be made of soft iron, and depend for their mag.
netism upon the magnetic bars before named placed around them.
In another form of machine both the magnets and armatures are
stationary, and the commutator alone has motion between the poles
of the horse-shoe magnets and the armatures, being mounted on a
spindle and caused to revolve by a band from some driving ma



532       THE PRACTICAL METAL-WORKER'S ASSISTANT.
chinery.  The commutator, or break-piece, is composed of a brass'centre, with four radial arms of soft iron, either solid or formed
of two or more plates." —See Repertory of Patent Inventions, vot. 18,
for 1851, and Sketches therein.
The quality of these machines fdr depositing depends:much upon
their sustaining power. Eight of these sets of plates or ~magnets,
containing altogether about 12 cwt. of steel, in a proper:state of
working, are said to form a battery capable of depositing from 12
to 20 ounces of silver per hour, but it is not stated, however, upon
What extent of surface this takes place. The:relative economy of;these magnets over the galvanic battery has not been so great as
to recommend their general adoption.  We havfe, however, no
doubt that, as such a machine gives electricityof great intensity, it
may be superior to the galvanic battery for some purposes, and
may give properties to the deposited metals which the ordinary
battery does not.*
Before concluding the description of batteries, we may briefly
notice one or two little conveniences which are indispensable to the
operation. The first of these is what are termed binding screws, by
which the parts of batteries, as we have shown by numerous figures,
are connected together, or by which their poles are connected to
the objects through which the voltaic current is to be-passed. They
are usually made of brass, and of various forms, according to the
shape of the objects that are to be connected.
Figures 561 to 566 represent some of the most useful kinds; Fig.
Figs                   561 is used to connect
561 562  563    564    565    566.    wirestogether; Figs. 563
and 565 are required for
t~~~ ia; ~ |Smee's battery (see Fig.
559); Fig. 565, to con— fi~  ~                           nect the plates of Grove's
battery (Fig. 557); Figs.
563 and 564 are used for
])aniell's battery; the latter for connection with a zinc rod, the
Figs. 567                 568.
* For some particulars of the working of electro-magnetic machines. see
Shaw's Manual of Electro-Metallurgy, 2d edition, 1843.




ELECTROTYPE PROCESSES.                 5~33
former to bind plates together. In all cases, the. parts that touch
the surfaces to be connected must be perfectly clear and bright.
In, many cases, when a complicated apparatus has been put
together, it is desirable to ascertain whether the connections are
all perfect. This is best determined by means of a galvanometer,
two varieties of which are. represented by Figs. 567 and 568.
CHAPTERI XXVL
ELECTROTYPE PROCESSBS.
SINGLE-CELL OPERATIONS.-We shall now proceed to detail
the process of electrotyping, the materials for which are of the
most simple nature. Let us suppose that the object of the student
is to copy a copper medal-for example, the side of a penny-piece
Dissolve a quantity of the crystals of' sulphate of copper in any
convenient vessel; if distilledc water can be had, the better. This
is. conveniently done by suspending the crystals in a coarse cloth
on the surface of' the water, or the crystals may be put into the
water, and well stirred, till dissolved; crushing the crystals facilitates their solution. The water should be kept cold and be fully
saturated with the salt, and the solution allowed to stand untouched
for several hours. This last precaution is not always essential, but
only necessary when the copper solution is not perfectly clear and
transparent.
The sulphate of' copper of commerce has often a large quantity
of iron in it, a portion of which becomes per-oxidized, and will
precipitate or fall to the bottom of the solution on standing; indeed, when it is known that the salt contains much iron, it is best,
to crush the salt very fine, and expose it to the air for some time;
when dissolved, after this exposure, a great quantity of iron will
settle at the bottom of the solution, which should be carefully
decanted and the last portion filtered. The clear solution should
now have about one-fourth of its quantity of water added to it, a*
a completely saturated solution is not the best. A newly-formed
solution does not deposit so freely as one that has been in use for
some time. The addition of a few drops of sulphuric acid, or, what,
we have found better, a little sulphate of zinc-about one ounce to,
the pound of sulphate of, copper -improves the condition of a new
solution.
Next, put the solution of sulphate of copper into the vessel in
tended for use, say it is a large jelly-pot, in which let a vessel of
unglazed porcelain (porous: vessel) be placed, filled to within half
an inch of the mouth with a mixture of 24 parts water and I sulphuric acid, taking care that the copper solution is of the same
depth as the solution in the porous cell.




[34      THE PRACTICAL METAL-WORKER'S ASSISTANT.
PREPARATION OF THE COIN.-A fine copper wire must now be
put round the edge of the coin and fastened by twisting. Then
cover the back part, upon which the deposit is not required, with
beeswax or tallow, or, what is better, imbed the back of the coin
with gutta percha. Have the fore part or face well cleaned, and
the surface moistened with sweet oil, by a camel's hair pencil, and
then cleaned off by a silk cloth, till the surface appears dry; or,
instead of oil, the surface may be brushed over with black lead, which
will impart to it a bronze appearance. The use of the oil or black
lead is to prevent the deposit adhering to the face of the coin. A
very common and excellent method to prevent the copper deposit
adhering to the copper mould is this: —Take a gill of rectified
spirits of turpentine, and add to it about the size of an ordinary
pea of beeswax. When this is dissolved, wet over the surface of
the mould with it, and then allow it to dry: the mould is then
ready to put into the solution. Medals taken from moulds so prepared retain their beautifully bright color for a long time. But
when fine line engravings are to be coated, the little wax dissolved
in the turpentine may be objectionable; so also is black lead, for
both have a tendency to fill up the fine lines. In this case, let the
wash with turpentine be wiped off by a silk handkerchief, instead
of drying it: but for ordinary medals this objection will scarcely
apply. This being done, the opposite end of the copper wire
round the penny-piece is to be connected with a piece of amalgamated zinc, either by means of a binding screw or a hole in the
zinc. Then place the zinc in the acid within the porous cell, and
put the penny-piece into the copper solution: bring the face of the
coin parallel to the zinc, at the distance of about half an inch or
one inch from the porous vessel. Deposition immediately begins,
and the metal thickens according to the length of time the action
is kept up. In about twenty-four hours, the deposit will be of the
thickness of a common card, and it may then be taken off. The
zinc is to be brushed and washed, before it is put aside. The wire
round the coin is now to be untwisted, and by a slight turn will
come off easily. The deposit is also easily separated from the
mould, which will be a perfect counterpart of the face of the pennypiece.
This mould is next to be treated exactly as described for obtaining it from the penny-piece, and the deposit from it will be a facsimile of one side of the penny-piece. With care, any number of
duplicates may be taken from this mould.
It need hardly be remarked, that as copper is deposited the
solution becomes proportionally exhausted, and in a short time the
current of electricity passing will be too much for the strength of
the solution, which will then give a deposit of a sandy consistence,
without tenacity.* It is therefore necessary, while the deposition
is going on, to suspend some crystals of sulphate of copper at the
* See Laws of Deposition, page 20.




ELECTROTYPE PROCESSES.                 535
top of the solution, which, as they dissolve, will maintain its
strength.
FORMS OF APPARATUS. —It will be observed that no particular
form of apparatus is required for electrotyping, but certain modifications may be adopted for convenience and economy. As every
portion of the zinc in the acid is capable of giving off electricity,
by placing the cell that contains the zinc in the centre of the copper solution, moulds may be suspended on each side of that cell.
We have'also observed that the zinc plate should not be allowed
to touch the cell, as the copper will be reduced upon it and the
cell destroyed. To avoid this, the zinc may be suspended by a
small wooden peg, put through it and made to rest upon the edges
of the cell. Figures 569, 570, 571, 572, represent several convenient
forms of apparatus for electrotyping.
Figs. 569           570              571.
Fig. 572 is a form of the apparatus which the author has used
for many years with great success, being both
cheap and effective. a is a large jelly-pot hold-  Fig. 572.
ing the copper solution; b is a flat porous cell,      B
about 4 inches square and half inch wide; z  
the zinc plate. Amalgamated metals may be
suspended upon both sides, and the strength
of the solution is maintained by suspending a _
few crystals of the salt in a little cloth bag
upon the surface of the solution.
Instead of porous vessels made of earthenware, a bladder may
be used, in which the acid and zinc are placed. We have also
seen a vessel divided by a porous partition, being either a plate of
biscuit porcelain, plaster of Paris, very thin sycamore wood, or
dressed skin. The porcelain, as before mentioned, is the best:
plaster is too porous, and the solution soon destroys it: wood is
too close, and the deposit is consequently very slow: skin does
very well for a short time, but it is soon destroyed. When porous
cells were not convenient, we have made electrotypes by wrapping
the zinc plates in two or three folds of stout cartridge paper, moistened with a solution of salt, and placing this in the copper solution
with the mould. Of course, this is only to be adopted when a
porous vessel cannot be obtained. The paper lasts but a short




58~'61   THE PRACTICAL METAL-WORKERS- ASSISTANT.
time, and- has, therefore, to be frequently renewed; besides which,
there is always a deposit of copper upon the paper, thus occasioning a loss;
Common coarse garden-pots answer excellently for porous vessels,
closing the aperture at bottom by a cork.
The precautions that have been given (see Daniell's Battery, p.
39), as to the preserving of the porous cells when not in use, are,
applicable to the cells or partitions used, in these processes, which,
when not ini use, should be kept in water, or should not be allowed:
to. dry until they have been in water long enough to dissolve out
the salts that were: within the pores of the cell; otherwise the salts
crystallize, and either crack the cell or cause it to scale off in small
pieces. Porous cells, when not thoroughly washed and freed from
salts, if laid aside for a few days, often thrown out an efflorescence,
or crystalline growth, like mould, of a soft silky texture, and from
one-half to one inch in length. An analysis of this efflorescent
matter gave
Oxide of zinc....   39'6
Sulphuric acid...   26'0
Water.....   34'2
99'8
COMPARATIVE VALUE OF EXCITING  SOLUTIONS.-We have
recommended the porous cell being filled by dilute sulphuric acid,
which we consider best; but other saline solutions will serve the
same purpose: solutions of common salt, sal ammoniac, sulphate,
of zinc, have been recommended, and each has been called best in
its turn. The following results of experiments with these solutions in the porous cell will show their relative qualities, and enable
the student to judge for himself. The size of the zinc plate in the
cell used in these experiments measured 6 inches by 6 inches; the
copper plates upon which the deposits were formed were the same
size; the solution of copper was kept at the same strength; the
time that each was in solution was 16; hours.




ELECTROTYPbe PROCESSES.                 537
Solution in porous Cell.  Zinc dissolved.  Copper deposited.
Sal ammoniac.         oz. dwt. gr.  oz. dwt. gr.
Saturated solution...      1    5   14    1    2   12
1 part saturated solution      1    8    5    1    3   10
1 part water.
1 part saturated solution      0   12   13    0   10   17
3 parts water...
Common Salt.
Saturated solution      0..       16    3    0   14   12:
1 part saturated solution      0   18    9    O-  17    8
1 part water.
1 part saturated solution      1    0f          0   19   1
3 parts water.              1          5 
Sulphate of Zinc.
Saturated solution.    1    3   18    0   19    0
1 part saturated solution   1    0    8    0   19  s18
I part water                         0
1 part saturated solution      0   14   1      0   14    8
3 parts water...
Sulphuric Acid.
1 part to 8 of water...  3    1    6    1    4    8
1 part to 16 of water..    2   11    8    2    1    8
1 part to 24 of water...  2    7    3    2    5    6
How OFTEN SOLUTIONS SHOULD BE CHANGED AND ZINC AMALGAMATED.-Students have often put this question to us: How often
should the solution in the cell be renewed, and the zinc plate be
amalgamated? The following are the results of many trials made
to ascertain the facts necessary to answer this inquiry.  The zinc
plates used were nearly one foot square, and the copper plate upon
which the deposit was made was of the same size as the zinc plates.
In the first series the zinc plates were not taken out either to
brush or re-amalgamate, neither were the solutions renewed during
the time specified.
Copper     Zinc
deposited.  dissolved.
oz.   dwt.  oz.   dwt.
2 lb. common salt in one  24 hours. 12   9    12, 17
48 hours    17  13    20  17
gallon of water   60 hours. 24  15    34   3
(24hours      9  13      9  18
21b. sulphate of zinc in one  48 hours    16   4    17  10
gallon of water         248hours     16 4        1   10
gallon of water   60hours. 23  10    24   8
1 lb. sulphuric acid to 241 24 hours. 15  17    17  15
of water                48 hours. 27  16    32   3




538      THE PRACTICAL METAL-WORKER'S ASSISTANT.
From these results it is evident that the best and most economical manner of treating the solution and the zinc would be to renew
the solution every 24 hours, as the second 24 hours do not give,
without renewal, above half the deposit of the first.24 hours, while
the waste of zinc is very little less than in the first.
The next series of experiments was with the same zinc and the
same kind of solutions, but the zinc was taken out every 24 hours,
and brushed, but not re-amalgamated, and put back again with new
solution in the porous cell.
Copper    Zinc
deposited.  dissolved.
oz.   dwt.  oz.   dwt.
Salt and water. 4 days of 24 hours. 49  16    51  8
Sulphate of zinc. 4 days of 24 hours. 47  14    48  9
Acid and water. 3 days of 24 hours. 48  13    53  7
These results give the most ample reply to the question so often
put, and will guide the manufacturer as well as the student in his
operations, whether time or material be of the greatest consequence
to him.
We may remark that the sulphate of zinc solution does not
require renewal, but simply that we half empty the cell and refill
it with water. The sulphate of zinc poured out being nearly saturated, may be crystallized, and will serve for other electro-metallurgical operations.
MAKING OF MouLDs.-The directions giving for obtaining a
mould from a penny-piece, by deposition, are applicable to taking
moulds from any metallic medal, engraving, or figure that is not
undercut; and for depositing within the moulds so produced. On
the first discovery of this art, the electrotypist was confined to
metallic moulds, as the deposition would not take place except
upon metallic surfaces; but the discovery that plumbago, or black
lead polished, had a conducting power similar to that of metal, and
that the deposit would take place upon its surface with nearly the
same facility as upon metal, freed the art at once from many of its
trammels, and enabled the operator to deposit upon any substance
-wood, plaster of Paris, wax, etc.-by brushing over the surface
with black lead. It obliged the electro-metallurgist, however, to
render himself expert in the art of moulding, since no good electrotype can be obtained without a perfect mould. We shall, for
this reason, endeavor now to give such instructions as will enable
the student to make good moulds after a very short practice; but
we need hardly add, that in this as well as in every operation,
however plain may be the instructions and easy the manipulations,
practice is necessary to ensure success; so that the student ought
not to lose patience should his first attempt not succeed to his
wishes. The substances used for taking moulds from objects to
be copied by electrotype are beeswax, stearine, plaster of Paris,
and fusible metal; recently, gutta percha has been very successfully used. The articles to be copied are generally composed either




ELECTROTYPE PROCESSES.               539
of plaster of Paris or metal. Suppose, in the first place, the article
to be copied is of metal, and a mould is to be taken from it in wax
or stearine. The latter we have not found to answer well alone;
when used it should be mixed with wax, about half-and-half.
PREPARATION OF WA. -Whether the beeswax have stearine
in it or not, it is best to prepare it in the following manner: —Put
some common virgin wax into an earthenware pot or pipkin, and
place it over a slow fire; and when it is all melted, stir into it a
little white lead (flake white)-say about one ounce of white lead
to the pound of wax; this mixture tends to prevent the mould from
cracking in the cooling, and from floating in the solution: the mixture should be re-melted two or three times before using it for the
first time.
To TAKE MOULDS IN WAx.-The medal to be copied must be
brushed over with a little sweet oil: a soft brush, called a painter's
sash tool, suits this purpose well: care must be taken to brush the
oil well into all parts of the medal, after which the superfluous oil
must be wiped off with a piece of cotton or cotton wool. If the
medal has a bright polished surface, very little oil is required, but
if the surface be matted or dead, it requires more care with the oil.
A slip of card-board or tin is now bound round the edge of the
medal, the edge of which slip should rise about one-fourth of an
inch higher than the highest part on the face of the medal: this
done, hold the medal with its rim a little sloping, then pour the
wax in the lowest portion, and gently bring it level, so that the
melted wax may gradually flow over; this will prevent the formation of air bubbles. Care must be taken not to pour the wax on
too hot, as that is one great cause of failure in getting good moulds;
it should be poured on just as it is beginning to set in the dish.
As soon as the composition poured on the medal is set (becomes
solid), undo the rim, for if it was allowed to remain on till the wax
became perfectly cool, the wax would adhere to it, and being thus
prevented from shrinking, which it always does a little, would be
liable to crack. Put the medal and wax in a cool place, and in
about an hour the two will separate easily. When they adhere,
the cause is either that too little oil has been used, or that the wax
was poured on too hot.
ROSIN WITH WAx.-IRosin has been recommended as a mixture
with wax; mixtures of which, in various proportions, we have used
with success; but when often used, decomposition, or some change
takes place, which makes the mixture granular and flexible, rendering it less useful for taking moulds. When rosin is used, the
mixture, when first melted, should be boiled, or nearly so, and
kept at that heat until effervescence ceases; it is then to be poured
out upon a flat plate to cool, after which it may be used as de
scribed.
MOULDS IN PLASTER.-If a plaster of Paris mould is to be taken
from the metallic medal, the preparation of the medal is the same
as described above; and when so prepared with the rim of card



540      THE PRACTICAL METAL-WORKER'S ASSISTANT.
board or tin, get a basin with as much water in it as will be suffi.cient to make a proper sized mould (a very little experience will'
enable the operator to know this), then take the finest plaster oft
Paris and sprinkle it into the water, stirring it till the mixture
becomes of the consistence of thick cream; then pour a small portion upon the face of the medal, and, with a brush similar to tha;
used for oiling it, gently brush the plaster into every part of the
surface, which will prevent the formation of air-bubbles; then pouron the remainder of the plaster till it rises to the edge of the rim:
if' the plaster is good, it will be ready for taking off in an hour;
The mould is then to be placed before a fire, or in an oven, until quite
dry, after which it is. to be, placed, back downwards, in a shallow
vessel containing melted wax, not of sufficient depth to flow over,
the face of the mould, allowing the whole to remain over a slow
fire until the wax has penetrated the plaster, and appears upon th e~
face. Having removed it to a cool place to harden, it will soon be
ready for electrotyping. If the mould is large and the plaster
thick, the wax may be put upon the surface, and only as much as,
will penetrate a small way into the plaster. In both these instances
the wax used is generally lost, and there is always liability of the.
copper solution passing through, and causing what is termed, sur.-.
face dposit, making the face of the medal rough. We may remarkthat, although occasionally there may be a very good electrotype
obtained from a plaster mould, still they are in general very in-,
ferior; as the saturating of the plaster has a tendency to blunt the
impression, and the wax used for the purpose of saturation becomes
expensive. It may be partially recovered by boiling the plaster
in water: the wax melts out, and is obtained when the water cools.
Plaster should not be used for moulds where wax can be employed,
being neither so good nor so econormical; but there are cases in
which the moulds being very large, the use of plaster is unavoid.
able.
MOULDS IN FUSIBLE ALLOY. —The next means of taking moulds
is by fusible metal. This. name is given to alloys of two or more.
metals which melt at a very low temperature; it suits the purpose
of taking moulds of small objects very, well. The following are
examples of such compositions:
Tin.      Lead.      Bismuth.     Zinc.
1          1           2           0
1          2           3           0
X             ~0    1           1
These all melt at a temperature below that of boiling water.
The ingredients are melted together in an iron ladle, poured out
upon a fiat stone, broken up, and re-melted in the same way two
or three times, in order that they may be thoroughly mixed. The
medal from which the mould is to be taken is prepared in the
same manner as described for wax.
The fusible alloy is melted and poured into a saucer, or, what



ELECTROTYPE PROCESSES.              541:does better, a small wooden tray. The operator now watches till
it cools down into a semifluid state, or to the poinm of setting, when
he brings the medal suddenly upon it, face downwards, and holds
it there until the alloy-has fairly set; he then allows it to cool, and
undoes the slip around the medal, from which the mould will easily
separate. The height of the slip of paper above the surface of
the medal determines, of course, the thickness of the mould. The
beginner very seldom succeeds in his first attempts at making
moulds in fusible alloy; but as a little experience teaches more
than the reading of an essay upon the subject, he will soon find
both his patience and labor rewarded with gratifying success.
Some of the finest moulds are taken by this process, but, from the
constant loss of the materials by oxidation, etc., it is expensive, so
that its use amongst electro-metallurgists is very limited.
MOULDS IN GUTTA PERCHA.-Gutta percha, as a material for
moulding, serves the purpose most admirably. We have seen
moulds of this substance equal if not superior to any that we ever
saw taken in wax, and of a depth of cutting which it would have
been very difficult to have taken in wax. The method adopted for
taking moulds is to heat the gutta percha in boiling water, or in a'chamber heated to the temperature of boiling water, which makes
it soft and pliable. The medal is fitted with a metallic rim, or
placed in the bottom of a metal saucer with a cylindrical rim a
little larger than the medal; the medal being placed back down, a
quantity of gutta percha is pressed into the saucer, and as much
added as will cause it to stand above the edge of the rim. It is
now placed in a common copying-press and kept under pressure
until it is quite cold and hard. The impressions taken in this way
are generally very fine. When the medal is not deep cut a less
pressure may suffice, but when the pressure is too little the impression will be blunt.
Gutta percha takes a coating of black lead readily, and the deposit goes over it easily.
A mixture of gutta percha and marine glue has been recomi
mended for moulds as superior to gutta percha alone. We have
not had an opportunity of using this mixture, but have every confidence in the recommendations given of it.
MOULDS FROM FERNS, SEA-WEED, ETC.-A method of taking
impressions of fern-leaves and sea-weeds has recently been proposed by Dr. F. Branson, in the Athenaeum. It is thus described:
"A piece of gutta percha, free from blemish, and the size of the
plate required, is placed in boiling water. When thoroughly
softened it is taken out and laid flat upon a smooth metal plate
and immediately dusted over with the finest bronze powder used
for printing gold letters. The object of this is threefold-to dry
the surface, to render the surface more smooth, and to prevent adhesion. The plant is then to be neatly laid out upon the bronze
surface and covered with a polished metal plate either of copper
or of German silver. The whole is then to be subjected to an




542      THE PRACTICAL METAL-WORKER S ASSISTANT.
amount of pressure sufficient to imbed the upper plate in the gutta
percha. When the gutta percha is cold, the metal plate may bo
removed and the fern gently withdrawn from its bed. A beautiful impression of the fern will remain."  An electrotype may be
deposited upon the bronzed or black leaded gutta percha.
We have seen many electrotype leaves done by this method,
which were certainly very pretty as electrotypes, and the process
is well adapted for flat leaves; but the pressure required renders
it unsuitable for some kinds of leaves-indeed, it destroys the
natural forms of the greater number both of leaves and sea-weeds.
The products of the process cannot, indeed, be compared with
those electrotype leaves the moulds of which are taken by wax.
The great merit of the process is its ease and simplicity. The
method given for taking the mould of the leaf is suitable for any
kind of flat mould in gutta percha. The mould of a leaf may be
taken in plaster by placing the leaf upon dry sand and pressing
the sand under and on each side to fill up the spaces under the
leaf so as to bear the pressure of the plaster, putting a collar of
paper round the sand to prevent its yielding, and then pouring the
plaster over the whole. When the plaster is set, the leaf is removed and the plaster trimmed round with a knife. This also has
its difficulties; for when leaves have hairs upon them they stick
into the plaster. The method of taking moulds of leaves in wax
is by holding the leaf in the hand and brushing a thin layer of
melted wax over the surface to be moulded; allowing this to
harden, and then brushing on another layer-and so on until the
wax is sufficiently thick to suffer handling. The leaf is then gently
drawn off the wax, which is to be black-leaded, and put into the
electrotype apparatus to receive the coating of copper. A type
of the leaf is by this means obtained with all its natural convolutions.
NATURE PRINTING.-A  further improvement upon making
moulds of leaves and other vegetable objects, has been practised
by an eminent firm in London. The leaf is carefully dried and
laid upon a smooth piece of milled lead, which is placed between
two steel plates, and passed between rollers, these press the leaf
into the lead, and produce a complete mould. Copies from this
may be taken with gutta percha or electrotype. Printed impressions of leaves, sea weed, and such like objects, prepared in this
way, may be seen in an excellent work published by Bradburv
and Evans, and a full detail of the process, with specimens, will be
found in the proceedings of the Royal Institution for 1854.
CASTING OF REPTILES, ETC. —Imbed the subject in a mould made
of four parts of plaster of Paris, one of unburnt lime powder, and
one of Flanders brick-dust. Dry the mould carefully, then make
it red hot, and burn the subject out of it, taking care to free the
mould from the ashes. Fusible metal may be cast in this mould,
and then be covered with copper, from which the alloy may be
afterwards melted, or a wax model may be taken of the object,




ELECTROTYPE PROCESSES.               543
pouring the wax in just before setting. In neither case must the
mould be melted until after the model, whether of alloy or wax,
is taken, when the whole is placed in water, the lime causes the
mould to dissolve or break up, and the figure modelled within it
may be taken and covered with copper; Flowers, insects, lizards,
and other little animals may be typed in this way. In all these
processes, perseverance and care are the best cures for little
difficulties.
WAX MOULDS FROM PLASTER.-If the object, which we assume
to be a medal, from which the mould is to be taken, be composed
of plaster of Paris, and the mould to be taken is in wax, the first
operation is to prepare the plaster medal. Some boiled linseedoil, such as is used by house painters, is to be laid over the surface of the medal with a camel's hair pencil, and continued until it
is perfectly saturated, which is known by the plaster ceasing to absorb any more of the oil. This operation succeeds best when the
medal is heated a little. The medal should now be laid aside till
the oil completely dries, when the plaster will be found to be quite
hard, and having the appearance of polished marble; it is, consequently, fit to be used for taking the wax mould, which is done in
the same manner as we have described for taking a wax mould
from a metallic medal.
Many prefer saturating the medal with water: this is best done
by placing the medal back down in the water, but not allowing it
to flow over the face; the water rises, by capillary attraction, to
the surface of the medal, rendering the face damp without being
wet. The rim being now tied on the plaster medal, the melted
wax is poured upon it. This method is equally good, but liability
to failures is much greater, caused generally by the wax being
too hot.
The plaster medal may also be saturated with skimmed milk
and then dried; by repeating this twice, the plaster assumes on the
surface an appearance like marble, and may be used for taking
wax moulds.
MOULD OF PLASTER FROM PLASTER MODELS.-When a plaster
mould is to be taken, the face of the model is prepared differently
to that described, in order to prevent the adhesion of the two
plasters. The best substance we have tried for this purpose is a
mixture of soft soap and tallow, universally used by potters for
preparing their moulds, and called by them lacquer. It is prepared in the following manner:-half-a-pound of soft soap is put
into three pints of clean water, which are set on a clear fire, and
kept in agitation by stirring; when the mixture begins to boil, add
from one ounce to an ounce and a-half of tallow, and keep boiling
till it is reduced in bulk to about two pints, when it is ready for
use. The surface of the medal must be washed over with this
lacquer, allowing it to absorb as much as it can, when it assumes
the appearance of polished marble; it is now prepared with a rim
of paper, and the mould taken as directed for taking plaster




544      THE PRACTICAL METAL-WORKER'S ASSISTANT.
moulds from metallic medals. When hardened, they will separate
easily.-Wetting the plaster model with a solution of soap before
taking the cast will do, or, if the plaster model has been saturated
with oil or milk, it has only to be moistened with sweet oil the
same as a metal model.
FUSIBLE ALLOY FROM PLASTER.-If a mould of fusible metal
be required from a plaster medal, the plaster may be saturated
either with boiling oil or the soap and tallow lacquer, and the
mould taken in the same manner as from a metallic medal.
COPPER MOULDS FROM PLASTER.-Many electro-metallurgists
prefer taking a mould in copper when the medal is of plaster of
Paris. This is done by the electrotype process; the plaster model
is saturated with wax over a slow fire, as already detailed, and then
prepared for taking an electrotype in the usual manner (see page
534). We need hardly mention that the model in this case is destroyed; but, notwithstanding, in the case of plaster models, to
take a copper mould is the most preferable, as it may be repaired
in case of slight defect, and it may be used over and over again
without deterioration.
When an electrotype is required of a model that is undercut, or
of a bust or figure, the process which we have described will not
answer, as the mould cannot separate from the model. In such
~circumstances the general method of prbceeding is to part the
mould in separate pieces, and then join these together.  The
material used for this purpose is plaster of Paris. The operation,
however, to be well done, requires a person of considerable experience.
ELASTIC MOULDING.-The process patented by Mr. Parks for
taking a mould of any kind of model in one piece, is excellently
adapted for the electrotypist. The material is composed of glue
and treacle. Twelve pounds of glue is steeped for several hours
in as much water as will moisten it thoroughly; this is put into a:metallic vessel, which is placed in boiling water as a hot bath.
When the glue falls into a fluid state, three pounds of treacle are
added, and the whole is well mixed by stirring. Suppose, now,
that the mould of a small bust is wanted, a cylindrical vessel is
chosen so deep that the bust may stand in it an inch or so under
the edge. The inside of this vessel is oiled, a piece of stout paper
is pasted on the bottom of the bust to prevent the fluid mixture
from going inside, and if it is composed of plaster, sand is put inside to prevent it from swimming. It is next completely drenched
in oil and placed upright in the vessel. This done, the melted
mixture of glue and treacle is poured in till the bust is covered to
the depth of an inch. The whole must stand for at least twentyfour hours, till it is perfectly cool throughout-after which it is
taken out by inverting the vessel upon a table, when, of course,
the bottom of the bust is presented bare. The mould is now cut
by means of a sharp knife, from the bottom  up the back of the
bust to the front of the head. It is next held open by the opera.




ELECTROTYPE PROCESSES.               545
tor, when an assistant lifts out the bust and the mould is allowed
to reclose. A piece of brown paper is tied round it to keep it
firm. The operator has now a complete mould of the bust in one
piece; but he cannot treat it like wax moulds, as its substance is
soluble in water, and would be destroyed if put into the solution.
A mixture of wax and rosin, with occasionally a little suet, is
melted and allowed to stand till it is on the point of setting, when
it is poured carefully into the mould and left to cool. The mould
is then untied and opened up as before; the wax bust is taken out;
and the mould may be tied up for other casts. Besides wax and rosin
there are several other mixtures used-deer's fat is preferable to
common suet, stearine, etc. The object is to get a mixture that
takes a good cast and becomes solid at a heat less than that which
would melt the mould.
MOULDING OF FIGURES.-If the model or figure be composed
of plaster of Paris, a mould is often taken in copper by deposition.
The figure is saturated with wax, as described for a medal, and
copper deposited upon it sufficiently thick to bear handling without damage when taken from the model. The figure with the
copper deposit is carefully sawn in two, and then boiled in water,
by'which the plaster is softened and easily separated from the copper, which now serves as the mould in which the deposit is to be
made. It is prepared in the same way as we have described for
depositing in copper moulds. When the deposit is made sufficiently thick, the copper mould is peeled off and the two halves of
the figure soldered together. The copper moulds which are deposited upon the wax models taken in the elastic moulding are
often treated in the same manner; but more generally these moulds
are used for depositing silver or gold into them, to obtain facsimiles of the object in these metals, in which case the copper
moulds are dissolved off by acids, as will be described in a subsequent section.
FIGURES COVERED WITH CoPPER. —When plaster busts or figures
are wanted in copper, the most usual way is to prepare the figure
with wax as described, and to coat it over with a thin deposit of
copper, letting the copper remain. Some operators, when it can
be done, remove the plaster and wash over the inside with an alloy
of tin and lead melted. In this case the copper must previously be
cleaned by washing first in a solution of potash, and then with
chloride of zinc. The latter mode will cause the alloy to adhere
to the copper and give it strength. In either of these cases the
deposit must not be very thick, or it will throw the figures out
of proportion, such as the features of a bust, etc. Any slight
roughness of deposit may be easily smoothed down by means of
fine emery.
THE PREPARATION OF NON —METALLIC MOULDS TO RECEIVE
DEPOSIT. —Having detailed what we have found best for obtaining
moulds of objects for the purpose of electrotyping, we proceed to
the manner of obtaining a deposit upon these moulds. Were any
35




546      THE PRACTICAL METAL-WORKER S ASSISTANT.
of the plaster or wax moulds attached to the zinc and immersed in
the copper solution in the same manner as described with the
penny-piece (page 534), no deposit would be obtained, because
neither the plaster nor the wax is a conductor of electricity. Some
substance must now be applied to the surface in order to give it
conducting power. There are several ways of communicating this
property, but the best and most simple for the articles under consideration is to apply common black lead (already referred to) in
the following manner: —A  copper wire is put round the edge of
the medal, or, if wax moulds are used, a thin slip of copper may
be inserted into the edge'of the tnould —or, being slightly heated
and laid upon the back, the two will adhere. A fine brush is now
taken (we have found a small hat-brush very suitable) and dipped
into fine black lead, and brushed over the surface of the medal.
The brushing is to be continued until all the face round to the wire
upon the edge, or slip of copper forming connection, has a complete metallic lustre. A bright polish is necessary to the obtaining a quick and good deposit.
In brushing on the black lead, care should be taken not to allow
any to go upon the back'or beyond the copper connection, or the
deposit will follow it, and so cause a loss of copper, and make the
mould more difficullt to separate from the deposit; being, as it
were, incased. If the electrotypist takes the labor himself of filing
off all the superfluous copper from the edge of his deposited medal,
it will do more than any written precautions to teach the necessity
of preventing as much as possible the deposit going further than
is necessary. When the face of the mould is properly blackleaded, the copper wire connected with it is attached to the zinc
plate in the porous cell, and the mould immersed in the copper
solution; the deposit will immediately begin upon the copper connection, and will soon spread over every part, covering the blacklead polish with less or more facility according to the state of the
solutioins and other circumstances to be afterwards noticed. When
the deposit is considered sufficiently thick for removing-which,
in 0ordinary circumstances, will require from two to three daysthe medal is taken out of the solution, and washed in cold water,
and the coannection is taken off. If the deposit has not gone far
over the edge of the mould, the two may be separated by a gentle.pull; if otherwise, the superfluous deposit must be eased off, and
if care be taken the wax may be fit to use over again: but when
the mould is plaster of Paris, however well it may be saturated
with wax, it is seldom in a condition to use again. If the plaster
mould'be large and thick, it is advisable to coat the back with wax
er tallow,'vwhich is done by brushing it over with either substance
in a melted state: the mould being cold will not absorb the wax
or tallow:'hence it may be recovered again. The sulphate of
copper possesses so penetrating a quality that if the slightest imperfection occurs in the saturation of the mould by wax, the solu
tion will penetrate through "it, and the copper will be deposited




ELECTROTYPE PROCESSES.               547
upon the face of the object adhering to the plaster, giving to the
metal a rough, matted appearance, and seriously injuring it.
USING METAL MOULDS.-The mould in fusible alloy does not
require to be black-leaded, but the back and edge must be protected by a coating of wax or other non-conducting material; it
may be connected in the same way as the penny-piece (page 534)
by putting a wire round its edge previous to laying on the nonconducting substance, such as tallow or wax, which should also
cover the wire. Or a slip of copper, or wire, may be laid upon
the back and fastened by a drop or two of sealing-wax; the back
is then coated: but care must be taken that the wax do not get
lbetween the connection and the medal which will prevent deposit.
The deposit on this mould goes on instantaneously, the same as
over the penny-piece. When sufficiently thick, it may be taken
off in the same manner as from the wax mould, the surface having
been prepared by turpentine (page 534) to prevent adherence.
These moulds may be used several times, if care be taken not to
heat them, as they easily melt.
The medals obtained from metallic moulds prepared with the
turpentine solutioA have a bright surface, which is not liable to
change easily, but if the mould has been prepared with oil or composed of wax or plaster, the metal will either be dark, or will very
easily tarnish. The means of preserving them, either by bronzing
or plating with other metals, will be detailed in a subsequent section.
PRECAUTIONS ON PUTTING TIHE MOULDS INTO A SOLUTION. -In
putting moulds into the copper solution, the operator is often an
noyed by small globules of air adhering to the surface, which
either prevent the deposit taking place upon these parts, or, when
they are very minute, permit the deposit to grow over them —
causing small hollows in the mould, which give a very ugly appearance to the face of the medal. To obviate this, give the mould,
when newly put into the solution, two or three shakes, or give the
wire attached to it, while the mould is in the solution, a smart tap
with a key or knife, or any thing convenient; but the most certain means we have tried, is to moisten the surface with alcohol
just previous to putting it into the copper solution. A little pra;tice in these manipulations will soon enable the student to avoid
these annoyances.
DEPOSITION ON LARGE OBJEcTS.-When busts or figures,
whether of wax or plaster of Paris, are to be coated with copper,
with no other conducting surface than black lead, it is attended
with considerable difficulty to the inexperienced electrotypist. The
deposit grows over all the prominent parts, leaving hollow places.
such as armpits, neck, etc., without any deposit; and when once
missed, it requires considerable management to get these parts
coated, as the coated parts give a sufficient passage for the current
of electricity. It is recommended by some electrotypists to take
out the bust, and coat the parts deposited upon with wax, to prevent any further deposit on them; but this practice is not good,




548      THE PRACTICAL METAL-WORKER'S ASSISTANT.
especially with plaster of Paris, for an electrotype ought never to
be taken out till finished. Sometimes the resistance of the hollow
parts is occasioned by the solution becoming exhausted from its
position in regard to the positive pole. In this case a change of
position effects a remedy. It may be remarked that when a bust
or any large surface having hollow parts upon it, is to be electrotyped, as many copper connections as possible ought to be made
between these parts and the zinc of the battery. Let the connections with the hollow parts be made with the finest wire which can
be had, and let the zinc plate in the cell have a large surface compared to the surface of the figure, and the battery be of considerable intensity; if attention is paid to these conditions, the most intricate figures and busts may be covered over in a few hours. Care
has to be observed in taking off the connections from the deposit,
or the operator may tear off a portion of the deposit: if the wires
used are fine, they should be cut off close to the deposited surface.
To MAKE BUSTS AND FIGURES.-Busts and figures, and other
complicated works of art, which cannot be perfectly coated with
black lead, may be covered by a film of silver or gold, which
serves as a conducting medium to the copper. This is effected by
a solution of phosphorus in sulphuret of carbon. The operation
being patented, we will take advantage of the description given of
it in the specification. "The solution of phosphorus is prepared
by adding to each pound of that substance 15 lbs. of the bisulphuret or other sulphuret of carbon, and then thoroughly agitating
the mixture; this solution is applicable to various uses, and
amongst others, to obtaining deposits of metal upon non-metallic
substances, either by combining it with the substances on which it
is to be deposited, as in the case of wax, or by coating the surface
thereof. Any of the known preparations of wax, may be treated
in this way, but the one preferred is composed of from 6 to 8
ounces of the solution: 5 lbs. of wax, and 5' lbs. of deer's fat,
melted together at a low heat, on account of the inflammable nature of the phosphorus. The article formed by this composition
is acted upon by a solution of silver or gold in the manner hereinafter described with respect to articles which have been coated
with the solution."*
COATING OF FLOWERS, ETC. —"If the solution is to be applied
to the surface of the article, an addition is made to it of one pound
of wax or tallow, one pint of spirits of turpentine, and two ounces
of India rubber, dissolved with one pound of asphalt, in bisulphuret of carbon, for every pound of phosphorus contained in
the solution. The wax and tallow being first melted, the solution
of India rubber and asphalt is stirred in; then the turpentine, and
after that the solution of phosphorus is added. The solution prepared in this manner is applied to the surfaces of non-metallic
substances, such as wood, flowers, etc., by immersion or brushing;
* Repertory of Patent Inventions, 1844.




ELECTROTYPE PROCESSES.                549
the article is then immersed in a dilute solution of nitrate of silver,
or chloride of gold; in a few minutes the surface is covered with
a fine film of metal, sufficient to insure a deposit of any required
thickness on the article being connected with any of the electrical
apparatus at present employed for coating articles with metal. The
solution intended to be used is prepared by dissolving four ounces
of silver in nitric acid, and afterwards diluting the same with
twelve gallons of water; the gold solution is formed by dissolving
one ounce of gold in nitro-muriatic acid, and then diluting it with
ten gallons of water."
We have frequently repeated the operations described by this
patentee with entire satisfaction, and were enabled to cover every
variety of surface with great facility.
The solutions of silver and gold, prepared as above, will last for
a long time, and do a great many articles. When it is convenient
it is best to use both solutions. The connecting wire should first
be attached to the article to be coated, before being dipped into
the phosphorus solution, but connected at such parts as will not
hurt the appearance of the object by leaving a mark when it is
taken off: Care should be taken not to touch the article with the
hands after it is dipped into the solution. The object supported
by the connections is immersed in the phosphorus solution, where
it remains for two or three minutes. When taken out it is dipped
into the silver solution, and as soon as the surface becomes black,
having the appearance of a piece of black china, it is to be dipped
several times in distilled water, and then immersed in the solution
of protochloride of gold about three minutes: the surface takes a
bronze tinge by the reduction of the gold. It is next washed in
distilled water by merely dipping, not by throwing water upon it.
The wire connection is now attached to the zinc of the oattery,
and then the article put into the copper solution, and in a few
minutes the article is coated over with a deposit of copper. A
thin copper surface may thus be given to small busts or figures
without sensibly distorting the features by want of proportion.
FIGURES FROM ELASTIC MOULDs.-When'taking a wax cast
from the elastic mould, described in page 544, we prefer the phosphorized mixture. After taking out the mould it is only necessary to make the connections, and pass it through the gold and
silver solutions, as described, and then to connect it with the
battery.
We may also mention that the principal object of making copper moulds by this process, in the manufactory, is not to make facsimiles in copper, but to make articles of solid silver or gold.
Copies of highly wrought work, either chased or engraved, or of
articles, duplicates of which cannot be obtained, or of which the
workmanship is costly, may by this means be made in solid silver
or gold, at little more expense than the cost of the metal. Having
obtained the copper mould, silver is deposited in it to any thickness, and the copper dissolved off. However. an extensive trade




550      THG  PRACTICAL METAL-WORKER'S ASSISTANT.
is now being carried on in figures and other works of art deposited
in copper and then bronzed, which gives them an appearance often
not much inferior to that of antique works of the highest art.
ELECTROTYPES FROM DAGUERREOTYPES.-What may be justly
termed the perfection of electrotyping, is the production of electrotypes from daguerreotypes. The daguerreotype picture being
taken, a small portion of the back is cleaned with sand-paper, taking
care not to allow any thing to touch the face; a little fine solder is
placed on this part; a piece of flattened wire, also cleaned, is
placed upon the solder, the whole moistened with dilute muriatic
acid, or chloride of zinc. The wire is now held over the gas or a
lamp about half an inch from the plate; the heat is transmitted
through the wire to the solder, which melts, and the wire is soldered to the type; the back is then protected by wax, and the
daguerreotype is now put into the copper solution in the same manner as a medal; the deposit proceeds rapidly, and when sufficiently
thick the two easily separate, and an impression of the picture is
obtained from the daguerreotype with an expression softer and
finer than the original; several electrotypes may, with care, be
taken from one picture. The electrotype may now be passed
through a weak solution of cyanide of gold and pota'ssium, in connection with a small battery, and thus a beautiful golden tint be
given to the picture, which serves to protect it from the action of
the atmosphere; but they should also be protected by a glass,
which may be fixed on in the manner pointed out in another section. The most successful operators that we have known in this
and every other department of electrotyping are Dr. Thomas
Paterson, of Glasgow, and Mr. Bawtree, of London.
DEPOSITING BY SEPARATE BATTERY. —Having described, so far
as we know them, the best and most simple means of obtaining
moulds, and their preparation for receiving the deposit of the
metal, we return again to the management of solutions and batteries, and the application to other metals besides copper.
Although in our account of the porous or single cell system
(page 533) we have recommended it as the best and most economical for electrotyping, still many eminent electro-metallurgists prefer
using the battery system; and indeed there are solutions of copper
and of other metals to which the porous cell system cannot be applied, from the nature of the solution and the necessity of intensity
to decompose them.
While depositing upon a mould by the single cell, let the wire
which connects them be cut in the middle, and a mould be attached
to the end of the portion remaining upon the zinc plate, and a
small plate of copper to the end of the wire remaining upon the
mould in the copper solution, and let these two be put into a second
vessel containing a solution of sulphate of copper. The action
between the zinc and medal in the double or first cell will go on
as before-namely, the electricity passing through the porous cell
and the solution to the medal; but on returning to the zinc it must




ELECTROTYPE PROCESSES.                651
pass through the copper solution, which is in the second vessel,
between the mould and copper plate, where it produces the same
effects as in the first cell. The sulphuric acid is liberated at the
copper plate and dissolves it, and the copper is deposited upon the
mould, so that the solution in this cell is maintained at one strength;
hence there is no necessity for hanging crystals of sulphate of
copper in this solution.
It will be observed that the electricity having to pass through a
second solution, is made to perform double duty, and must consequently be much more economical. We found the results to be
these: A single cell, with a mould, was placed two inches from the
porous cell, and of the same size as the zinc plate; and another,
similarly arranged, but connected with a metal mould and copper.
plate of similar size to the zinc and copper, was placed one inch
apart in the copper solution of second cell. The mould in the
single cell had gained 100 grains, and the zinc plate lost 108
grains. The mould in the battery cell of the other arrangement
had only deposited upon it
g0 grains-the zinc plate                rig. 573.
had lost 35 grains; but the
mould in the second or de-.x
composition cell had also
deposited upon it 30 grains,
making in all 60 grains deposited for 35 zinc dissolved,
but taking nearly double the
time. These arrangements,
as we have before observed,
are simply a modification
of a single pair of Daniell's battery connected with a decomposition cell, the advantages of which are not                 Fig. 574.
applicable to any other
battery, as in no other
battery does deposition  
take place within the
battery cells: indeed this
method of using a com-                i   iii i i
pound depositing appa-                         i
ratus is very seldom employed.  Batteries of a
different form, as Smee's
are generally adopted.
Figure 573 represents a
Smee's battery, connected with a medal and copper plate in a separate or decomposition cell; and Fig. 574 is a large decomposition
trough for doing several medals at one time. Of course any battery may be attached to these medals and plate by the brass connections seen on the end of the trough. Bear in remembrance




552      THE PRACTICAL METAL-WORKER'S ASSISTANT.
that the zinc of the battery is connected with the medals, and
the copper or platinized silver with the copper in the decomposition dell.
SIZE OF THE ELECTRODES. —When a separate battery is used for
the purpose of depositing in a decomposition cell, there are several
conditions which are well to be observed, as they influence the
amount and character of the deposit. The first is the size of the
electrodes or medals, in relation to the zinc in the battery. The
results we have obtained may be expressed in general terms.
When the deposit upon electrodes of the same size as the zinc
plates in a Wollaston's battery equals 100, that upon electrodes one
half the size of the zinc plates in the battery will be equal to 57,
and upon electrodes double the size of the zincsof the battery 190;
but this last condition is affected, by the intensity of the arrangement.
RELATIVE POWER OF BATTERIES.-The following experiments,
made with electrodes double the size of the zinc plates of the batteries, all at equal distances (1 inch apart), will show the relative
power of the batteries. The time in action was one hour each:
only one pair of plates constituted the battery.
Grove's battery deposited.  104 grains.
Single cell.......   62   "
Daniell's.                    33 "
Smee's.22 "
Wollaston's.                 18   "
CONSTANCY OF BATTERIES. —But the first hour of the action of
most batteries differs from an hour afterwards, so that one kind of
battery may be most useful for a short time, and another sort if
the action is to be continued for a length of time. The following
table will illustrate this remark, the condition being the same as in
last experiment, or the last experiments being continued, and the
results taken every hour for seven successive hours:
hour. hours. hours. hours, hours  hours. hours.  Total.
Grove's battery. 104  86  66  60  54  49  45   464 grs.
Single cell..    62  57  54  46  39  29  24   311"
Daniell's... 33  35  34  32  32  30  31   227 
Smee's....    22  16  14  11  12  11  10    96"
Wollaston's.. 18  14  15  12  11  10  10    90"
To make this comparision more practical, larger plates were used
for the battery, and proportionately larger electrodes, and the battery kept in operation until one pound of copper was deposited,




ELECTROTYPE PROCESSES.                553
renewing the acid, and brushing the zincs every 24 hours. The
time taken to effect this was:
Grove's Battery..... 19 hours.
Single cell.....    45    "
Daniell's*.               49  "
Smee's......147 "
Wollaston's.. 151    "
COMPARATIVE PRODUCE OF BATTERIES. —The expense of the
materials used in these experiments was as follows (of course the
materials will differ in cost both at different times and in different
localities, and more common materials may be used):
By the process with Grove's battery,,one pound of deposited
copper costs
1 lb. Copper, from positive electrodes..  25 cts.
1j lb. Amalgamated zinc.......   21
11 lb. Nitric acid.                         19 "
Sulphuric acid.02 "
67 cts.
Add time, say one cent per hour, for comparison..   20 "
87 cts.
By single cell apparatus, one pound of deposited copper costs
1 lb. Sulphuric acid.                      04 cts.
Y1  lb. Amalgamated zinc......              17 "
4 lb. Sulphate of copper........   37 "
58 cts.
Time, at one cent per hour.........    45"
$1.03
By Daniell's battery, one pound of deposited copper costs
1A lb. Amalgamated zinc......    19 cts.
4 lb. Sulphate of copper.......   37"
I lb. Copper from electrode.......   25"
Sulphuric acid........   02"
83 cts.
Time, at one cent per hour........   49
$1.32
* The Daniell's battery used in this experiment had flat plates, not circular,
as described at page 523.




554      THE PRACTICAL METAL-WORKER'S ASSISTANT.
By Smee's battery, one pound of deposited copper costs
12 lb. Amalgamated zinc..      21 cts.
3 lb. Sulphuric acid........              12"
1 lb. Copper from electrode......    25"
58 cts.
Time, at one cent per hour...... $1.47
$2.05
By Wollaston's battery, one pound of deposited copper costs
1 lb. Copper from electrode.           25 cts.
1 2 lb. Amalgamated zinc.......   19"
3 lb. Sulphuric acid..                   12"
55 cts.'rime, at one cent per hour.......         $1.51
$2.06
By thus adding the time, at a given rate, it serves to illustrate
what we have before stated respecting the necessity of placing the
value of time against the cost of materials. In manufactories,
where time has to be paid for, it may be cheapest to use the battery with the most costly materials; but where time is of no consideration, or, as is often the case, if, while the operations are going
on, the workmen are employed in other necessary labor, a cheaper
apparatus will answer: but the student or manufacturer will, by the
above general results, be enabled to choose the process most suitable for his purposes. It must be borne in mind that an allowance
has to be made on the first, second, and third, for wear and tear of
the porous vessels, not included in the above estimate. Although
the results of'these experiments give, exclusive of time, the cost of
one pound of electrotyped copper-thus
Grove's battery.     67 cts.
Single cell.....  58 
Daniell's..       83"
Smee's..   58 "
Wollaston's..      55 "
still we know from long experience in the use of single cell, Smee's,
and Wollaston's batteries, for manufacturing purposes, that the
price of the pound of copper deposited may be more correctly
stated at 62 cents-there being always loss in making,the purest
article (the copper) from impure materials, as the sulphate of copper, or the ordinary copper of commerce which is used as elec.
trodes.
Mr. Smee, in his "Advice to capitalists who propose entering




ELECTROTYPE PROCESSES.                 555
upon the business of electro-metallurgy," gives a table of expenses
incurred by the use of different batteries. But his rules are based
too exclusively upon theoretical considerations, and without that
regard for practical conditions which are so important to the manufacturer. Mr. Smee recommends for use what he calls "an oddsand-ends battery," composed of odd scraps of zinc put into acid,
having in the same vessel a piece of copper or platinized silver and
a wire placed in contact with them which forms the electrode.
This battery may be convenient for the amateur electrotypist, as it1
enables him to use up all his waste zinc. Raw zinc, or spelter, Mr,
Smee says, may also be used in this way, constituting the cheapest
of all batteries for manufacturing purposes. The data of his calculations are as follows:-The copper sheet forming the positive
electrode is quoted at 25 cents per lb.; wrought zinc, 14 cents per
lb.; raw zinc at a little more than half the price of wrought zinc,
which we will call 8 cents per lb., although he rates it at 10 cents.
Iron is given at from 2 to 4 cents per lb. The equivalent weight
of copper is given at 32, of zinc at 32, and of iron at 28; that is
to say, 32 parts (say ounces) of zinc dissolved in a battery will, or
should deposit 32 ounces of copper; and if iron be used, 28 ounces
of iron should deposit 32 ounces of copper. Hence, in the plain
language of a manufacturer, we should say that, with an odds-andends battery and raw zinc, there would be, for every pound of copper deposited,
16 oz. of zinc used... 08 cts.
16 oz. of copper dissolved.    25 "
33 cts.
And when iron is used, the expense of depositing 1 lb of copper
would be,
16 oz. of iron, say.     04 cts.
16 oz. of copper.....  25 "
29 cts.
Notwithstanding these results, Mr. Smee proves, by several fractional formulae and an algebraic equation, that the cost of deposit.
ing a pound of copper is
By iron..                37 cts.
By odds-and-ends battery.    25 " *
62 cts.
To this it may be replied by the manufacturer, that, in the first
place, raw zinc or spelter used in the way described for an odds-andends battery would lose two or three times the quantity that is
stated for every equivalent of copper; and secondly, that this form
* Smee's Elements of Electro-metallurgy, 3d edition, p. 112.




556      THE PRACTICAL METAL-WORKER'S ASSISTANT.
of battery is altogether unsuitable for manufacturing purposeA
even when amalgamated scrap zincs are used; and, as regards the
calculation, it is not easy to see that, while a pound of copper, dissolved from the positive electrode, originally costs 25 cents, it
could, notwithstanding, be deposited by the destruction of 1 lb. of
zinc, not including acid, etc., at the expense of only 25 cents. It
ought always to be remembered, that, for manufacturing purposes,
the surface upon which the metal is to be deposited in general
amounts to several square feet. The article may be, for example, a
large ornamental vase, having four square feet of surface. An
odds-and-ends battery, or an iron single pair battery would be too
weak. To deposit, with a separate battery, upon a surface such as that
of the vase, it requires two or three pairs of plates to give what we
may call economical power.
RECOVERY OF MERCURY FROM WASTE ZINc.-The general
practice of manufacturers, when the scraps of zinc become small,
is either to treat them as referred to at page 512, to distil the mercury from the zinc, or to sell the scraps to parties who do distil
them. This is done by putting the scraps into an iron retort, subjecting it to a red heat, and allowing the beak of the retort to pass
into a condenser, which has a tube dipping into water.' The mercury distils over, and condenses in the water. The zinc left in
the retort is found to be so impure as not to be fit to melt and roll
again, but it may be used in the composition of common brass.
Mr. De la Rue, in a communication to the Chemical Society,* gives
the results of several analytical experiments upon scrap zinc. Before distillation the scraps usually give the following results in 100
parts:
Zinc.. 673
Mercury....  4'3
Dross and loss.    28-4
100.0
The composition of the zinc left after distillation is given asZinc.. 90Iron....  2'56
Lead.... 6Copper....    1-44
100-00
COMPOUND CELL PROCESS.-Another method of economizing
power was proposed in what is termed the compound cell system,
by which it was said that the electricity passing through a series
of cells would be able to produce the same quantity of work in
every celi with no more cost. This plan may be stated thus:
A is a Smee's battery; the wire z is conducting the electricity to
* Memoirs and Proceedings of the Chemical Society, vol. ii. page 393.




ELECTROTYPE PROCESSES.                557'
the compound trough which is composed of a series of water-tight
cells, as a a, and is connected with a piece of copper c, forming a
positive electrode; in the same cell, and facing this electrode, is a
medal, connected by a copper wire to a piece of copper placed in
the second cell, opposite which is another medal connected in the
Fig. 575.
same manner with another piece of copper, and so on through the
series, which terminates with a medal attached to the wire of the
battery. The electricity from the battery passes through all these
cells, and reduces its equivalent in each cell. Thus the reduction
of 32 grains of zinc in the battery would deposit 32 grains of
copper multiplied by 6 times, or as many times as there are cells.
This is correct in principle, and at first sight seems to be exceedingly economical; but it is not so, for every cell adds so much to
the resistance of the current, that intensity batteries must be used;
so that, supposing we have a compound cell of six divisions, in
which are placed six separate medals, it would require a battery
of six pairs of plates to give intensity sufficient to overcome the
resistance, and the same number of medals could be made of the
same weight by six separate zincs, and in less than half the time
they could be made by this arrangement, and with a less destruction of zinc. For large operations, where the articles receiving
the deposits and the electrode are necessarily a good way apart,
the process is altogether impracticable in a commercial point of
view. This is one of the remarkable instances where theoretical
possibility and commercial economy are at variance.
EFFECTS OF RESISTANCE.-At page 551 we mentioned, that if a
single cell deposits 100 grains in a given time, and it be converted
into a battery having the two electrodes in a solution of sulphate
of copper, there will only be deposited in the same time 30 grains.
This is caused by the extra resistance which the solution between
the two electrodes, in the decomposition cell, offers to the passage
of the electricity, the amount of which corresponds to the amount
deposited-the latter depending upon the former.
If we take two small plates of copper and zinc amalgamated,
and place them in dilute sulphuric acid, in contact, but not so close
as to prevent the gas evolved from the copper plate to escape, aund
allow them to remain until there have been dissolved from the zinc




558      THE PRACTICAL METAL-WORKER'S ASSISTANT.
100 grains, and we call this the measure of the maximum amount
of electricity which that surface of zinc and copper can give out
in the time taken to dissolve the 100 grains: then, if the two
metals in the acid be separated one inch, being connected by a
wire or slip of copper above the liquid, and kept in action the
same length of time as the former, there will be dissolved from the
zinc only about 56 grains. If the wire in connection with the zinc
and copper be extended and cut in the middle, and have a piece
of copper attached to each of the same size as the zinc plate in
acid, and these be placed in another vessel containing a solution
of sulphate of copper (as Fig. 544), and put an inch apart, and
the whole kept in action the same length of time as before, it will
be found in this case that only 10 grains of zinc are dissolved.
From these experiments we see that the resistance of the one
inch of acid between the zinc and copper in the battery, and the
one inch of solution of sulphate of copper in the second or decomposition cell, is 90 or nine-tenths —only yielding one-tenth of
the electricity which the zinc and copper are capable of giving.
INTENSITY.-If we now take another zinc and copper plate of
the same size as the former, and arrange them in the acid solution,
and connect them with the copper plates in the decomposition cell,!as shown in Fig. 544, and keep
Fig. 576.          them in action the same length,of time as in the former experiments, there -will be dissolved
from the zinc about 19 grains,
and deposited upon the copper:plate attached to the zinc in the
decomposition cell 18 grains of
copper.
If three zincs and coppers be
arranged as described and placed in the'acid, there will be dissolved from the zinc plate 26 grains, and deposited upon the copper
25 grains. If six pairs zinc and copper be arranged as above and
placed in acid, there will be deposited 36 grains of copper, which
we will also take as the measure of whatis dissolved from the zinc;
and if nine pairs of zinc and copper be used, there will be deposited 43 grains, and so on until the quantity dissolved from each
zinc, or deposited on the copper plate be 100, equal to that obtained by the close contact of the zinc and copper in acid, which
will require upwards of 30 pairs of zinc and copper. It must be
borne in mind that the same quantity of zinc will be dissolved'from every plate in the arrangement. Thus, in nine pairs where
43 grains were deposited, there would be dissolved from every zinc
in the battery 43 grains.
It will now'be apparent that the use of several pairs in the battery is to overcome resistance, by which quantity is gained at the
same time up to a given point; but quantity gained by this means
is expensive.  The 10 grains deposited by the single pair of




ELECTROTYPE PROCESSES.                 559
zinc and copper only required 10 grains of zinc, but the 43
grains by the nine pairs would require 405 grains of zinc to be
dissolved.
RELATIVE INTENSITY OF BATTERIES. —Different batteries have,
different degrees of power to overcome resistance-greater intensity. The following experiments will illustrate this: A single
pair of a Wollaston's, Smee's, and Grove's batteries were fitted up
as nearly equal in circumstances as the different arrangements
would allow —each exposing the same surface of zinc, and connected with electrodes placed in a solution of -sulphate of copper,
first 1 inch, then 2 inches, 3 inches, and 4 inches apart-half an
hour in each. They were then reversed, beginning with the electrodes at 4 inches and coining to 1 inch. These experiments were
repeated several times, and a mean of the whole taken. The results were:
Deposited —              Wollaston.  Smee.    Grove.
Electrodes 1 inch... 8-8 grains   12-0   31-0
2 inches.. 66   "       6-8     26-0
3 inches.. 4'7           60      1'70
4 inches.. 80   "       4-6     14-0
From this it will be seen that Wollaston's stands lowest in intensity, which is more apparent as the distance of the electrodes is
increased. Smee's is one-third more than Wollaston's at 1 inch,
and one-half more at 4 inches; while Grove's is three and a-half
more than Wollaston's, and two and a-half more than Smee's at
1 inch, but four and a-half more than Wollaston's and three
more than Smee's at 4 inches.  If we take the mean of these
results as a comparison of batteries, their value will stand as
under:
One of Grove's equal to three of Smee's,
and to three and three-fourths of Wollaston's.
The following table gives the results of different batteries, arranged in series, kept in action the same length of time, namely,
one hour.  The battery plates were very small, the electrodes
twice the size of the battery plates:
One  Two  Four;Six  Nine
Pair.    Pairs.   Pairs.    Pairs.    Pairs.
Grove's..  55   72   93   97   98
Daniell's.                       15   35   60   77   86
Smee's                            11   19   29   41   58
Wollaston's                        8   15   24   33   48. 2   _




560      THE PRACTICAL METAL-WORKER'S ASSISTANT.
This table gives results approaching to and in principle the same
as the others: it will be observed that one pair of Grove's is equal
to nine pairs of either Wollaston's or Smee's. It is also worthy of
remark, that Grove's increases slowly in quantity above four pairs,
the intensity being sufficient at four pairs to overcome the resistance offered to the current of electricity. For ordinary electrotyping, intensity arrangements are unnecessary, except where the
article upon which the deposit is being made is of such a character
as will not allow the positive electrode to be brought close to it, or
when there are deep cut objects, or any circumstance that increases
distance and necessitates power to overcome resistance.
MODE OF SUSPENDING OBJECTS FOR COATING.-In beginning to
operate in the art of electrotyping, the student often pauses, and asks
the question, What is the best position in which a medal should be
hung in the solution? Convenience has brought into general practice the suspending of it perpendicularly in the solution, having the
positive electrode or pole facing it in a parallel
Fig. 577.    direction; but to this method there are some
objections. If, for instance, the porous diaphb f-~'   ragm, or single-cell system be used, for obtaining the medals, it is found that upon the lower
I  portion of the medal the deposition is much....      thicker than upon the upper portion. Indeed,
when even ordinary attention is not paid, the
lower part becomes not only thicker, but studded over with round nodules of copper, or with lines composed of
these nodules, while the upper part remains thin, and is covered over
with what is termed the sandy deposit copper, in dark brown grains,
capable of being rubbed off with the slightest friction. No doubt
this is in a great measure prevented by agitating the solution; but
it is inconvenient, and requires constant attention.
If a separate battery is used, and the deposition of the medal is
effected in a separate vessel, by having a copper positive electrode,
the same inconvenience takes place to a greater or less extent,
according to the distance at which the two poles are placed. These
inconveniences are known to all electrotypists, and the cause is
ascribed to the different densities of the solution. The reason why
the solution becomes of different densities is easily understood in
the single cell process, there being no copper pole to maintain the
strength of the solution; as it becomes exhausted of copper by the
deposition, the lighter portion floats on the top, and the heavier
portion remains below; and although crystals of sulphate of copper be suspended in the solution, as they dissolve they sink by their
gravity, and cause a flow upon the lower portion of the medal, and
consequently a much more powerful deposit. But why the same
should take place with a separate battery, where there is a positive electrode of copper being dissolved, just in proportion to the
copper extracted from the solution by the medals, was for a long
time not known.




ELECTROTYPE PROCESSES.                 561
NON-TRANSFER OF ELEMENTS.-TIn a paper read upon this subject before the Royal Society by the late Professor Daniell and
Professor Miller, they gave, as the results of their investigations, that certain metals are transferred by the electric current in
small proportion, differing in different metals.* About the same
time the author had observed, when operating upon the large scale,
results which led him to the conclusion, that no metal is transferred in any quantity by the electric current, nor any element
taking the position of the metal in an electrotype, but that the
acid element was always transferred equivalent to the electricity
passing. It was thus shown that during the deposition of metal,
say copper, in electrotyping, the acid, when exhausted of the copper at the surface of the medal, is transferred to the positive pole,
and dissolves a portion of copper; but this portion is not transferred
by the electric current to the medal: hence it will be observed,
that the solution next the medal will become exhausted of copper, and will consequently rise to the surface from its greater
lightness. There is no doubt a flow of stronger solution in a horizontal direction from the positive pole to the medal, caused by the
lighter portion ascending; but this does not mend the evil: the
light portion is increasing on the surface, and the whole solution
soon becomes of different densities from the surface to the bottom
of the medal; and this constant current of the
solution flowing up the surface upon which the    Fig. 578.
electrotypist is depositing, causes the lines that
are observed in deposits under certain circum-   /
stances, and which are sometimes very annoying. If a small hollow be in the mould, or
even if a small portion of a plain surface resist,
the metal will accumulate round the edge of
the resisting portion, giving the deposit an appearance as if made in a flowing stream, like a
stone standing up in a current of water. The black point in the
centre represents the resisting spot around which the deposit will
thicken, causing a ridge of metal to radiate to a point immediately
above the resisting portion. These disappointments are much
more annoying in solutions of gold and silver than in sulphate of
copper, as will be noticed when we come to treat of plating and
gilding. A point of grease or dirt, or small hole not cleaned out,
hardly visible to the naked eye, will give a very prominent effect
upon the plain polished surface of a piece of metal.
From these observations, the reader will now be able to answer
the question-what is the best position to place a medal in the
solution? To make it still more apparent, take a glass jar, filled
with a solution of sulphate of copper; place a piece of copper
upon the bottom of the jar, and suspend the medal at the top,
* Philosophical Transactions, Part 1, for 1844; and Memoirs and Proceedings
of the Chemical Society,Vol. iii. page 53.
36




562      THE PRACTICAL METAL-WORKER'S ASSISTANT.
having their two faces parallel; connect them with a battery; in
a short time the solution round the medal becomes exhausted, and
even colorless, the medal covered with a dirty brown powder, and
no further deposit will take place. But reverse the case; place
the medal at the bottom, and the copper positive electrode at the
top; the deposition goes on constant and smooth; the solution is
maintained in the same condition as it was at the first, there being
a constant transfer; the acid is transferred by the current from the
medal to the copper pole: the sulphate of copper formed descends
by its gravity to the medal. There are, no doubt, a few slight
objections to placing the medal under the positive electrode-such
as the impurities in the copper. getting disintegrated, and falling
upon the surface, but a piece of cloth wrapped round the pole prevents this. However, when a fine surface is wanted, care ought
always to be taken to have clean solutions filtered, and kept covered from dust; and when the single cell is used, the crystals. of
sulphate of copper should be suspended in a fine linen bag, or the
shelf holding them be lined with linen.
EFFECTS OF DIFFERENCE IN THE DENSITY OF SOLUTION.-Although in principle this is the best method, we believe that very
few practice it, because of the trouble attending the arrangement
ot the electrodes in this position. When the medals are small the
annoyances from unequal density are not so material, but if the
surface of the article which is being deposited be large-say eight
inches or upwards —the difference in the thickness of the lower
and upper portion of the medal is very great. When suspended
perpendicularly, they should be shifted several times, making the
upper portion the lower, besides occasionally stirring the solution,
or shaking the article. Indeed when convenient, the article receiving the deposit should be kept as much in motion as possible,
as it regulates the deposit, making it smoother and less brittle.
CRYSTALS OF COPPER ON ELECTRODES.-It will be found, when
working with a battery, that the sulphate of copper solution will
become stronger round the positive electrode, which is gradually
dissolved by the transferred acid. A frequent effect is, that the
electrode often gets coated over with crystals of sulphate of copper, which adhere with great tenacity, and stop the electric action.
Under such circumstances, it is only necessary to clean the electrode from the crystals and to add a little water to the solution,
which will prevent a recurrence of the crystals for a time. But
the stirring of the solution occasionally will do much to prevent
this crystallization.




ELECTROTYPE PROCESSES.               563
CHAPTER XXVII.
MISCELLANEOUS APPLICATIONS OF THE PROCESS OF COATING
WITH COPPER.
BESIDES the applications and processes which we have described
a. der the general term of electrotyping, there are various applicatU ns of the process of depositing metals upon other substances,
which have been, and may be still more usefully applied. We
may, at a trifling cost, impart a coating of copper to cornices for
decorating buildings, to terra cotta, engravings on wood, etc., etc.
Cloth may also be easily covered, and made to assume the appearance of a sheet of copper, having the lightness and pliability of
cloth. Lace has been covered with copper, and used for battery
plates, and has also been gilt and made into beautiful ornaments.
Table-covers with metallic ornaments richly gilt, and book-covers,
have all been tried with more or less success, although they have
not yet been profitably produced.
COPPERED CLOTH.-Ordinary cloth, covered with copper, was
prepared a few years ago in considerable quantities for the covering of roofs, wagons, etc.; but the necessary price precluded its
use when competing with the ordinary materials for these purposes, although it possesses many eminent qualities for some of
these uses-such as forming fire-proof covers to shelter wagons
from the sparks discharged by a locomotive. The choice of the
kind of cloth was another difficulty; linen was too expensive, and
required a good coating of copper to make it water-tight; the best
substance was a felted cotton with India-rubber, but after a few
months exposure the India-rubber in the cloth decomposed. The
operations of coating cloth with copper were the same as described
for the wax medals: the cloth was brushed over with a polish of
black lead, and then stretched upon a frame of wood having a
copper band round it, in which were placed small hooks or pins,
and the cloth attached to these. A vat, four feet deep and twelve
yards long, was made of brick and cement; this was divided
lengthwise by a wooden frame with panes the same as a window,
which were filled in with unglazed earthenware plates, cemented
by marine glue, and the whole made water-tight.. Into one divi
sion of the vat were placed the dilute acid and sheets of zinc; in
the other the solution of copper, in which was placed the cloth
upon the frame. The arrangement was so perfect that we have
often seen pieces of cloth, twelve yards long by one yard wide.
completely covered with copper in one hour. The result of many
trials was, that one pound weight of copper gave a perfect solid
covering to twenty superficial square feet of cloth.
A similar thickness is quite sufficient for other surfaces for mere
exposure to the atmosphere, such as wood-work, cornices, etc.. and




564      THE PRACTICAL METAL-WORKER'S ASSISTANT.
may be produced at the same rate, about 2s. 6d. per pound of
copper.
Besides these applications, many others have been suggested
and tried with variable success. Some have probably been abandoned too soon, others have had both capital and talent applied,
and success is yet to come. We shall only name a few of these
applications.
CALICO PRINTERS' ROLLERS. —SO early as 1841 active means
were tried to apply the electro-deposition of copper to the preparation of rollers for printing calicoes, both by depositing the copper
upon wax or other moulds, to make an entire roller of copper, or
to deposit a surface of copper on other metals, such as iron or
brass; but none of them have yet succeeded. To make an entire
roller is much more expensive, without an equivalent advantage
over the ordinary method of casting, rolling and boring. To deposit a layer of copper on iron is attended with many practical
difficulties, both in protecting the iron from the acid solution for
so long a time as is required to deposit the proper thickness, and
in securing the adhesion of the two metals during the subsequent
operations. It requires a deposit of about a quarter of an inch in
thickness to allow for turning before engraving. There is then
the annealing to soften the copper, etc., which interferes with the
adhesion of the two metals, probably from their different rates of
expansion, and other causes. Similar objections may be made to
the coating of brass rollers with copper. Numerous and varied
have been the experiments made, but all without success; nevertheless we have every confidence that means will be?btained for
producing rollers by the electro process.
ETCHING OF ROLLERS.-Another application of the process to
printers' rollers was to plate the surface of the roller with silver for
the purpose of etching. The engraving is then made through the
silver coating; the roller is next passed through nitric acid, which
acts upon the exposed copper, the silver taking the place of varnish in ordinary etching: but practical difficulties have caused the
abandonment of this application also.
PRINTING.-The electro-metallurgical process has been applied to
many operations in ordinary printing. Mr. Warren de la Rue has
been eminently successful in many of these applications. It has also
been applied to plates for printing music, and for embossing soft
materials, such as leather. By depositing a sheet of copper upon
a skin of morocco leather, it may be used for imparting an impression to other skins of leather, giving them the appearance of
fine morocco.
The printing of music has also been successfully done by electrotyping the plate from a stereotype cast. The same may be done
from ordinary stereotype plates.
GLYPOGRAPHY.-A process which Mr. Palmer, the inventor,
named Glyphography, has been one of the most successful attempts to apply the electrotype to the art of engraving.  The




ELECTROTYPE PROCESSES.                 563
principle of the invention consists in depositing copper in the
grooves or engravings made in a layer of some soft substance
spread on a sheet of copper, and covering the whole with a sheet
of electrotype copper. The counterpart of the engraving thus
produced is used for printing from in the same manner as letterpress printers' types or woodcuts. It may therefore be called a
mode of stereotyping, with this difference, that it is made directly
from the drawing by the artist. The drawing, however, must be
made in a particular way, which, with the other necessary manipulations, is thus given by Mr. Palmer: *
"A piece of ordinary copper plate, such as is used for engraving,
is stained black on one side, over which is spread a very thin layer
of white opaque composition, resembling white wax both in its
nature and appearance. This done, the plate is ready for use.
" In order to draw properly on these plates various sorts of
points are used (according to the directions here given), which remove, wherever they are passed, a portion of the white composition, whereby the blackened surface of the plate is exposed, forming a striking contrast with the surrounding white ground, so that
the artist sees his effect at once.
"The drawing, being thus completed, is put into the hands of
one who inspects it very carefully and minutely, to see that no part
of the work has been damaged or filled-in with dirt or dust; from
thence it passes into a third person's hands, by whom it is brought
in contact with a substance having a chemical attraction or
affinity for the remaining portions of the composition thereon,
whereby they are heighted ad libitum. Thus, by a careful manipulation, the lights of the drawing become thickened all over the
plate equally, and the main difficulty is at once overcome. A little
more however remains to be done. The depth of these non-printing parts of the block must be in some degree proportionate to
their width, consequently the larger breadths of lights require to
be thickened on the plate to a much greater extent in order to produce this depth. This part of the process is purely mechanical
and easily accomplished.
"It is indispensably necessary that the printing surfaces of a
block prepared for the press should project in such relief from the
block itself' as shall prevent the probability of the inking-roller
touching the interstices of the same whilst passing over them,
This is accomplished in wood engraving by cutting out these intervening parts, which form the lights of the print, to a sufficient
depth; but in glyphography the depth of these parts is formed by
the remaining portions of the white composition on the plate,
analogous to the thickness or height of which must be the depth
on the block, seeing that the latter is, in fact (to simplify the matter), a cast or reverse of the former. But if this composition were
* Glyphography, or engraved drawing, for printing at the typo press after
the manner of woodcuts, 1844.




566      THE PRACTICAL METAL-WORKER'S ASSISTANT.
spread on the plate as thickly as required for this purpose, it
would be impossible for the artist to put either close, fine, or free
work thereon; consequently the thinnest possible coating is put on
the plate previously to the drawing being made, and the required
thickness obtained ultimately as described.
"The plate thus prepared is again carefully inspected through a
powerful lens, and closely scrutinized to see that it is ready for the
next stage of the process, which is to place it in a trough and submit it to the action of a galvanic battery, by means of which copper
is deposited into the indentations thereof, and, continuing to fill
them up, it gradually spreads itself all over the surface of the composition until a sufficiently thick plate of copper is obtained, which
on being separated will be found to be a perfect cast of the drawing which formed the clichge.
"Lastly, the metallic plate thus produced is soldered to another
piece of metal to strengthen it, and then mounted on a piece of
wood to bring it to the height of the printer's type. This completes the process, and the glyphographic block is now ready for
the press.
"It should however have been stated previously, that if any
parts of the block require to be lowered, it is done with the greatest
facility in the process of mounting."
This process has however not come into much use as a substitute for wood engraving, in consequence of the impossibility of
finding a suitable varnish for the use of the artist or engraver. It
has, in fact, given way to another process, also embraced in Mr.
Palmer's patent, which is worked thus: A copper plate is etched
by the p-rocess commonly employed by engravers, the lines being
cut into the copper with a bold stroke. The lines are then bitten
deeper by nitric acid. The etching is made direct, not reversed, as
it is upon a plate that is to be worked at the copperplate press.
When the engraving is ready, the etching varnish through which
the drawing is cut is covered with a conducting substance, and an
electrotype plate is deposited upon the etching. When this is removed from the mould it requires to be trimmed, for it is impossible to etch a plate, or to bite the etching, so that all the lines shall
be exactly of the same depth. To remedy this the face of the
electrotype is levelled by grinding and burnishing. The following
instructions for artists are published by the patentee:
INSTRUCTIONS ON GLYPHOGRAPHY FOR THE AMATEUR.- "The
amateur must remember that he is producing a work of art for the
surface press, and not for copperplate printing.
"The drawing or etching should not be made with lines of:equal thickness in all the tints. If it is so treated with a thick line,
and if the cross hatching be kept of the same strength as the principal line, it will appear like a coarse pen-and-ink drawing. If it
is treated in the above manner with a fine line, and the work laid
very close, it will have the appearance of one of the old etchings.
The amateur, therefore, will do well to remark, that it is only by a




ELECTROTYPE PROCESSES.                 567
judicious mixture of bold and delicate work that beauty of style
can be obtained; and as the darkest shades are generally foremost,
and become gradually lighter to the distance, so that the darkest
or nearest tones should generally be formed by the boldest work,
and gradually increase in delicacy to the offscape.
"Etching is a process nearly resembling drawing with a very
fine pen or pencil, and should be proceeded with as follows:
"Having obtained a polished copper-plate with an etching ground
properly laid, proceed to put your design upon the plate.
"If it is a print or miniature that is being copied, you must
make a sketch or tracing of the same with a black lead-pencil: it
must then be traced on to the plate, remembering always, that the
proof from the block will be in the same position as the etching;
and that nothing must be etched or written backwards, as for the
ordinary copperplate printing.
"In order to trace the object on to the plate, take a piece of
transfer paper,* place it face downwards upon the plate, secure the
corners with a piece of wall wax or paste, or hold it steadily down,
if there is not much to trace; then place on your sketch or tracing, go over the outline with your etching-needle or a very hard
black lead-pencil, removing a corner at a time to see that all is
correctly transferred, and nothing omitted, or that the outline be
not too heavy and thick, in which case you must trace lighter.
"Having thus got your subject, as it were, sketched upon the
plate, proceed in all respects with your etching-needle as if making
a drawing with a black lead-pencil, only working more firmly,
taking care always slightly to cut the copper.
"Be careful not to try to form the dark touches and the black
parts of the subject with a number of lines crossing and recrossing
each other, but scrape them away entirely with the point of your
penknife, or any other convenient instrument.
"In commencing the etching of a view, it is usual to begin with
the offscape, etching the same as neatly and as close as the nature
of the printing will admit, working more firmly and boldly in every
progressive tone, until you reach the foreground. In portraits it
is usual to commence with the eye; and in draperies at the top,
working downwards.
"Owing to the great difference between surface and copperplate
printing, depth of tone should be sought as much from the breadth
or thickness of the lines, as from laying them close together; and
on the contrary, lightness of tint must be obtained by the distance
of the lines from each other, as well as from their delicacy.
"If you make a false line, or wish to efface any portion of the
work, a little Brunswick black (which can be procured at most oil
and color shops), spread thinly, may be used to stoD it out; or rub
* To prepare the transfer paper, take some thin post or tissue paper, rub
the surface well with black lead, vermilion, red chalk, or any coloring matter:
wipe this preparation well off with a piece of clean rag, and it will be ready
for use.




568      THE PRACTICAL METAL-WORKER'S ASSISTANT.
a little of the superfluous ground from the side of the plate with a
camel's hair pencil and turpentine: when this is dry the work can
be re-etched and finished at pleasure."
This last process has afforded some excellent work in the shape
of maps, among which we may cite the Penny Atlas, published by
Messrs. Chapman and Hall. Among subjects of a more picturesque nature executed by glyphography, we may instance Mr.
George Cruikshank's etchings of The Bottle. These are sufficient
to show that the art of electrotyping engravings, though yet in its
infancy, promises to be hereafter of importance in the fine arts.
COPYING OF COPPERPLATE ENGRAVINGS.-Copperplate engravings, of all sizes, and of every degree of excellence, have been
copied by electrotype. The process is exactly the same as that of
making a copy of a penny-piece, as described at page 533; namely,
an electrotype mould is first made in copper, on which, of course,
the engraving appears in relief; upon which mould any number of
electrotype copies of the copperplate engraving may be deposited
successively. The duplicates thus made are accurate copies of the
original engraving; but they are rapidly worn away by the friction
they undergo in the ordinary process of copperplate printing. The
process has therefore not displaced the use of engravings on steel.
COATING OF GLASS AND PORCELAIN.-This is done by putting
a fine coating of copal varnish over the glass, then black-leading
it, and depositing the copper. Another method has been proposed,
namely, to make a varnish of two parts asphaltum and one part
mastic, by fusing these together, and, when cool, dissolving the
mixture in spirits of turpentine to a syrup consistence. To prevent the deposit coming off the glass, the vessel is first corroded
by the fumes of hydrofluoric acid. A solution of gutta percha or
benzole has also been proposed as a varnish for fixing on the
black-lead and deposit.*
Retorts, basins, and other chemical vessels, are sometimes covered with copper for their protection during boiling and evaporation. China saucepans have also been made and covered with
copper to take the place of tinned copper vessels, but the adhesion
of the metal upQn these substances, even when we attempt to secure
it by the means above referred to, is never so perfect but that after
a short use the deposit of copper loosens from the vessels. There
is then great liability for liquids to get between the coating and
the vessel, and when heat is afterwards applied these liquids saturated with verdigris boil out. Consequently such coverings are
not well adapted either for culinary purposes or delicate chemical
operations.  They have, notwithstanding, been highly recommended, and the practice of covering the bulbs of large plain retorts, etc., may be useful in a few large manufacturing operations,
but our experience is certainly not favorable to their general use.
Mr. John Ridgway, of Cauldon-place, Staffordshire, china manunt Progress of General Science, vol. ii.; and Pharm. Journal, vol. viii.




ELECTROTYPE PROCESSES.                 569
facturer, has recently patented certain improvements in the method
or process of ornamenting or decorating articles of glass, china,
earthenware, or other ceramic manufactures. In the specification
of his patent, just enrolled, Mr. Ridgway states that his first object
is to apply a new glaze, which shall enable the metallic coating to
adhere firmly, by capillary attraction, and give affinity for copper
as a first coating. In pursuance of this, he first submits the
article to an alcoholic solution, or a gelatinous solution. He then
brushes over it an impalpable powder, composed of half carburet
of iron, and half sulphate of copper. The article thus treated is
then to be corroded by the fumes of hydrofluoric acid. T4warticle
is then to be smoothed, by brushing it over with silver sand, br by
the scratch-brush; but when the shape and nature of the article
will not admit of this, it is to be plunged into a liquor, consisting
of 6 quarts sulphuric acid, 4 quarts aquafortis, J oz. muriatic acid,
and 6 quarts water. Grease is to be carefully removed from the
article, and a thin film of mercury is to be applied. The solution
of copper consists of 1 sulphate of copper, and 4 filtered water.
Suitable solutions for silvering or gilding are to be applied, in accordance with the practice of electrotyping. The claim is not to
the solutions the coating as such, but to the application of "electrotyping," or electro-metallurgy, to the objects stated in the title,
provided the articles be so prepared as to allow them to combine
from an alloy with them.
ON GALVANIC SOLDERING. —Among the many applications of
the deposition of metals, there is one we have been often asked
about, namely, if it would not be possible to solder different metals
together by that process. The following article, which is taken
from the Technologist, will give a full reply to all who may be
still inquiring for this application:
"Under the name of galvanic soldering, a process is known by
means of which two pieces of metal may be united by means of
another metal, which is precipitated thereon through the agency
of a galvanic current. This mode of soldering by the'wet
method' has been often recommended in various periodicals relating
to the industrial arts; but it has been objected that, practically
speaking, the union between two pieces of metal could not be
effected by means of a metal precipitated by galvanic agency. In
order, however, to arrive at a definite conclusion upon this question, M. Elsner undertook the following experiments, the results of
which are in favor of the practical use of the operation of soldering by galvanic agency. In conducting these experiments, the
kind of battery known as Daniell's'constant battery'- was employed; and upon the end of the copper wire, which formed the
negative electrode, a strong ring of sheet-copper was placed. This
ring was cut asunder at one point, and the distance left between
the several parts was about the sixtieth of an inch. At the end
of a few days (during which time the exciting liquors were several times l-newed) the space in the severed portion of the ring




570      THE PRACTICAL METAL-WORKER'S ASSISTANT.
was completely filled up with copper regulus, which had been precipitated; and on partially cutting with a file through the part
thus filled up, and examining it with a lens, it was observed to be
very equally filled with solid and coherent copper.
"Another copper ring was then cut into two parts, and the two
semi-angular segments thus obtained were placed with the faces of
the sections opposite each other, and submitted to the action of a
galvanic current. At the end of a few days, the segments were
united by the copper precipitated, thus forming again a complete
ring. It was also found in this case, on removing with a file a
portion of the thickness of the ring at the points of contact, that
the spaces had been completely filled up by copper galvanically
precipitated, which had united the whole. On observing these
points carefully with a lens, the regular deposition of the copper
could be readily traced between the formerly separated portions of
the ring.
"A third experiment was made in the following manner: Two
strong rings of sheet-copper were laid with their freshly-cut faces
one upon another, so that the two rings constituted a cylinder.
These rings were surrounded by a band of sheet-tin which was
coated with a solution of wax, so that the two rings were equally
surrounded by a conducting material. Thus disposed, these rings
were attached to the negative wire of the battery and immersed
in the bath of sulphate of copper. At the end of a few days the
interior surface of the rings was covered with precipitated copper,
and between the contact surfaces of the two rings copper was also
precipitated. These rings had only been submitted to the galvanic current to such an extent as to cover their interior surface
with a thin coating of precipitated copper, and yet they were
already completely re-united, and formed a cylinder consisting of
a single piece. The exterior conducting covering, consisting of
a sheet of tin, was of course removed before testing the cohesion
or persistence of the galvanic precipitate. It may be remarked
that these rings, after being for a certain time in contact (during
the galvanic action), together with the plate of copper upon which
they rested, became so encrusted with precipitated metallic copper
that some force was found necessary to effect their detachment
from the copper wire.
"There would appear to be no doubt, then, according to the
results obtained in the preceding experiments, that two pieces of
metal may be firmly united by means of galvanically-precipitated
copper: in a word, that soldering by galvanic agency is perfectly
practicable. It will therefore be possible to firmly unite the different parts of a large piece of metal, and to make a perfect figure
of them by galvanic precipitation of a metal (copper, in ordinary
cases). If solutions of salts of gold or silver were employed in as
concentrated a form as those of copper above mentioned, there is
reason to believe that galvanic soldering would also result. In
fact, M. de Hackewitz states that in some experiments on a larger




ELECTROTYPE PROCESSES.                571
scale which ne undertook, to obtain hollow figures by galvanoplastic means, he had remarked that galvanic union often took
place between the pieces operated upon. M. Elsner states that
while conducting the experiments above-mentioned, he remarked
that by employing too powerful a current, the negative electrodes
of copper, and even the plate of copper, and ring of the same metal
resting thereon, became covered with a deep brown substance, in
the same manner as this occurs under similar circumstances in galvanic gilding, -as is well known. After several unsuccessful
attempts to prevent the formation of this brown coating, M. Elsner
found that it was possible to remove it entirely on immersing the
articles covered therewith during a few seconds in a mixture of
sulphuric and nitric acids. By this means the precipitated copper
was made to assume its natural red color. The possibility of practically effecting the operation of soldering by galvanic agency may
be explained in a few words, in a theoretical point of view. The
article is in fact in an electro-negative state of excitation, whilst
the zinc operates positively. The result is, that the faces which
are placed opposite each other, when the ring has been cut, are
negative; that is to say, in an electric' condition of the same denomination. During the progress of the electrolytic decomposition
of the metallic salt in solution (sulphate of copper in the above
case), the electro-positive molecules of copper which are detached
simultaneously arrange themselves upon the two opposite faces,
and in the direction of the break. Now, from the moment that
these molecules are deposited, they constitute with the piece a
homogeneous mass, and from that time act negatively upon the
copper which is contained in the solution, and again precipitate
copper in the form of regulus. This method of operation continues until the space which existed between the two separate
pieces of metal is filled up with metallic copper-in fact the layers
of copper which become deposited in an equal manner upon the
contiguous faces of the metal gradually diminish the distance which
separated the latter, until at length the metallic layers which cross
in the opposite direction meet each other; the result being, that
the whole of the break which originally existed between the faces
will have disappeared and become filled up with copper.
"With respect to the solidity (the degree of cohesion) of the
galvanic soldering, it is the same as that of copper or other metal
precipitated by galvanic agency. It will moreover be well understood that too energetic galvanic excitation must have an injurious
influence upon the cohesion of the metal precipitated; and in this
case precisely the same phenomena will be observed as those which
have long manifested themselves in ordinary galvano-plastic operations."-L. ELSNER, Technologist.
We mention another application of the electro deposition, which
might be extended.
GALVANO-PLASTIC NIELLO.-Niello, a peculiar style of enamelling, consists in engraving or stamping figures on a plate of silver




572      THE PRACTICAL METAL-WORKER'S ASSISTANT.
or gold, and then filling the incised lines or impressed pattern with
a sort of enamel —differing, however, from true enamel —which is
a kind of glass, by being formed of a mixture of the sulphurets
of lead, silver, and copper. This mixture is of a black colorhence the name niello, from nigellum, derived from niger, blackand when melted into the intaglio parts of a plate gives it somewhat the appearance of an inked engraved copperplate. A new
kind of niello work has lately been introduced on the Continent,
in which, however, the figures are not produced by an enamel of
sulphuret of silver, as in the true niello, but by a different-colored
metal; thus on a plate of gold may be produced fine engravings,
the lines of which are in silver, and so on. This can be effected
in two ways: first, by covering the plate to be ornamented with a
varnish exactly as is used in etching; the pattern or ornament is
then to be engraved on this varnish, and the metallic surface
etched out to the proper depth. The engraved plate is to be
placed in a solution of the metal intended to form the pattern, and
a deposit allowed to form in the usual way adopted in all galvanoplastic works. When the intaglio lines have been completely
filled up by the deposited metal, the plate is removed from the
solution and ground, when the pattern will be fully developed.
The* second method consists in sketching the ornament on a sheet
of paper with lithographic ink, placing this, with the side upon
which the drawing was made, upon a plate of silver or other metal
to be ornamented, and pressing them together; the paper is now
removed with water, slightly acidified, leaving the ink adhering to
the plate, which is to be sprinkled with sand. When the ink has
fully dried, the sand is blown away; the plate is placed in a solution of the metal which it is intended should form the ground, and
put in connection with the battery. By this means a deposit will
be formed over the whole surface, except the parts protected by
the ink. On the removal of the latter with alcohol or spirits of
turpentine, etc., the original metal will be exposed, forming a pattern. Many highly ornamental and useful applications might be
made of these processes, especially in the manufacture of church
furniture. Instead of simply engraving the name and legend upon
pieces of plate presented to persons, it might be put in in letters
of gold at very little more expense.
CHAPTER XXVIII.
BRONZING.
WE have already mentioned that when a medal has been made
from a metallic mould, protected by a little wax dissolved in turpentine, it retains its bright copper lustre for a long time, even




BRONZING.                      573
when exposed to the air; but generally the copper medals and other
objects are very liable to tarnish, for which reason it is usual to
give them a coating of bronze, that they may acquire a permanently
agreeable appearance.
BROWN- BRoNzEs.-Bronzing is effected by several very simple
methods, the most common of which is the following:
Take a wine-glass of water, and add to it four or five drops of
nitric acid; with this solution wet the medal (which ought to have
been previously well cleaned from oil or grease) and then allow it
to dry; when dry impart to it a gradual and equable heat, by which
the surface will be darkened in proportion to the heat applied.
ANOTHER METHOD.-Make a thin paste of crocus and water: lay
this paste on the face of the medal, which must then be put into an
oven, or laid on an iron plate over a slow fire; when the paste is
perfectly reduced to powder, brush it off and lay on another coating; at the same time quicken the fire, taking care that the additional heat is uniform; as soon as the second application of paste is
thoroughly dried, brush it off. The medal being now effectually
secured from grease, which often occasions failures in bronzing,
coat it a third time, but add to the strength of the fire, and sustain
the heat for a considerable time: a little experience will soon enable
the amateur to decide when the medal may be withdrawn; the third
coating being removed, the surface will present a beautiful brown
bronze. If the bronze is deemed too light the process can be
repeated.
Another very simple method is this: after the medal is well
cleaned from wax or grease, by washing it in a little caustic alkali,
brush some black lead over the face of it, and then heat it in the
same way as described for crocus; or a thin paste of black lead may
be used, and the processes already referred to be repeated until the
desired brown tint is obtained. In this kind of bronze a little
Hematitic iron ore, which has an unctuous feel, may be brushed
over the face of the bronze, by which a beautiful lustre is imparted
to it, and a considerable variety in the shade may be obtained. In
the brown bronzes the copper is slightly oxidized on the surface.
BLACK BRONZEs.-A very dark colored bronze may be obtained
by using a little sulphuretted alkali (sulphuret of ammonia is best).
The face of the medal is washed over with the solution, which
should be dilute, and the medal is to be dried at a gentle heat. It
should afterwards be polished by a hard hair brush. Sulphuretted
hydrogen gas is sometimes employed to give this black bronze,
but the effect of it is not so good, and the gas is very deleterious
when breathed. In these bronzes the surface of the copper is converted into a sulphuret.
Many metallic solutions, such as weak acid solutions of platinum,
gold, palladium, antimony, etc., will impart a dark color to the
surface of medals when they are dipped into them. The medal
after being dipped into the metallic solution is to be well washed
and brushed. In such bronzes the metals contained in the solu



574      THE PRACTICAL METAL-WORKER'S ASSISTANT.
tion are precipitated upon the face of the copper medal, which
effect is accompanied by a partial solution of the copper.
GREEN BRONzES.-Green bronzes require a little more time than
those already described. They depend upon the formation of an
acetate, carbonate, or other green salt of copper upon the surface
of the medal. Steeping for some days in a strong solution of common salt will give a partial bronzing which is very beautiful, and
if washed in water, and allowed to dry slowly, is very permanent.
Sal ammoniac may be substituted for common salt. Even a strong
solution of sugar, alone, or with a little acetic or oxalic acid, will
produce a green bronze; so also will exposure to the fumes of dilute
acetic acid, to weak fumes of hydrochloric acid, and to several
other vapors. A dilute solution of ammonia allowed to dry upon
the copper surface will leave a green tint, but not very permanent.
Electrotypes may also be bronzed green, having the appearance
of ancient bronze, by a very simple process: take a small portion
of bleaching powder, place it in the bottom of a dry vessel, and
suspend the medal over it, and cover the vessel: in a short time
the medal will take on a green coating, the depth of which may be
regulated by the quantity of bleaching powder used, or the time
that the medal is suspended in its fumes: of course any sort of
vessel, or any means by which the electrotype may be exposed to
the fumes of the powder, will answer the purpose: a few grains of
the powder is all that is required. According as the medal is
clean or tarnished, dry or wet, when suspended. different dints
with different degrees of adhesion will be obtained.
The green bronzes are generally applied to figures and busts.
These directions and hints will enable the student to vary his
bronzes. Practice will give him perfection, and enable him to fix
upon that which best pleases his taste. Scarcely two electrotypists
agree upon the same method of bronzing, but differ in some little
-details of practice, or on some point of taste. Each prefers the
plan that has given to him his best results, and which he can
hardly impart by description to another.
Should the electrotypist wish to coat the copper medal with
another metal, as silver and gold, directions will be given under
plating and gilding how to proceed to effect his purpose.
CHAPTER XXIX.
DEPOSITION OF METALS UPON ONE ANOTHER.
COATING OF IRON WITH COPPER.-Besides making articles of
solid copper, we may at a small cost give a coating of copper to
another metal, such as iron, which if kept in a dry place, will retain




COATING OF IRON WITH COE Pl"I"R.          575
the appearance of copper for any length of time. But in covering
iron with copper, or any one metal with another, great care must be
taken that a proper kind of solution be used.
It is a familiar fact, that if a piece of iron, such as the blade of a
knife, be dipped into a solution of sulphate of copper, it receives a
coating of that metal. This is often described as the result of galvanic action, but there is no more galvanic action in this than in
any ordinary chemical combination; it is simply a case of chemical
substitution; the acid that is in union with the copper having a
stronger attraction for iron, leaves the copper, tnd combines with
the iron: the copper is left on the surface of the iron, but the two
metals not having sufficient polar attraction to cause them to adhere
so firmly as to exclude the action of the acid, the copper is undermined, and falls to the bottom of the solution as a powder. After
some copper has fallen upon the surface of the iron, local galvanic
action is induced between it and the iron; but this secondary
action is altogether distinct from that which first takes place.
Any solution that has the power to give a metallic coating to a
metal when dipped into it, should not be used to coat that metal
by electricity.
The attraction of the common mineral acids for the ordinary
metals is as follows: Zinc, iron, copper, nickel, silver, gold, platinum.
If the metal to be deposited be copper held in soluti6n by an
acid, say sulphuric acid, then iron or zinc cannot be coated with
copper from this solution; the acid having a greater attraction for
these metals, will leave the copper and combine with them as described above: but if the metal to be coated be any of those under
copper, in the above table, then no chemical action will take place,
and no deposit will be made, except as the effect of the electric
current introduced by the battery. This we believe is the cause
why De la Rive, Spencer, and others, failed, at an early stage of
the art, in their experiments in plating and gilding, as they employed acid solutions, which are quite impracticable when used for
depositing upon inferior metals. Under these circumstances, other
solvents for the metals must be used, which have a different relative attraction for the metals than the acids have. The substance
first applied for this purpose is, after sixteen years experience, still
found to be the best-namely, cyanide of potassium.
CYANIDE OF POTASSIUM.-This substance may be prepared by
exposing ferrocyanide of potassium (yellow prussiate of potash) to
a red heat in an iron crucible; then pounding the mass, and boiling it in alcohol of about spec. grav. 0'900: cyanide of potassium
crystallizes on cooling the resulting solution. It is now, however,
almost universally prepared for electro-metallurgical purposes, by
a process which was first suggested by Messrs. F. and E. Rodgers,
but afterwards more fully explained by Professor Liebig, and hence
called "Liebig's Process:" it is at once both simple and easy of
performance.




576      THE PRACTICAL METAL-WORKER'S ASSISTANT.
Ferrocyanide of potassium, pounded fine, is dried over a slow
fire (we have found an iron plate, or clean shovel, to serve the purpose very well): it must be constantly stirred to prevent its forming a cake upon the hot iron; when perfectly free frontmoisture, 8
parts must be thoroughly well mixed with three parts of carbonate
of potash, also well dried: put a cast-iron crucible into the fire, and,
when it is red hot, nearly fill it with the mixture, and keep up the
heat by occasional augmentations of fuel: the crucible should be
kept covered as much as possible. In a short time the whole fuses
into a beautiful licuid with the evolution of gas. It should be kept
in this state for 10 or 15 minutes, being occasionally stirred with
an iron rod: the portion adhering to the red should be examined
from time to time, and when the liquid on it cools white, it is an
indication that it is ready to be removed from the fire; but the first
time a cast-iron crucible is used, this test will not be so accurate,
the salt having then a light gray color. When the crucible is
removed from the fire, it should be placed upon a stone. the mass
stirred, and then allowed to settle for a short time, after which the
clear, or liquid part, is to be poured off into a clean iron vessel.
The sediment should be scraped clean out of the crucible while it
is hot, as the crucible will do to use again several times; but if the
mass at bottom be allowed to cool it will be difficult to remove it
from the crucible afterwards. The clear liquid poured off is cyanide
of potassium, having from 25 to 30 per cent. of cyanate of potash,
and other impurities generally contained in commercial yellow
prussiate of potash: 80 per cent. of cyanide of potassium is the
greatest proportion that this process can give.  We have occasionally obtained it at 78 per cent. from commercial materials, but
more generally at 70 and 72 per cent; and we have found cyanide
of potassium in the market containing as little as 49 per cent. of
pure cyanide.
The results of the manufacture of this salt on a large scale, from
the ordinary materials of commerce, show that 55 lbs. of yellow
prussiate, dried as directed above, yield 48 lbs.; and 19 lbs. of
carbonate of potash give 18 lbs. of dry salts; in all 66 lbs. of the
proper mixture. The crucible used was of this shape,
Fig. 579, capable of holding from two to three pints;  Fig. 579.
in. general two of them were used up in making the
above quantity of cyanide, even when great care was
taken. One great cause of the crucible giving way is
the depth of the fire, and openness of the bars of the
grate. The bottom of the crucible, between each pair
of bars, fuses from the great heat concentrated near the opening.
To remedy this evil, a square tile of fire-clay should be laid upon
the bars upon which the crucible is to rest. The tile must not
cover all the bars, else the draught will be stopped-an equal
space must be left at each side of the tile, which will preserve a
regular heat around the crucible.
The quantity of clean cyanide of potassium obtained from the




COATING OF IRON WITH COPPER.            577
above quantity of materials was about 38 lbs.; the sediment
scraped out of the crucible, being put into water, yielded about 6
lbs. more in solution, but of inferior quality —good enough, however, for precipitations, the cleaning of silver, and other general
purposes in the factory.
It may be mentioned that in these operations the crucible is
never allowed to cool, but as soon as the sediment is scraped out,
It is again put into the furnace. If the iron sediment is not well
cleaned out, it imbibes oxygen rapidly, and the charge next taken
from the crucible will have an excess of cyanate of potash, besides
lessening the capacity of the crucible. Generally speaking, however, even when the utmost care is taken, the last charge has more
cyanate of potash than the first.
CYANIDE OF COPPER.-To prepare copper solutions, by means
of cyanide of potassium, for covering iron and other positive
metals, there are several methods.
First Method.-To a solution of sulphate of copper, add by degrees a solution of cyanide of potassium, which will give a yellowish green precipitate, with slight effervescence. There will be
evolved a gas, having a most pungent odor, to prevent the inhalation of which the most watchful carefulness has to be exercised, as
it is very deleterious. It will be found that the copper is not all
precipitated by the cyanide of potassium, for according to this
mode, when a precipitate ceases to be formed, the solution remains
greenish blue, probably owing to the decomposition of the cyanate
of potash, and the formation of ammonia, which holds copper in
solution, and forms also some complicated compounds with the
cyanides of copper. If cyanide of potassium is added until the
blue solution disappears, still copper is held in the solution, and
may be detected by taking out a little, and adding to it a few drops
of sulphuric acid, which will give a white precipitate of subcyanide
of copper. The loss of copper sustained is the only objection to
this mode of preparing a copper solution. The cyanide of potassium is added until a precipitate is no longer formed; it is then
allowed to settle, the ciear liquid is poured off, and the vessel is to
be filled with water: when the precipitate has again settled, the
liquor is poured off, and this washing is repeated four or five times,
in order to wash out the sulphate of potash which is formed during
the precipitation. After being thus washed, a solution of cyanide
of potassium is added to the precipitate until it dissolves. The
coppering solution is now complete: it is of a light yellow color,
and is well adapted for ordinary purposes. The loss of copper is,
however, considerable, being about one-fifth of the whole.
Second Method. —A coppering solution may also be prepared by
adding cyanide of potassium, to oxide of copper, or to carbonate
of copper, until it is dissolved. But these solutions are object
tionable, the latter especially so, as it contains a great quantity of
carbonate of potash, formed from the mutual decomposition of the
carbonate of copper and cyanide of potassium, and the carbonate
37




578      THE PRACTICAL METAL-WORKER S ASSISTANT.
of potash deteriorates the solution;, the former leaves potash in
the solution, but this is not so bad as the carbonate of potash.
Third Method.-The method we have adopted in manufacturing
purposes is as follows:-To a solution of sulphate of copper, we
add a solution of ferrocyanide of potassium, so long as a precipitate continues to be formed: this is allowed to settle, and the clear
liquor being decanted, the vessel is filled with water, and when
the precipitate settles, the liquor is again decanted, and we continue to repeat these washings until the sulphate of potash is
washed quite out. This is known by adding a little chloride of
barium to a small quantity of the washings, and when there is no
white precipitate formed by this test, the precipitate is sufficiently
washed. A solution of cyanide of potassium is now added to this
precipitate until it is dissolved, during which process the solution
becomes warm by the chemical reaction that takes place. The
solution is filtered, and allowed to repose all night. If the solution of cyanide of potassium that is used is strong, the greater
portion of the ferrocyanide of potassium crystallizes in the solution, and may be collected and preserved for use again. If the
solution of cyanide of potassium used to dissolve the precipitate is
dilute, it will be necessary to condense the liquor by evaporation,
to obtain the yellow prussiate in crystals; the remaining solution
is the coppering solution. Should it not be convenient to separate
the yellow prussiate by crystallization, the presence of that salt in
the solution does not deteriorate it, nor interfere with its power of
depositing copper.
PECULIARITIES IN WORKING CYANIDE OF COPPER SOLUTION.The true composition of the salts thus formed by copper and
cyanide of potassium has not yet been determined, being both
various and complicated, but their relations to the battery and
electrolyzation are peculiar. The solution must be worked at a
heat of not less than from 1500 to 2000 Fahrenheit. All other
solutions we have tried follow the laws laid down by Spencer and
Smee, namely, that if the electricity is so strong as to cause gas to
be evolved at the electrode, the metal will be deposited in a sandy
or powdered state; but the solution of cyanide of copper and potassium is an exception to these laws, and there is no reguline deposit obtained unless gas is freely evolved from the surface of the
article upon which the deposit is taking place. This necessitates
the use of batteries of several pairs intensity, varying from five to
nine pairs of Wollaston's battery, according to the heat and the
state of the solution.
As this solution is used hot, a considerable evaporation takes
place, which requires that additions be made to the solution from
time to time. If water alone is used for this purpose, it will precipitate a great quantity of copper as a white powder, but this is
prevented by dissolving a little cyanide of potassium in the water
at the rate of about four ounces to the gallon. The vessels used
in factories for this solution are generally of copper, which are




COATING OF IRON WI'H  COPPER.             579
heated over a flue, or on a sand-bath-the vessel itself serving as
the positive electrode of the battery; but any vessel will suit if a
copper electrode is employed, when the vessel is not of copper.
PREPARATION OF IRON FOR COATING WITH COPPER.-When it
is required to cover an iron article with copper, it is first steeped
in hot caustic potash or soda, to remove any grease or oil. Being
washed from that, it is placed for a short time in dilute sulphuric
acid, consisting of about one part of acid to sixteen parts of water,
which removes any oxide that may exist. It is then washed in
water, and scoured with sand till the surface is perfectly clean, and
finally attached to the battery, and immersed in the cyanide solution. All this must be done with despatch, so as to prevent the
iron from combining with oxygen. An immersion of five minutes
duration in the cyanide solution is sufficient to deposit upon the
iron a film of copper. But it is necessary to the complete protection of the iron, that it should have a considerable thick coating:
and, as the cyanide process is expensive, it is preferable, when
the iron has received a film of copper by the cyanide solution, to
take it out, wash it in water, and attach it to a single cell or weak
battery, and put it into a solution of sulphate of copper. If there
is any part not sufficiently covered with copper by the cyanide
solution, the sulphate will make these parts of a dark color, which
a touch of the finger will remove. When such is the case, the
article must be taken out, scoured, and put again into the cyanide
solution till perfectly covered. A little practice will render this
very easy. The sulphate solution for covering iron should be prepared by adding to it by degrees a little caustic soda, so long as
the precipitate formed is re-dissolved. This neutralizes a great
portion of the sulphuric acid, and thus the iron is not so readily
acted upon.
EFFECTS OF CONDUCTING POWER IN SOLUTIONS AND METALS.In covering iron, platinum, or such comparatively bad-conducting
metals, with other metals that are good conductors, or the solutions
of which are good conductors, the property of conduction in relation to the solution is beautifully illustrated. If we take a copper
wire, say 8 or 10 feet long, one end of which is attached to the
zinc of a battery, and laid parallel with the positive electrode into
a solution for the purpose of receiving a deposit, it will be found
that the greatest amount of deposit has taken place at the end
furthest from the battery: but if an iron or platinum wire be substituted for the copper one,'the contrary result will take place; for
the end furthest from the battery will be the last to receive the
coating, and will have the least quantity of metal deposited upon
it. If the copper wire was 30 feet long, little alteration would be
seen in the deposit; but upon an iron or platinum wire of that
length the deposit proceeds only a certain distance, and no deposit,-will take place on the end furthest from the battery until the current has passed a considerable time, after which the deposit is
observed to advance gradually. The copper as it becomes deposited




580      THE PRACTICAL METAL- %'CILRER'S ASSISTANT.
on the iron acts as a conductor, transmitting the deposit further
onwards to its final point, as well as adding to the deposition already
effected upon the iron. The length of deposit that would be formed
on the first immersion of the wire depends upon the conducting
power of the solution; for, as already stated, solutions vary in this
property as well as metals. We have found that a few feet of iron
wire offer a greater resistance to the passage of the current than
the solution between the iron wire and the positive electrode, which
is only about 2 or 3 inches; but their exact relations to each other
we have not yet had an opportunity of investigating.
Under these circumstances, it may be asked, why not increase
the intensity of the battery, and so force it along the wire? But
this, as will be apparent, can only be done within certain limits;
for by increasing the intensity of the battery it may be rendered
too strong for the solution near the battery, and thus a sandy
deposit will be given at the one end and none at the other. The
electro-metallurgist, when coating long rods of iron wire with any
metal, has to make connections with the battery every few feet.
The wire is generally coiled up in the form of a cork-screw, and
suspended by copper wires. We have found it very convenient to
coil it upon a reel, having its armatures tipped with copper, and
connected with the battery. This plan insures a regular coating,
but the position of the wire requires to be changed during the
operation, otherwise the parts which press upon the arms of the
reel will be left without deposit.
ILLUSTRATION OF CONDUCTION.-AS an illustration of the property of conduction, we mention the following circumstance:-Having a large iron shaft, or rod, about 12 feet long and 3 inches average diameter, to cover with copper, we had it properly cleaned,
placed in a hot solution of cyanide of copper and potassium, and
surrounded by sheets of copper as a positive electrode. Two batteries of 7 pairs intensity were attached, one at each end of the
shaft; but, by an oversight, one of the batteries was not properly
connected, the copper terminal of the battery having been attached
to the shaft. Had the shaft been of copper, the one battery would
have neutralized the other, so that there would not have been any
deposit; or, had the one battery been stronger than the other, there
would have been a current and deposit equal to the excess of power
of the one over the other. But, under the ztated circumstances, a
different result was obtained. After the batteries had been in
action two hours, we found that a beautiful copper coating was imparted to that half of the shaft which extended from the point properly connected, while the other half was quite bare-no deposit
having taken place upon it: but a deposit had been made upon the
copper electrode opposite this non-affected half. The batteries did
not (as we could perceive) affect one another, except that the one
improperly connectqd prevented the deposit effected by the other
proceeding further than the half length of the shaft; but it made the
deposit obtained more perfect than would have been the case had
there been only one battery at one end.




COATING OF IRON WITH OTHER METALS.          581
In this instance, the distance of the shaft from the electrode was
6 inches, so that the resistance of 6 feet of the iron was more than
6 inches of the solution; hence the influence of the contra-acting
battery could not reach further: or if any power passed further it
was neutralized by the other battery-which we are inclined to
think did not take place-as the amount or thickness of deposit
upon the one half was fully more than we would have anticipated
upon the whole, had the batteries been properly connected.
NON-ADHERENCE OF DEPOSIT.-Objections have been made to
covering iron with copper for its protection, fiom an impression
that the copper will not adhere to the iron; but if the operation is
carefully performed the copper will adhere; when it does not, it
will generally be found that it is the copper deposited from the sulphate which loosens from the copper deposited from the cyanideoccasioned no doubt, by the article not having been sufficiently
washed from the cyanide solution, and thus having a thin film of
cyanide of copper precipitated upon the surface, which prevents
the adhesion of the after deposit. Or, as it happens sometimes,
that the cyanide of copper solution has not much free cyanide of
potassium, and, consequently on putting the article into water, the
cyanide of copper is decomposed by the water, and precipitated
upon the surface. If a little cyanide of potassium is dissolved in
the first water used for washing out the depositing solution, this
will be prevented.
We have repeatedly deposited copper upon iron wire, and afterwards had it drawn out to twice its original length without the
copper striping off; but, as the copper becomes hard and brittle, it
is liable to break if the wire is much bent, and if it be made red
hot, to anneal or soften it, the copper will oxidize, and if the coating is thin, the iron will be left bare in some places. We have
seen iron bolts, covered with copper, driven through 17 inch wood,
and nails of all sizes subjected to rough work, without the deposit
being injured. Some iron work coated in 1842, and exposed to
the atmosphere, remains in good condition still. These remarks are
also applicable to iron covered with zinc. The coating of iron with
copper has been tried in a great variety of ways for large opera.
tions, but in general these trials have, commercially, ended unsuccess
fully; the labor and cost is greater than the advantages sought will
warrant for ordinary purposes. Many years ago trials were made to
cover cast-iron with copper, and then gild or plate for ornamental
use, but only with partial success. More recently, however, a patent
has been taken out for the same purpose, and which, being one of
these applications that would be useful in beautifying and improving the taste of the community, we give an abstract of the specifition as follows:
COATING CAST-IRON WITH OTHER METALS.-" Mr.W. Newton (fot
a correspondent) has patented the coating cast-iron permanently with
copper, by depositing the copper by galvanic action, from a solu
tion' prepared by first taking a saturated solution of sulphate ol




582      THE PRACTICAL METAL-WORKER'S ASSISTANT.
copper in water and precipitating with carbonate of potash, and
then re-dissolving in cyanide of potassium, whether the copper be
deposited directly on the surface of the cast iron, or on zinc previously deposited thereon. The second part of this invention consists of coating cast-iron with the alloy of copper called brass, by
first coating the cast-iron with copper, or zinc, or both, and then
depositing the brass thereon, by galvanic action, from a solution
formed by mixing with the solution of copper employed in the first
part of the invention, a solution of zinc prepared in substantially
the same manner. The iron articles thus coated, may be subsequently coated with gold or silver, so as to give them the appearance of these latter metals. The articles of cast-iron to be coated
or plated are first to be cleansed by what is known as the'pickling' process, with dilute sulphuric acid, and then'scratch.brushed,'
as it is termed, to free the surface from scale, sand, and other foreign
substances which may not have been removed by the acid; and
after this the castings are to be immersed in dilute nitro-muriatic
acid. Any other mode of thoroughly cleansing the surface may
be substituted for that above indicated. A solution of zinc is then
prepared in the following manner:-Dissolve the sulphate of zinc
in water until the water is saturated, and precipitate by means of
prussiate of potash. The precipitate is then collected in a filter,
and re-dissolved in cyanide of potassium. This constitutes solution number one. A solution of copper is then prepared in the
same manner, by dissolving sulphate of copper in water, and precipitating with carbonate of potash: this precipitate is dissolved in
cyanide of potassium, and is called the second or copper solution.
The third, or what may be termed the brass solution, is then prepared by mixing together the first or zinc solution with the second
or copper solution, in such proportions as to produce the shade of
color required-increasing the proportional quantity of the one or
the other at the discretion of the operator. The iron castings having been thoroughly cleansed, are first immersed in the first or
zinc solution, and the galvanic battery applied in the usual manner of electrotyping  and continued until the required thickness of zinc is deposited on the surface of and caused to unite
with the surface of the cast-iron, which is a carbonate of iron.
The castings thus coated or plated with zinc, are then to be
immersed in the second or copper solution, and the galvanic battery applied, as with the first or zinc solution, and continued until
the required thickness of copper shall have been deposited. In
this way it will be found that the copper coating has become
thoroughly attached to the zinc, and the zinc to the iron, so that
they cannot be removed except by filing or cutting, as in the case
of a solid mass of copper; so that articles, of whatever form desired,
which can be made of cast-iron-that is, of carbonate of iron-can
be coated with copper, so as to answer nearly if not all the purposes to which they could be applied if made of solid copper; thus
greatly economizing the cost. After the surface of cast-iron has




COATING OF IRON WITH ZINC.               583
been coated with zinc, or with copper, or with zinc and then with
copper, which latter is much the best, if it be desired to coat it
with brass, it is to be immersed in the third or brass solution, and
the galvanic battery applied, until the required thickness shall
have been deposited. In doing this it is important that the positive pole of the battery should be made of brass, and as nearly as
practicable of the shade of the brass to be deposited; for if a copper pole be applied, it will deposit in excess the copper portion of
the solution. If desired, the brass can be deposited on the coating of zinc instead of the coating of copper; but it will be f6und
decidedly better to deposit the brass on the coating of copper,
whether the copper be deposited directly on the cast-iron or on a
coating of zinc, although the latter is the best. In this way articles
are produced, having all the appearance, and answering nearly if
not all the same purposes as if made entirely of brass, and at much
less cost. The cast-iron being thus coated with brass, the surface
may be bronzed in the usual and well-known manner of bronzing
brass; and as the process of bronzing on brass and copper is well
known, it will be unnecessary to give a detailed description of it.
The surface of the cast-iron being thus coated with brass, or with
copper, can then be coated effectually with silver or gold in any of
the well known modes of coating brass or copper with those fine
metals; it will not, however, be necessary to give the details of
such mode or modes, as they are well known in the arts. The
patentee remarks that it will be found better to deposit the silver
or gold on the brass coating than on the copper coating, on account
of the color-particularly when, from reasons of economy, it is
desired to make the coating of fine metal very thin. The patentee
claims the process herein described, or any mere modification
thereof, for coating cast-iron (carbonate of iron) with copper, by
causing the copper, from a solution such as above described, to
deposit, by galvanic action, directly on the surface of the cast-iron,
or on the zinc previously deposited thereon, as set forth. And
also the process herein described, or any mere modification thereof,
for coating cast-iron with the alloy of copper, known as brass, by
causing the brass, from a solution such as above described, to
deposit, by galvanic action, on to the surface of the cast-iron, previously coated with zinc, or copper, or both, as specified."
COATING OF IRON WITH ZINC.-In covering iron with zinc, the precautions necessary for copper are not required: zinc being the positive metal, acids have a stronger affinity for it than for iron, and
therefore an acid solution may be used. The one generally used
is the,sulphate.
SULPHATE OF ZINc.-Zinc dissolves easily in sulphuric acid, and
the solution by evaporation yields crystals of sulphate of zinc; but
as the salt is very cheap and abundant in the market, it is more
convenient and economical to buy than to make it. The solution
for depositing is made by dissolving 2 lbs of the crystallized salt
in one gallon of water. The single cell process cannot be used




584      THE PRACTICAL METAL-WORKER'S ASSISTANT.
advantageously with this solution. A separate battery is necessary,
and a zinc positive electrode. The metal is very easily deposited
-one or two pairs of Wollaston's battery being sufficient for coating small articles.
Zinc may be deposited upon black-leaded surfaces in the same
manner as copper; but, unless more than ordinary precautions are
observed, an article formed in this manner is so brittle that it can
hardly be handled without breaking, from its crystalline character.
When the deposition upon black-lead is attempted, the best method
is to have the solution saturated with salt, employing a battery of
six or seven pairs of plates, and keeping the articles on which the
deposit is taking place constantly in motion.
The use of cyanide of zinc has been recommended, but for what good
reason it is hard to know. It is unnecessary, and its use presents great
practical difficulties. The positive electrode becomes coated, after a
few minutes working, with a white pasty matter which prevents
further action and stops the current. Some of this white coating
collected, washed, and dried in the air, gave by analysis,
Oxide of zinc..51-3
Cyanogen........  17
Iron.                        trace
Potash..                     23
Carbonic acid.               278
Matter insoluble in HC1..     2-5.
Water.                       14'8
100-4
The zinc is converted into carbonate of zinc: the potash is combined with the cyanogen as cyanide of potassium.
USE OF ZINC COATING.-The principal application of zinc is
upon iron, to protect it from corrosion, which it does, not only as a
coating, but, from its more electro-positive character, it protects it
by a galvanic influence. The voltaic influence of zinc for protecting iron is a subject that has occupied the attention of practical
men for a long time; it is one of high importance: nevertheless
there seems yet a great deficiency in our knowledge of the extent
of this influence, and how and when it is effective.
Upon this subject, Professor Faraday, in the Report of the Harbors of Refuge Commissioners, states, "Zinced iron would no doubt
resist the action of sea-water so long as the surface was covered
with zinc, or even when partially denuded of that metal: but zinc
dissolves rapidly in sea-water, and after it is gone, the iron would
follow.
"As to voltaic protection, it has often struck me that the castiron piles proposed for lighthouses, or beacons, might be protected
by zinc in the same manner as Davy proposed to protect copper by
iron; but there is no doubt the corrosion of the zinc would be rapid.
If not found too expensive, the object would be to apply the zinc




INFLUENCE OF GALVANISM IN PROTECTING.          585
protectors in a place where they could be examined often, and
replaced when rendered ineffective. In this manner I have little
doubt that iron would be protected in sea-water."
INFLUENCE OF GALVANISM IN PROTECTING METALS FROM DESTRUCTION BY OXIDATION AND SOLUTION.-The galvanic influence
of one metal in protecting another is in relation to their negative
and positive qualities together with their conducting powers (p.
515). Their relations in sea-water are-silver, copper, bismuth,
antimony, iron, tin, lead, cadmium, zinc; the first the most negative,
the last the most positive in the series. So that, according to this
scale, the further apart the metals may be which are selected for
experiment, the more decided- will be the power of the positive to
protect the negative. Copper and zinc operate more strongly
together than iron and zinc.
A metal that is insoluble when placed singly in a fluid, may be
made soluble by connection with a relatively negative metal placed
in the same fluid. For example, pure zinc put into muriatic acid
is unaffected, but when connected with copper in the same fluid it
is rapidly operated upon. Or a metal may be soluble in a fluid
alone, but may be rendered insoluble by connection with a relatively
positive metal which undergoes decomposition instead. Thus: copper is dissolved in sea-water when alone, but when a piece of zinc
is connected with it, the copper is unaffected. This last effect is
the substance of Davy's method of protection alluded to by Dr.
Faraday, in applying the principle of which it is necessary to take
into consideration,
1st, The amount and power of electricity generated by the connected metals in the same fluid; and
2d, The conducting power of the metal which is being protected.
Ist. The amount and power of the electricity evolved is in proportion to the difference of the relative negative and positive condition of the metals employed. The more negative the coated metal
is, the less it requires protection, although its powers of protection
are the greatest. And the more positive the coated metal, the more
liable it is to be destroyed, and the greater the amount of electricity
required to protect it; but unfortunately it is less able to generate
this electricity when in contact with another metal. Thus these two
conditions are opposed to the application of galvanic influence for
protecting iron.
Suppose, for example, that 4 square inches of zinc, in connection
with 4 square feet of copper, give out sufficient electricity to protect the copper from sea-water, it will be found that to obtain the
same amount of electricity by iron and zinc, 2 square feet of the
latter to 4 square feet of the former are required.* Besides which,
the same quantity of electricity that protects copper will not pro* These proportions, given in round numbers, are nearly accurate; but they
vary according to the kind of iron, the state sf the water, the distance of tbs
metals, etc.




686      THE PRACTICAL METAL-WORKER'S ASSISTANT.
tect iron; nor will any quantity of zinc protect iron from corrosion
in sea-water-even a bar of iron placed in a zinc vessel filled with
sea-water is not completely protected.
2d. The conducting power of the negative or protected metal subFig. 580.            jected to submarine im
mersion is a subject of very
great importance. Suppose
Z id~     e Nc~~  - b-             a piece of copper and a
b     =-_               piece of zinc be connected
under a solution — say a
c                  copper bar (c) 4 feet long,
with a piece of zinc (z) 4 inches in length, erected on one end, as in
the annexed sketch:
The conducting power of the copper is so much superior to that
of the solution that the whole length of the bar will become instantly negative, and the current of electricity will pass to and from
all parts of the bar at the same time in the lines b, b, b; but the current will be more active towards the point of contact than towards
the distant extremity-the resistance of the solution being less in pro
portion to the proximity of the metals. But if a bar of iron, and a
piece of zinc as a protector, be placed in the same circumstances,
the phenomena assume quite a different aspect: the conducting
power of iron being much less than that of copper, the distant extremity will not be affected by the electric current, which will find
a more easy passage, as indicated by the dotted lines e, e, e. beyond
which the electric effort ceases; and even in that portion of the bar
which is under the influence of the current, the part nearest the
zinc is better defended than those parts which are farther distant. This partial protection, while it induces a negative state at
the near end, renders the other end more positive. Such a diversity of condition gives rise to voltaic action between the two extremities of the bar, and the result is the destruction of the far
end. In all cases of voltaic protection the more equal the influence over the whole surface protected, the more perfect is the protection. An inequality of protection, such as we have described,
is productive of numerous evils. It is, we believe, the source of
many of the injuries occurring in our day to copper sheathing.
One part of a sheet becoming, by some local cause, negative, the
other parts are thus rendered positive; the result is, that upon the
lborders of an individual sheet either overlapping or underlying its
neighboring sheet, an electric current is excited, passing through
the stratum of moisture which may intervene, and the ultimate
effect is that the positive edge is dissolved as effectually as if cut
by a knife. The evil arising in one place may be so contagious as
to affect a whole neighborhood-sometimes the whole side of a
ship's bottom.
In fresh water iron cannot be protected any length of time, for
the zinc coating speedily passes into a blackish substance, which
peels off and exposes the iron to rust. When iron is simply ex



ELECTRO-PLATING.                  587
posed to the air, a good coating of zinc is a sure protection. We
have seen iron of various qualities coated by the electro-procoesses
and exposed to the atmosphere, in all weathers, for several years,
without being more affected than a piece of zinc would be. In
spots where abrasion has taken place by accident, the protecting
power of the zinc is lost, and the iron rusts as if there were no zinc
present. No other result, however, could be anticipated, as there
can be no electric excitation without a liquid to connect the two
metals.
The iron to be coated by zinc is to be cleaned and prepared in
the same manner as we have described for the purpose of covering
it with copper (page 579).
CHAPTER XXX.
ELECTRO-PLATING.
THrE next applications of the electro-deposition we have to
notice are those relating to silver and gold, embracing the arts of
electro-plating and gilding- arts which are gradually revolutionizing some extensive branches of manufacture, having the same
object but acting by a different means.
To MAKE SILVER SOLUTION.-The solution of silver used for
plating consists of cyanide of silver dissolved in cyanide of potassium which may be prepared in various ways. We shall first describe some of the preparations most in use, and also point out
practical objections which, in special cases, have occurred under our
own observation, not omitting to specify and recommend those
methods which have approved themselves to us as being most
simple and effective.
The method generally adopted is as follows: —Metallic. silver is
dissolved in four parts of nitric acid, diluted with one part of water:
the diluted acid is heated in a vessel, and the silver is added by
degrees. The operator must avoid breathing the fumes which
ascend, as they are highly deleterious. The metal being dissolved,
the solution is transferred to a large vessel, and diluted with water.
To this is added a solution of cyanide of potassium so long as a
white precipitate is formed. This precipitate is cyanide of silver,
and the action which ensues may be thus represented:
Substances used:            Substances produced:
Nitrate of silver = AgO, NO5' Nitrate of potash = KO, NO'
Cyanide of potassium=- KCy  Cyanide of silver = AgCy
AgO, N05 +KCy-KO, NO5 +AgCy
The propriety of diluting the nitrate of silver before precipitat
ing by the cyanide of potassium arises from the fact, that the salts
of potash and soda (such as the nitrates, chlorides and sulphates),




588       THE PRACTICAL METAL-WORKER'S ASSISTANT.
when in strong solution, dissolve small quantities of the silver salt,
and thus cause a loss, which is prevented by previous dilution with
water.
When the precipitate of cyanide of silver has settled, the clear
solution is carefully decanted, and the vessel filled up with water,
which is again decanted as soon as the precipitate has settled. This
process is to be repeated three or four times, so as effectually to
wash out the soluble salts. When properly washed, a solution of
cyanide of potassium is added to the precipitate, until it is all dissolved. The resulting solution constitutes the cyanide of potassium
and silver, and forms the plating solution. It ought to be filtered
previous to using, as there is always formed a black sediment, composed of iron, silver, and cyanogen, which, if left in the solution,
would fall upon the surface of the article receiving the deposit, and
make it rough. The sediment, however, must not be thrown away,
as it contains silver. The cyanide of potassium, used to dissolve
the cyanide of silver, may be so diluted that the plating solution,
when formed, shall contain one ounce of silver in the gallon: of
course the proportion of silver may be larger or smaller, but that
given is what we consider best for plating.
In dissolving 100 ounces of silver, the following proportions of
each ingredient are those which we have found in practice to be the
best. Take 7 pounds of the best nitric acid* and 61 ounces of
cyanide of potassium, of the average quality described at page 576;
this quantity will precipitate the 100 ounces of silver dissolved in the
acid solution. After this is washed, take 62 ounces more of cyanide
of potassium, the solution of which will dissolve the precipitate:
this being done, the plating solution is then formed. Of course,
these proportions will vary according to the difference in the quality
of the materials; but they will serve to give an idea of the cost of
the silver solution prepared in this manner.
CYANIDE OF SILVER DISSOLVED IN YELLOW PRUSSIATE OF POTASH.-WWe have occasionally dissolved the cyanide of silver by
yellow prussiate of potash, three pounds of which are required to
dissolve one ounce of silver. This forms an excellent plating solution, and yields a beautiful surface of silver. It must have a weak
battery power, and consequently the silver is very soft. The positive electrode does not dissolve in this solution: there is formed
upon its surface a white scaly crust, which drops off and falls to
the bottom; and the solution soon becomes exhausted of silver.
SOLUTION MADE WITH OXIDE OF SILVER.-It has been recommended to dissolve the oxide of silver in cyanide of potassium,
which forms a solution of cyanide of potassium and silver; but this
preparation is less economical, because the materials used in converting the silver into an oxide are lost: it requires the same amount
* The nitric acid must be free from hydrochloric (muriatic) acid: to a small
tuantityof the acid add a few drops of solution of nitrate of silver; if it gives a
milly white precipitate, it contains muriatic acid, and should be rejected.




ELECTRO-PLATIR G.                589
of cyanide of potassium as the process just described, and brings,
moreover, an equivalent of potash into the solution, which is a disadvantage. The following diagram shows the reactions that occur:
Substances used:            Substances produced:
Oxide of silver -=  AgO  Potash = KO
Cyanide of potassium =  KCy  Cyanide of silver  _KCy AgCy
Cyanide of potassium =  KCy    and potassiuln    K      Ag y
AgO + 2 KCy = KO + KC, AgCy.
SOLUTION MADE WITH CHLORIDE OF SILVER.-The nitrate of
silver may also be precipitated by adding a solution of common
salt to it, and treating it in the same way as described for precipitation by cyanide of potassium: this would form chloride of silver,
which may be dissolved in cyanide of potassium, thus forming the
silver solution. But the objection urged against the use of oxide
of silver is equally applicable in the case of chloride; and much
greater care is required in precipitating large quantities and strong
solutions of silver by common salt, than by cyanide of potassium,
the chloride of silver being more soluble in the salts of the alkalies-as the nitrates, chlorides, and sulphates-than cyanide of
silver is; and there is therefore great liability to loss by this
process, in which we have not the redeeming quality of a saving
of materials, as the following diagram will show:
Substances used:           Substances produced:
Chloride of silver    = AgC1 Chloride of potassium   = KC1
Cyanide of potassium = KCy   Cyanide of silver' _CyA
Oyanide of potassium = KCy   and potassium        CyAgCy
AgCl +2 KCy = KC1 + KCy, AgCy.
Thus, we observe, that the action taking place is not mere solution, but decomposition; which upon one hundred ounces of silver
in this preparation produces an impurity of seventy ounces of
chloride of potassium, which, although not very injurious to the
solution, would be much better away.
THE BEST METHOD OF MAKING SILVER SOLUTION.-The best
and cheapest method of making up the silver solution is by the
battery, which saves all expense of acids and the labor of precipitation. This is effected by taking advantage of the principle of
non-transfer of metal in electrolytes (see page 561). To prepare a
silver solution which is intended to have an ounce of silver to the
gallon (see p. 588), observe the following directions: Dissolve 123
ounces of cyanide of potassium in 100 gallons of water; get one
or two flat porous vessels, and place them in this solution to within
half an inch of the mouth, and fill them to the same height with
the solution; in these porous vessels place small plates or sheets
of iron or copper, and connect them with the zinc terminal of a
battery: in the large solution place a sheet or sheets of silver colnnected with the copper terminal of the battery. This arrangement




590      THE PRACTICAL METAL-WORKER'S ASSISTANT.
being made at night, and the power employed being two of Wol.
laston's batteries, of five pairs of plates, the zincs 7 inches square,
it will be found in the morning that there will be dissolved from
60 to 80 ounces of silver from the sheets. The solution is now
ready for use: and by observing that the articles to be plated have
less surface than the silver plate forming the positive electrode,
for the first two days, the solution will then have the proper
quantity of silver in it. We have occasionally found a little silver
in the porous cell: it is therefore not advisable to throw away the
solution in them without first testing it for silver, which is done by
adding a little muriatic acid to it.
The amateur electrotypist may, from this description, make up
a small quantity of solution for silvering his medals or figures.
For example, a half-ounce of silver to the gallon of solution will
do very well; a small quantity may be prepared in little more
than an hour.
As the cyanide of potassium dissolves silver without the aid
of a battery, by merely allowing a piece of silver to steep in
this solution for a few days, a plating liquor may be formed;
but this is tedious and uncertain, although for small operations,
and where porous vessels are not convenient, it will serve the
purpose.
Other solutions of silver may be employed if the law stated at
page 575 is strictly observed. Indeed, every salt of silver has not
only been tried, but is either the subject of a patent, or prominently included in it. None of them, however, with the exception
of'two, have we found of any practical value, besides that already
described: these are the chloride of silver dissolved in hyposulphite of soda, and the sulphite of silver dissolved in sulphite of
potash or sulphite of soda.
HYPOSULPHITE OF SILVER SOLUTION. —The simplest method
known to us for forming the hyposulphite of silver solution is this:
Take one pound of pure carbonate of soda, well dried, as described at page 576; mix it intimately with five ounces of flour
of sulphur; place the mixture over a slow fire without flame in a
porcelain or stoneware basin, which must be supported by an iron
trelis, or any convenient support, to prevent it touching the red
coal or flame; keep the mixture constantly stirring, and maintain
the heat till the sulphur melts, and the mass inclines to get pasty
and rough. While in this state keep stirring for about fifteen
minutes, in order to bring every part in contact with the air. Set
the mixture to cool-after which dissolve in water. Boil the solution for some time, adding sulphur; then filter it, and allow it to
evaporate at a slow heat. The crystals formed are hyposulphite
of soda.
To prepare the silver solution, the silver is first dissolved in
nitric acid, and then precipitated by a solution of common salt,
and washed, with the precautions stated at page 587. When the
precipitated chloride of silver is well washed, some of the crystals




ELECTRO-PLATING.                     091
of hyposulphite of soda are dissolved, and the solution is added t6
the chloride of silver, which it dissolves, forming the plating solution. It is not necessary to crystallize the hyposulphite of soda,
if used as soon as made.
The hyposulphite of silver solution is very easily decomposed
by the electric current, so that a weak battery will suffice to plate
by it: but its great objection is its liability to decompose in the
light, and to deposit the silver as sulphuret: unless great care is
exercised, the silver deposited from it will be in a granular condition, which is a great objection in plating.
SULPHITE OF SILVER PLATING SOLUTION. —The sulphite of
silver solution is prepared in the following manner, as described
by the patentee of the process:
"The solution which I use is made in the following manner: I
take of the best pearl-ash of commerce 28 lbs (avoirdupois) and
add to it 30 lbs (avoirdupois) of water, and boil them in an iron
vessel until the pearl-ash is dissolved; the solution should then be
poured into an earthenware or other suitable vessel, and suffered
to stand until the liquor becomes cold. It should then be filtered,
and 14 lbs (avoirdupois) of distilled water added thereto; sulphurous
acid gas (obtained by any of the known processes) should then be
passed into the filtered liquor until it is saturated, taking care not
to add sulphurous acid gas in excess. The liquor should be again
filtered, and the liquor so filtered is what I term the solvent) or
sulphite of potash.
"To make the silvering liquor which I use in coating with silver
the surface of articles formed of metal or
metallic alloys, I dissolve 12 oz. (avoir-     Fig. 581.
dupois) of crystallized nitrate of silver
in 3 lbs. of distilled water (in a clean
earthenware vessel), and add to the solution, by a little at a time, the beforementioned solvent, so long as a whitish
colored precipitate is produced (care
being taken not to add more of the
solvent than is necessary). After the
precipitate has subsided, I pour off the
supernatant liquor, and wash the precipitate with distilled water. To the
precipitate I add as much of the beforementioned solvent as will dissolve it,
and afterwards add about ~th part more    i1 P11(1
of the solvent, so that the solvent may
be in excess; I then stir them well together and let them remain
about 24 hours, and then filter the solution, when it will be ready
for use. This is what I designate silvering liquor."*
Sulphurous acid gas for making the above liquor may be pre* Repertory of Patent Inventions, 5th series, p. 210, 1843.




592      THE PRACTICAL METAL-WORKER'S ASSISTANT.
pared by heating sulphuric acid, undiluted, in a flask or any convenient vessel, to which should be added small pieces of copper or
charcoal: the gas escaping is made to pass into the solution to be
saturated with it.
Fig. 581 is a very convenient apparatus for the preparation of
this gas for saturating solutions.
This solution is also very easily decomposed by the electric current, and serves the purposes of plating very well; but it is also
liable to decomposition by light, and is not so good in practice as
the solution of cyanide of potassium and silver. The latter solution is, however, liable to a kind of decomposition not yet fully
investigated, but it is wholly confined to its impurities, and it never
deposits its silver; whereas the decomposition that takes place in
the sulphite or hyposulphite affects the silver compound, and precipitates the silver from solution.
To RECOVER SILVER FROM SOLUTION.-When a silver solution
gets out of order, and cannot be rendered fit for use again, the
silver may be recovered by adding to the solution any acid that
will neutralize the alkali; if nitric or sulphuric acid be used, the
silver precipitates as cyanide, but if hydrochloric acid be used, the
silver will be precipitated as a chloride: in either case the solution
should be diluted, or a portion of the precipitate will be re-dissolved.
The precipitate is allowed to deposit, the clear liquor decanted, and
the vessel filled with water to wash the precipitate, which is afterwards collected upon a filter and dried, and then mixed with twice
its weight of carbonate of potash, and fused in a Hessian crucible
for 15 minutes, or until the fused fluid ceases to effervesce. On
removing the crucible, and pouring the whole into an iron ladle,
when cool the silver will be found in the metallic state at the bottom of the ladle.
In these operations when pouring the acid into the cyanide
solution, great care must be taken not to inhale the fumes given
off, which are very abundant, sickening, and poisonous. The
operation should be done in the open air, and even then it is bad.
Instead of throwing down the silver by an acid it is better to evaporate the solution to dryness, and to fuse the product as described;
in which case the cyanide is an excellent reducing flux, requiring
no addition of carbonate of potash, and saves the necessity of evolving poisonous fumes.
When the solution has contained yellow prussiate of potash, it
is found that during this fusion portions of the metal sometimes
form a scoriaceous nodule at the bottom of the crucible, and all the
heat that can be applied by an ordinary assay furnace will not fuse
it. This refractory piece, when cooled, has generally a rough
scoriaceous surface, and is exceedingly hard. When filed it has more
the color of German silver than of real silver; it has considerable
malleability, and retains its bright appearance for a long time witEout tarnish. An analysis of this alloy gave —




ELECTRO-PLATING.                  593
Silver.                 82'15
Copper.......   9'12
Iron.....                 7'50
Carbonaceous matter..   *46
99'23
If we suppose the carbonaceous matter to be an accidental impurity, this alloy will nearly agree with the formula AgS Cu Fe.
PREPARATION OF ARTICLES FOR PLATING.-Articles that are to
be plated are first boiled in an alkaline ley, to free them from
grease, then washed from the ley, and dipped into dilute nitric
acid, which removes any oxide that may be formed upon the surface; they are afterwards brushed over with a hard brush and sand,
of which a kind obtained from the Isle of Wight, and known as
silver-sand is best. The alkaline ley should be in a caustic state,
which is easily effected by boiling the carbonated alkali with slaked
lime, until, on the addition of a little acid to a small drop of the solution, no effervescence occurs. The lime is then allowed to settle, and
the clear liquor is fit for use. The ley should have about half-apound of soda-ash, or pearl ash, to the gallon of water. The nitric
acid, into which the article is dipped, may be diluted to such an
extent that it will merely act upon the metal. Any old acid will
do for this purpose. In large factories the acid used for dipping
before plating is generally afterwards employed for the above purpose of cleaning.
The article being thoroughly cleaned and dried, has a copper
wire attached to it, either by twisting it round the article or putting
it through any open part of it, to maintain it in suspension. It is
then dipped into nitric acid as quickly as possible, and washed
through water, and then immersed in the silver solution, suspending it by the wire which crosses the mouth of the vessel from the zinc
of the battery. The nitric acid generally used and found best for
dipping has a specific gravity 1'518, contains 10 per cent. sulphuric
acid, and is got at about 6 cts. per lb. The article is instantaneously
coated with silver, and ought to be taken out after a few seconds
and well brushed. On a large scale, brushes of brass wire attached
to a lath are used for this purpose; but a hard hair brush with a
little fine sand will do for small work. This brushing is used in
case any particle of foreign matter may be still on the surface. It
is then replaced in the solution, and in the course of a few hours a
coating of the thickness of tissue-paper is deposited on it, having
the beautiful matted appearance of dead silver. If it is desired to
preserve the surface in this condition, the article must be taken
out, care being taken not to touch it by the hand, and immersed in
boiling distilled water for a few minutes. On being withdrawn,
sufficient heat has been imparted to the metal to dry it instantly. If
it is a medal, it ought to be put in an air-tight frame immediately,
or if a figure, it may be at once placed under a glass shade, as a
38




59,4:     THE PRACTICAL METAL-WORKER'S ASSISTANT.
very few days exposure to the air tarnishes it, by the formation of
sulphuret of silver, and that more especially in a room where there
is fire or gas. If the article is not wanted to have a dead surface,
it is brushed with a wire brush, and old ale, beer, or water containing in solution a little gum, glue, or sugar, but the amateur may use
a hard hair brush. It may be afterwards burnished according to
the usual method of burnishing, by rubbing the surface with considerable pressure with polished steel or the mineral termed blood.
stone.
We may remark, that in depositing silver from the solution, a
weak battery may be used; though when the battery is weak the
silver deposited is soft, but if used as strong as the solution will
allow, say 8 or 9 pairs, the silver will be equal in hardness to rolled
or hammered silver. If the battery is stronger than the solution
will stand, or the article very small compared to the size of the
plate of silver forming the positive electrode, the silver will be deposited as a powder. The average cost of depositing silver in this
way is 4 cts. per ounce. Gas should never be seen escaping from
either pole: and the surface of the article should always correspond
as nearly as possible with that of the positive electrode, otherwise
the deposit runs the risk of not being good; it requires more care,
and the solution is apt to be altered in strength, because if the
positive electrode be large compared with the negative, the solution will become stronger in silver, while if smaller in proportion
the solution will become exhausted of silver.
In plating large articles (such as those plated in factories), it is
not always sufficient to dip them in nitric acid; wash and immerse
them in the solution, in order to effect a perfect adhesion of the
two metals. -To secure this, a small portion of quicksilver is dissolved in nitric acid, and a little of this solution is added to water,
in sufficient quantity to enable it to give a white silvery tint to a
piece of copper when dipped into it: the article then, whether made
of copper, brass, or German silver, is, after being dipped in the
nitric acid. and washed, dipped into the nitrate of mercury solution
till the. surface is white: it is then well washed by plunging it into
two separate vessels containing clean water, and finally put into
the plating solution. This secures perfect adhesion of the metals.
One ounce of quicksilver thus dissolved will do for a long time,
though the liquor is. used. every day. When the mercury in this
solution is exhausted, it is. liable to turn the article black upon
being dipped into it: this must be avoided, as in that case it also
causes the deposited metal to strip of.
PRACTICAL INSTRUCTIONS IN PLATING.-We need hardly add
that it is necessary that the battery should be so arranged, that the
quantity of electricity generated should correspond with the surface of the articles to be coated, and that the intensity should bear
reference to the state of the solutions; that is to say, that the
quantity should be sufficient to give the required coating of metal
in a.given time, and the intensity such.as to cause the electricity to




ELECTRO-PLATING.                   595
pass through the solution to the articles. It is also essential for
regular working, as stated above, that the plates of metal forming
the positive pole in the solution should be of corresponding surface to the articles to be coated, and face them on both sides.
The following is the arrangement adopted in some of the large
plating manufactories:-The vat, or plating vessel measures about
61 feet in length, by 33 inches in breadth, and 33 inches in depth,
and generally contains from 200 to 250 gallons of solution; the
silver plates serving as electrodes, which were formerly nailed
upon frames of wood, are now generally fixed upon light iron
frames, these not being affected by the solution: two battery
troughs are arranged as seen in Fig. 582, consisting of 6 batteries
of three pairs intensity. The zinc plates immersed in the acid
measure 6 inches by 7 inches, the exposed surfaces of which
measure 84 square inches: these multiplied by 6 give 504 square
inches, from which electricity is disengaged. The surface of the
silver electrodes exposed to the-articles receiving the deposit vary
from 3000 to 4000 square inches of surface.
The following figure, with explanation, will illustrate these observations:
Fig. 582.
A,Vat orvessel containing the solution; B, Battery with zinc pole
z, connected with rods R R; and copper pole c, connected with the
metallic sheets P P, in the solution, by means of the copper slip F;
D D, are articles suspended in the solution by wires from the rods
B R; S, the solution. So soon as the articles, which are connected
with the negative pole of the battery, and the metallic sheets, con



596      THE PRACTICAL METAL-WORKER'S ASSISTANT.
nected with the positive pole, are both immersed in the solution,
the galvanic circuit is completed.
In most plating establishments the batteries are now placed out.
side the house, and the connecting rods are brought from them into
the vats, so as to preserve the workmen from the injury arising
from inhaling the hydrogen gas which is given off by the zincs, as
it often contains arsenic, and hence is highly injurious to health;
the gas of the battery has a strong effect upon the nostril, exciting
dryness with pain. Wherever the batteries are placed, they should
not be exposed to cold, as their operation is much affected by the
temperature.
In the early days of electro-plating the batteries used were round.
They consisted of a copper cylindrical vessel, about 20 inches deep,
and 5 inches diameter, filled with dilute sulphuric acid. A piece of
wood was placed at the bottom of this vessel, and a cylinder of zinc,
the same depth as the copper vessel, and about 3 inches diameter,
was placed inside the copper vessel. A wooden ring, floating on
the surface of the acid, prevented the zinc and copper touching-a
binding screw was attached to each, and formed a battery of a single
pair. Six batteries of this size were connected with such a vat as is
described above. The test of strength employed to determine
whether the working power was sufficient, was that, when connected
with an electro-magnet, it should support a 7 lb. weight. We believe that many platers and gilders still use such batteries, and that,
when the solutions and apparatus are all in good condition, they do
well. They are, however, far from being so economical as the battery with square plates shown above. Some electro-metallurgists
use large and deep stoneware vessels in which are placed the zinc
and copper-the plates having several square feet of surface. We
have already shown, when treating of batteries, that very large
plates are not consistent with economy.
To ascertain the amount of metal deposited, it is only necessary
to weigh the articles carefully before and after plating. But between the first weighing and the immersion of the articles in the
plating solution there is the dipping into nitric acid to be accounted for: this, on an average, will cause a loss of about one
pennyweight upon an article of the size of a foot square; thus, if a
waiter of a foot square, made of copper or German silver, shows,
when coated, a difference in weight of 19 pennyweights, the silver
laid on must be estimated at an ounce, or 20 pennyweights. When
the article is a "replate," i. e., an old plated article that has become
bare of silver in parts, the allowance or reduction for the dipping in
the acid is only to include the portions left bare, for the silvered
parts are not acted upon by it. One of the practical difficulties
which the inexperienced will occasionally meet with when a " replate" is dipped in the nitric acid, is, that a galvanic action is produced between the silver and the copper portions, which causes a
black line round the edge of the silver:- this ought immediately to
be rubbed off, but even with rapid and careful rubbing there is




ELECTRO-PLATING.                    597
great danger that the coating will loosen and blister at those parts;
and beside this, it happens that the parts of the "replate" which
are sound, the silver not being acted upon by the acid, but rather
protected by the galvanic action, are not in a fit state to receive and
maintain a perfect adhesion of the deposit, and therefore the risk is
great that the new coating will separate from the old, or, in technical
language, that the part will strip.  Under these circumstances
experience has taught that the best way to proceed is to take all
the old silver off the article, and deposit an entirely new coating.
There are two methods of taking off the silver:
TAKING SILVER FROM COPPER, ETC. —First, stripping or dissolving
it off; this is done by putting into a stoneware or copper pan some
strong sulphuric acid (vitriol), to which a little nitrate of potash is
added: the article is laid into this solution, which will dissolve the
silver without materially affecting the copper; saltpetre is added
by degrees, as occasion requires; and if the action is slow a little
heat is applied to the vessel. The silver being removed, the article
is washed well and then passed through the potash solution, and
finished for plating. When the sulphuric acid becomes saturated
with silver it is diluted, and the silver is precipitated by a solution
of common salt: the chloride of silver formed is collected and fused
in a crucible with carbonate of potash, when the silver is obtained
in a metallic state, as a knob or button. The crucible should not
be over two-thirds full and should be kept in fusion till effervescence
ceases. The crucible is then removed from the fire, and, when cool,
it is broken.
The article thus stripped by acids often shows a little roughness,
not from the effects of the acid, but because the copper under the
silver has not been polished; it is therefore a necessary practice in
the electro-plating factories to polish the articles before plating.
This is done by means of a circular brush, more or less hard as required, fixed upon a lath, and a thin paste made of oil and pumicestone ground as fine as flour. By this process the surface of any
article can be smoothened and polished; but a little experience is
required to ensure success, and enable the operator to polish the
surface equally without leaving brush marks. We need scarcely
say, that after this process the article must be cleaned in potash
before it is plated.
Second Method.-Instead of stripping off the silver by means of
acid, it is a more common and preferable mode to brush off the
silver by the operation just described. In this case the brushings
must be collected, dried, and burned; this may be done in an iron
pan, keeping it at a red heat until all carbonaceous matters are
consumed, the remainder is fused with carbonate of soda or potash,
when the silver is obtained, in combination with a little copper.
CYANIDE OF SILVER AND POTASSIUM, ITS DECOMPOSITION DURING THE PLATING PROCESS.-The silver salt in the plating solution
is a true double salt, being, as already described, a compound of
one equivalent of cyanide of silver, and one of cyanide of potassium




598      THE PRACTICAL METAL-WORKER'S ASSISTANT.
-two distinct salts. In the decomposition of the silver solution
by the electric current, the former, cyanide of silver, is alone
affected: the silver is deposited, and the cyanogen passes to the
positive plate or electrode. The cyanide of potassium is therefore
set at liberty upon the surface of the article receiving the silver
deposition, and its solution being specifically lighter than the general mass of the plating solution, rises to the top: this causes a
current to take place along the face of the article being plated. If
the article has a flat surface, suppose that of a waiter or tray, upon
which a prominence exists, as a mounting round the edge, such as
a gadroon, see Fig. 583, it will cause lines and ridges from the botFig. 583.    tom to the top, as already described at page
561. Newly-formed solutionsaremost subject to produce this annoyance.
OTHER EFFECTS PRODUCED IN WORKING.
-As the cyanogen combines with the silver
plate forming the positive electrode, it is dissolved by the free cyanide of potassium,
which the solution must have; and, being
specifically heavier, sinks to the bottom, by
which a current downwards is excited: this
is of no greater annoyance than that it reny ( ~'ti'1i!l1   ders the -solution of unequal density, which
in its turn yields an unequal deposit, more
being laid upon the lower parts of the
article than on the upper: the silver plate
gI'y ll       l  also is destroyed more rapidly at the bottom
than at the top, except at the surface of the
solution, if the silver be above it, where the
plate gets cut through. In a new solution,
which contained 11 ounces of silver to the gallon, we have found,
just before taking out the articles, that the top part of the solution contained 200 grains of silver less, and the bottom part 2.00 grains more
per gallon, than when the articles were put into it. These difficulties
and annoyances may, however, be nearly surmounted by keeping the
articles in motion: agitating or stirring the solution occasionally
would also obviate these annoyances; but this is not advisable, for
if the sediment (which always forms) were stirred up it would settle
upon the face of the articles and make them rough. Where there is
engine power it is an easy matter to keep the articles in motion;
but where this power is not available, a very simple apparatus, invented by Mr. Alexander Mitchell, of Glasgow, may be fitted up at
a trifling cost, to give the necessary motion by clockwork. The
annexed sketch exhibits this apparatus.
MACHINE FOR MOVING GOODS WHILE SUBJECTING TO THE ELEC-'RO-PLATING PROCESS.-Fig. 584, side elevation, with front frame
off;. Fig. 585, end elevation of that part of front frame where the
fly is held; Figs. 586 and 587, the plating vat, with frame moving
on inclined plane.




ELECTRO-PLATING.                  599
The large wheel A, Fig. 585, is propelled by a weight suspended
from the roof by a card which winds round its barrel, the same as
common clockwork. The circumference is studded with small pins
which catch the arm B, moving it in a downward direction, and
consequently moving the arm c in a forward direction. The latter,
being attached to the frame by a small rod R, Figs. 585 and 587,
moves it up the inclined plane E, Fig. 587, until the pin fixed in
the wheel A passes the end of the arm B. The frame then moving
down the incline E, brings B in gear with the next pin, and the
same motion again takes place, and so on successively. The speed
Figs. 584                585.
Figs. 584                           586.the train moving in an enless screw fitte on the
is regulated by the train moving in an endless screw fitted on the
last wheel of the arbor of a fan. The four holes in Fig. 585 are
for bolts or pillows for screwing the two frames together. The
frame has four pulleys and inclines, the latter adjustable to a
greater or less degree by the screw and grove at E.
DEPOSIT DISSOLVING OFF IN SOLUTION.-In depositing any
metal, but more particularly such as require solutions having an
excess of the solvent, such as of cyanide of potassium in the depositing of gold and silver, care should be taken that nothing stops




600      THE PRACTICAL METAL-WORKER'S ASSISTANT.
the current of electricity suddenly, while the article being deposited
upon remains in the solution, otherwise the metal deposited will
speedily dissolve off. This we have often experienced, and many
others have no doubt done. the same. Indeed, we have seen a
beautiful deposit going on, and left the operation with great hope
of excellent results, but on returning shortly after have found the
whole dissolved off. And often, when the process was apparently
going on well, and the articles had been in the solution the usual
time to receive a fair coating of metal, upon taking them out and
weighing them there was hardly any perceptible difference from
the original weight-in short, there had been no material deposit.
These phenomena will be found to occur with the greatest frequency when the solutions and the batteries are in the best condition for working, and when the article upon which the deposit
is going on, and the pole or plate of metal forming the positive
Fig. 586.
TROUCG OR VAt
Fig. 587.8      7.RAME
Fig. 587.  -    FRAME. 
VAT                  I
electrode are at a considerable distance from each other. But before explaining what we consider to be the cause of these annoyances we will refer to another phenomenon connected with
them.
OPPOSITE CURRENTS OF ELECTRICITY FROM VATS.-If, under
the circumstances referred to, and when the deposit has gone on for
some time, the wires connecting the battery with the electrodes in
the depositing solution be disconnected from the battery, and their
two ends be joined together, a current of electricity nearly as
strong as that from the battery will pass through the wires, but
in the opposite direction from that which was obtained by the battery; and if two pieces of metal were attached to these wires and
put into a solution of copper, or any metal, a deposition would




ELECTRO-PLATING.                   601
occur, the original electrodes now constituting a battery in relation
to this second decomposition cell: the current, however, would
gradually weaken until it ceased. The cause of all these actions
and reactions is this: The article being plated with silver in connection with the battery, exhausts the solution of silver around it,
leaving free cyanide of potassium in solution, while around the
sheet of silver which is serving as the positive electrode, the solution is on the contrary becoming saturated with silver, so that we
have all the conditions necessary to constitute a battery, having
silver in two kinds of solution-the one capable of dissolving
silver, the other not. In these conditions lies the source of the
annoyances described above. From the moment the deposition of
metal begins, there also arises an opposite current of electricity,
tending to neutralize the effects of the battery, which current goes
on increasing in quantity until the two currents neutralize each
other, or it may be until the current from the trough overpowers
that from the battery. In the latter case, as we have said, there
may, at the termination of the ordinary period, be little or no
silver deposited on the articles intended to be plated. Motion in
the silver or depositing solution will prevent all these annoyances; and this being now generally adopted, these phenomena are
not now observed, but the effects take place less or more in every
solution.
TEST FOR THE QUANTITY OF FREE CYANIDE OF POTASSIUM IN
SOLUTIONS.-It has been already mentioned that the cyanide of
silver, as it forms upon the surface of the silver plate, is dissolved
by the cyanide of potassium. T'his renders it necessary to have
always in the solution free cyanide of potassium. Were we to
use the pure crystalline salt of cyanide of potassium and silver,
dissolved in water, without any free cyanide of
potassium, we should not obtain a deposit be-     Fig. 588.
yond a momentary blush; as the silver plate or
electrode would get an instantaneous coating of    a
cyanide of silver, and this not being dissolved
the current would stop. The quantity of free
cyanide of potassium required in the solution
varies according to the amount of silver that is
present, and the rapidity of the deposition. If
there be too little of it, the deposit will go on
slowly; if there be too much, the silver plate
will be dissolved in greater proportion than the
quantity deposited, and the solution will consequently get stronger. The proportion we have
found best is about half by weight of free cyanide
of potassium to the quantity of silver in solution;
thus, if the solution contains two ounces of silver
to the gallon, it should have one ounce of free
cyanide of potassium per gallon. This is known
by taking some nitrate of silver, dissolving it in distilled water




602      THE PRACTICAL METAL-WORKER'S ASSISTANT.
and placing it in a common alkalimeter, graduated into 100 parts,
Fig. 588. The proportion of the nitrate of silver in the solution is
that every two graduations of the solution should contain 1 grain.
A given quantity of the plating solution is now taken-say 1 ounce
by measure, and the test solution of nitrate of silver is added to it
by degrees, so long as the precipitate formed is redissolved. When
this ceases the number of graduations is then noted, and the following equation gives the quantity of free cyanide. Every 175 nitrate
of silver are equal to 130 cyanide of potassium in solution. Suppose 20 graduations were taken, equal to 10 grains nitrate of silver,
then 175: 130:: 10: 7.4 grains free cyanide of potassium. This,
multiplied by 160, the number of fluid ounces per gallon, will make
about 2j ounces. We have taken 2 graduations to one grain of
nitrate of silver, that the solution may be considerably dilute and
less liable to error. The following table is calculated at a half
grain nitrate of silver to the graduation, and will be a guide to the
student or workman. The quantity of solution tested is one ounce
by measure.
Number of                    Free cyanide per gallon.
graduations used.                 oz. dwt.  gr.
1.......... 0 2 13
2                           0    5    3
3                           0    7   16
4... 0 10 6
5..                         0 12 19
6                           0   15    9
7.0 17 22
8.1.........   1     0   13
9..1 3 1
0.. I1 5 12
11.1 8 5
12..........               1   10  19
13....1.....113 8
14............ I 15 22
15..........18 11
16..........2 1 2
17.......... 3 14
18............ 2 6 2
19.... 2 8 11
20.2 11 0
Another method may be adopted. If, for instance, we dissolve
a small quantity of sulphate of copper and add to it an excess of
ammonia, there is produced a deep blue color. Cyanide of potassium will destroy the blue color, in a fixed chemical proportion.
To obtain this proportion, take ten grains of pure cyanide of potassium and dissolve in water; then take a certain quantity, say
100 grains, of sulphate of copper and convert it into ammoniuret,
the whole measuring a given quantity, and pour from an alkalime




ELECTRO-PLATING.                   603
ter this blue liquor into the cyanide of potassium till it ceases to
destroy the color, then mark the number of graduations required,
and that amount of copper solution will represent 10 grains cyanide
of potassium-a quantitative test will thus be got for the full cyanide of potassium in the solution, and should be used as follows:
Say that the color of 60 graduations of the blue solution was destroyed by the 10 grains of cyanide of potassium, then to test the
quantity of free cyanide of potassium in the plating solution, take
60 graduations of the blue liquor in any convenient vessel, and
add to it from an alkalimeter the plating solution till the color of
the blue liquor is destroyed, then note the quantity which contains
10 grains free cyanide, from which the quantity in the whole
solution may be calculated.
RATE OF DEPOSITING SILVER.-When articles are taken out of,the solution they are swilled in water, and then put into boiling
water. They are afterwards put into hot sawdust, which dries
them perfectly. Their color is chalk-white. They are generally
weighed before being scratch-brushed; that is, brushed with the
fine wire brushes and stale beer as already described. Although
this operation does not displace any of the silver, still, in taking
off the chalky appearance, there is a slight loss of weight. The
appearance after scratching is that of bright metallic silver. Any
thickness of silver may be given to a plate by continuing the
operation a proper length of time. One ounce and a quarter to one
ounce and a half of silver to the square foot of surface, will give
an excellent plate about the thickness of ordinary writing paper.
BRIGHT DEPOSIT.-A little sulphuret of carbon added to the
plating solution prevents the chalky appearance, and gives the
deposit the appearance of metallic silver; the reaction which takes
place in this mixture is not yet understood. The best method of
applying the sulphuret of carbon is to put one or two ounces into
a large bottle, then fill it with strong silver solution, having an
excess of cyanide of potassium, and let it repose for several days,
shaking it occasionally. A little of this silver solution is added,
as required, to this plating solution, which will give the articles
plated the same appearance as if scratched. It is also found that
the presence of sulphuret of carbon prevents the solution from
going out of order; indeed we have seen a solution that has been
constantly working from two to three years, while, generally, they
were subject to go out of order for a time, in less than one year —
although, after standing a time, they would recover-but these are
curious reactions not yet investigated.
DIFFERENT METALS FOR PLATING.-Silver may be depdsited
upon any metal, but not upon all with equal facility. Copper,
brass, and German silver, are the best metals to plate; iron, zinc,
tin, pewter, and Britannia metal, are much more difficult; lead is
easier, but it is not a good metal, because of the rapidity with which
it tarnishes, and, from its softness, easily yields to the pressure of
the burnisher: nevertheless all these metals and alloys may be,




604      THE PRACTICAL METAL-WORKER'S ASSISTANT.
and are, plated, but cannot give the satisfaction which brass, copper, or German silver afford. In plating upon alloys having tin
in them, such as Britannia metal, they must not be dipped into
nitric acid previous to plating; but into a hot and strong solution
of caustic potash or soda for five minutes, and put directly into the
plating solution (which should have an excess of cyanide of potassium, and the battery be as strong as the liquor will admit of without gas being evolved), until covered, when the silver may be
thickened by an ordinary solution and battery.
ELECTRICITY GIVEN OFF FROM  SANDY DEPOSITS. —We may
mention that when depositing silver upon a large surface, and the
solution or battery being in the condition to give the sandy deposit,
or rather when the deposit has gone on for a long time and the
solution not been agitated, so that it has become very much
exhausted of silver round the article, the deposit towards the end
of the time has been almost impalpable to the touch, like flour:
sometimes the grains were a little coarser. The practice, in such
cases, is to lift the articles from the solution, and to place them in
boiling water, and after steeping there some time, to take them out,
when the heat of the metal soon causes it to dry. Under these
circumstances, when the deposit was of the sort stated, we have
seen on a large waiter or tray, when the hand was rapidly drawn
over the surface, after it was dried in the manner described, the
same effect produced as when the hand is drawn over an electrified
handkerchief, or sheet of paper, accompanied with a crackling
noise and pricking sensation. We have repeatedly observed these
phenomena, but never having chanced to be in the dark, no light
was visible from the surface rubbed. Although these are the conditions under which the observations were made, the phenomena
were not produced every time these conditions were found.. It is
probably caused by the fact that this kind of deposit, which is of a
chalky appearance, is a bad conductor of electricity, and as the
boiling water was often very impure, holding salts in solution, the
rapid evaporation of the water from the surface of this sort of
deposit might leave it excited for a short time, and the hand being
drawn across at the time of excitation, the electricity was liberated.
THE OLD METHOD OF PLATING.-Many objections have been
urged against the application of electro-deposition to the purposes
of plating, as a branch of manufacture, either as a competitor or
substitute for the old method, technically called Sheffield plate-so
called because Sheffield is a principal seat of that manufacture.
To enable our readers to form a proper estimate of the objections
urged, by enabling them to judge of the relative importance and
value of the two processes, we shall add a brief description of the
old method.
An ingot of copper being cast, was filed square and smooth,
and a piece of silver was placed upon it, the two surfaces being
perfectly clean: a little borax having been introduced between the
two metals, they were bound together with iron wire, and then




ELECTRO-PLATING.                   605
heated in a furnace nearly to the melting point; the small quantity of borax increased the fusibility of the two metals at their
surface, and thus they were fused together. When fusion was
effected the metals were subjected to the dilating process of heavy
rollers, the dimensions in length and width being regulated according to the articles to be made. This sheet formed the base or
foundation of every article, of whatever shape or form, and however it was to be ornamented when finished.
To produce ornaments, leaf silver was stamped in iron dies
representing the ornaments required, which, when removed from
the dies, were filled with an alloy of lead and tin. These were
then soldered upon the flat or shaped plain surface with soft
solder, which melts at a very low temperature: thus were produced the silver edges, or mounts.
The quality of the ornament depended entirely upon the price
of the article; but whatever the quality, all ornaments in the old
mode of plating were thus made, the only difference being the
thickness of the silver leaf used:-Ornamental feet, handles, knobs,
etc., were made in the same manner, being struck up in two parts,
filled with lead and tin, soldered together with soft solder, and
afterwards soldered to the main body. Articles (such as table
candlesticks) which would be too heavy if filled with lead, were
filled with rosin, pitch or any other similar substance, for the purpose of preventing the article being flattened by pressure. Hence
it is evident that no solid article could be made by the old mode of
plating, the only way of producing articles being to work them up
by the hammer, or to strike them in dies from a flat surface: and
being restricted to the use of soft solder, on account of the plated
metal and the shells of silver, forming the edges, not supporting
the required heat to melt silver solder, it is equally evident that
the joinings so constructed would be easily removed either by
force or heat.
The nearest approach to solid articles made by the old method
of plating, were forks and spoons: these were generally made of
iron, thin silver being soldered upon the surface, which was afterwards dressed smooth, and polished.
The heat used in this operation was merely that of an ordinary
soldering iron; because, were a greater heat applied, the silver
would form an alloy with the tin and lead of the solder, and melt:
the same heat that cemented the metals in the first instance would
be sufficient to disunite them; and thus, when these forks were
exposed in hot gravy, the solder was liable to become soft, and
the silver covering, yielding readily to the knife, to peel up or
become abraided, in consequence of the soft intervening metal.
ADVANTAGES OF ELECTRO-PLATING.-The advantages offered
to the plater by the electro-process are many, arising from the fact
of the articles being plated after, instead of before, being manufactured. This at once entirely removed all those restrictions on
taste and design, under which the plater was forced, by the nature
of his process, to labor.




606      THE PRACTICAL METAL-WORKER'S ASSISTANT.
The following may be considered some of the principal differences existing in the two processes of plating-the old method:
and the electro-process:
1. The electro-plater is not limited in the use of the metal upon
which he plates. There is generally used, as the basis of all electro-plated goods, a hard white metal, which possesses the sound,
and approaches very nearly to the color, of silver. Inferior goods
are sometimes made in brass.
2. The electro-plater is not restricted to the use of soft solder,
which melts at a very low temperature, and forms a very insufficient
joint, besides preventing any sound or ring in the article so soldered.
Where cheap goods are required, this may be used in this process
as well as in the old, but is always open to the same objection.
All goods of superior quality, made for the electro-process, are
soldered with what is termed in the trade hard silver solder, composed of 2 parts of silver and 1 part of brass melted together,
which is not affected by any ordinary degree of heat, and presents
a joint as strong as the metal itself., The common solder of braziers may also be used with advantage: it is very hard and durable and requires a strong heat to
melt it.
3. The electro-plater, in producing ornamental articles, is not
obliged to incur the expense of cutting iron dies for every minute
portion; being under no restriction, he models his pattern, and by
casting and chasing in solid metal, produces an exact copy, which
is afterwards plated or gilt.
Thus any pattern which can be executed in silver may be readily
made in plate by this method.
4. The junction of the plating with the metal below, by the
electro-process, is perfect, without the presence of anyintervening
substance: the forks and spoons thus made are- not open to the
objection of the old process, and are found to answer all the purposes of silver, in sound, appearance, and wear: they- are generally
tested, previously to polishing, by exposure in a furnace to a red heat.
5. From the facility with which old goods may be now restored,
these goods bear an intrinsic value; whereas before the introduction of the electro-process, a plated article worn through in any
part was valueless.
OBJECTIONS TO ELECTRO-PLATING.-Several objections to the
electro-process have been keenly urged; but they may all be reduced to the following:
1st objection: Deposited metal is crystalline, and therefore,
though it may impart in appearance a silver coating, it must necessarily be full of minute interstices between the crystals: hence
when a metal, such as copper, is plated, it is liable to be acted upon
by the atmosphere, or injured by whatever is brought into contact
with it
This objection was not without foundation, as all deposited
metals are crystalline in texture, but they do not necessarily leave




ELECTRO-PLATING.                  607
interstices; the objection, however, is almost entirely removed by
keeping the articles in motion during the deposition: by motion
and proper arrangement of battery we have deposited silver of as
high specific gravity as hammered silver, which could not be the
case if it were porous.
2d objection: As only pure silver is deposited, it must necessarily
be soft, and consequently liable to abrasion, and more rapid wear.
This objection is also partly true. Only pure silver can be
deposited; but it is not necessarily soft: the quality of the deposit,
in this respect, depends (as already noticed) a great deal upon the
nature of the solution and the battery power. Intensity of battery
gives hardness to the metal deposited. There is no complaint
more common amongst the burnishers of electro-plated articles,
than that the metal is hard; and it is far from being an uncommon
occurrence, that some goods have to be heated so that they may be
more easily burnished or polished. How far this annealing may
affect the wear of the goods is not yet ascertained. That the silver
is pure we think an advantage-hence the superior color which
electro-plated goods possess: besides which, purchasers are not
subject to the risk of having a plate much alloyed.
3d objection: The mounts or prominences of articles, which
must have the greatest wear, have the least and thinnest deposit.
This objection is entirely without foundation, as the prominences
have always the greatest portion of deposit, and the hollow parts
the least.
SOLID SILVER ARTICLES MADE BY TIE BATTERY.-Silver may
be deposited from its cyanide solution upon wax moulds polished
with black lead, almost as easily as copper; but for this purpose
it is better to have the solution much stronger in silver than for
plating. We have found that 8 ounces of silver to the gallon of
solution make a very good strength. Nevertheless, no articles are
made in silver by depositing upon wax in this manner. Strong
solutions of cyanide of potassium and silver act upon wax, and
would soon destroy a mould. The method of making articles in
solid silver by the electro-process has been already explained (page
544,) namely, a copper mould is made by the electrotype, and the
silver is deposited within this mould to the proper thickness; after
which it is kept in a hot solution of crocus and muriatic acid, or
boiled in dilute hydrochloric acid, which dissolves the copper without injuring the silver.
The method which we esteem as best for dissolving off the cop
per is this: an iron solution is first made by dissolving a quantity
of copperas in water, placing it on a fire till it begins to boil: a
little nitric acid is then added-nitrates of potash and soda will do
just as well-the iron, which is thus peroxidized, may be precipi
tated either by ammonia, or carbonate of soda; the precipitate
being washed, muriatic acid is added till the oxide of iron is dis.
solved. This forms the solution for dissolving the copper. When
the solution beoomes almost colorless, and has-ceased to act on the




608      THE PRACTICAL METAL-WORKER'S ASSISTANT.
copper, the addition of a little ammonia will precipitate the iron
again; after a little exposure, the copper remains in solution, which
is decanted off and preserved for recovering the copper; this is
done by neutralizing the ammonia by an acid, and putting in pieces
of iron, which deposit the copper in the metallic state. The precipitate of iron is again dissolved in muriatic acid, and employed
in dissolving the copper. Thus the iron may be used over and
over again with little trouble, and the persalt of iron will be found
to dissolve the copper more rapidly than an acid; persulphate of
iron must not be used, as it dissolves the silver along with the copper. The silver article is then cleaned in the usual way (page 593),
and heated to redness over a clear charcoal fire, which gives it the
appearance of dead silver, in which state it may be kept, or, if
desired, it may be scratched and burnished.
When ammonia is first added to the above solution of copper
and iron, both these metals are precipitated together as a brown
precipitate. After a little exposure, the copper dissolves, and the
iron is at the same time peroxidized, having been previously
reduced to the protoxide by the copper dissolving. When the
persulphate of iron is used for dissolving copper, and ammonia is
then added to the solution, the same results take place:-the precipitation of both copper and iron. But the compound seems not
so stable, the copper passing more quickly into an oxide, which
dissolves in the ammonia. However, with free ammonia, either
with the chloride or sulphate, the oxidation of the metals is slower
than with water alone.
Copper moulds intended for receiving a deposit must be protected on the back, but if the solution is very strong, there is every
danger that it will decompose the protecting substance, thus rendering the solution very dirty, and causing a sediment. For the
purpose of protecting the mould, various suggestions and experiments' have been made; amongst other substances, pitch has been
tried: it is easily affected alone, but on boiling a little of it in potash, a heavy and dirty sediment is left, destitute of any adhesive
property; on putting a quantity of this sediment into a pot nearly
filled with melted pitch, a violent effervescence will take place, setting free a volume of white fumes having a creosotic smell. After
all effervescence has ceased, which will not be before a considerable
time, and when all the mass seems to have been acted upon, the
process of making an excellent protecting coating is completed-a
coating which will not yield in the solution, and which is at once
both good and cheap, its only fault being its brittleness.
In the manufacture of solid silver articles, the electro-process
has not yet been of extensive application: and in making duplicates of rare objects of art, and costly chased or engraved articles
in silver, one prevailing objection has been felt, namely, they have
no "ring," and seem, when laid suddenly upon a table, to be
cracked or unsound, or like so much lead; this disadvantage is no
doubt partly owed to the crystalline character of the deposit, and




ELECTRO-PLATING.                  609
partly to the pure character of the silver, in which state it has not
a sound like standard or alloyed silver. That this latter cause is
the principal one, appears from the fact that a piece of silver thus
deposited is not much improved in sound by being heated and
halmmered, which would destroy all crystallization.
We may mention that the same objections are applicable to
articles made in gold by the electro-deposit; nevertheless, for figures and ornaments, these objections are of little weight. When
in Marlborough House a few months back, we were shown a plate
of antique pattern in deposited silver, which was all but free from
these defects.
DEAD SILVERING FOR MEDALS.-The perfect smoothness which a
medal generally possesses on the surface, renders it very difficult to
obtain a coating of dead silver upon it, having the beautiful silky
lustre which characterizes that kind of work, except by giving it a
very thick coating of silver, which takes away the sharpness of the
impression. This dead appearance can be easily obtained by putting the medal, previous to silvering, in a solution of copper, and
depositing upon it, by means of a weak current, a mere blush of copper, which gives the face of the medal that beautiful crystalline rich
ness that deposited copper is known to give. The medal is then
to be washed from the copper solution, and immediately to be put
into the silver solution. A very slight coating of silver will suffice
to give the dead frosty lustre so much admired, and in general so
difficult to obtain.
OXIDIZING SILVER.-A very beautiful effect is produced upon
the surface of silver articles technically termed oxidizing, which
gives the surface an appearance of polished steel. This can be
easily effected by taking a little chloride of platinum, prepared as
described at page 527, heating the solution and applying it to the
silver when an oxidized surface is required, and allowing the solution to dry upon the silver. The darkness of the color produced
varies according to the strength of the platinum solution, from a
light steel gray to nearly black. The effects of this process, when
done along with what is termed dead work, is very pretty, and may
be easily applied to medals, giving scope for the exercise of taste.
Upon this we quote the following:
"The high appreciation in which ornaments in oxidized silver
are now held, render a notice of the process followed interesting.
There are two distinct shades in use, one produced by chloride,
which has a brownish tint, and the other by sulphur, which has a
bluish black tint. To produce the former, it is only necessary to
wash the article with a solution of sal-ammoniac; a much more
beautiful tint may, however, be obtained by employing a solution
composed of equal parts of sulphate of copper and sal-ammoniac
in vinegar. The fine black tint may be produced by a slightly
warm solution of sulphuret of potassium or eodium." — Chem. Tec/ln.
Mittheilungen von Dr. Ellsner.
PROTECTION OF SILVER SURFACE.-All silver or plated articles
39




610      THE PRACTICAL METAL-WORKER'S ASSISTANT.
are subject to tarnish by exposure to the air, especially in this cli
mate, and where coals containing so much sulphur are used; the
tarnish being generally a sulphuret of silver. Deposited silver is
more easily tarnished than standard silver.
Medals or figures silvered for the sake of their appearance ought
to be protected from the air, or they very soon lose their silver
color; a medal may be put into a frame air-tight, and a figure
should be covered with a glass shade: if the silver has been left
dead, any attempt to clean it destroys its appearance. Varnishes
have been tried to protect the silver from the atmosphere; but all
varnishes, however colorless, detract from the silver lustre, and are
not good. For ordinary purposes, medals may be very conveniently protected by laying a piece of common glass over the surface, cut to the exact size, and held close by a piece of paper pasted
round the edges of both, and then a stout piece on the back. We
have had silver medals, preserved by this means, for more than ten
years. Little round medals may be conveniently covered by watchglasses, fastened on in the same manner.
CLEANING OF SILVER.-A weak solution of cyanide of potassium,
used as a wash over tarnished silver, will brighten it. This solution was, and we believe is still, sold in small bottles for this purpose, but it is not good, as it dissolves the silver rapidly, and is
such a deadly poison that it must be used with great caution on
articles that may be required for domestic purposes.
A variety of cleaning pastes and powders are used for silver or
plated goods. Those containing mercury and oxide of lead should
be avoided, for although they give a dark color when newly put
on, it soon blackens. The best paste we have found is a mixture
of fine precipitated chalk, carbonate of magnesia, and oxide of iron.
These materials are made into a paste, and rubbed upon the plate
with soft leather: for wrought or chased surfaces a hard brush is
best. The goods should be finished by polishing with leather and
a little of this mixture in a dry state, which will give that fine dark
mirror-looking color so much admired. Common coarse whiting
and flannel cloths should not be used, as thev wear the silver
rapidly.
CHAPTER XXXI.
ELECTRO-GILDING.
THE operation of gilding, or covering other metals with a coatiug of gold, is performed in the same manner as the operation of
)plating, with the exception of a few practical modifications, which
*e shall now notice in detail.
PREPARATION OF SOLUTION OF GOLD.-The gold solution for




ELECTRO-GILDING.                  611
gilding is prepared by dissolving gold in three parts of muriatic
acid and one of nitric acid, which forms the chloride of gold.
This is digested with calcined magnesia, and the gold is precipi
tated as an oxide. The oxide is boiled in strong nitric acid, which
dissolves any magnesia in union with it: the oxide being well
washed is dissolved in cyanide of potassium, which gives cyanide
of gold and potassium; thus:Substances used:            Substances produced:
Oxide of Gold       =- AuO  Cyanide of Gold       Cy
2. Cyanide of Potassium=2KCy   and Potassium   KCy + AuCy
Potash         =KO
Auo+2 KCy=KO + (KCy +AuCy.)
By this method a proportion of potash is formed in the solution,
as an impurity; it is not, however, very detrimental to the process.
In preparing the oxide of gold there is always a little of the gold
lost, to recover which the washings should be kept, evaporated to
dryness, and fused.
Another and very simple method is this:-Add a solution of
cyanide of potassium to the chloride of gold until all the precipitate is redissolved; but this gives chloride of potassium in the solution, which is not good. In the preparation of the solution by
this means there are some interesting reactions. As the chloride
of gold has always an excess of acid, the addition of cyanide of
potassium causes violent effervescence, and no precipitate of gold
takes place until all the free acid is neutralized, which causes a
considerable loss to. the cyanide of potassium. There is always
formed in this deposition a quantity of ammonia and carbonic acid,
from the deposition of the cyanate of potash; and if the chloride
of gold be recently prepared and hot, there is often formed some
aurate of ammonia (fulminate of gold), which precipitates with the
cyanide of gold. Were this precipitate to be collected and dried,
it would explode when slightly heated. On previously diluting
the chloride of gold, or using it cold, this compound is not formed.
After the free acid is neutralized by the potash, further addition
of the cyanide of potassium precipitates the gold as cyanide of
gold, having a light yellow color; but as this is slightly soluble in
ammonia and some of the alkaline salts, it is not advisable to wash
the precipitate lest there be a loss of gold. Cyanide of potassium
is generally added until the precipitate is redissolved; consequently much impurity is formed in the solution, namely, nitrate and carbonate of potash with chloride of potassium and
ammonia. Notwithstanding, this solution works very well for
a short time, and it is very good for operations on a small
scale.
BATTERY PROCESS OF PREPARING GOLD SOLUTION.-The best
method of preparing the gold solution is that described for silver
(p. 589). Say the operator wishes to prepare a gallon of gold so



612      THE PRACTICAL METAL-WORKER'S ASSISTANT.
lution, he dissolves four ounces of cyanide of potassium in one
gallon of water, and heats the solution to 1500 Fah.; he now takes
a small porous cell and fills it with this cyanide solution, and places
it inside the gallon of solution: into this cell is put a small plate
of iron or copper, and attached by a wire to the zinc of a battery.
A piece of gold is placed into the large solution, facing the plate
in the porous cell, and attached to the copper of the battery. The
whole is allowed to remain in action until the gold, which is to be
taken out from time to time and weighed, has lost the'quantity required in solution. By this means a solution of any strength can
be made, according to the time allowed. The solution in the
porous cell, except the action has continued long, will have no
gold, and may be thrown away. Half an hour will suffice for p
small quantity of solution-of course any quantity of solution
may be made up by the same means. For all the operations of
gilding by the cyanide solution, it must be heated to at least 1300
Fah. The articles to be gilt are cleaned in the way described for
silver, but are not dipped into nitric acid previously to being put
in the gold solution. Three or four minutes is sufficient time to
gild any small article. After the articles are cleaned and dried
they are weighed-and when gilt they are weighed again; thus
the quantity of gold deposited is ascertained. Any convenient
means may be adopted for heating the solution. The one generally
adopted is to put a stoneware pan containing the solution into an
iron or tinplate vessel filled with water, which is kept at the boiling point either by being placed upon a hot plate or over gas.
The hotter the solution the less battery power is required. Generally three or four pairs of plates are used for gilding, and the
solution is kept at 1300 to 150~ Fah. But one pair will answer
if the solution is heated to 200~.
PROCESS OF GILDING.- The process of gilding is generally performed upon silver articles. The method of proceeding is as follows: When the articles are cleaned as described in our chapter
on plating, they are weighed, and well scratched with wire brushes,
which cleanse away any tarnish from the surface, and prevents the
formation of air-bubbles. They are then kept in clean water until
it is convenient to immerse them in the gold solution. One immersion is then given, which merely imparts a blush of gold;
they are taken out and again brushed; they are then put back into
the solution and kept there for three or four minutes, which will
be sufficient if the solution and battery are in good condition; but
the length of time necessarily depends on these two conditions,
which must be studied and regulated by the operator.
Iron, tin, and lead, are very difficult to gild direct; they therefore generally have a thin coating of copper deposited upon them
by the cyanide of copper solution and immediately put into the
gilding solution.
CONDITIONS REQUIRED IN GILDING.-The gilding solution generally contains from one-half to an ounce of gold in the gallon, but




ELECTRO-GILDING.                    613
for covering small articles, such as medals, for tinging daguerreotypes, gilding rings, thimbles, etc., a weaker solution will do. The
solution should be sufficient in quantity to gild the articles at once,
so that it should not have to be done bit by bit; for when there is
a part in the solution and a part out, there will generally be a line
mark at the point touching the surface of the solution.  The
rapidity with which metals are acted upon at the surface line of the
solution is remarkable.  If the positive electrode is not wholly
immersed in the solution, it will, in a short time, be cut through
at the surface of the water, as if cut by a knife. This is also
the case in silver, copper, and other solutions, as before referred to.
MAINTAINING THE GOLD SOLUTION. —As the gold solution
Evaporates by being hot, distilled water must from time to time be
added. The water should always be added when the operation
of gilding is over, not when it is about to be commenced, or the
solution will not give so satisfactory a result. When the gilding
operation is continued successively for several days, the water
should be added at night. The average cost of depositing gold is
about 4 cts. per pennyweight.
The means of testing the free cyanide of potassium, with nitrate
of silver, as described for silver, is not applicable to the gold solution; but it may be tested by the ammoniuret of copper, see p. 603.
To obtain a deposit of a good color much depends upon the state
of the solution and battery; it is therefore necessary that strict
attention be paid to these, and more so as the gold solution is very.liable to change if the relative size of the article receiving the
deposit is not according to that of the positive plate.
The result of a series of observations and experiments, continued daily throughout a period of nine months, showed that in
five instances only the deposit was exactly equal to the quantity
dissolved from the positive plate. In many cases the difference
did not exceed 3 per cent., though occasionally it rose to 50 per cent.
The average difference however was 25 per cent. In some cases
double the quantity dissolved was deposited, in others the reverse
occurred-both resulting from alterations made in the respective
processes; for in these experiments we varied, as far as practicable,
the state of the solution and the relative sizes of the negative and
positive electrodes.
The most simple method of keeping a constant register of the
state of the solution is to weigh the gold electrode before putting
it into the solution; and, when taking it out, to compare the loss
with the amount deposited: a little allowance, however, must be
made for small portions of metal dissolved in the solution, from
the articles that are gilt, which, when gilding is performed daily,
is considerable in a year. A constant control can thus be exercised over the solution, to which there will have to be added from
time to time a little cyanide of potassium, a simple test of requirement being that the gold pole should always come out clean-for
if it has a film or crust it is a certain indication that the solution




614      THE PRACTICAL METAL-WORKER'S ASSISTANT.
is deficient of cyanide of potassium. Care must be taken to diLtinguish this crust, which is occasionally dark-green or black, from
a black appearance which the gold pole will take when very small
in comparison to the article being gilt, and which is caused by
the tendency to evolve gas. In this case an addition of cyanide
of potassium would increase the evil. The black appearance from
the tendency to the escape of gas has a slimy appearance. This
generally takes place when the solution is nearly exhausted of
gold, of which fact this appearance, taken conjointly with the relative sizes of the electrodes, are a sure guide.
To REGULATE THE COLOR OF THE GILDING.-The gold upon
the gilt article, on coming out of the solution should be of a darkyellow color, approaching to brown, but this when scratched will
yield a beautifully-rich deep gold. If the color is blackish it
ought not to be finished, for it will never either brush or burnish
a good color. If the battery is too strong, and gas is given off
from the article, the color will be black; if the solution is too
told, or the battery rather weak, the gold will be light-colored;
so that every variety of shade may be imparted. A very rich dead
gild may be made by adding ammoniuret of gold to the solution
just as the articles are being put in, or what is better, add some
sulphuret of carbon in the same way as for silver solutions, which
affects the color and appearance of the gold in the same way as it
does the silver.
COLORING OF GILDING.-A defective colored gilding may be improved by the same method as that adopted in the old process to
color gilding or gold, namely, by the help of the following mixture
3 parts Nitrate of Potash
1  Alum
12 Sulphate of Zinc
11 Common Salt.
These ingredients are put into a small quantity of water, to form
a sort of paste, which is put upon the articles to be colored: they
are then placed upon an iron plate over a clear fire, so that they will
attain nearly to a black heat, when they are suddenly plunged into
cold water: this gives them a beautiful high color. Different hues
may be had by a variation in the mixture.
To DISSOLVE GOLD FROM GILT ARTICLES. —-Before regilding
articles which are partly covered with gold, or when the gilding is
imperfect, and the articles require regilding, the gold should be
removed from them by putting them into strong nitric acid; and
when the articles have been placed in the acid, by adding some
common salt, not in solution, but in crystals. By this method gold
may be dissolved from any metal, even from iron, without injuring
it in the least. After coming out of the acid, the articles must be
polished. The best method, however, is to brush off the gold as
described for silver (page 597), which gives the polish at the same
time,




ELECTRO-GILDING.                  615
To RECOVER THE GOLD.-When the gold is dissolved off by the
acid after it is saturated, or when it ceases to dissolve the gold
rapidly, the acid is diluted with several times its bulk of water,
and then soda or potash added till the greater portion of the acid
is neutralized. A solution of sulphate of iron (copperas) is then
added, so long as a precipitate is formed; when this settles down
it is carefully collected upon a paper filter, washed and dried, and
then fused in a crucible with a little borax and common salt, when
the gold is found as a button at the bottom of the crucible.
When the gold is brushed off, the brushings are burned at a red
heat, and the residue fused with carbonate of soda and a little
borax: in this case, the gold will not be pure and will have to be
refined.
OBJECTIONS TO ELECTRO-GILDING.-Objections have also been
made to the application of electro-gilding to the arts, of the same
kind as those urged against electro-plating; but the now almost
universal adoption of this process by gilders, because of the perfection to which the articles are brought, forms the best answer we
can give to such objections. However, let us take a hasty glance
at the old process and its consequences, that we may be enabled
to judge of the comparative merits of both methods.
Before the introduction of electro-deposition, the only method of
gilding was by forming an amalgam of gold and mercury, which,
at the consistence of a thin paste, was brushed upon the articles
over a strong heat; the mercury being gradually dissipated, the
gold remained fixed upon the articles. This process is most pernicious, and destructive to human life; the mercury, volatilized by
the heat, insinuates itself into the bodies of the workmen, notwithstanding the greatest care; and those who are so fortunate as to
escape for a time absolute disease, are constantly liable to salivation from its effects. Paralysis is common among them, and the
average of their lives is very short; it has been estimated as not
exceeding 35 years. It is difficult to believe that men could beo
found to engage in such a business, reckless of the consequences so
fearfully exhibited before them; and it would naturally be thought
they would hail with pleasure the introduction of any process
which would be put a stop to such a dreadful sacrifice of human
life. But it is very difficult to overcome interest and preju*e,;
even when the object to be gained is of such vast importance.
EFFECTS OF CYANOGEN ON HEALTH. —The effects produced
upon the health of those who work constantly over cyanide solutions are not yet fully tested, by which we could form a comparison with the old process; for every new trade, or operation, gives
rise to a new disease, or some new forms of an old disease. Having ourselves inhaled much of the fumes of that "ominous" gas
given off from the cyanide of potassium solution, we are not pre —
pared to stand its advocate, but would rather warn all employed, at
the business, or who may in any degree have to do with these solutions, to be very careful not to use too much freedom. The




616      THE PRACTICAL METAL-WORKER'S ASSISTANT.
hands of those engaged in gilding or plating are subjected to ulceration, particularly if they have been immersed in the solution. The
ulcers are not only annoying but painful; and, on their first appearance, if care is not properly taken to wash them in strong cyanide
of potassium, and then in acid water, the operator will, in a short
time, have to take a few days rest. We have repeatedly seen, by
the aid of a magnifying glass, gold and silver reduced in these
ulcerations. We have also known of eruptions breaking out over
the bodies of workmen after inhaling those deleterious fumes
when they were very bad, as when solutions were precipitated by
acids or being evaporated to dryness in a close apartment for the
recovery of the metal. Repeatedly have we seen the legs of workmen thus afflicted, and always after they have been exposed to
extra fumes.
The following statement of the general effects of electro-plating
and gilding on the health of those engaged in them, as experienced
by ourselves and others, may not be uninteresting to our readers:
but it is necessary to premise that the apartments in which we
were employed were improperly ventilated.
The gas has a heavy sickening smell, and gives to the mouth a
saline taste, and scarcity of saliva; the saliva secreted is frothy.
The nose becomes dry and itchy, and small pimples are found
within the nostrils, which are very painful (we have felt these
effects in the nose from the hydrogen of the batteries, where there
were no cyanide solutions). Then follows a general languor of
body; disinclination to take food, and a want of relish. After
being in this state for some time, there follows a benumbing sensation in the head, with pains, not acute, shooting along the brow;
the head feels as a heavy mass, without any individuality in its
operations. Then there is bleeding at the nose in the mornings
when newly out of bed; after that comes giddiness; objects are
seen flitting before the eyes, and momentary feelings as of the earth
lifting up, and then leaving the feet, so as to cause a stagger. This
is accompanied with feelings of terror, gloomy apprehension, and
irritability of temper. Then follows a rushing of blood to the
head; the rush is felt behind the ears with a kind of hissing noise,
causing severe pain and blindness: this passes off in a few seconds,
leaving a giddiness which lasts for several minutes. In our own
case the rushing of blood was without pain, but attended with instant blindness, and then followed with giddiness. For months
afterwards a dimness remained as if a mist intervened between us
and the objects looked at: it was always worse towards evening,
when we grew very languid and inclined to sleep. We rose comparatively well in the morning: yet were restless, our stomach
was acid, visage pale, features sharp, eyes sunk in the head, and
round them dark in color: these effects were slowly developed.
Our experience was nearly three years.
We have been thus particular in detailing these effects, as a
warning to all employed in the process; but we have no doubt that




COATING WITH VARIOUS METALS.             617
in lofty rooms, airy and well ventilated, these effects would not be
felt. Employers would do well to look to this matter; and amateurs, who only use a small solution in a tumbler, should not, as
the custom sometimes is, keep it in their bed-rooms; the practice is
decidedly dangerous.
PRACTICAL SUGGESTIONS IN GILDING.-According to the amount
of gold deposited, so will be its durability: a few grains will serve
to give a gold color to a very large surface, but it will not last: this
proves, however, that the process may be used for the most inferior
quality of gilding. Gold thinly laid upon silver will be of a light
color, because of the property of gold to transmit light. The solution for gilding silver should be made very hot, but for copper
it should be at its minimum heat. A mere blush may be sufficient
for articles not subjected to wear; but on watch-cases, pencil-cases,
chains, and the like, a good coating should be given. An ordinary sized watch-case should have from 20 grains to a pennyweight; a mere coloring will be sufficient for the inside, but the
outside should have as much as possible. A watch-case thus gilt,
for ordinary wear, will last five or six years without becoming
bare. We have known some to be in use full six years without
losing their covering. Small silver chains, such as those sold at
eight shillings, should have 12 grains; pencil-cases, of ordinary
size should have from 3 to 5 grains; a thimble from 1 to 2 grains.
These suggestions will serve as a guide to amateur gilders, many
of whom, having imparted only a color to their pencil-cases, feel
chagrin and disappointment upon seeing them speedily become
bare; hence arises much of the obloquy thrown upon the process.
CHAPTER XXXII.
RESULTS OF EXPERIMENTS ON THE DEPOSITION ON OTHER METALS
AS COATINGS.
COATING WITH PLATINUM.-This metal has never yet been successfully deposited as a protecting coating to other metals. A solution may be made by dissolving it in a mixture of nitric and muriatic acids, the same as is employed in dissolving gold; but heat
must be applied. The solution is then evaporated to dryness, and
to the remaining mass is added a solution of cyanide of potassium;
next, it must be slightly heated for a short time, and then filtered
This solution, evaporated, yields beautiful crystals of cyanide of
platinum and potassium; but it is unnecessaryto crystallize the salt.
A very weak battery power is required to deposit the metal: the
solution should be heated to 100~. Great care must be taken to
obtain a fine metallic deposit: indeed the operator may not sue.




618      THE PRACTICAL METAL-WORKER'S ASSISTANT.
ceed once in twenty times in getting more than a mere coloring of
metal over the surface, and that not very adhesive. The causes of
the difficulty are probably these: the platinum used as an electrode
is not acted upon; the quantity of salt in solution is very little; it
requires a particular battery strength to gives a good deposit, and
the slightest strength beyond this gives a black deposit; so that,
were the proper relations obtained, whenever there is any deposit,
the relations of battery and solution are changed, and the black
pulverulent deposit follows.
We have occasionally succeeded in obtaining a bright metallic
deposit of platinum, possessing the qualities of adhesion and durability: some of the articles thus covered presented no signs of
change after many years: but we have never been so fortunate as
to get a platinum deposit that could protect any metal from'the
action of acids, or other fluids by which the metal could be affected.
We have covered iron, such as the end of a glass-blower's blowpipe, so that it could be made red-hot without the iron rusting, but
rather taking the characteristic appearance of platinum: but even
that did not protect the iron from rusting when it was put a short
time into water, or kept exposed to moist air. We have seen again
and again recommendations of certain solutions of platinum for the
purpose of obtaining a reguline metal, and no doubt it has been
obtained, but, as stated above, we believe more incidentally than
at will. The protoxalate of platinum has been strongly recommended for covering copper and brass with platinum.*
COATING WITH PALLADIUM.-Palladium is a metal very easily
deposited. The solution is prepared by dissolving the metal in
nitro-muriatic acid, and evaporating the solution nearly to dryness; then adding cyanide of potassium till the whole is dissolved:
the solution is then filtered and ready for use. The cyanide of
potassium holds a large quantity of this metal in solution, and the
electrode is acted upon while the deposit is proceeding. Articles
covered with this metal assumne the appearance of the metal; but
so far as we are aware, it has not yet been applied to any practical
purpose. It requires rather a thick deposit to protect metals from
the action of acids, which is, probably, the only use it can be
applied to.
COATINrG WITH NICKEL.-Nickel is very easily deposited; and
may be prepared for this purpose by dissolving it in nitric acid,
then adding cyanide of potassium to precipitate the metal; after
which the precipitate is washed and dissolved by the addition of
more cyanide of potassium. Or the nitrate solution may be precipitated by carbonate of potash; this should be well washed, and
then dissolved in cyanide of potassium; a proportion of carbonate
of potash will be in the solution, which we have not found to be
detrimental. This latter method of preparing the nickel plating
solution is simple, and, therefore, has our recommendation. The
* Polytechni. Constah. 1855.




COATING WITH VARIOUS METALS.             619
metal is very easily deposited; it yields a color approaching to
silver, which is not liable to tarnish on exposure to the air..&
coating of this metal would be very useful for covering common
work such as gasaliers, and other gas-fittings, and even common
plate. The great difficulty experienced is to obtain a positive
electrode: the metal is very difficult to fuse, and so brittle that we
have never been able to obtain either a plate or a sheet of it.
Could this difficulty be easily overcome, the application of nickel
to the coating of other metals would be extensive, and the property
of not being liable to tarnish would make it eminently useful for
all general purposes. We coated articles with nickel in 1845,
which were exposed to the air for many years without tarnish,
and when last seen by the author exhibited no change.
ANTIMONY, ARSENIC, TIN, IRON, LEAD, BISMUTH. AND CADMIUM.
-We have deposited these metals from their solutions in cyanide
of potassium; but not for any useful application.
IRON.-Iron may be very easily deposited from its sulphate:
dissolve a little crystalline sulphate of iron in water, and add a few
drops of sulphuric acid to the solution: one pair of Smee's battery
may be used to deposit the iron upon copper or brass. The metal
in this pure state has a very bright and beautiful silver color.
LEAD.-Lead may be deposited from a solution of an acid salt,
such as the acetate, but requires some management or strength of
battery: it may also be deposited from its solution in potash or
soda.
ALUMINIUM AND SILICTUM. —Since the publication of the former
edition of this work, new methods have been discovered for obtaining the base or metal of alumina and silica, or clay and sand, in
the metallic state possessing extraordinary properties. One of the
methods successfully adopted, is by fusing in a small crucible
some chloride or fluoride of aluminium, and when in fusion, inserting two steel poles in connection with a battery which reduces
the salt, giving small globules of the metal aluminium.
Attempts have also been made to deposit the metals from their
cyanous solution as coating upon other metals in the usual way.
We have not ourselves tried any experiments upon these metals,
but we take the following results of experiments from Mr. G. Gore
of Birmingham, who seems to have given the subject a good deal
of attention:
"It has long been known to chemists that all kinds of clay,
stone, and sand, of which the earth is composed, consist of metals
combined with oxygen, carbonic acid, sulphuric acid, and other
non-metallic elements, forming therewith oxides, carbonates, sulphates, etc.; thus clay is an oxide of aluminium, sand an oxide of
silicium, limestone a carbonate of calcium; but the separation of
the metallic bases from the non-metallic elements with which they are
combined has been a matter of so great difficulty, that few chemists
have put themselves to the' trouble of accomplishing it, and those
who have done so have made use of the most powerful means and




620      THE PRACTICAL METAL-WORKER'S ASSISTANT.
reducing agents, such as large voltaic batteries, potassium, etc,
and have then obtained them in a state of alloy or combination
with mercury. Sir Humphrey Davy, the discoverer of most of
these bases, in his experiments on the decomposition of the alkalies
and earths, used a powerful battery, consisting of 500 pairs of
plates, and then succeeded in obtaining them combined with mercury, from which they were afterwards separated. Wh6}ler and
Berzelius, in their discoveries of the means of separating the metals
aluminium and silicium from their respective compounds, clay and
sand, used a high temperature and potassium, and then succeeded
in obtaining them in the condition of dull metallic powders, nearly
infusible.
"By a means recently discovered, and described in the March
number of the Philosophical Magazine for this year, I have succeeded in depositing the metals aluminium from clay, and silicium
from sandstone, each in a perfect metallic condition, by dissolving
pipe clay, common red sand, pounded stone, etc., in various chemical
liquids, and passing currents of electricity from ordinary small
voltaic batteries through the solutions.
"My attention has since been directed to produce simple processes, whereby any person not possessing a knowledge of chemistry may readily coat articles with those metals, and thus cause
the discovery to be immediately applied to human benefit in the
arts and manufactures, and the following are the results of my experiments:
" To coat articles of copper, brass, or German silver, with aluminium, take equal measures of sulphuric acid and water, or take one
measure each of sulphuric and hydrochloric acids and two measures of water; add to the water a small quantity of pipe-clay, in
the proportion of 5 or 10 grs. by weight to every ounce by measure of water (or i oz. to the pint): rub the clay with the water
until the two are perfectly mixed, then add the acid to the clay
solution, and boil the mixture in a covered glass vessel one hour.
Allow the liquid to settle, take the clear, supernatant solution,
while hot, and immerse in it an earthen porous cell, containing a
mixture of one measure of sulphuric acid and ten measures of
water, together with a rod or plate of amalgamated zinc; take a
small Smee's battery, of three or four pairs of plates, connected
together intensity fashion, and connect its positive pole by a wire,
with a piece of zinc in the porous cell. Having perfectly cleaned
the surface of the article to be coated, connect it by a wire with
the negative pole of the battery, and immerse it in the hot clay
solution; immediately abundance of gas will be evolved from the
whole of the immersed surface of the article, and in a few minutes,
if the size of the article is adapted to the quantity of the current
of electricity passing through it, a fine white deposit of aluminium
will appear all over the surface. It may then be taken, out, washed
quickly in clean water, and wiped dry, and polished; but if a
thicker coating is required, it must be taken out when the deposit




COATING WITH VARIOUS METALS.              621
becomes dull in appearance, washed, dried, polished. and re-inlmersed; and this must be repeated at intervals, as often as it becomes dull, until the required thickness is obtained. With small
articles it is not absolutely necessary, either in this or the following process, that a separate battery be employed, as the article to
be coated may be connected by a wire with a piece of zinc in the
porous cell, and immersed in the outer liquid, when it will receive
a deposit, but more slowly than when a battery is employed.
"To coat articles with silicium, take the following proportions:
three-quarters of an ounce, by measure, of hydrofluoric acid, i oz.
of hydrochloric acid, and 40 or 50 grs. either of precipitated silica,
or of fine white sand (the former dissolves most freely), and boil the
whole together for a few minutes, until no more silica is dissolved.
Use this solution exactly in the same manner as the clay solution,
and a fine white deposit of metallic silicium will be obtained, provided that the size of the article is adapted to the quantity of the
electric current: common red sand, or indeed any kind of silicious
stone, finely powdered, may be used in place of the white sand, and
with equal success, if it be previously boiled in hydrochloric acid,
to remove the red oxide of iron or other impurities.
"Both in depositing aluminium and silicium, it is necessary to
well saturate the acid with the solid ingredients by boiling, otherwise very little deposit of metal will be obtained.
"'Among the many experiments I'have made upon this subject,
the following are a few of the most interesting:"Experiment 1.-Boiled some pipe-clay in caustic potash and
water, poured the clear part of the solution into a glass vessel, and
immersed in it a small earthen porous cell, containing dilute sulphuric
acid and a piece of amalgamated zinc; immersed a similar piece of
bright sheet copper in the alkaline liquid, and connected it with
the negative pole of a small Smee's battery of three pairs of plates,
connected the zinc plate with the positive pole, and let the whole
stand undisturbed all night; on examining it next morning I found
the piece of copper coated with a white silver-like deposit of metallic aluminium.
"Experiment 2.-Obtained from a railway cutting in the town
a small piece of the sand rock upon which Birmingham is built,
boiled it in hydrochloric acid, to remove the red oxide of iron,
washed it clean with water, and dissolving it by boiling it in a mnixture of hydrofluoric acid, nitric acid, and water; immersed in this
solution, a porous cell with dilute acid and zinc, as before; connected a piece of brass with the zinc by a wire, and suspended it
in the outer liquid, which was kept hot by a small spirit lamp beneath; after allowing the action to proceed several hours, I found
the piece of brass beautifully coated with white metallic silicium.
"Experiment 3.-Took one part, by weight, of the same sandstone, after being purified by the hydrochloric acid, anbe2 parts of
carbonate of potash, fused them togetherJ' crucible until all
evolution of gas ceased, and a perfect glass'"was formed; poured




622      THE PRACTICAL METAL-WORKER'S ASSISTANT.
out the melted glass, and when cold, dissolved it in water, and used
this solution in the same manner as the former ones, allowing the
action to proceed about 12 hours, when a good white deposit of
metallic silicium was obtained.
"Experiment 4.-Took some stones with which the streets of
Birmingham are macadamised, pounded them fine in a mortar, boiled
the powder in hydrochloric acid, to purify it from iron, washed it
well in water, and dissolved it by boiling an excess of it in a mixture of I oz., by measure, of hydrofluoric acid, 1 oz. of water, and
oz. each of nitric and hydrochloric acids, until no more would
dissolve; used the clear portion of this solution in the same manner as the former liquids, and readily coated in it a piece of brass
with a beautifully white deposit either of aluminium or silicium.
From these, and many other experiments which I have tried, it is
quite clear that common metal articles may be readily coated with
white metals, possessing similar characters to silver, from solutions
of the most common and abundant materials, and thus bring within
the purchase of the poorer classes articles of taste and cleanliness
which are at present only to be obtained by the comparatively
wealthy."
TIN.-Tin is easily deposited from a solution of protochloride
of tin. If the two poles or electrodes be kept about two inches
apart, a most beautiful phenomenon may be observed. The decomposition ofv the solution is so rapid that it shoots out from the
negative electrode like tentacula, or feelers, towards the positive,
which it reaches in a few seconds. The space between the poles
seems like a mass of crystallized threads, and the electric current
passes through them without effecting further decomposition. So
tender are these metallic threads that when lifted out of the solution they fall upon the plate like cobweb. Seen through a glass
they exhibit a beautiful crystalline structure. If a circular electrode of tin is used, and a small wire put in the centre of the
chloride solution, the thread-like crystals will shoot out all round,
and give quite a metallic confervee. Tin may also be deposited
from its solution in caustic potash or soda.
ANTIMONY.-In the deposition of antimony Mr. Gore has observed a curious and interesting phenomenon, that the metal during
its deposition, and after some has been deposited, explodes occasionally, the particles being thrown about by the shock.
DEPOSITION OF ALLOYS.-Many attempts have been made to
deposit alloys of metals from their solutions. That two or more
metals can be deposited from a solution we have seen sufficient
evidence; but the means to regulate the proportions of each, and
to make such a process practical, have yet to be discovered. It is
hardly possible to get a mixed solution of any two metals that are
exactly equally decomposable; or, in other words, that the metals
under the circumstances in which they are placed are exactly of
equal conducting power. Hence the electric current will always
travel through the one that offers the least resistance, and there




COATING WITH VARIOUS METALS.             623
will be none of the other metallic solution decomposed, or metal
deposited, until the quantity of electricity is greater than the best
conducting metal in the solution will allow to pass; then the other
metal will be deposited in proportion to the extra electrical power
that passes. As, for example, take a mixture of cyanide of gold,
silver, and copper, in cyanide of potassium. The silver in this
state is so much superior in its conducting power to the other salts,
that all the silver may be deposited from the solution by a weak
battery without any of the other metals. If the solution be afterwards heated, and the battery power kept so that no gas is allowed
to escape from the articles, the gold may be deposited without any
copper; but if the gas is allowed to flow froun the article receiving
the deposit, the copper will be deposited, and often more abundantly than the gold, as the escape of gas is not consistent with a
reguline deposit of gold. We have thus deposited an alloy of,gold and copper; we have also deposited gold and silver, but the
alloy was very inferior and irregular. Alloys can be obtained
from silver and palladium, from cyanide solutions, from zinc and
copper, from a solution of their sulphates; but in no instance have
we found good alloys, or alloys that could pass as such in name or
appearance. We have seen articles, such as iron, covered with
copper and zinc in this manner, or in alternate layers, and the
articles having the coating heated in charcoal, by which meais a
brass of fair appearance was obtained, but the process is attended
with practical difficulty, and the product cannot be called deposited
brass.
Several patents have been taken out for the deposition of
alloys of various sorts. The following, by Morris and Johnson,
embraces a wide range, and being well described we will copy the
specification:
"This invention consists in the employment of solutions composed of cyanide of potassium and carbonate of ammonia, to
which are added cyanides, carbonates, and other compounds of
metals, in proportions according to the amount of deposit required
to be made.
"In order that the invention may be fully understood and carried into effect, the patentees proceed to describe the means pursued
by them as follows: These improvements consist in the employment of solutions composed of carbonate of ammoLia (the carbonate of ammonia of commerce, or the sesqui-carbonate of ammonia
of chemists), and cyanide of potassium, to which are added carbonates, cyanides, or other compounds of metals, in various proportions. For the well-known alloy, brass, carbonate of ammonia
and cyanide of potassium are used in the following proportions,
namely-To each or every gallon of water are added 1 lb. of
carbonate of ammonia, 1 lb. of cyanide of potassium, 2 ozs. of
cyanide of copper, and 1 oz. of cyanide of zinc. These proportions may be varied to a considerable extent. Or the patentees
take the before-named solution of carbonate of ammonia and




624      THE PRACTICAL METAL-WORKER'S ASSISTANT.
cyanide of potassium, in the proportion of 1 lb. of each to one
gallon of water; and they take a large sheet of brass of the desired quality, and make it the anode or positive electrode, in the
aforesaid solution, of a powerful galvanic battery or magnetoelectric machine, and a small piece of metal, and make it the
cathode or negative electrode, from which hydrogen must be
freely evolved. This operation is continued till the solution has
taken up a sufficient quantity of the brass to produce a reguline
deposit. The solution may be used cold; but it is desirable, in
many cases, to heat it (according to the nature of the article or
articles to be deposited upon) up to 212' Fahr. For wrought or
fancy work about 150~ Fahr. will give excellent results. The
galvanic battery, or magneto-electric machine, must be capable of
evolving hydrogen freely from the cathode or negative electrode,
or article attached thereto. It is preferred to have a large anode or
positive electrode, as this favors the evolution of hydrogen. The
article or articles treated as before described will immediately become coated with brass. By continuing the process any desired
thickness may be obtained. Should the copper have a tendency to
come down in a greater proportion than is desired, which may be
known by the deposit assuming too red an appearance, it is corrected by the addition of carbonate of ammonia, or by a reduction
of temperature, when the solution is heated. Should the zinc have
a tendency to come down in too great a proportion, which may be
seen by the deposit being too pale in its appearance, this is corrected by the addition of cyanide of potassium or by an increase
of temperature.
"The alloy, German silver, is deposited by means of a solution
consisting of carbonate of ammonia and cyanide of potassium (in
the proportions previously given for the brass), and cyanides or
other compounds of nickel, copper, and zinc, in the requisite proportions to constitute German silver. It is however preferred to
make the solution by means of the galvanic battery or magnetoelectric machine, as above described for brass. Should the copper
of the German silver come down in too great a proportion, this is
corrected by adding carbonate of ammonia, which brings down the
zinc more freely; and should it be necessary to bring down the
copper in greater quantity, cyanide of potassium is added-such
treatment being similar to that of the brass before described.
"The solutions for the alloys of gold, silver, and other alloys of
metals, are made in the same manner as above stated, by employing anodes of the alloy or alloys to be deposited; or by adding to
the solutions the carbonates, cyanides or other compounds, in the
proportions forming the various alloys-always using in depositing
an anode of the required alloy. These solutions are subject to the
same treatment and control as those of the brass and German silver
before described.
"The patentees claim the combination of the carbonate of ammonia, before named or other carbonates of-ammonia and cyanide




COATING WITH VARIOUS METALS.             625
of potassium, as the ingredients for their solutions for aepositing
alloys of metals."
The expense of depositing common metals will remain a barrier
to the use of electro-metallurgy in making such alloys as brass, a
consideration which some patentees do not seem to consider. We
have the following given as methods for mixing up solutions for
depositing brass, which will prove our position:
"As an illustration of this invention we take the patentee's
method of depositing a coating of brass by galvanic agency, in
which he employs the following: —1. A solution of the double
chloride of zinc and ammonia.-2. A solution of the double chloride of zinc and potassium.-3. A solution of the double chloride
of zinc and sodium. -4. A solution of the double acetate of zinc
and ammonia.-5. A  solution of the double acetate of zinc and
potassium. —6. A solution of the acetate of zinc and soda.-7. A
saturated solution of carbonate of zinc, and carbonate of ammonia.
-8. A solution of the double tartrate of zinc, and of potash, soda,
or ammonia. (To one thousand parts of the solution of tartrate
of zinc, indicating three degrees on the salinometer, thirty parts of
hydrochlorate of ammonia, and eighty parts of hydrochloric acid
must be added.)-9. A solution of citrate of zinc rendered soluble
by an excess of citric acid.-10. A solution of tartrate of zinc in
potash or soda. With each of the above solutions an analogous
solution of copper must be mixed in the proportion suitable for
obtaining the required depth of color."
Besides the ordinary electro-metallurgical operations, the public
are from time to time told through the press that the process has
been applied to the extraction of metals from their ores, but on
examination the statement is invariably found to be incorrect, the
metal being in all cases separated from the ore by means of an acid
or acids, and the electro-metallurgical operations not applied till
after this separation takes place; so that its application is altogether
apart from the extraction of the metal from the ore. Such an application for common metals is commercially absurd; and nothing
can exhibit the want of practical application so much as some of
the patents taken out for this object. The greater number of these
patents are intended for copper ores, upon which we will offer a
few remarks. It will be seen from the principles of deposition,
that, allowing the copper was all in solution to be deposited by a
battery, the cheapest form known will give the loss of one ton of
zinc and sulphuric acid to get one ton of copper, which would be
upwards of ~20 for the materials destroyed, while a ton of copper
may be smelted by the ordinary process for half that sum. We
give the following extract of a patent as an illustration, not because it is worse than others, but being more definite in its methods
and battery than most of these patents, and the patentee an excellent electrician.
"Mr. Andrew Crosse, of Broomfield, the electrician, has just
specified his patent for improvements in the extraction of metals
40




626      THE PRACTICAL METAL-WORKER'S ASSISTANT.
fromn their ores. The apparatus employed for this purpose consists of a wooden or earthenware vessel capable of holding from
250 to 300 quarts, at a short distance above the bottom of which
is a movable platinum frame covered with a netting of platinum
wire, the meshes being about 1 inch each way. This frame is connected to the positive pole of a Daniell's battery by a platinum
wire, covered with a non-conducting material throughout those
parts of it exposed to the liquid in the vessel; the negative pole
of the battery being connected to a copper wire, from which is
suspended by three smaller wires, in the interior of the vessel, a
bowl of wood lined with sheet copper and covered with a copper wire netting. The battery in connection with the apparatus should consist of 20 pairs of plates, each in a gallon glass
vessel, filled with a saturated solution of sulphate of copper,
to which has been added from 1-20th to 1-10th part of sulphuric
acid.
The mode of operating is as follows: The vessel is partially
filled with water acidulated with sulphuric acid-230 quarts of
water and 5 quarts of sulphuric acid being a convenient quantity.
About 15 lbs. of the copper' ore, previously calcined and reduced
to powder, is then stirred into the liquid in the vessel and allowed
to subside, after which the platinum frame is lowered on to the
surface of the ore, and the copper-lined bowl suspended in its
place, when the electric current immediately begins to act; but it
is preferred to allow the ore to remain four or five days in the
acidulated water before applying the electric current. The liquid
during the process should be kept heated even as high as the boiling point, by which the separation of the copper and its deposition
in the bowl will be facilitated. The time occupied in effecting this
is generally three or four days, when the whole of the copper is
removed. The acid liquid and sediment, which will contain any
other metals that may have been present, are run out through a
plug-hole in the bottom of the vessel. The sediment should be
tested to ascertain if it still contains any proportion of copper;
and if so, it can be mixed with fresh calcined ore and again operated on. The liquid does not require any fresh quantity of acid
to be added to it during the process, and afterwards it may again
be similarly used.
Here we have 20 pairs of plates recommended to be used in the
battery, making a destruction of 20 tons of zinc and acid for one
ton of copper, and taking four days to deposit. Twenty-one tons of
copper per week would be but a small quantity of copper made,
compared with smelting; and at the ordinary per centage of ore
to get this, there will have to be operated upon 300 tons of ore,
requiring acres of tanks, heated according to specification, independent of the furnace for calcining. Having got the ore calcined
and free of sulphur, it would be preferable to fuse it with carbonaceous matters and get the copper direct. Notwithstanding
the commercial absurdity of all these applications and patents, still




COATING WITH VARIOUS METALS.             627
there are several ingenious adaptations worthy of the attention of
the electro-metallurgist as a study in his profession.
DEPOSITION OF BRONZE.-The following solutions of different
metals are given by Brunel, Bisson, and Gaugain, as being capable
of giving a deposit of bronze:
50 parts Carbonate of Potash.
2  "  Chloride of Copper
4  "  Sulphate of Zinc.
25  "  Nitrate of Ammonia.
A bronze plate is used as the positive electrode. The deposit
given by this solution has been seen by Becquerel, who mentions
that it bears comparison with any ordinary bronze in appearance.*
A solution of the above materials in water strikes the ear as somewhat hypothetical: that a mixed solution of copper and zinc will
give, under certain conditions, a compound deposit we know, and
also that, with a quantity of other salts present, will give peculiar
tints of color, a circumstance which may be obtained without a
compound deposit. But the difficulty to be overcome is to proportion the deposit of different metals, so that we may make up a
solution and battery that will deposit either Mantz's yellow metal,
Stirling's yellow metal, gun metal, or common brass, at pleasure;
and that we may be able to produce compounds that are constant
and unvarying: so that, for example, we could deposit silver or
gold of the standard quality, all which, notwithstanding the many
statements that have been made in print, have yet to be discovered.
We have thus given a brief review of the practical operations
of Electro-Metallurgy for the guidance of the student, who as he
proceeds, will find that the difficulties which at first beset his path
will gradually disappear: easier modifications of processes will
suggest themselves, as all operators cannot with equal facility follow the same directions. New facts will reveal themselves to his
inquiries; a wide field of interesting and profitable research will
open up before his mind; and the steady and persevering experi
menter and observer will not fail to reap an abundant harvest of
honor and gratification, in being an instrument in )romoting th,
knowledge of the working of the laws of Nature.
* Progress of General Science, vol. ii.




628      THE PRACTICAL METAL-WORKER'S ASSISTANT.
CIAPITER XXXIII.
THEORETICAL OBSERVATIONS.
WE have described at considerable length the practical details
connected with the art of electro-metallurgy, without pausing to
inquire into the philosophy of the action of the electric currents
by which the effects are produced. It will be unnecessary to enter
into a long discussion of the numerous theories that have been
advanced from time to time to explain the action that takes place
in a battery or decomposing cell, while the current is passing
through the solution-a brief reference to the more commonly
received opinions being sufficient for the present purpose.
ACTION OF SULPHATE OF COPPER ON IRON.-In order to convey our ideas accurately, let us suppose that the solution undergoing decomposition is sulphate of copper. This salt is composed of
sulphuric acid and copper, which may be represented as S04+Cu:
these are held together according to the law of chemical affinity;
but if iron is put into the solution, the combination of the acid and
copper will be dissolved by the attraction of the acid to the iron,
for which it has a stronger affinity than for the copper. Hence
iron, put into sulphate of copper, decomposes it thus:
Cu, S4 + Fe -   e, S04 + Cu.
Were we to put a piece of copper into a solution of sulphate of
copper, there would be no action, the forces being equal; but if
by any means we were to communicate to this piece of copper a
higher attractive force for the SO4 than that of the copper which is
already in union with it, we should cause the acid to leave the
copper it was originally combined with, and to combine with the
new piece of copper. Bearing these general principles in view, we
shall proceed to state the different opinions of authors on this
subject..
FARADAY'S THEORY OF ELECTROLYSIS. - Professor Faraday
says —"Passing to the consideration of electro-chemical decomposition, it appears to me that the effect is produced by an internal
corpuscular action, excited according to the direction of the electric
current, and that it is due to a force either superadded to, or giving
direction to, the ordinary chemical affinity of the bodies present.
The body under decomposition (say sulphate of copper), may be
considered as a mass of acting particles, all those which are included
in the course of the electric current contributing to the final effect;
and it is because the ordinary chemical affinity is relieved, weakened, or partly neutralized by the influence of the electric current
in one direction parallel to the course of the latter, and strengthened or added to in the opposite direction, that the combining par.
tides have a tendency to pass in opposite courses.
" In this view the effect is considered as essentially dependent upon




THEORETICAL OBSERVATIONS.                629
the mutual chemical afinity of the particles of opposite kinds.
Particles aa could not be transferred or travel from one pole N,
towards the other pole P, unless they
found particles of the opposite kind,
bb, ready to pass in the contrary direc- (,a ~    a 
tion; for it is by virtue of their in.,           ~    C
creased affinity for those particles, combined with their diminished affinity for such as are behind them
in their course, that they are urged forward.
"I conceive the effects to arise from forces which are internal,
relative to the matter under decomposition, and not external, as
they might be considered, if directly dependent upon the poles. I
suppose that the effects are due to a modification by the electric
current of the chemical affinity of the particles, through or by
which that current is passing, giving them the power of acting
more forcibly in one direction than in another, and consequently
making them travel by a series of successive decompositions, in
opposite directions, and finally causing their expulsion or exclusion at the boundaries of the body under decomposition, in the
direction of the current, and that in larger or smaller quantities,
according as the current is more or less powerful."*
In the above figure, the particles aa may be termed copper Cu,
and the particles bb, sulphuric acid S04, which will enable us to
follow the comparison of the different views.
GRAHAM'S THEORY OF ELECTROLYSIS.-Professor Graham supposes that the compound particles, such as sulphate of copper,
possess polarity, so that the particles in the battery or decomposition cell will stand in rela-    Fig. 590.
tion to each other in a polar chain, as in Fig.
590.
He then represents electrotyping by the
porous cell system, as follows:
"The liquids on either side of the porous division may also be
different, provided they have both a polar molecule. Thus, in
Fig. 591 the polar chain is composed of molecules of hydrochloric
acid, extending from the zinc to the porous division at a, and of
molecules of chloride of copper from a, to the copper plate. When
the C1l of molecule 1 unites with zinc, the H of that molecule
unites with the C1 of molecule 2 (as indicated by the connecting
bracket below); the H of molecule 2 with the C1 of molecule 3;
the Cu of molecule 3 with the C1 of molecule 4; and the Cu of
this molecule being the last in the chain, is deposited upon the
copper plate. Dilute sulphuric acid in contact with an amalgamated zinc plate, and the same acid fluid saturated with sulphate
of copper in contact with the copper plate, are a combination of
fluids of most frequent application."t  According to this theory
* Faraday's Experimental Researches, vol. i. paragraphs 518, 519, 524
t Graham's Elements of Chemistry, 2d edition, 1859.




630       THE PRACTICAL METAL-WORKER'S ASSISTANT.
all the particles between the zinc and copper during the action of
the batteries will be performing a whirling motion; for, when the
Cl of molecule 1 is liberated, the H of 1 will combine the C1 of 2,
which compound molecule must whirl round to be in its proper
polar position, which will necessitate that interchange distinctly
referred to by Professor Faraday-a mutual transfer of the elements; the C1 will pass towards the zinc plate, and the II and Cu
towards the copper plate.
Fig. 591.
Zinc.                        4tC                 Copper.
DANIELL'S AND MILLER'S VIEWS.-Theories varying little from
these were held by the late Professor Daniell, till, by a series of
interesting experiments, in company with Professor Miller, he
found that there is no mutual transfer of the elements; that the
negative element, or that represented above as C1 or SO4, is transferred from the copper to the zinc, or in a decomposition cell from
the negative electrode to the positive electrode: but the positive
element-that represented by H or Cu-is not transferred; therefore, the theories of Professors Faraday and Graham are opposed
to a fundamental truth experimentally proved. Professors Daniell
and Miller conclude their paper, read before the Royal Society, by
the following observations:
" These facts are, we believe, irreconcilable with any of the molecular hypotheses which have been hitherto imagined to account for
the phenomena of electrolysis, nor have we any more satisfactory
at present to substitute for them; we shall therefore prefer leaving
them to the elucidation of further investigations to adding one
more to the already too numerous list of hasty generalizations."*
In this paper, the authors state that they found certain positive
elements transferred in small proportions; thus, potassium from
sulphate of potash in i of an equivalent; barium, from nitrate of
barytes, i equivalent; and magnesia, from sulphate of magnesia,
TI' equivalent. This was a difficulty for forming any theory, but
we have shown that this difficulty does not exist.
In all cases where two liquids are separated by a porous diaphragm, there is a mutual transfer of the liquids in distinct ratios,
according to time, either by what is called endosmosis, or by a diffusion; and the rate of transfer is materially affected by a galvanic
current passing through them. From observations and operations
made on a large scale, and from experiments on various kinds of
* Philosophical Transactions, Part I. for 1844.




THEORETICAL OBSERVATIONS.               631
solutions, we believe that the fractional transfers of Professors
Daniell and Miller are the results of endosmosis or diffusion, and
not of electrolytic transfer. According to recent experiments by
Professor Graham, diffusion takes place in definite proportions.
We believe that no transfer of any base or positive element takes
place by electrolysis.
PROPOSED THEORY. —Having carefully considered the various
phenomena attending electrolysis, in the decomposition of metallic
salts, we think that the electricity is conducted through the solution by the base, or positive element, in the electrolyte, which it
does as if it was a solid chain of particles-or wire. We have
already said, that if to a solution of sulphate of copper we put a
piece of iron, the acid in union with the copper will leave it and
combine with the iron. If a piece of copper be put into the same
solution, no change will take place; but if we by any means give
to this copper an increased tendency to unite with the acid, it will
attract the acid from the copper in solution by virtue of this increased attraction. Suppose two wires coming from a battery are
Fig. 592.
OQC~SO1 a
placed in a solution of sulphate of copper, thus, (Fig. 592): the
double row representing the compound atoms of sulphate of copper
forming the electrolyte: C C the copper or positive element, and
S04 the sulphuric acid or negative element of the solution. The
two single rows C C, etc., at each end of the double row, represent
the wire or solid conductors of the electricity, from the battery to
the decomposition cell: the last particle of the single rows p n
nearest the double row may be viewed as the electrodes. The
sulphuric acid S04', and the copper C, in solution, are held together
by their affinity for each other.
Now let it be supposed that an equivalent of electricity leaves
the positive terminal of the battery P, and passes along the solid
particles of the conductor, that particle upon which the electricity
is, must be for the time in a higher state of excitement than the
other particles. When the electric current comes to the last particle of the solid chain p, which is in contact with the electrolyte,
its increased excitement causes it to attract and combine with the
acid particle S04 nearest it; the electricity being dynamic, passes




632      THE PRACTICAL METAL-WORKER S ASSISTANT.
to the first basic particle C1, giving it an exalted excitement, which
causes it to unite with the acid particle S042, the electric force
passing to C2, which becomes excited in turn, and takes the particles S043; and so on through the chain till the last particle C5,
which, having no further acid to combine with, gives its electricity
to the solid conductor, or electrode n, and passes along to the battery, the particle C5 being thus left adhering to the solid chain of
particles, or electrode.
By this we observe that every equivalent of decomposition will
carry an equivalent of acid to the positive electrode, without taking
the metallic element to the other or opposite electrode. This is
exactly the fact of the case, the result that takes place in all solutions undergoing decomposition by the current, and also in the
battery between the zinc and copper. In these explanations we
have spoken of electricity as a material substance, passing along
the line, being more easily conceived than the theory of vibrations, etc.; but the effects are the same, and we have seen no phenomena in electric decomposition which are inconsistent with the
views here given.




INDEX.
Acid, nitric, for dipping, 593       Batteries, connected, against each other
for dissolving silver, 588         680
Action of sulphate of copper upon iron,  round, used for plating, 596
628                                Battery, the first, 490
Adhering of electrotypes to moulds, pre-  use of separate, 505
vention of, 502                        description of, 510
Advantages of electro-plating, 605       single pair, 510
Advice to capitalists, by Smee, 554        distance between plates, 513
Alkali, preparation of, for removing       different elements, 513
grease and oil, 579                      properties of metals fit for, 515
Alkalimeter test for cyanide of potassium,  Babington's, 517
601                                    Wollaston's, 618
Alloy of zinc and mercury, 556             modification, 518
Alloy of silver, copper, and iron, 692     common acid, defects of, 519
Alloy, fusible, for moulds, 640          Daniell's, 622
Alloys, deposition of, 622               Grove's, 524
solution for depositing, 622         Smee's, 527
Aluminium, 619                           Bunsen's, 526
Amalgamation of zinc for batteries, 511  earth, the, 629
economy of zinc plates, 512          solutions, comparative value of, 536
experiments upon economy of, 512     solutions of, how often changed, 537
its advantages, 513                  depositing by separate battery, 550
how often needful, 537               formed by solution of silver, 600
Analysis of black matter upon positive Battery process for making solutions,
electrode, 620       5' 89, 611
Analysis of efflorescence, 536       Bawtree, Mr., 550
Anodes, anions of battery, 509       Best method of making silver solution,
Antimony, curious phenomenon in de-   689
positing of, 622               Binding-screws, varieties of, 532
deposition of, 619               Bismuth, deposition of, 619
Apparatus, forms of, for electrotyping, Black appearance of gold pole, 614
635                                Black lead as a conductor, 505
Applications of coating with copper, 563 Black leading non-metallic moulds, 505
Arrangements for plating in factories, 594 Black matter upon positive electrode, 520
Arsenic, deposition of, 619'  Book covers electrotyped, 563
Articles prepared for plating, how, 593  Branson, Dr. F., on ferns and sea-weeds,
Attraction of acids for metals, table of,  541
575                                Brass, depositing of, 624
Aurate of ammonia, 611               Bright plating, how done, 603
Bronze, deposition of, 627
Babington's battery, 517             Bronze powder used as a conducting meBatteries, description of, 509         dium, 504
respective peculiarities, 509    Bronzing, varieties of, 572
of different metals, 516             brown, 573
comparative constancy of different   black, 573
kinds, 652                         green, 574
relative power of, 552           Brugnatelli's experiments on deposition,
comparative produce of, 558        491
comparative cost of, 554         Brushes for scratching plated goods, 593
relative intensity of, 559       Brushing silver off copper goods, 597
I AQ  N




634                             INDEX.
Burnishing of plated and gilded goods, Copper moulds, from plaster models, 544
593                                    cloth, 563
Busts and figures, how made, 548         quantity deposited on square foot of
cloth, 563
Cadmium, depositing of, 519              plate engraving, copying of, 568
Calico-printers' rollers, 564            solutions for coating iron, 577
etching of, 564                      mould dissolved from silver, 607
covering iron rollers with copper, 564  mould, protection of, from  silver
Cathode, cations, 509                      deposit, 607
Chains gilt, quantity of gold required, 617  from ores by battery, 526
Chemical vessels, coated with copper, Coppering an iron shaft, 580
objections to, 568                 Copying copper-plate engravings, 568
China saucepans lined by electrotype, Cost of different batteries, 553
568                                    compound cell process, 556
Chloride of silver dissolved in cyanide of Covering iron with zinc, 583
potassium, 589                     Crucibles for cyanide of potassium, 576
Chlorous and zincous, proposed terms for Cruikshank's battery, 517
electrode, &c., 509                Crystals of sulphate of copper on eleoClaims of originality made by experi-  trodes, 562
menters, 506                       Cyanide of copper, modes of preparation,
Clay coated with copper, 50                577
Cleaning of silver, 610                  by adding cyanide of potassium to
Cleaning articles for plating, 593         sulphate of copper, 577
Cleaning powders, 610                    or to oxide of copper, 577
Cloth covered with copper, 563           from ferrocyanide of copper, 578
Coating of figures with copper, 545      solutions, peculiarity of, 578
flowers, 548                     Cyanide of potassium, mode of preparing,
cornice, carvings, 563                  575.
terra cotta, 563                     impurities in, 576
cloth, 563                           cost of manufacture, 576
glass and porcelain, 568             precautions required in making, 576
iron with copper, 574, 579           quantity for 100 ounces of silver,
other metals upon cast iron, 581       589
metals with platinum, 617        Cyanide of silver, preparations of, 587
nickel, 618                        dissolved in yellow prussiate of potpalladium, 618                       ash, 588
Coin, how to take a copy of, 534         by dissolving oxide of silver in CyK,
Coloring of gilding, 614                    588
Common acid batteries, their defects, 619  by dissolving chloride of silver in
Comparative cost of different batteries,   CyK, 589
554                                Cyanogen fumes, effects of breathing
Comparative produce of different batte-   upon health, 615
ries, 553                          Cyanide solution, decompositions, 597
Comparative value of exciting solutions,
517, 536                         Daguerreotypes, electrotyping of, 550
common salt, sal ammoniac, 537     Daniell's experiments on depositing, 492
sulphate of zinc and sulphuric acid, 537  Nomenclature, 501
Composition for taking casts in elastic  battery, how constructed, 622
moulds, 549                                properties of, 522
Compound cell process for electrotyping, Daniell's and Miller's experiments upon
55q                                  electrolysis, 630
Conditions required in gilding, 612  Dead silvering upon medals, 609
Conducting power of metals, 515      Decomposition effected by the pile, 490
Conducting power of solutions, 579            battery, 490
Conduction, illustration of, 580     Decomposition cell, 524
Conduction of metals, effect of, in bat- Decomposition of cyanide solutions, 597
tery, 515                              of plating solution, 597
Constancy of batteries, experiments on, Deer's fat and suet, 545, 548
552                                Defects in batteries, 519
Constant battery, 523                De la Rive and Spencer's failure in gildCopper deposited on lead, 503          ing, cause of, 575
stereotypes, 504                 De la Rue, Mr., 494, 556
impurities in, used for electrodes, 521 Deposit on battery coppers, 520. solutions how made, 533             how to prevent adhesion of, 534




INDEX.                                6305
Deposit, how to make a non-metallic Electro-decompositions, how affecting the
mould, 545                         discovery of electro-metallurgy, 491
non-adherence of, 581              Electro-gilding, 610
dissolving off in solutions, 599       objections to, 615
Deposited metal, quantity of, depending Electro-metallurgy, its discovery, 492
on thickness of plaster, 499                  Smee's opinion of, 492
Depositing by separate battery, 550        description of, first published, 493
silver, 607                            name first applied, 508
lead, iron, and tin, 619               works published upon, 508
Deposition of metals upon one another, Electro-plating, 587
574                                      solutions for, 587
Deposition of one metal on another, 491    advantages of, 605
on other metals as coatings, 617       objections to, 615
of alloys, 622                     Electro relations of metals in different'of bronze, 627                      solutions, 514
Depositions in large moulds or objects, Electrodes, definition of, 509
547                                      size of, 552
Different densities of solutions, 562, 593  crystals of sulphate of copper upon,
effects of, 562                      562
Different metals used for plating, 603     relative size and effects, 595
Dipping articles in acid for plating, 593  unequal action upon, 613
in nitrate of mercury, 693         Electrolysis, Faraday's theory of, 621
partially coated articles, 596         Graham's theory of, 629
Dirck's, Mr., notices of Jordan's claims,  Daniell's theory of, 630
496                                      proposed theory of, 631
Discovery of electro-metallurgy, 492   Electrolyte, 510
Smee's opinion of, 492        Electrotype, Spencer's first paper upon,
Dissolving silver from copper, 597           497
off deposited metal in solution, 559
copper moulds from silver, 607       processes, 533
gold from gilt articles, 614  Electrotypes from daguerreotypes, 550
Distance between battery plates, 613   Electrotyping, forms of apparatus for,
experiments upon, 613
Distillation of mercury from zinc, 556    Electrotyping leaves and ferns, 541
Drawing for glyphographs, 564          Elements, different, of batteries, 513
Drying articles from solution, 592         of electrolytes, non-transfer of, 561
Elkington's patent for silvering, 508
Early deposition of metals, 491        Elsner upon galvanic soldering, 569
Earth battery, properties of, 529      Enamelling by galvanism, 571
Earth and Wollaston's battery compared, Endosmosis of solution, 630
529                                  Engraved copper plates, copying of, 568
Economy of amalgamating zincs, 512     Engraving by galvanism, 494
Effect of conducting power of solutions Etching, experiment on, 500
and metals, 5 79                     Etching of rollers, 564
Effects of conduction for a protection Evils by dipping articles partially coated
coating, 586                           with silver, 596
Effects of cynanogen on health, 615    Exciting solutions for batteries, compara,
Effects of decomposition of cyanide solu-   tive value of, 536
tions, 598                           Experiments on galvanic soldering, 569
Effects of different densities of solutions, Experiments upon distance of battery
562, 598                               plates, 513
Effects of light upon silver solutions, 592
Effects of resistance in batteries, 557  Fallacy of the compound-cell system, 556
Effects of size of electrodes, 595     Faraday's nomenclature, 509
Efflorescence on porous cells, 536         Report to Harbor of Refuge ComnElastic moulding, 544                        missioners, 585
to take figures by, 549                theory of electrolysis, 628
Electric acid, 491                     Ferns, how to copy, 541
Electricity viewed as an acid (electric Ferrocyanide of copper, to make soluacid), 491                             tion, 578
Electricity from sandy deposits, 604   Figures. moulding of, 545
from vats, 600                         covering with copper, 545
Electro-decompositions, early  opinions    and busts, how msde, 548
concerning, 491                      from elastic moulds, 549




636                              INDEX.
First printed description of electro-metal- Instruction to amateurs in glyphography,
iurgy, 494                           566
Flowers, coating of, 648             Intensity explained, 558
Forks and spoons plated by old process,    table of relative batteries, 559
605                                Iron, coated with copper, 574
Fourcroy, 491                            preparation of, for coating, 579
Fusible metal moulds, 540                action with sulphate of copper, 575,
from plaster, 544                      628
shaft covered with copper, 580
Galvanic soldering, 569                  wire drawn after coating, 581
protection of metals, 579            bolts and nails coated, and driven
principles and rate of protection, 585  into wood, 581
protection, none in air, 586         cast, coatedwith other metal, 581
action between the silver and copper  coated with zinc, 583
in dipping, 596                    solution for dissolving copper from
Galvanometers, 533                         silver, 607
Galvano plastic niello, 571              gilding of, 612
German silver, depositing of, 624        coated with platinum, 618
Gilding in 1805. Brugnatelli's experi-   coating of other metals with, 619
ments, 491
Gilding electrotyped daguerreotypes, 550 Jacobi's experiments in deposition, 493
Gilding, electro, 610                Jacobi's, Jordan's, and Spencer's respecprocess of, 612                    tive claims to originality, 496
how to regulate the color of, 614    Jordan's experiments in deposition, 493
by mercury, 615
practical suggestions on, 617    Kind of solutions to be used for coating
Gilt articles, coloring of, 614        metals, 674
Glass and porcelain, coating of, 568
preparation of, for coating, 568  Lace covered with copper, 563
Glyphography, 564                    Lacquer for plaster moulds, 543
instruction in, 566              Large objects, deposition on, 547
Gold, reduction of, by phosphorus, 548 Laws regulating depositions pointed out
preparing solution of, 611         by Spencer, 600
strength of solution, how maintain- Laws of deposition, 506
ed, 613                                claimed by Smee, 507
dissolving from gilt articles, 614    Laws to be observed in coating one metal
quantity necessary to deposit on   with another, 575
some articles, 617             Lead moulds, how prepared, 503
GolJ leaf, used as a conductor, 505         from wood engraving, 503
GraIam's, Prof., Nomenclature, 509       as an element in batteries, 515
theory of electrolysis, 629          gilding upon, 612
Graham's green bronze, 674               coating with, 619
Grove's battery, how constructed, 524   Leather, depositing upon, for printing,
properties of, 525             664
defects of, 526              Light, effects of, upon silver solutions, 592
Gutta percha moulds, 541             Lines upon surface of deposited metal,
with marine glue, 541          cause of, 561, 598
used as a varnish, 568       Loss of weight by dipping, 596
Health, effects on of the mercury gilding, Machine for moving goods while being
615                              plated, 599
of breathing cynanogen fumes, 615  Magneto-electric machine, 530
History of the art of electro-metallurgy,  improved, 530
489                                Maintaining gold solution of proper
Historical anomaly relative to the dis-   strength, 613
covery of the art, 496             Marine glue, with gutta percha, 514
Hyposulphite of soda, preparation of, 591 Mason's application of separate battery,
silver solution, 590               505
Medal, preparation of, for depositing
Illustration of conduction, 580        upon, 534
Impurities in sulphate of copper, 533    Medals, dead silvering of, 609
cyanide of potassium, 576        Mercury absorbed by zinc, 512
Influence of galvanism  in protecting    recovery from waste zincs, 512, 556
metals, 585                            dissolved in nitric acid, 593




INDEX.                              637
Mercury, gilding by means of, 615    Opinions concerning electro-deposition,
Metal moulds, 547                      491
Metallic veins, on the production of, 501 Opposite currents of electricity from vats,
Metals, properties of, fit for batteries,   600
515                                Ornaments, how made, and applied to
Metals, their conductingpowers as affect-   old plate, 604
ing deposit, 580                   Overcoming resistance in solution, 557
Method of working cyanide of copper so- Oxide of silver, 588
lution, 578                        Oxidized silver, 609
Millward's magneto machine, 530
Mitchell's mathine for motion, 598   Palladium, coating with, 618
Mixture for coloring gold, 614       Palmer's glyphography, 564
Mode of suspending electrotypes, 560    Partitions in battery troughs, 519
Motion, machine for producing, 599   Paterson, Dr. Thomas, 550
Moulds in lead, how prepared, 503    Patent for electro-magneto plating, 530
from wood engravings, 503        for depositing alloys, 623
directions for making, 538           for coating china and glass, 568
substances for making, 539           for extracting copper from ores, 625
preparation of wax for, 539      Patents for electro-metallurgy, 508
to take, in wax, 539             Peculiarity in depositing copper from cyin plaster of Paris, 539       anide solution, 578
in fusible metal, 540        Pencil case, gold required to gild, 617
in gutta percha, 541         Phosphorus solution for reducing gold
of wax, taken from plaster, 543    and silver, 548
of fusible alloy from plaster, 544    Pile, chemical decomposition by, 490
in plaster from plaster, 543     Pitch, preparation for protecting copper
of copper from plaster, 544        from deposit, 608
non-metallic prepared to receive de- Plaster of Paris, coated with copper, 504
posits, 545                    Plaster of Paris moulds, how taken, 539
precautions necessary in putting         taken from plaster models, 543
them into solutions, 547       Platinizing silver, 527
Moulding, elastic, how made, 544     Platinode, 509
of figures, 545                  Platinum as an element in batteries, 575
Mounts, silver, how made, 604        Platinum, coating with, 617
Murray's, Robert, discovery of the use Platinum, nitro-muriate,527
of plumbago, 505                       solutions of, 617
Music, printing of, 564              Plating, electro, 587
solution, how prepared, 587
Nature printing, 542                     practical instructions in, 594
Negative pole, 509                       in large factories, 594
Newton's patent for coating cast iron, 581  metals best suited for, 603
Nicholson's experiments, 491             old method, 604
Nickel, coating metals with, 618     Plumbago as a conducting medium, discoating, use of, for gas pipes, &c.,  covered, 505
619                            Poles, positive and negative, defined, 509
Nitric acid for dipping (dipper's aqua- Porcelain covered with copper, 568
fortis), 593                       Porous cell, depositions on, 523
Nomenclature, 509                    Porous cells, how preserved, 523
Faraday's, 509                   Porous vessel and diaphragm, 535
Daniell's 509                    Position of electrotypes in solutions, 560
Graham's, 509                    Positive pole, 509
Non-adherence of deposit, 581        Potash, sulphite, how prepared, 591
Non-metallic moulds, preparation of, for Potassium, cyanide of, mode of preparing
deposits, 545                            it, 576
Non-transfer of elements in electrolysis,  cost of making, 576
561                                Practical instructions in plating, 594
objections to solid deposit, 607
Objections to electro-plating, 606       suggestions on gilding, 617
silver articles made by battery, Precautions on putting moulds into so608                          lution, 547
electro-gilding, 615         Preparation of non-metallic moulds for
Observed facts, use of, 493                receiving deposit, 645
Old method of gilding, 615               glyphotypes, 564
plating, 604                     transfer paper, 565




638                              INDEX.
Preparation of silver, 587            Silver, hyposulphite solution, 590
articles for plating, 593             recovered from solutions, 592
solutions of gold, 610                curious alloy of, 592
Preventing electrotypes adhering, 502     hardness of, effected by battery, 594
Principles of galvanic protection, 579    mounts in the old process, 604
Printing, difficulties experienced in pre-  articles made by battery, 607
paring plates for, 499                  solution for making solid articles,
Printing by electrotype plates, proposed    607
by Spencer, 499, 506                    made by electrotype, objections to,
Printing by electrotypes, 564               608
Printing of leather by electrotypes, 564  protection of, in air, E)9
Printing by glyphography, 566             cleaning of, 610
Process of gilding, 612               Silvering, dead, upon medals, 609
Properties of metals fit for batteries, 515 Single cell operation, 533
Protection of silver coating, 593     Single pair of plates, 510
surface, 602                  Size of electrodes, 552
Smee's advice to capitalists, 554
Quality of magneto-machines, 523          claims to the original discovery of
Quality of metal regulated by battery,      the laws of electro-deposition, 506
594                                 Smee's battery, how constructed, 527
Quantity of cyanide of potassium to pre-      modifications of, 528
cipitate 100 ounces of silver, 589          properties of, 528
Quantity of metals deposited, how known,      compound, 528
596                                 Soda, hyposulphite, preparation of, 590
Quantity of nitric acid to dissolve 100 Soldering by deposition, 569
ounces of silver, 588               Solid silver articles made by battery, 607
Solutions for battery, how often changed,
Rate of depositing silver, 603              537,Recovery of gold from solutions, 615      different density of, 562
Recovery of silver from solution, 592     silver, best method of making, 589
Regulating of the color of gilding, 614     for amateurs, 590
Relative intensity of batteries, 559      best sort, for depositing solid silver,.
Relative power of batteries, 652            607
Removing of grease or oil from metals,    of gold, preparation of, 610
579                                       by acid, 611
Reptiles, moulding of, 542                  by battery, 611
Resistance, effects on deposits, 551, 557  of aluminium, 619
Rollers for printing, 564                 of silicium, 621
Rosin and wax moulds, 539                 for deposition of alloys, 622
Sources of defects in batteries, 511
Sal ammoniac, solution of, for batteries, Spencer and De la Rive's failure in gild537                                  ing, 575
Salt, solution of, for batteries, 491  Spencer, his first experiments, 493
Salts of cyanide of copper and potassium,  his first paper upon electrotyping,
676                                       495
Sand used for scouring, 593               effects of it when first published, 496
Sandy deposit, 534                        Jacobi's and Jordan's claims, 496
electricity from, 604             manipulations for electrotypes, 497
Scratch brushes, 593                      first electrotype, 501
Sea-weeds, how to copy, 541           Stearine for moulds, 545
Shaw's manual of electro-metallurgy, 508 Stereotyping in copperby electrotype, 504
Ships, sheathing of, how destroyed, 586 Stripping silver from copper, 597
Single cell, 533                          gold from gilt articles, 614
experiments with, 533         Sturgeon's art of electrotyping, 508
Single pair of plates, 510            Substitute for silver in Smee's battery,
Silicium, 619                           528
Silver platinizing, 527               Sulphate of copper, impurities, 533
salts reduced by phosphorus, 548          zinc for batteries, 536, 537
solutions for plating, 587, 588, 589      zinc, solution for coating, 583
dissolved in acids, 587, 588              action upon iron, 628
oxide of, dissolved in cyanide of po- Sulphate of copper and cyanide of potastassium, 588                      sium, mixed, 576
chloride of, dissolved in cyanide of Sulphite of silver solution, 591
potassium, 589                      potash, preparation of, 591




INDEX.                               639
Sulphuret of carbon, used for bright Voltaic pile, how constructed, 489
plating, 603
Sulphuric acid for batteries, 537      Walker's manipulations, 508
Sulphurous acid, how prepared, 592    Waste zinc. recovery of mercury from, 556
Suspending electrotypes, mode of, 560    Watch case gilt, how much gold required,
Sustaining battery, 621                  617
Wax, to prepare for moulds, 539
Table of exciting solutions for batteries,  to take moulds in, 539
537                                 and rosin, 539
relative intensity of batteries, 559   Wax moulds taken from plaster models,
test of free cyanide of potassium in   543
solutions, 602                  Weight of silver deposited, how ascerTable covers, gilt, 563                     tained, 596
Taking silver from copper, 597             loss of, by dipping, 596
Testing cyanide of potassium in gold so- Wire, iron, coated, 579
lution, 613                         Wollaston's experiments on galvanism,
Tests for cyanide of potassium, 601      492
Thenard, 491                          Wollaston's battery, 518
Theoretical observations, 628                  modification, 518
Theory of electrolysis proposed, 631       and earth battery compared, 530
Thimble, gold required to gild, 617   Woolrich's magneto-electric machine, 530
Time taken by' different batteries to de- Works published upon  electro-metalposit 1 lb. of copper, 653            lurgy, 508
Tin, gilding upon, 612
depositing of, 619                Yellow prussiate of potash, used for dissolutions of, 622                   solving cyanide of silver, 588
confervae, phenomenon of, 622
Transfer-paper, preparation of, 567   Zincode, proposed term, 509
Transfer of solutions. 629            Zincous and chlorous, 509
Transfer of elements of electrolyte, 629  Zinc, how to amalgamate plates of, 511
best sort for batteries, 512
Unequal action upon electrodes, 613        reduced in battery, 520
Use of metal moulds, 547                   how often the plates should be
of intensity batteries, 558              amalgamated, 537
of zinc coating for iron, 584         sulphate solution of, for batteries,
of dipping in nitrate of mercury, 594    637
Uses of observed facts, 493                recovery of mercury from, 556
solution of, for coating iron, 583
Van Mons, 491                              deposit of, on black lead, 584
Vauquelin, 491                             use of a coating of, 583
Veins, metallic, 501                  Zinced iron, Dr. Faraday's opinion of,
Volta's discovery, 489                   584








CATALOGUE
OF
PRACTICAL AND SCIENTIFIC BOOKS,
PUBLISHED BY
HENRY CAREY BAIRD,
INDUSTRIAL PUBLISHER,
TNo- 406  WALNTUT STREET,
PHILADELPHIA.
U   Any of the Books comprised in this Catalogue will be sent by mail,
free of postage, at the publication price.
I'Y NEW AND ENLARGED CATALOGUE, 95 pages Svo., with full descriptions
of Books, will be sent, free of postage, to any one who will favor me
with his address.
ARMENGAUD, AMOUROUX, AND JOHNSON. —THE PRACTICAL
DRAUGHTSMAN'S BOOK OF INDUSTRIAL DESIGN, AND
MACHINIST'S AND ENGINEER'S DRAWING COMPANION:
Forming a complete course of Mechanical Engineering and
Architectural Drawing. From the French of M. Armengaud
the elder, Prof. of Design in the Conservatoire of Arts and
Industry, Paris, and MM. Armengaud the younger and Amouroux, Civil Engineers. Rewritten and arranged, with additional matter and plates, selections from and examples of the
most useful and generally employed mechanism of the day.
By WILLIAM JOHNSON, Assoc. Inst. C. E., Editor of "The
Practical Mechanic's Journal." Illustrated by 50 folio steel
plates and 50 wood-cuts.  A new edition, 4to.. $10 00
ARLOT.-A COMPLETE GUIDE FOR COACH PAINTERS.
Translated from the French of M. ARLOT, Coach Painter; late
Master Painter for eleven years with M. Ehtler, Coach Manufacturer, Paris. With important American additions.. $1 25
ARROWSMITH.-PAPER-HANGER'S COMPANION:
A Treatise in which the Practical Operations of the Trade are
Systematically laid down: with Copious Directions Preparatory to Papering; Preventives against the Effect of Damp on
Walls; the Various Cements and Pastes adapted to the Several Purposes of the Trade; Observations and Directions for
the Panelling and Ornamenting of Rooms, &c. By JAIuES
ARROWSMITH. 12mo., cloth.                          $1 25




2         HENRY CAREY BAIRD'S CATALOGUE.
BAIRD.-THE AMERICAN COTTON SPINNER, AND MANA.
GER'S AND CARDER'S GUIDE:
A Practical Treatise on Cotton Spinning; giving the Dimensions and Speed of Machinery, Draught and Twist Calculations, etc.; with notices of recent Improvements: together
with Rules and Examples for making changes in the sizes and
numbers of Roving and Yarn. Compiled from the papers of
the late ROBERT IH. BAIRD. 12mo....   1 50
BAKER.-LONG-SPAN RAILWAY BRIDGES:
Comprising Investigations of the Comparative Theoretical and
Practical Advantages of the various Adopted or Proposed Type
Systems of Construction; with numerous Formulve and Tables. By B. Baker. 12mo..$2 00
BAXEWELL.-A MANUAL OF ELECTRICITY-PRACTICAL AND
THIEORETICAL:
By F. C. BAKEWELL, Inventor of the Copying Telegraph. Se,
cond Edition. Revised and enlarged. Illustrated by numerous engravings. 12mo. Cloth
BEANS.-A TREATISE ON RAILROAD CURVES AND THE LOCATION OF RAILROADS:
By E. W. BEANS, C. E. 12mo..                   $. 00)
BLENKARN.-PRACTICAL SPECIFICATIONS OF WORKS EXECUTED IN  ARCHITECTURE, CIVIL AND MECHANICAL
ENGINEERING, AND IN ROAD MAKING AND SEWERING:
To which are added a series of practically useful Agreements
and Reports. By JOHN BLEN1KARN. Illustrated by fifteen
large folding plates. 8yo... $9 00
BLINN.-A. PRACTICAL WORKSHOP COMPANION FOR TIN,
SHEET-IRON, AND COPPER-PLATE WORKERS:
Containing Rules for Describing various kinds of Patterns
used by Tin, Sheet-iron, and Copper-plate Workers; Practical
Geometry; Mensuration of Surfaces and Solids; Tables of the
Weight of Metals, Lead Pipe, etc.; Tables of Areas and Circumferences of Circles; Japans, Varnishes, Lackers, Cements,
Compositions, etc. etc. By LEROY J. BLINN, Master Mechanic. With over One Hundred Illustrations. 12mo. $2 50




HENRY CAREY BAIRD'S CATALOGUE.                 3
B00TH.-MARBLE WORKER'S MANUAL:
Containing Practical Information respecting Marbles in general, their Cutting, Working, and Polishing; Veneering of
Marble; Mosaics; Composition and Use of Artificial Marble,
Stuccos, Cements, Receipts, Secrets, etc. etc. Translated
from the French by M. L. BOOTH. With an Appendix concerning American Marbles. 12mo., cloth. $1 50
BOOTH AND MORFIT.-THE ENCYCLOPEDIA OF CHEMISTRY,
PRACTICAL AND, THEORETICAL:
Embracing its application to the Arts, Metallurgy, Mineralogy,
Geology, Medicine, and Pharmacy. By JAMES C. BOOTH,
Melter and Refiner in the United States Mint, Professor of
Applied Chemistry in the Franklin Institute, etc., assisted by
CAMPBELL MORFIT, author of "Chemical Manipulations," etc.
Seventh edition. Complete in one volume, royal 8vo., 978
pages, with numerous wood-cuts and other illustrations. $5 00
B OWDITCH.-ANALYSIS, TECHNICAL VALUATION, PURIFICATION, AND USE OF COAL GAS:
By Rev. W. R. BOWDITCM Illustrated with wood engravings. 8vo.                                       $6 50
BOX.-PRACTICAL HYDRAULICS:
A Series of Rules and Tables for the use of Engineers, etc.
By THOMAS Box. 12mo..$2 50
B.UCKMASTER.-THE ELEMENTS OF MECHANICAL PHYSICS:
By J. C. BUCKMASTER, late Student in the Government School
of Mines; Certified Teacher of Science by the Department of
Science and Art; Examiner in Chemistry and Physics in the
Royal College of Preceptors; and late Lecturer in Chemistry
and Physics of the Royal Polytechnic Institute. Illustrated
with numerous engravings. In one vol. 12mo.. $1 50
BULLOCK.-THE AMERICAN COTTAGE BUILDER:
A Series of Designs, Plans, and Specifications, from $200 to
to $20,000 for Homes for the People; together with Warming, Ventilation, Drainage, Painting, and Landscape Gardening. By JOHN BULLOCK, Architect, Civil Engineer, Mechanician, and Editor of "The Rudiments of Architecture and
Building," etc. Illustrated by 75 engravings. In one vol.
8vo.                                             $3 50




4         HENRY CAREY BAIRD'S CATALOGUE.
B ULLOCK. - THE  RUDIMENTS  02? ARCHITECTURE  AND
BUILDING:
For the use of Architects, Builders, Draughtsmen, Machinists, Engineers, and Mechanics. Edited by JOHN BULLOCK,
author of " The American Cottage Builder." Illustrated by
250 engravings. In one volume 8vo.... $3 50
BURGH.-PRACTICAL ILLUSTRATIONS OF LAND AND MARINE ENGINES:
Showing in detail the Modern Improvements of High and Low
Pressure, Surface Condensation, and Super-heating, together
with Land and Marine Boilers. By N. P. BURGH, Engineer.
Illustrated by twenty plates, double elephant folio, with text.
$21 00
BURGH.-PRACTICAL RULES FOR THE PROPORTIONS OF
MODERN ENGINES AND BOILERS FOR LAND AND MARINE PURPOSES.
By N. P. BURGH, Engineer. 12mo... $2 00
BJURGH.-THE SLIDE-VALVE PRACTICALLY CONSIDERED:
By N. P. BURGH, author of " A Treatise on Sugar Machinery,"
"Practical Illustrations of Land and Marine Engines," "A
Pocket-Book of Practical Rules for Designing Land and Marine Engines, Boilers," etc. etc. etc. Completely illustrated.
12mo.                                            $2 00
BYRN.-THE COMPLETE PRACTICAL BREWER:
Or, Plain, Accurate, and Thorough Instructions in the Art of
Brewing Beer, Ale, Porter, including the Process of making
Bavarian Beer, all the Small Beers, such as Root-beer, Gingerpop, Sarsaparilla-beer, Mead, Spruce beer, etc. etc. Adapted
to the use of Public Brewers and Private Families. By M. L.
FAYETTE BYRN, M. D. With illustrations. 12mo.   $1 25
BYRr. —THE COMPLETE PRACTICAL DISTILLER:
Comprising the most perfect and exact Theoretical and Practical Description of the Art of Distillation and Rectification;
including all of the most recent improvements in distilling
apparatus; instructions for preparing spirits from the numerous vegetables, fruits, etc.; directions for the distillation and
preparation of all kinds of brandies and other spirits, spirituous and other compounds, etc. etc.; all of which is so siniplified that it is adapted not only to the use of extensive distillers, but for every farmer, or others who may wish to engage
in the art of distilling. By M. LA FAYETTE BYRN, 1. D.
With numerous engravings. In one volume, 12mo.   $1 50




tENRY CAREY BAIRD'S CATALOGUE                 5
BYRNE.-POCKET BOOK FOR RAILROAD AND CIVIL ENGINEERS:
Containing New, Exact, and Concise Methods for Laying out
Railroad Curves, Switches, Frog Angles and Crossings; the
Staking out of work; Levelling; the Calculation of Cuttings; Embankments; Earth-work, etc. By OLIVER BYRNE.
Illustrated, 18mo., full bound...         $1 75
BYRNE.-THE HANDBOOK FOR THE ARTISAN, IJECHANIC,
AND ENGINEER:
By OLIVER BYRNE. Illustrated by 185 Wood Engravings. Svo.
$5 00
BYRNE.-THE ESSENTIAL ELEMENTS OF PRACTICAL MECHANICS:
For Engineering Students, based on the Principle of Work.
By OLIVER BYRNE. Illustrated by Numerous Wood Engravings, 12mo.                                      $3 63
BYRNE. —THE PRACTICAL METAL-WORKER'S ASSISTANT:
Comprising Metallurgic Chemistry; the Arts of Working all
Metals and Alloys; Forging of Iron and Steel; Hardening and
Tempering; Melting and Mixing; Casting and Founding;
Works in Sheet Metal; the Processes Dependent on the
Ductility of the Metals; Soldering; and the most Improved
Processes and Tools employed by Metal-Workers. With the
Application of the Art of Electro-Metallurgy to Manufacturing Processes; collected from Original Sources, and from the
Works of Holtzapffel, Bergeron, Leupold, Plumier, Napier, and
others. By OLIVER BYRNE. A New, Revised, and improved
Edition, with Additions by John Scoffern, M. B, William Clay,
Wm. Fairbairn, F. R. S., and James Napier. With Five Hundred and Ninety-two Engravings; Illustrating every Branch
of the Subject. In one volume, 8vo. 652 pages. $7 00
BYRNE.-THE PRACTICAL MODEL CALCULATOR:
For the Engineer, Mechanic, Manufacturer of Engine Work,
Naval Architect, Miner, and Millwright. By OLIVER BYRNE.
1 volume, 8vo., nearly 600 pages.... $4 50
EMXROSE].-MANUAL OF WOOD CARVIN3*: With Practical Illustrations for Learners of the Art, and Original and Selected designs. By WILLIAM BEeNROSE, Jr. With an Introduction by
LLEWELLYN JEWITT, F. S. A., etc. With 128 Illustrations. 4to.,
cloth.......    $3 00




6          I~HENRY CAREY BAIRD'S CATALOGUE.
B AIRD. —:-PROTECTION OF HOME LABOR AND HOME PRODUCTIONS NECESSARY TO THE PROSPERITY  OF THE
AMERICAN FARMER:
By HENRY CAREY BAIRD. 8vo., paper...   10
BAIRD.-THE RIGHTS OF AMERICAN PRODUCERS, AND THE
WRONGS OF BRITISH FREE TRADE REVENUE REFORM.
By HENRY CAREY BAIRD. (1870)....    5
B AIRD.-SOME OF THE FALLACIES OF BRITISH-FREE-TRADE
REVENUE-REFORM.
Two Letters to Prof. A. L. Perry, of Williams College, Mass. By
HENRY CAREY BAIRD. (1871.) Paper....    5
BAIRD.-STANDARD WAGES COMPUTING TABLES:
An Improvement in all former Methods of Computation, so arranged that wages for days, hours, or fractions of hours, at a specified rate per day or hour, may be ascertained at a glance. By
T. SPANGLER BAIRD. Oblong folio.                  $5 00
BAUERMAN. —TREATISE ON THE METALLURGY OF IRON.
Illustrated. 12mo.                                 $2 50
BICKNELL'S VILLAGE BUILDER.
55 large plates. 4to.                              $10 00
BISHOP.-A HISTORY OF AMERICAN MANUFACTURES:
From 1608 to 1866; exhibiting the Origin and Growth of the Principal Mechanic Arts and Manufactures, from the Earliest Colonial
Period to the Present Time; By J. LEANDER BISHOP, M. D., EDWARD YOUNG, and EDWIN T. FREEDLEY. Three vols. 8vo.,
$10 00
B OX;-A PRACTICAL TREATISE ON HEAT AS APPLIED TO
THE USEFUL ARTS:
For the use of Engineers, Architects, etc. By THOMAS Box, author of "Practical Hydraulics."  Illustrated by 14 plates, containing 114 figures. 12mo.                         $4 25
CABINET MAKER'S ALBUM OF FURNITURE:
Comprising a Collection of Designs for the Newest and Most
Elegant Styles of Furniture. Illustrated by Forty-eight Large
and Beautifully Engraved Plates. In one volume, oblong
$3 C00
CHAPMAN.-A TREATISE ON ROPE-MARING:
As practised in private and public Rope-yards, with a Description
of the Manufacture, Rules, Tables of Weights, etc., adapted to the
Trade; Shipping, Mining, Railways, Builders, etc. By ROBERT
CHAPMAN. 24mo....     $1 50




HENRY CAREY BAIRD'S CATALOGUE.                7
C RAIr-THE PRACTICAL AMERICAN  MILLWRIGHT AND
MILLER.
Comprising the Elementary Principles of Mechanics, Mechanism, and Motive Power, Hydraulics and Hydraulic
Motors, Mill-dams, Saw Mills, Grist Mills, the Oat Meal Mill,
the Barley Mill, Wool Carding, and Cloth Fulling and Dressing, Wind Mills, Steam Power, &c. By DAVID CRAIK, Millwright. Illustrated by numerous wood engravings, and five
folding plates. 1 vol. 8vo.... $5 00
C AMPIN.-A PRACTICAL TREATISE ON MECHANICAL ENGINEERING:
Comprising Metallurgy, Moulding, Casting, Forging, Tools,
Workshop Machinery, Mechanical Manipulation, Manufacture
of Steam-engines, etc. etc. With an Appendix on the Analysis of Iron and Iron Ores. By FRANCIS CAMPIN, C. E. TG
which are added, Observations on the Construction of Steam
Boilers, and Remarks upon Furnaces used for Smoke Prevention; with a Chapter on Explosions. By R. Armstrong, C. E.,
and John Bourne. Rules for Calculating the Change Wheels
for Screws on a Turning Lathe, and for a Wheel-cutting
Machine. By J. LA NICCA. Management of Steel, including
Forging, Hardening, Tempering, Annealing, Shrinking, and
Expansion. And the Case-hardening of Iron. By G. EDE.
8vo. Illustrated with 29 plates and 100 wood engravings.
$6 00
(AMPIXN.-THE PRACTICE OF HAND-TURNING IN WOOD,
IVORY, SHELL, ETC.:
With Instructions for Turning such works in Metal as may be
required in the Practice of Turning Wood, Ivory, etc. Also
an Appendix on Ornamental Turning. By FRANCIS CAMPIN,
with Numerous Illustrations, 12mo., cloth.. $3 00
C APRON DE DOLE,-DUSSAUCE.-BLUES AND CARMINES OF
INDIGO.
A Practical Treatise on the Fabrication of every Commercial
Product derived from Indigo. By FELICIEN CAPRON DE DOLE.
Translated, with important additions, by Professor H. Duvs
SAUCE. 12mo.




H ENRY CAREY BAIRD'S CATALOGUE.
CIREY.-THE WORKS OF HENRY C. CAREY:
CONTRACTION OR EXPANSION? REPUDIATION OR RESUMPTION? Letters to Hon. Hugh McCulloch. 8vo.   38
FINANCIAL CRISES, their Causes and Effects. 8vo. paper
25
HARMONY OF INTERESTS; Agricultural, Manufacturing,
and Commercial. 8vo., paper..          $1 00
Do.      do.           cloth... $1 50
LETTERS TO THE PRESIDENT OF THE UNITED STATES.
Paper...$1 00
MANUAL OF SOCIAL SCIENCE.  Condensed from Carey's
"Principles of Social Science."  By KATE McKEAN. 1 vol.
lmo.......... $2 25
MISCELLANEOUS WORKS: comprising "Harmony of Interests," "Money," "Letters to the President," "French and
American Tariffs," "Financial Crises," "The Way to Outdo
England without Fighting Her," "Resources of the Union,"
"The Public Debt," "Contraction or Expansion," "Review
of the Decade 1857-'67," " Reconstruction," etc. etc. 1 vol.
8vo., cloth..$4 50
MONEY: A LECTURE before the N. Y. Geographical and Statistical Society. 8vo., paper..                     25
PAST, PRESENT, AND FUTURE. 8vo..              -. $2 50
PRINCIPLES OF SOCIAL SCIENCE. 3 volumes 8vo., cloth
$10 00
REVIEW  OF THE DECADE 1857-'67. 8vo., paper            50
RECONSTRUCTION: INDUSTRIAL, FINANCIAL, AND POLITICAL. Letters to the Hon. Henry Wilson, U. S. S. 8vo,
paper...                                            50
THE PUBLIC DEBT, LOCAL AND  NATIONAL.  How to
provide for its discharge while lessening the burden of Taxation. Letter to David A. Wells, Esq., U. S. Revenue Commission. 8vo., paper..                        25
THE RESOURCES OF THE UNION. A Lecture read, Dec.
1865, before the American Geographical and Statistical Society, N. Y., and before the American Association for the Advancement of Social Science, Boston...       50
THE SLAVE TRADE, DOMESTIC AND FOREIGN; Why it
Exists, and How itmay be Extinguished. 12mo., cloth  $1 5Q




HENRY CAREY BAIRD'S CATALOGUE.                 9
LETTERS  ON  INTERNATIONAL  COPYRIGHT.  (1867.)
Paper.50
REVIEW OF THE FARMERS' QUESTION. (1870.) Paper 25
RESUMPTION! HOW IT MAY PROFITABLY BE BROUGHT
AROUT. (1869.) 8vo., paper....    50
REVIEW OF THE REPORT OF HON. D. A. WELLS, Special
Commissioner of the Revenue. (1869.) 8vo., paper    50
SHALL WE HAVE PEACE? Peace Financial and Peace Political. Letters to the President Elect. (1868.) 8vo., paper 50
THE FINANCE MINISTER AND THE CURRENCY, AND
THE PUBLIC DEBT. (1868.) 8vo., paper.   -.    50
THE WAY TO OUTDO ENGLAND WITHOUT FIGHTING
HER. Letters to Hon. Schuyler Colfax. (1865.) 8vo., paper
$1 00
WEALTH! OF WHAT DOES IT CONSIST? (1870.) Paper 25
IAMUS.-A TREATISE ON THE TEETH OF WHEELS:
Demonstrating the best forms which can be given to them for the
purposes of Machinery, such as Mill-work and Clock-work. Translated from the French of M. CAMus.  By JOHN I. HIAWKINS.
Illustrated by 40 plates. 8vo....  $3 00
COXE.-XINING LEGISLATION.
A paper read before the Am. Social Science Association.  By
ECKLEY B. COXE. Paper.                             20
3DLBURN.-THE GAS-WORKS OF LONDON:
Comprising a sketch of the Gas-works of the city, Process of
Manufacture, Quantity Produced, Cost, Profit, etc. By ZERAH
COLBURN. 8vo., cloth......        5
C 3LBURN.-THE LOCOMOTIVE ENGINE:
Including a Description of its Structure, Rules for Estimating its Capabilities, and Practical Observations on its Construction and Management. By ZERAH COLBURN. Illustrated. A
new edition. 12mo..                         $1 25
0OLBURN AND XAW.-THE WATER-WORKS OF LONDON:
Together with a Series of Articles on various other Waterworks. By ZERAH COLBURN and W. MAW. Reprinted from
",Engineering."  In one volume, 8vo.. $4 00
D &GUERREOTYPIST AND PHOTOGRAPHER'S COMPANION:
12mo., cloth........                         1 25




10        HENRY CAREY BAIRD'S CATALOGUE.
DIRCgS,-PERPETUAL MOTION:
Or Search for Self-Motive Power during the 17th, 18th, and
19th centuries. Illustrated from various authentic sources in
Papers, Essays, Letters, Paragraphs, and numerous Patent
Specifications, with an Introductory Essay by 1IENRY DIRCuS,
C. E.  Illustrated by numerous engravings of machines.
12mo., cloth........ $3 50
DIXON.-THE PRACTICAL MILLWRIGHT'S AND ENGINEER'S
GUIDE:
Or Tables for Finding the Diameter and Power of Cogwheels;
Diameter, Weight, and Power of Shafts; Diameter and Strength
of Bolts, etc. etc. By THOMAS DIXON. 12mo., cloth. $1 50
DUNCAN.-PRACTICAL SURVEYOR'S GUIDE:
Containing the necessary information to make any person, of
common capacity, a finished land surveyor without the aid of
a teacher. By ANDREW DUNCAN. Illustrated. 12mo., cloth.
$1 25
DUSSAtCE.-A  NEW  AND  COMPLETE TREATISE  ON THE
ARTS OF TANNING, CURRYING, AND LEATHER DRESSING:
Comprising all the Discoveries and Improvements made in
France, Great Britain, and the United States. Edited from
Notes and Documents of Messrs. Sallerou, Grouvelle, Duval,
Dessables, Labarraque, Payen, Rend, De Fontenelle, IMalapeyre, etc. etc. By Prof. H. DussAucE, Chemist. Illustrated
by 212 wood engravings. 8vo.                     $10 00
DUSSAUCE.-A GENERAL TREATISE ON THE MANUFACTURE
OF SOAP, THEORETICAL AND PRACTICAL:
Comprising the Chemistry of the Art, a Description of all the Raw
Materials and their Uses. Directions for the Establishment of a
Soap Factory, with the necessary Apparatus, Instructions in the
Manufacture of every variety of Soap, the Assay and Determination
of the Value of Alkalies, Fatty Substances, Soaps, etc. etc. By
PROFESSOR H. DUSSAUCE. With an Appendix, containing Extracts from the Reports of the International Jury on Soaps, as
exhibited in the Paris Universal Exposition, 1867, numerous
Tables, etc. etc. Illustrated by engravings. In one volume Svo.
of over 800 pages.. $10 00
DUSSAUCE.-PRACTICAL TREATISE ON THE FABRICATION
OF MATCHES, GUN COTTON, AND FULMINATING POWDERS.
By Professor H. DussAucE. 12mo.... $3 00




HENRY CAREY BAIRD'S CATALOGUE.
DUSSAUCE. —,  PRACTICAL GUIDE FOR THE PERFUMER:
Being a New Treatise on Perfumery the most favorable to the
Beauty without being injurious to the Health, comprising a
Description of the substances used in Perfumery, the Formulse of more than one thousand Preparations, such as Cosmetics, Perfumed Oils, Tooth Powders, Waters, Extracts, Tinctures, Infusions, Vinaigres, Essential Oils, Pastels, Creams,
Soaps, and many new Hygienic Products not hitherto described.
Edited from Notes and Documents of Messrs. Debay, Lunel,
etc. With additions by Professor H. DusSAUCE, Chemist. 12mo.
$3 00
DUSSAUCE.-A GENERAL TREATISE ON THE MANUFACTURE
OF VINEGAR, THEORETICAL AND PRACTICAL.
Comprising the various methods, by the slow and the quick pro.
cesses, with Alcohol, Wine, Grain, Cider, and Molasses, as well
as the Fabrication of Wood Vinegar, etc. By Prof. H. DussAUCE.
i2mo.                                               $5 00
fUPLAIS.-A COMPLETE TREATISE ON THE DISTILLATION
AND MANUFACTURE OF ALCOHOLIC LIQUORS:
From the French of M. DUPLAIS. Translated and Edited by M.
McKENNIE, Ml D. Illustrated by numerous large plates and wood
engravings of the best apparatus calculated for producing the
finest products. In one vol. royal 8vo.            $10 00
07  This is a treatise. of the highest scientific merit and of the
greatest practical value, surpassing in these respects, as well as
in the variety of its contents, any similar volume in the English
language.
DE GRAFF.-THE GEOMETRICAL STAIR-BUILDERS' GUIDE:
Being a Plain Practical System of Hand-Railing, embracing all
its necessary Details, and Geometrically Illustrated by 22 Steel
Engravings; together with the use of the most approved princi.
ples of Practical Geometry. By SIMON DE GRAFN, Architect.
4to......                                 $5 09
DYER A'ID COLOR-MAKER'S COMPANION:
Containing upwards of two hundred Receipts for making Colors, on the most approved principles, for all the various styles
and fabrics now in existence; with the Scouring Process, and
plain Directions for Preparing, Washing-off, and Finishing the
Goods. In one vol. 12mo.                           $1 25




12        HENRY CAREY BAIRD'S CATALOGUE.
E ASTON.-A PRACTICAL TREATISE ON STREET OR HORSEPOWER RAILWAYS:
Their Location, Construction, and Management; with General
Plans and Rules for their Organization and Operation; together with Examinations as to their Comparative Advantages
over the Omnibus System, and Inquiries as to their Value for
Investment; including Copies of Municipal Ordinances relating thereto. By ALEXANDER EASTON, C. E. Illustrated by 23
plates, 8vo., cloth.....         $2 00
F 3RSYTH.-BOOK OF DESIGNS FOR HEAD-STONES, MURAL,
AND OTHER MONUMENTS:
Containing 78 Elaborate and E;squisite Designs. By FORSYTH.
4to., cloth.                                    $5 00
**t This volume, for the beauty and variety of its designs, has
never been surpassed by any publication of the kind, and should
be in the hands of every marble-worker who does fine monumental
work.
]FAIRBAIRN.-THE PRINCIPLES OF MECHANISM AND MACHINERY OF TRANSMISSION:
Comprising the Principles of Mechanism, Wheels, and Pulleys,
Strength and Proportions of Shafts, Couplings of Shafts, and
Engaging and Disengaging Gear. By WILLIAM FAIRBAIRN,
Esq., C. E., LL. D., F. R. S., F. G. S., Corresponding Member
of the National Institute of France, and of the Royal Academy
of Turin; Chevalier of the Legion of Honor, etc. etc. Beautifully illustrated by over 150 wood-cuts. In one volume 12mo.
$2 50
IRBAIRN. —PRIME-MOVERS:
Comprising the Accumulation of Water-power; the Construction of Water-wheels and Turbines; the Properties of Steam;
the Varieties of Steam-engines and Boilers and Wind-mills.
By WILLIAM FAIRBAIRN, C. E., LL. D., F. R. S., F. G. S. Author'of "Principles of Mechanism and the Machinery of Transmission." With Numerous Illustrations. In one volume. (In
press.)
GILBART.-A PRACTICAL TREATISE ON BANXING:
By JAMES WILLIAM GILBART. TO which is added: THE NATIONAL BANK ACT AS NOW IN FORCE. 8VO..   $4 50
GESNER.-A PRACTICAL TREATISE ON COAL, PETROLEUM,
AND OTHER DISTILLED OILS.
By ABRAHAM GESNER, M.D., F. G. S. Second edition, revised
and enlarged. By GEORGE WELTDEN GESNER, Consulting
Chemist and Engineer. Illustrated. 8vo... $3 50




HENRT CAREY BAIRD'S CATALOGUE.               13
GOTHIC ALBUMS FOR CABINET MAKERS:
Comprising a Collection of Designs for Gothic Furniture. Illustrated by twenty-three large and beautifully engraved
plates. Oblong..           $3 00
GRANT. —BEET-ROOT SUGAR AND CULTIVATION OF THE
BEET:
By E. B. GRANT. 12mo.. $1 25
GREGORY. —MATHEMATICS FOR PRACTICAL MEN:
Adapted to the Pursuits of Surveyors, Architects, Mechanics,
and Civil Engineers. By OLINTHUS GREaORY. 8vo., plates,
cloth.. $3 00
iGRISWOLD.-RAILROAD ENGINEER'S POCKET COMPANION.
Comprising Rules for Calculating Deflection Distances and
Angles, Tangential Distances and Angles, and all Necessary
Tables for Engineers; also the art of Levelling from Preliminary Survey to the Construction of Railroads, intended Expressly for the Young Engineer, together with Numerous Valuable Rules and Examples. By W. GRISWOLD. 12mo., tucks.
$1 75
fUETTIER.-METALLIC ALLOYS:
Being a Practical Guide to their Chemical and Physical Properties, their Preparation, Composition, and Uses. Translated
from the French of A. GUETTIER, Engineer and Director of
Founderies, author of "La Fouderie en France," etc. etc. By
A. A. FESQUET, Chemist and Engineer. In one volume, 12mo.
$3 oo
HATS AND FELTING:
A Practical Treatise on their Manfacture. By a Practical
Hatter. Illustrated by Drawings of Machinery, &c., 8vo.
$1 25
HAY.-THE INTERIOR DECORATOR:
The Laws of Harmonious Coloring adapted to Interior Decorations: with aPractical Treatise on House-Painting. By D.
R. HAY, House-Painter and Decorator. Illustrated by a Diagram of the Primary, Secondary, and Tertiary Colors. 12mo.
$2 25
HUGHES.-AXERICAN  XILLER AND  MILLWRIGHT'S ASSISTANT:
By WMr. CARTER HUGHES. A new edition. In one volume,
12mo..... $1 60




14        HENRY CAREY BAIRD'S CATALOGUE.
HUNT. —THE PRACTICE OF PHOTOGRAPHY.
By ROBERT HUNT, Vice-President of the Photographic Society,
London. With numerous illustrations. 12mo., cloth.    75
HUURST.-A HAND-BOOK FOR ARCHITECTURAL SURVEYORS:
Comprising Formulae, useful in Designing Builders' work, Table
of Weights, of the materials used in Building, Memoranda
connected with Builders' work, Mensuration, the Practice of
Builders' Measurement, Contracts of Labor, Valuation of Property, Summary of the Practice in Dilapidation, etc. etc. By
J. F. HURST, C. E. 2d edition, pocket-book form, full bound
$2 50
JERVIS.-RAILWAY PROPERTY:
A Treatise on the Construction and Management of Railways;
designed to afford useful knowledge, in the popular style, to the
holders of this class of property; as well as Railway Managers, Officers, and Agents. By JOHN B. JERVIs, late Chief
Engineer of the Hudson River Railroad, Croton Aqueduct, &c.
One- vol. 12mo., cloth..... $2 00
J OHNSON.-A REPORT TO THE NAVY DEPARTMENT OF THE
UNITED STATES ON AMERICAN COALS:
Applicable to Steam Navigation and to other purposes. By
WALTER R. JOHNSON. With numerous illustrations. 607 pp.
8vo...... $10 00
JOHNSTON.-INSTRUCTIONS FOR THE ANALYSIS OF SOILS,
LIMESTONES, AND MANURES
By J. W. F. JOHNSTON. 12mo..                    35
KEENE. — A HAND-BOOK OF PRACTICAL GAUGING,
For the Use of Beginners, to which is added a Chapter on Distillation, describing the process in operation at the Custom
House for ascertaining the strength of wines. By JAMEs B.
K]EENE, of H. M. Customs. 8vo... $1 25




HENRY CAREY BAIRD'S CATALOGUE.               15
hENTISH.-   A TREATISE ON A BOX OF INSTRUMENTS,
And the Slide Rule; with the Theory of Trigonometry and Logarithms, including Practical Geometry, Surveying, Measuring of Timber, Cask and Malt Gauging, Heights, and Distances.
By THOMAS KENTISI. In one volume. 12mo...      $1 25
KOBELLE.-ERNI.-MINERALOGY SIMPLIFIED:
A short method of Determining and Classifying Minerals, by
means of simple Chemical Experiments in the Wet Way.
Translated from the last German Edition of F. VON KOBELL,
with an Introduction to Blowpipe Analysis and other additions. By HENRI ERNI, M. D., Chief Chemist, Department of
Agriculture, author of "Coal Oil and Petroleum." In one
volume. 12mo.   $.....       2 50
LANDRIN.-A TREATISE ON STEEL:
Comprising its Theory, Metallurgy, Properties, PracticalWorking, and Use. By M. H. C. LANDRIN, Jr., Civil Engineer.
Translated from the French, with Notes, by A. A. FESQUET,
Chemist and Engineer. With an Appendix on the Bessemer
and the Martin Processes for Manufacturing Steel, from the
Report of ABRAM S. HEWITT, United States Commissioner to
the Universal Exposition, Paris, 1867. 12mo... $3 00
L ARKIN.-THE PRACTICAL BRASS AND IRON FOUNDER'S
GUIDE.
A Concise Treatise on Brass Founding, Moulding, the Metals
and their Alloys, etc.; to which are added Recent Improvements in the Manufacture of Iron, Steel by the Bessemer Process, etc. etc. By JAMES LARKIN, late Conductor of the Brass
Foundry Department in Reany, Neafie & Co.'s Penn Works,
Philadelphia. Fifth edition, revised, with extensive Additions. In one volume. 12mo..                      25




TI        HENRY CAREY BAIRD'S CATALOGUE.
TEAVITT.-FACTS ABOUT PEAT AS AN ARTICLE OF FUEL:
With Remarks upon its Origin and Composition, the Localities
an which it is found, the Methods of Preparation and Manun
facture, and the various Uses to which it is applicable; together with many other matters of Practical and Scientific Interest. To which is added a chapter on the Utilization of Coal
Dust with Peat for the Production of an Excellent Fuel at
Moderate Cost, especially adapted for Steam Service. By H.
T. LEAVITT. Third edition. 12mo..         $1 75
EBROUX,-A  PRACTICAL TREATISE  ON  THE  MANUFACTURE OF WORSTEDS AND CARDED YARNS:
Translated from the French of CHARLES LEROUx, Mechanical
Engineer, and Superintendent of a Spinning Mill. By Dr. II.
PAINE, and A. A. FESQUET. Illustrated by 12 large plates, In
one volume 8vo.                                   $5 00
LESLIE (MISS).-COMPLETE COOKERY:
Directions for Cookery in its Various Branches.  By Miss
LESLIE.  60th edition.   Thoroughly revised, with the addition of New Receipts. In I vol. 12mo., cloth.. $1 50
ESLIE (MISS>. LADIES' HOUSE BOOK:
a Manual of Domestic Economy. 20th revised edition. 12mo.,
cloth.... $1 25
LESLIE  (MISS).-TWO  HUNDRED  RECEIPTS IN  FRENCH
COOKERY.
12mo.........                                      5
LIEBER.-ASSAYER'S GUIDE:
Or, Practical Directions to Assayers, Miners, and Smelters, for
the Tests and Assays, by Heat and by Wet Processes, for the
Ores of all the principal Metals, of Gold and Silver Coins and
Alloys, and of Coal, etc. By OSCAR M. LIEBER. 12mo., cloth
$1 25
LOVE. —THE. ART OF DYEING, CLEANING, SCOURING, AND
FINISHING:
On the most approved English and French methods; being
Practical Instructions in Dyeing Silks, Woollens, and Cottons,
Feathers, Chips, Straw, etc.; Scouring and Cleaning Bed and
Window Curtains, Carpets, Rugs, etc.; French and English
Cleaning, etc. By THOMAS LOVE. Second American Edition,'to
which are added General Instructions for the Use of Aniline
Colors. 8vo.                                       5 00




HENRY CAREY BAIRD'S CATALOGUE.                  17
MAIN AND BROWN.-QUESTIONS ON SUBJECTS CONNECTED
WITH THE MARINE STEAM-ENGINE:
And Examination Papers; with Hints for their Solution.  By
THOMAS J. MAIN, Professor of Mathematics, Royal Naval College,
and THOMAS BROWN, Chief Engineer, R. N.  12mo., cloth $1 50
MAIN AND BROWN.-THE INDICATOR AND DYNAMOMETER:
With their Practical Applications to the Steam-Engine.  By
THOMAS J. MAIN, M. A. F. R., Ass't Prof. Royal Naval College,
Portsmouth, and THOMAS BROWN, Assoc. Inst. C. E., Chief Engineer, R. N., attached to the R. N. College. Illustrated. From
the Fourth London Edition. 8vo..... $1 50
MAIN AND BROWN.-THE MARINE STEAM-ENGINE.
By THOMAS J. MAIN, F. R. Ass't S. Mathematical Professor at
Royal Naval College, and THOMAS BROWN, Assoc. Inst. C. E.
Chief Engineer, R. N.  Attached to the Royal Naval College.
Authors of "Questions Connected with the Marine Steam-Engine," and the "Indicator and Dynamometer."  With numerous
Illustrations. In one volume 8vo...        $5 00
MARTIN.-SCREW-CUTTING TABLES, FOR THE USE OF MECHANICAL ENGINEERS:
Showing the Proper Arrangement of Wheels for Cutting the
Threads of Screws of any required Pitch; with a Table for
Making the Universal Gas-Pipe Thread and Taps. By W. A.
MARTIN, Engineer. 8vo..    50
MILES-A PLAIN TREATISE ON HORSE-SHOEING.
With Illustrations. By WILLIAM MILES, author of " The Horse's
Foot"
M3LESWORTH.-POCKET-BOOK OF USEFUL FORMULE AND
MEMORANDA FOR CIVIL AND MECHANICAL ENGINEERS.
By GUILFORD L. MOLESWORTH, Member of the Institution of
Civil Engineers, Chief Resident Engineer of the Ceylon Railway.
Second American from  the Tenth London Edition.  In one
volume, full bound in pocket-book form..         $2 00
MOORE.-THE INVENTOR'S GUIDE:
Patent Office and Patent Laws: or, a Guide to Inventors, and a
Book of Reference for Judges, Lawyers, Magistrates, and others.
By J G. MOORE. 12mo., cloth.. $1 25
NAPIER.-A MANUAL OF ELECTRO-METALLURGY:
Including the Application of tle Art to Manufacturing Processes.
By TAMES NAPIER. Fourth American, from the Fourth London
edition, revised and enlarged; Illustrated by engravings. In
one volume, 8vo.                                    $2 00




18         HENRY CAREY BAIRD'S CATALOGUE.
NAPIER.-A SYSTEM OF CHEMISTRY APPLIED TO DYEING:
BY JAMES NAPIER, F. C. S. A New and Thoroughly Revised
Edition, completely brought up to the present state of the
Science, including the Chemistry of Coal Tar Colors. By A. A.
FESQUET, Chemist and Engineer. With an Appendix on Dyeing
and Calico Printing, as shown at the Paris Universal Exposition
of 1867, from the Reports of the International Jury, etc. Illustrated. In one volume 8vo., 400 pages.... $5 00
NEWBERY.- GLEANINGS FROM ORNAMENTAL ART OF
EVERY STYLE;
Drawn from Examples in the British, South Kensington, Indian,
Crystal Palace, and other Museums, the Exhibitions of 1851 and
1862, and the best English and Foreign works. In a series of one
hundred exquisitely drawn Plates, containing many hundred examples. By ROBERT NEWBERY. 4to.                      $15 00
NICHOLSON.-A MANUAL OF THE ART OF BOOK-BINDING:
Containing full instructions in the different Branches of Forwarding, Gilding, and Finishing. Also, the Art of Marbling Bookedges and Paper. By JAMES B. NICHOLSON. Illustrated. 12mo.
cloth.....$2 25
NORRIS.-A HAND-BOOK FOR LOCOMOTIVE ENGINEERS AND
MACHINISTS:
Comprising the Proportions and Calculations for Constructing
Locomotives; Manner of Setting Valves; Tables of Squares,
Cubes, Areas, etc. etc. By SEPTIMUS NORRIS, Civil and Mechanical Engineer. New edition. Illustrated, 12mo., cloth
$2 00
NYSTROM. - ON  TECHNOLOGICAL  EDUCATION  AND  THE
CONSTRUCTION OF SHIPS AND SCREW  PROPELLERS:
For Naval and Marine Engineers. By JOHN W. NYSTROM, late
Acting Chief Engineer U. S. N. Second edition, revised with
additional matter. Illustrated by seven engravings. 12mo.
$2 50
0'NEILL.-A DICTIONARY OF DYEING AND CALICO PRINTING:
Containing a brief account of all the Substances and Processes in
use in the Art of Dyeing and Printing Textile Fabrics: with Practical Receipts and Scientific Information. By CHARLES O'NEILL,
Analytical Chemist; Fellow of the Chemical Society of London;
Member of the Literary and Philosophical Society of Manchester;
Author of" Chemistry of Calico Printing and Dyeing." To which
is added An Essay on Coal Tar Colors and their Application to




HENRY CAREY BAIRD'S CATALOGUE.                  19
Dyeing and Calico Printing. By A. A. FESQUET, Chemist and
Engineer. With an Appendix on Dyeing and Calico Printing, as
shown at the Exposition of 1867, from the Reports of the Interna.
tional Jury, etc. In one volume 8vo., 491 pages. $6 00
OSBORN.-THE METALLURGY OF IRON AND STEEL:
Theoretical and Practical: In all its Branches; With Special Reference to American Materials and Processes. By H. S. OSBORN,
LL. D., Professor of Mining and Metallurgy in Lafayette College,
Easton, Pa. Illustrated by 230 Engravings on Wood, and 6
Folding Plates. 8vo., 972 pages..$10 00
$SBORN.-AMERICAN MINES AND MINING:
Theoretically and Practically Considered. By Prof. H. S. OsBORN, Illustrated by numerous engravings. 8vo. (In preparation.)
PAINTER, GILDER, AND VARNISHER'S COMPANION:
Containing Rules and Regulations in everything relating to the
Arts of Painting, Gilding, Varnishing, and. Glass Staining, with
numerous useful and valuable Receipts; Tests for the Detection
of Adulterations in Oils and Colors, and a statement of the Diseases and Accidents to which Painters, Gilders, and Varnishers
are particularly liable, with the simplest methods of Prevention
and Remedy. With Directions for Graining, Marbling, Sign Writing, and Gilding on Glass. To which are added COMPLETE INSTRI-CTIONS FOR COACH PAINTING AND VARNISHING. 12mo., cloth, $1 50
PALLETT. -THE  MILLER'S,  MILLWRIGHT'S, AND  ENGINEER'S GUIDE.
By HENRY PALLETT. Illustrated. In one vol. 12mo.. $3 00
P ERKINS. —GAS AND VENTILATION.
Practical Treatise on Gas and Ventilation. With Special Relation
to Illuminating, Heating, and Cooking by Gas. Including Scientific Helps to Engineer-students and others.  With illustrated
Diagrams. By E. E. PERKINS. 12mo., cloth..   $1 25.EBRKINS AND STOWE.-A NEW GUIDE TO THE SHEET-IRON
AND BOILER PLATE ROLLER:
Containing a Series of Tables showing the Weight of Slabs and
Piles to Produce Boiler Plates, and of the Weight of Piles and the
Sizes of Bars to Produce Sheet-iron; the Thickness of the Bar
Gauge in Decimals; the Weight per foot, and the Thickness on
the Bar or Wire Gauge of the fractional parts of an inch; the
Weight per sheet, and the Thickness on the Wire Gauge of Sheetiron of various dimensions to weigh 112 lbs. per bundle; and the
conversion of Short Weight into Long Weight, and Long Weight
into Short. Estimated and collected by G. H. PERKINS and J. GSTOWE..... $2 5{




20         HENRY CAREY BAIRD'S CATALOGUE.
PHILLIPS AND DARLINGTON.-RECORDS OF MINING AND
METALLURGY:
Or, Facts and Memoranda for the use of the Mine Agent and
Smelter., By J. ARTHUR PHILLIPS, Mining Engineer, Graduate of
the Imperial School of Mines, France, etc., and JouN DARLINGTON.
Illustrated by numerous engravings. In one vol. 12mo.. $2 00
pRADAL, MALEPEYRE, AND  DUSSAUCE. —A  COMPLETE
TREATISE ON PERFUMERY:
Containing notices of the Raw Material used in the AIt, and the
Best Formuk]e. According to the most approved Methods followed
in France, England, and the United States. By M. P. PRADAL,
Perfumer-Chemist, and M. F. MALEPEYRE. Translated from the
French, with extensive additions, by Prof. H. DussAucE. 8vo. $10
ROTEAUX.-PRACTICAL GUIDE FOR THE MANUFACTURE
OF PAPER AND BOARDS.
By A. PROTEAUX, Civil Engineer, and Graduate of the School of
Arts and Manufactures, Director of Thiers's Paper Mill,'Puy-deD6m6. With additions, by L. S. LE NORMAND. Translated from
the French, with Notes, by HORATIO PAINE, A. B., M. D. To
which is added a Chapter on the Manufacture of Paper from Wood
in the United States, by HENRY T. BROWN, of the "American
Artisan." Illustrated by six plates, containing Drawings of Raw
Materials, Machinery, Plans of Paper-Mills, etc. etc. 8vo. $5 00
R EGNAULT.-ELEMENTS OF CHEMISTRY.
By M. V. REGNAULT. Translated from the French by T. FORREST BENTON, M. IB., and edited, with notes, by JAMES C. BOOTH,
Melter and Refiner U. S. Mint, and WE. L. FABER, Metallurgist
and Mining Engineer. Illustrated bynearly 700 wood engravings.
Comprising nearly 1500 pages. In two vols. 8vo., cloth $10 00
REID.-A PRACTICAL TREATISE ON THE MANUFACTURE OF
PORTLAND CEMENT:
By HENRY REID, C. E. To which is added a Translation of M.
A. Lipowitz's Work, describing a new method adopted in Germany
of Manufacturing that Cement. By W. F. REID. Illustrated by
plates and wood engravings. 8vo.                    $7 00
RIFFAULT,  VERGNAUD, AND  TOUSSAINT.-A  PRACTICAL
TREATISE  ON THE  MANUFACTURE  OF  COLORS FOR
PAINTING:
Containing the best Formulae and the Processes the Newest and
in most General Use. By MM. RIFFAULT, VERGNAUD, and TovsSAINT. Revised and Edited by M. F. MALEPEYRE and Dr. EMITL
WINCKLER. Illustrated by Engravings. In one vol. 8vo.'In
preparation. )




HENRY CAREY BAIRD'S CATALOGUE.                   21
RIFFAULr, VERGNAUD,  AND  TOUSSAINT. —A  PRACTICAL
TREATISE ON THE MANUFACTURE OF VARNISHES:
By MM. RIFFAULT, VERGNAUD, and TOUSSAINT. Revised and
Edited by M. F. MALEPEYRE and Dr. EMIL TWINCKLER. Illustrated. In one vol. 8vo. (Ins preparation.)
VHUNK.-A PRACTICAL TREATISE  ON  RAILWAY  CURVES
AND LOCATION, FOR YOUNG ENGINEERS.
By WM. F. SHUNK, Civil Engineer. 12mo., tucks.. $2 00
SXEATON.-BUILDER'S POCKET COMPANION:
Containing the Elements of Building, Surveying, and Architec.
ture; with Practical Rules and Instructions connected with the subject. By A. C. SMEATON, Civil Engineer, etc. In one volume,
12mo.                                                 $1 50
XMITH.-THE DYER'S INSTRUCTOR:
Comprising Practical Instructions in the Art of Dyeing Silk, Cotton, Wool, and Worsted, and Woollen Goods: containing nearly
800 Receipts. To which is added a Treatise on the Art of Padding; and the Printing of Silk Warps, Skeins, and Handkerchiefs,
and the various Mordants and Colors for the different styles of
such work. By DAVID SMITII, Pattern Dyer, 12mo., cloth
$3 00
qMITH.-THE PRACTICAL DYER'S GUIDE:
Comprising Practical Instructions in the Dyeing of Shot Cobourgs,
Silk Striped Orleans, Colored Orleans from Black Warps, ditto
from White Warps, Colored Cobourgs from White Warps, Merinos,
Yarns, Woollen Cloths, etc. Containing nearly 300 Receipts, to
most of which a Dyed Pattern is annexed. Also, a Treatise on
the Art of Padding. By DAVID SMITH. In one vol. 8vo. $25 00
sHAW.-CIVIL ARCHITECTURE:
Being a Complete Theoretical and Practical System of Building,
containing the Fundamental Principles of the Art. By EDWARD
SHAW, Architect. To which is added a Treatise on Gothic Architecture, &c. By THOM3AS W. SILLOWAY and GEORGE M. IIARDING, Architects. The whole illustrated by 102 quarto plates finely
engraved on copper. Eleventh Edition. 4to. Cloth.   $10 00
SLOAN.-AMERICAN HOUSES:
A variety of Original Designs for Rural Buildings. Illustrated by
26 colored Engravings, with Descriptive References. By SAMUEL
SLOAN, Architect, author of the " Model Architect," etc. etc. 8vo.
$2 50
SCHINZ. —RESEARCHES ON  THE ACTION  OF TEE BLAST.
FURNACE.
By CHAS. SCHINZ. Seven plates. 12mo.. $4 25




22         HENRY CAREY BAIRD'S CATALOGUE.
KMITH.-PARKS AND PLEASURE GROUNDS:
Or, Practical Notes on Country Residences, Villas, Public Parks,
and Gardens. By CHARLES H. J. SMITH, Landscape Gardener
and Garden Architect, etc. etc. 12mo.                 $2 25
STOKES.-CABINET-MAKER'S AND UPHOLSTERER'S COMPANION:
Comprising the Rudiments and Principles of Cabinet-making and
I   Upholstery, with Familiar Instructions, Illustrated by Examples
for attaining a Proficiency in the Art of Drawing, as applicable
to cabinet-work; The Processes of Veneering, Inlaying, and
Buhl-work; the Art of Dyeing and Staining Wood, Bone, Tortoise
Shell, etc. Directions for Lackering, Japanning, and Varnishing;
to make French Polish; to prepare the Best Glues, Cements, and
Compositions, and anumber of Receipts, particularly for workmen
generally. By J. STOKES. In one vol. 12mo. With illustrations
$1 25
XTRENGTH AND OTHER PROPERTIES OF METALS.
Reports of Experiments on the Strength and other Properties of
Metals for Cannon. With a Description of the Machines for Testing Metals, and of the Classification of Cannon in service. By
Officers of the Ordnance Department U. S. Army. By authority
of the Secretary of War. Illustrated by 25 large steel plates. In
1 vol. quarto.. $10 00
SULLIVAN.-PROTECTION TO NATIVE INDUSTRY.
By Sir EDWARD SULLIVAN, Baronet. (1870.) 8vo.. $1 50
TABLES SHOWING THE WEIGHT OF ROUND, SQUARE, AND
FLAT BAR IRON, STEEL, ETC.
By Measurement. Cloth.63
TAYLOR.-STATISTICS OF COAL:
Including Mineral Bituminous Substances employeL in Arts and
Manufactures; with their Geographical, Geological, and Commercial Distribution and amount of Production and Consumption on
the American Continent. With Incidental Statistics of the Iron
Manufacture. By R. C. TAYLOR. Second edition, revised by S.
S. HALDECMAN. Illustrated by five Maps and many wood engravings. 8vo., cloth.            ~...          $6 00
TEMPLETON.-THE  PRACTICAL EXAMINATOR  ON  STEAM
AND THE STEAM-ENGINE:
With Instructive References relative thereto, for the Use of Engineers, Students, and others. By WTr. TEMIPLETON, Engineer. 12mo.
$1 25




HENRY CAREY BAIRD'S CATALOGUE. /                23
THOMAS.-THE MODERN PRACTICE OF PHOTOGRAPHY.
By R. W. THOMAS, F. C. 8. Svo., cloth....    75
THOMSON. —FREIGHT CHARGES CALCULATOR.
By ANDREW THOMSON, Freight Agent.... $1 25
1URNING: SPECIMENS OF FANCY TURNING EXECUTED ON
THE HAND OA FOOT LATHE:
With Geometric, Oval, and Eccentric Chucks, and Elliptical Cutting Frame. By an Amateur. Illustrated by 30 exquisite Photographs. 4to.                                      $3 00
URNER'S (THE) COMPANION:
Containing Instructions in Concentric, Elliptic, and Eccentric
Turning; also various Plates of Chucks, Tools, and Instruments; and Directions for using the Eccentric Cutter, Drill,
Vertical Cutter, and Circular Rest; with Patterns and Instructions for working them. A new edition in 1 vol. 12mo.   $1 50
URBIN — BRULL. -A  PRACTICAL  GUIDE FOR  PUDDLING
IRON AND STEEL.
By ED. URBIN, Engineer of Arts and Manufactures. A Prize
Essay read before the Association of Engineers, Graduate of the
School of Mines, of Liege, Belgium, at the Meeting of 1865-6.
To which is added a COMPARIsoN OF THE RESISTING PROPERTIES
OF IRON AND STEEL. By A. BRULL. Translated from the French
by A. A. FESQUET, Chemist and Engineer. In one volume, 8vo.
$1 00
VOGDES.-iTHE ARCHITECT'S AND BUILDER'S POCKEI COMPANION AND PRICE BOOK.
By F. W. VOGDES, Architect. Illustrated. Full bound in pocketbook form.                                          $2 00
In book form, 18mo., muslin                          1 50
WARN. —THE SHEET METAL WORKER'S INSTRUCTOR, FOR
ZINC, SHEET-IRON, COPPER AND  TIN  PLATE WORKERS, &c.
By REUBEN tIENRY WARN, Practical Tin Plate Worker. I':ustrated by 32 plates and 37 wood engravings. 8vo..   $3 (0O
WATSON.-A MANUAL OF THE HAND-LATHE.
By EGBERT P. WATSON, Late of the " Scientific American," Author of " Modern Practice of American Machinists and Engi.neers,"  In one volume, 12mo.. $1 50




24         HENRY CAREY BAIRD'S CATALOGUE.
WATSON.-THE MODERN PRACTICE OF AMERICAN MACHINISTS AND ENGINEERS:
Including the Construction, Application, and Use of Drills, Lathe
Tools, Cutters for Boring Cylinders, and Hollow'Work Generally,
with the most Economical Speed of the same, the Results verified
by Actual Practice at the Lathe, the Vice, and on the Floor.
Together with Workshop management, Economy of Manufacture,
the Steam-Engine, Boilers, Gears, Belting, etc. etc. By EGBERT
P. WATSON, late of the "Scientific American."  Illustrated by
eighty-six engravings. 12mo.. $2 50
WATSON.-THE THEORY AND PRACTICE OF THE ART OF
WEAVING BY HAND AND POWER:
With Calculations and Tables for the use of those connected with
the Trade. By JOHN WATSON, Manufacturer and Practical Machine
Maker. Illustrated by large drawings of the best Power-Looms.
8vo.                                                $10 00
WEATHERLY.-TREATISE  ON.THE ART OF BOILING  SUGAR, CRYSTALLIZING,  LOZENGE-MAKING,  COMFITS,
GUM GOODS,
And other processes for Confectionery, &c. In which are explained, in an easy and familiar manner, the various Methods
of Manufacturing every description of Raw and Refined Sugar
Goods, as sold by Confectioners and others... $2 00
W  ILL-TABLES FOR QUALITATIVE CHEMICAL ANALYSIS.
By Prof. HEINRICH WILL, of Giessen, Germany. Seventh edition. Translated by CHARLES F. HIMES, Ph. D., Professor of
Natural Science, Dickinson College, Carlisle, Pa... $1 25
WqILLIAMS.-O-N HEAT AND STEAM:
Embracing New Views of Vaporization, Condensation, and Expansion. By CHARLES WYE WILLIAMS, A. I. C. E. Illustrated. 8vo.
$3 50
WORSSAM.-ON MECHANICAL SAWS:
From the Transactions of the Society of Engineers, 1867. By
S. W. WORSSAM, Jr. Illustrated by 18 large folding plates. Svo.
$5 00
WOHLRIR.-A HAND-BOOK OF MINERAL ANALYSIS.
By F. WiHLER. Edited by H. B. NASON, Professor of Chemistry,
Rensselaer Institute, Troy, N. Y. With numerous Illustrations.
12mo.                                                $3 00