HANDBOOK OF CHEMISTRY,
FOR
SCHOOL AND HOME USE.
BY
W. J. ROLFE AND J. A. GILLET,
TEACHERS IN THE HIGH SCHOOL, CAMBRIDGE, MASS.
BOSTON:
WOOLWORTH, AINSWORTH, & CO.
NEW YORK: A. S. BARNES & CO.
I869.




Entered according to Act of Congress, in the year i868, by
W. J. ROLFE AND J. A. GILLET,
In the Clerk's Office of the District Court of the District of Massachusetts.
CAMBRIDGE:
PRESS OF JOHN WILSON AND SON.




PREFACE.
WE have prepared this book at the urgent request of many teachers who desire something easier
and briefer than the " Chemistry " of the Cambridge
Course of Physics. This is a more elementary
work, and therefore less theoretical. It is, in a
word, a manual of the elementary facts and principles of Chemistry. While there is little that is
strictly theoretical in the body of the book, we have
not forgotten that Chemistry is not a mere mass of
dead facts, but a living science. We have therefore aimed to present the facts in such a way as to
awaken a love for the science itself, no less than to
show its utility. Our object has been not only
to describe the properties of the leading elements
and compounds, but also to show the wonderful part
played by the chemical force in nature, as well
as to illustrate its practical applications in the arts.
We have endeavored to give the young student a
glimpse of--  the circle of eternal change,
Which is the life of nature,"a life whose fountain-head is the sun, and whose




iv                 PREFACE.
processes we trace in the chemistry of the atmosphere. In this indirect but natural way, we have
introduced as much of orga-nic chemistry as could
well find place in an elementary manual.
The metals we have grouped more according to
their uses than according to their chemical relations,
with a view to make the subject less dry and more
practical.
It is difficult to write a book suited to the wants
of different schools, or even of successive classes in
the same school; since the schools vary in grade,
and the classes in ability. We have attempted to
meet this difficulty by putting into the body of the
book the simpler and more practical portions of the
subject, which can be readily mastered by young
pupils of average ability, and by adding in the
Appendix a concise statement of the elements of
chemical philosophy as now understood. In this
way, the simpler and the more difficult parts,
instead of being confusedly mixed together, distinguished merely by the common and clumsy expedient of coarse and fine print, are treated separately,
so that each may be complete and symmetrical. At
the same time, the two parts do not overlap, but
form successive chapters progressively arranged.
Our experience as teachers has convinced us, that
this is, on the whole, the best method of meeting
the wants of successive classes; and the marked
favor with which our " Handbook of the Stars," an
elementary "Astronomy" on precisely the same




PREFACE.                 V
plan, has been received, shows that the experience
of many of our fellow-teachers has been pretty much
the same as our own.
We have not forgotten that the theories of chemistry have been revolutionized within a few years;
and we have of course used the new symbols and
notation, without which it is as impossible to teach
modern chemistry as it would be to teach modern
astronomy in the language of the old astrologers.
Until within a year or two, there was some excuse
for clinging to the old notation, as rival systems
were contending for the supremacy. But even as
long ago as October, I866, Miller, the first English
authority on the subject, wrote as follows: "The
change in notation is certain to be adopted, since
in none of the recent investigations in this country,
and in very few of those on the Continent, is the old
method made use of." Since that time, the system
of symbols and notation used by us in this book has
been formally adopted by the Chemical Society
of London, whose decision is recognized as law in
England; and it is now taught in Harvard College,
which will certainly be acknowledged as one of the
highest authorities in this country.
In the chapter on the Chemistry of the Atmosphere, we have been especially indebted to the Lectures on " Religion and Chemistry" (New York,
i866), by Professor Josiah P. Cooke, Jr., of Harvard
College; and the chapter on Chemical Philosophy
is almost wholly drawn from the "First Principles




vi                    PREFACE.
of Chemical Philosophy " (Cambridge, I868), by the
same eminent author. His remarkable power of
presenting difficult subjects in a way at once clear
and attractive, makes these books especially valuable
to the teacher.
We have been under obligations, also, to Miller's
"Elements of Chemistry" (London, I866), and
Roscoe's "Elementary Chemistry" (London, I866).
These books (both of which, we are glad to see,
have been recently reprinted here) as well as
Hofmann's "Modern Chemistry" (London, 1865),
and Wurtz's " Introduction to Chemical Philosophy "
(London, I867), the teacher will find useful for
purposes of reference.
CAMBRIDGE, December io, I868.
Teachers will observe that, except in the Appendix,
either the old chemical name or the ordinary commercial name
of the substance is generally added, in parentheses, to the new
chemical name.




TABLE OF CONTENTS.
PAGE
THE NON-METALLIC ELEMENTS.......
COMPOUNDS AND ELEMENTS........               3
OXYGEN.................   IO
HYDROGEN............ 15
WATER.................. I7
NITROGEN................ 2
CARBON................ 28
SULPHUR.............   30
CHLORINE................. 36
BROMINE..............  40
IODINE.................. 40
FLUORINE............. 4I
PHOSPHORUS............         42
ARSENIC.................   43
BORON.................                44
SILICON...............  44
SUMMARY................. 45
THE METALS................                          49
GENERAL PROPERTIES OF THE METALS......49
THE MOST USEFUL METALS.......... 51
THE NOBLE METALS............64
LESS USEFUL METALS....                        71
METALS NOT USED IN A FREE STATE, BUT VALUABLE
FOR THEIR SALTS............. 83
THE RARER METALS............. 89
SUMMARY................ 
CHEMISTRY OF THE ATMOSPHERE....   9I
COMBUSTION............ 91




Viii                  CONTENTS.
PAGE
SLOW COMBUSTION............. I00
THE GROWTH OF PLANTS..........   8
NATURAL VEGETABLE PRODUCTS... 120
SUMMARY............. 131
DESTRUCTIVE  DISTILLATION  AND  ITS PRODUCTS................                            33
COAL-OILS................ I39
COAL-GAS...............                I42
ILLUMINATION...............   I45
SUMMARY.................  49
FERMENTATION............ II
SUMMARY................. I59
APPENDIX..........                         I6i
CHEMICAL PHILOSOPHY...........  6
NOTES ON EXPERIMENTS........               I8
OQUESTIONS FOR REVIEW AND EXAMINATION... 193
INDEX...................  201




HANDBOOK OF CHEMISTRY.








THE NON-METALLIC ELEMENTS.
COMPOUNDS AND ELEMENTS.
I. /]ltriatic Acid. - Into a bottle arranged as shown
in Figure I, put a few bits of zinc, and pour a little muriatic acid over them. Effervescence at once takes place,
and a colorless gas passes through the bent tube into the
jar, which has been previously filled with water, and inFig. I.
verted over the trough  When the a is full of gas raise
verted over the trough. When the jar is full of gas, raise
it from the water, and apply a lighted taper to its mouth.
The gas takes fire with a slight explosion, and burns with a
pale flame. This gas is called hydrogen, and comes from
the muriatic acid.
Pour a little of the muriatic acid into a flask (Figure 2),
add a little black oxide of manganese, mix them thor



4            COMPOUNDS AND ELEMENTS.
oughly, and heat gently. A greenish-yellow gas passes
into the jar inverted over the water-trough. WVhen the
jar is full, close its mouth with a glass plate, remove it
from the trough, and set it on the table. Moisten a piece
of litmus-paper or colored cotton cloth, and hold it inside
the jar. It will be instantly bleached. This gas is called
ch/orine, and, like the hydrogen, comes from the muriFig. 2.
atic acid. Chlorine may be recognized by its bleaching
power, and also by its color and its suffocating odor.
We have now got from muriatic acid two gases, hydrogen and chlorine.
If a small glass jar be filled with equal parts of these
two gases, and a light be applied to its mouth, the mixture will take fire with an explosion. If a little dish of
ammonia be standing by, a dense white cloud will appear
when the gases burn.
Now this cloud shows that muriatic acid has been
produced; for, if we dip a glass rod in muriatic acid,
and hold it over the ammonia, the white cloud at
once appears.
Muriatic acid, then, contains nothing but hydrogen and
chlorine.




COMPOUNDS AND ELEMENTS.              5
2. Waler. - If a bit of sodium be thrust beneath the
mouth of an inverted jar, filled with water, as shown in
Figure 3, bubbles of gas rise and fill the jar. On raising
the jar, and applying a taper to its mouth, we see, by the
way in which the gas takes fire, that it is hydrogen.
Fill a tall glass jar with chlorine water (that is, water
which has absorbed chlorine gas), invert it, with its
Fig, 3,
mouth in a shallow dish of water, and leave it for ten or
twelve hours in the sunshine. Bubbles of gas will be
seen to rise, and collect in the top of the jar. If now we
set the jar upright, and plunge a lighted taper into the
gas, the taper burns much more brightly than in the air.
This gas is called oxygen.
We have thus got hydrogen and oxygen from water.
If, now, we burn a jet of hydrogen in a jar of oxygen,
moisture will collect on the sides.  This moisture is
water, and comes from the union of the hydrogen and
the oxygen. This shows that there is nothing but oxygen
and hydrogen in water.




6           COMIPOUNDS AND ELEIENTS.
3. Ammonia. — Fill with chlorine a long glass tube,
closed at one end.  Close
Fig. 4.
the other end with a cork,
through which passes a drop/   ping tube. (Figure 4.) If,
Xh       /\~J  ~ now, a little ammonia be
va~       >>          dropped into the tube, flashes
_'  of light and dense white
fumes appear within. Next
allow water to run into the
tube as long as it will, and
test the gas which remains,
by putting a piece of litmuspaper into it. The paper is
not bleached, hence the gas
is not chlorine. Plunge a
lighted taper into it, and it
goes out, and the gas does
not take fire; hence the gas
is neither oxygen nor hydrogen. It is zitrogenz, and it
always, as in this case, extinguishes a lighted taper.
This nitrogen must have come firom the ammonia, since
there was no nitrogen in the water poured into the tube.
The white fumes which appeared in the tube, when
the ammonia was dropped in, showed that muriatic acid
was formed. Now we have learned that muriatic acid is
made up of chlorine and hydrogen. The hydrogen must
also have come from the ammonia.
Ammonia, then, contains nitrogen and hydrogen. It
has been found by experiment that it contains nothing but
these two gases.
4. Compounds and Elements. -We have now seen
that muriatic acid, water, and ammonia, are made up of




COMPOUNDS AND ELEMENTS.                       7
other substances, which we can separate from them. In
other words, they are compound substances, and we have
decomposed them.  But no means has been found of decomposing oxygen, hydrogen, chlorine, and nitrogen into
simpler substances. These, and other substances which
cannot be decomposed, are called elements.
Most substances with which we are familiar are compounds.  The metals, however, are all elements.
There are only about sixty-five elements in all, and
many of these are very rare substances.
5. JlVames and Symnbos of Elements. - Elements have
been divided into two classes, metallic and non-metallic.
The  following  list contains  the  names of the  most
important elements usually put in each class, together
with the abbreviations of these names commonly used.
These abbreviations are called symbols.
NON-METALLIC ELEMENTS.
NANI1E      SYMBOL.    A        NAME ~        SYMIBOL.  ATOMIC
SBO.   WEIGHT.                       WEIGHT,
Boron          B         II    Iodine           I        127
Bromine        Br        80     Nitrogen        N          4
Carbon         C         1 2    Oxygen          0          6
Chlorine       C1        35.5   Phosphorus      P         31
Fluorine       F         19     Silicon         Si        28
Hydrogen       H          I     Sulphur         S         32
METALLIC ELEMENTS.
Aluminium      Al        27.4    Magnesium      Mg        24
Antimony (slibitm) Sb   122     Manganese       Mn        55
Arsenic        As        75     Mercury (hydrargyrurn) Hg   200
Barium         Ba       137     Nickel          Ni        58.7
Bismuth        Bi       2IO     Platinum         Pt      I97.5
Calcium        Ca        40     Potassium (kalium) K      39
Chromium       Cr        52.5    Silver (argenetmn)  Ag  Io8
Cobalt         Co        58.7    Sodium (natrium)  Na     23
Copper (csuhrzim)  Cu    63.5    Strontium       Sr       87.5
Gold (aurum)    Au      197     Tin (stanznm)   Sn       118
Iron V(errum)    Fe      56     Zinc            Zn        65.2
Lead (jhlunzbum)  Pb    207




8            COMPOUNDS AND ELEMENTS.
It will be noticed that in some cases the symbol is an
abbreviation of the Latin name of the element.
6. Affinity. -The force which draws elements together, and locks them up in compounds, is called azinity,
or chemzcal force.
One of the characteristics of this force is, that it chanfges
/lhe properties of t/e substances wAh'ic it brings together.
It not only unites different substances, but unites them so
as to form a new substance. It combines them.
This characteristic is well illustrated in the case of
water, a substance wholly unlike hydrogen, which is
combustible, and oxygen, which aids combustion.
The second characteristic of affinity is, that it always
acts between definite quantities of matter. This may
be illustrated by the following experiment: -
Partially fill the closed arm of the U tube (Figure 5)
Fig.; 5  with a mixture of hydrogen and oxygen, using more than twice as much
hydrogen as oxygen. Explode the mixture by means of an electric spark from
a Leyden jar. The hydrogen and the
oxygen combine to form  water, but
some gas remains, which, if tested with
a taper, is found to be hydrogen.
If now we put into the tube a mixr      =,___=_ ture containing less than twice as much
hydrogen as oxygen, the gas which re=___    mains after the explosion is found to be
oxygen.
In both cases, the oxygen combines with exactly twice
its bulk of hydrogen, and this will be true in whatever
proportions the gases may be mixed.
This experiment also illustrates the third characteristic
of affinity, which is, that it is often dormant until it is
roused to activity by heat, or some other force.  The




COMPOUNDS AND ELEMENTS.              9
oxygen and the hydrogen showed no disposition to combine until the spark was sent through them.
7. ilfoleczles and Atomns.- It is supposed that all
bodies are made up of small particles called molecules,
and that these molecules are made up of smaller particles, which are called afoms (that is, not to be divided),
since we are not able to subdivide them.
In an elementary substance, the atoms are supposed to
be all alike in form and weight, but those of one element
differ in weight from those of another. In a coinpound substance, the moleczules are supposed to be alike, each being
made up of a fixed number of atoms of each of the component elements; but the molecules of one compound
differ from those of another in their atomic constitution.
This theory of the composition of substances is called the
atomic theory.
Thus the molecules of muzriatic acid are supposed to
be made up of one atom of hydrogen and one of chlorine;
the molecules of water to be made up of tIwo atoms of
hydrogen and one of oxygen; and the molecules of anmmnonia to be made up of three atoms of hydrogen and one
of nitrogen.
8. Symzbols of Comzpounds.  The symbol of a compound is made up of the symbols of its elements. It also
indicates the atomic constitution of the molecules of the
compound. The symbol of each element represents one
atom of that element. If there is more than one atom of
the element in the molecule, this is indicated by a small
figure placed at the right of the symbol. Thus the symbol for muriatic acid is HC1; indicating that muriatic
acid is a compound of hydrogen and chlorine, and that a
molecule of muriatic acid is made up of one atom of
hydrogen and one of chlorine. The symbol for water is
H20, since water is a compound, whose molecule contains two atoms of hydrogen and one of oxygen. The




IO          COMPOUNDS AND ELEMENTS.
symbol of ammonia is H3N, its molecule being made up
of three atoms of hydrogen and one of nitrogen.
9. Atomic Weights. - According to the atomic theory,
an atom of chlorine weighs 35.5 times as much as an atom
of hydrogen; an atom of oxygen weighs I6 times as much
as one of hydrogen; and an atom of nitrogen 14 times as
much as one of hydrogen. If then we represent the
weight of an atom of hydrogen by I, the weight of an
atom of chlorine will be 35.5; that of an atom of oxygen,
I6; and that of an atom of nitrogen, 14. These numbers
are called the atomnic wzeigfts of these elements. (5.)
We now see that the symbol of a compound represents
not merely the atomic constitution of the compound, but
also the relative weights of its elements. Thus muriatic
acid, HC1, contains I part by weight of hydrogen to 35.5
parts by weight of chlorine; water, HO, contains 2 parts
by weight of hydrogen to I6 of oxygen; and ammonia,
H3N, contains 3 parts by weight of hydrogen to I4 of
nitrogen.
OXYGEN.
Io. Prejparation of Oxygen. -Oxygen is most readily
obtained from potassic chlorate (chlorate of potash), a substance of whose weight it forms about 40 per cent. The
chlorate is heated in a flask (Figure 6), and the gas is
Fig. 6.
6'a; \LT




COMPOUNDS AND ELEMENTS.            I I
collected over water. Potassic chlorate is a compound of
chlorine, potassium, and oxygen, and its symbol is KCO13.
The oxygen is set free by the heat, leaving the chlorine
and potassium as a compound called potassic chloride.
A chemical change of this kind is called a reaction,
and may be expressed in the form of an equation. In
this case the equation will be -
KC10  = KC1 + 03
indicating that the potassic chlorate, KC103, has been
broken up into potassic chloride, KC1, and oxygen, 0.
If a small quantity of black oxide of manganese be
mixed with the potassic chlorate, the gas is given off at a
much lower temperature, and more gradually. The manganese, however, undergoes no change in the process.
i I. Properties of Oxygen. — We have already seen
(2) that a taper burns much more vividly in oxygen than
in the air.
If a piece of charcoal be lighted and plunged into a jar
of oxygen, it burns with a very brilliant white light.
Pour now some clear lime-water into the jar, and shake it.
The liquid becomes milky white, showing that the gas
has undergone a change; for oxygen has no effect upon
lime-water. Charcoal is a form of the element carbon,
and the oxygen has combined with it. The compound
produced is called carbonic anrhydride (carbonic acid),
and its composition is represented by the symbol, CO,.
If a bit of sulphur be ignited and put into a jar of oxygen, it burns wvith a vivid blue light and a suffocating
odor. The sulphur and the oxygen have combined to
form sulkhurous ankhydride (su1ithurous acid), the symbol of which is SO2.
Phosphorus burns in oxygen with dazzling brilliancy,
producing dense, white fumes of phosphoric anhydride
(phosphoric acid), P205.




I 2         COMPOUNDS AND ELEMENTS.
Thus far, we have found that substances which burn in
the air burn more rapidly and more brightly in oxygen.
If, now, we fasten a bit of wood to a steel watch-sprinig,
ignite the wood, and plunge the whole into a jar of oxygen, the watch-spring takes fire, and burns as readily as a
splint of wood burns in the air. In this case the iron and
the oxygen combine, forming a mixture of two oxides of
iron, FeO, ferrous oxide, and Fe203,ferric oxide.
The above experiments illustrate several properties of
oxygen: (I) the passive state in wzhich it exists ucnder
ordinzary circutmsatnces, it being necessary to hzeat it in
order to make it combine rapidly with any substance; (2)
the inztense energy wi/t which it enters into comlz3ination
zwhen once aroused; and (3) the wide range of its affinilies. It combines with every known element, except
fluorine.
2. Ozone. — If a series of electric sparks be sent
through dry oxygen, the gas undergoes a change. It acquires more active properties and a peculiar odor from
which it takes its name, ozone.*  The odor perceived
when an electrical machine is worked is owing to the
presence of ozone.
If a paper moistened with a solution of potss'c iodide
(iodide of polassiumz), 1KI, and starch paste be held opposite a point on the conductor of an electrical machine,
the paper becomes blue. The iodine is set free by the
ozone, and unites with the starch, forming a blue compound, which colors the paper. Ordinary oxygen has no
such power to separate iodine from its combination with
potassium.
There has been much discussion concerning the nature
of ozone. It appears, however, to be simply oxygen in
a modified and condensed form.
* Ozone is derived from a Greek word which means to emit a
bad odor.




COMPOUNDS AND ELEMENTS.              I3
This iartially active state of oxygen is intermediate
between the active and passive states already mentioned.
13. Ailotro~pic States. - There are other elements
which exist in states in which their properties are as unlike as those of oxygen and ozone. These different states
of an element are called allotroi'ic states.
14. Oxides. "-  The simple compounds of the elements
with oxygen are called oxides, and the specific names of
the different oxides are formed by placing before the word
oxide the name of the element, but changing the termination into ic or ozcs, to indicate different degrees of
oxidation, and using the Latin name of the element in
preference to the English, both for the sake of euphony
and in order to secure more general agreement among
different languages. WVhen the same element unites with
oxygen in more than two proportions, the Latin prepositions or numeral adverbs, sub, per, bis, etc., are prefixed
to the word oxide in order to indicate the additional degrees. Formerly these compounds were called the oxides
of the different elements, the degrees of oxidation being
indicated solely by the prefixes." *
The ending ous indicates a lower degree of oxidation
than the ending ic.
I5. Acids. —Very many of the non-metallic oxides
combine with water, forming compounds which turn blue
litmus-paper red. Such oxides are called acid oxides, or
an/hydrides, and their compounds with water are called
acids. Thus SO2    H20 - H2IISO. SO2 is szt//ihurozus
an/hydride, often improperly called sztlp/ztrozss acid, a
name which properly belongs to H2SO3. So H20 + S03
(sulphuric anihydride) = H2SO4 (suiZUZric acid).
Here, too, as in the case of oxides, the ending ous
denotes a lower degree of oxidation than the ending ic.
* First Principles of Chemical Philosophy. By Josiah P.
Cooke, Jr., I868, p. 69.




14          COMPOUNDS AND ELEMENTS.
When more than two acids are formed by the same
elements, the prefixes,hypo (less) and /hyeer or per
(more) are used. Thus, hydrogen, chlorine, and oxygen
form four acids: HC10, /hypocilorous acid; HC102, chlorous acid; HC103, cloric acid; and HC104, hyperchloric ac'd, or perchloric acid.
It will be noticed that these acids are named from the
element with which the oxygen combines to form an acid
oxide; suzlzhuzric and suZplhurozs acid from suz/tphur, and
so on. It will be seen also that in the symbols of the
acids the hydrogezn is placedclfrst, and the oxygen last.
i6. Bases. -- Many of the metallic oxides combine
with water to form compounds whose properties are the
opposite of those of the acids. These are called basic
oxides, and their compounds with water are called bases.
The specific name of a base is made an adjective in ic or
ous formed from the Latin name of the metal, followed
by the term hydrate. Thus, I (H20 + K20) - HKO.
K20 is potassic oxide, and HIKO is pot/assic hydrate.
So H0 + BaO (baric oxide)  H2BaO2 (baric hzydrate).
The polassic and sodic hydrates (HKO and HNaO)
and some others are called alkalies. They differ from
the remaining hydrates in that they cannot be decomposed by heat.
I7. Nezutrals. - Those oxides which, like water, are
neither acid nor basic, are called neutral oxides, or nezttrals.
8S. Salts. -A  metal may take the place of the hydrogen in an acid, and the compound thus formed is called a
salt. Thus, the metal polassiunz may take the place of
the hydrogen in H,2SO3 and H2SO4, forming the salts
K2SO3 and K2SO4. A salt is named from the acid, the
ending ic being changed to ate, and the ending ous to
zie, with the name of the metal prefixed with the ending
ic or ous. Thus, K2SO3 is potassic suljhite, and KoSO4,




COMPOUNDS AND ELEMENTS.             15
otlassic sulibhate.  FeSO4 is ferrous suliphatc, and
Fe23SO4, ferric sulpthte.
I9. Biniary and Ternary Conzsouncds. - Compounds
like the oxides, which contain two elements, are called
binary compounds; and compounds like the acids mentioned above (I5) which contain three elements, are
called ternary compounds.
HYDROGEN.
20. Preparation of Hydrogen. —The most convenient way of preparing hydrogen is by the action of zinc
on dilute sulphuric acid. The apparatus required is
shown in Figure 7.
Fig. 7.
The reaction between the zinc and the sulphuric acid
is shown in the following equation:H2SO4 +- Zn = Zn S04 + H2.
The zinc changes places with the hydrogen, forming the
salt known as zincic su/ihate, or whZile vitriol, while
the hydrogen is set free.
21. Properties of Hfydrogen.-If soap-bubbles are
blown with a mixture of two measures of hydrogen to
one of oxygen, they will explode violently when touched
with a lighted taper; showing the intense energy with




I6           COMPOUNDS AND ELEMENTS.
which hydrogen and oxygen combine at a high temperature. If a mixture of hydrogen and atmospheric air
be used, a similar explosion wvill take place. Hence, in
preparing hydrogen for experiments, great care must be
taken to expel all air from the apparatus before any of
the gas is collected.
If a small rubber balloon be filled with hydrogen, it
rises readily in the air, showing that the gas is lighter
than air. It is, in fact, the lightest substance known,
being I4.5 times lighter than air, and i6 times lighter
than oxygen. It was formerly used in filling balloons;
but coal-gas, which, though not so light, is much cheaper, is now commonly employed instead.
The lightness of hydrogen and the energy with which
it combines with oxygen, are its two most important
characteristics.
22. T/ue Oxy-yydrogen BlowjzpIe. - The energy with
which hydrogen and oxygen combine develops intense
heat. This may be shown by means of the oxy-h/ydrogen
6lowpizP6e, represented in Figure 8.  The hydrogen is
Fig. 8.          forced through the tube
h, and  the  oxygen
> o 4                      through the tube 0;
and it will be seen that
A=    the two can mix only at
the mouth of the jet
where they are burned,
so that there is no danger of an explosion. The gases may be kept in a gasomeler (Figure 9), or, more conveniently, in gas-bags
of india-rubber.
Hold a copper or iron wire in the flame of this blowpipe, and it burns as readily as a pine shaving held in
the flame of a lamp. A steel watch-spring burns with
brilliant scintillations. If a bit of zinc be placed on a




COMPOUNDS AND ELEMENTS.              17
piece of charcoal hollowed out for the purpose, and the
flame of the blowpipe be directed upon it, the metal
quickly melts and burns. An-         Fig. 9.
timony, bismuth, and many
other metals will burn in the
same way, each with a characteristic light.  Cast- iron     i   l e  K _iiv vir
burns with a shower of bright
sparks.  Platinum, which is
one of the most infusible of
substances, is readily melted,
and even converted into vapor.
A small cylinder of lime    i E
placed in the blowpipe flame
becomes white-hot, and glows
with most intense brilliancy, 
forming what is known as   
the lime lig1ht or Drummond    l
lzg~zt. When the rays of this   -     e
light have been gathered and
reflected by a mirror, it has
been seen at a distance of one hundred miles in full
daylight.
WATER.
23. The Prof erties of Walter. - The most important
compound of hydrogen is water, which, as we have
already learned (2), contains hydrogen and oxygen.
At ordinary temperatures, water is a clear, colorless
transparent liquid, without taste or smell. It freezes at
32~, and under the ordinary pressure of the atmosphere
it boils at about 212~.
It is the most universal solvent known. There are but
few substances which are not dissolved by it. Even those
which we call insoluble, generally differ from the rest
2




I8           COMPOUNDS AND ELEMENTS.
only in degree. Spring water dissolves lime-rocks, and
almost all other mineral substances. The beautiful crystals found in the rocks are almost invariably deposited
from a solution of the mineral in water, though in many
cases it may have taken thousands of years to form them.
Water dissolves almost all gases as well as solids. It
is on the gases dissolved in the water that all aquatic
plants and animals live.
24. Various kinds of JNatural Waters. — Owing to
its solvent powers, water is never found in nature in a state
of purity. Rain water, collected after long-continued
wet weather, comes nearest to it; but even this always
contains small quantities of atmospheric air, and the gases
floating in the air.
Spring water always contains more or less of saline
matter, which it has dissolved from the soil. The salts
most frequently found in it are common salt, calcic carbonate and sulphate (carbonate and sulphate of lime),
and magnesic carbonate and sulphate (carbonate and
sulphate of magnesia). Most spring water contains carbonic acid, to which it owes its sprightly taste.
Mrineral waters are waters which contain an unusually
large proportion of any of the salts just named, or of other
and rarer substances. In many cases they have medicinal
qualities, which vary with the salts held in solution.
They sometimes contain salts of iron, and are then called
chalybeate springs. In other instances, carbonic acid is
so abundant as to give them an efervescent character.
Less frequently suijZhur is the chief ingredient, giving the
water a nauseous taste and smell.
Water is familiarly called hard or soft, according to its
action on soap. Hard waters contain salts of calcium or
magnesium, which cause the soap to curdle, that is, to
become insoluble. Soft waters do not contain these salts,
and dissolve the soap without difficulty. Many hard




COMPOUNDS AND ELEMENTS.               19
waters become soft by boiling, the salts held in solution
being deposited, as a fur or crust, on the inside of the
boiler.
Sea water contains a large amount of common salt and
of magnesic chloride (chloride of magnesium), to which
it owes its saline, bitter taste. Smaller quantities of many
other salts are found in it. All this matter has been
washed out of the soil by the rivers which flow into the
sea. It remains in the sea, since the water which evaporates from the surface is almost perfectly pure; but the
surplus is continually taken up by marine plants and animals, so that the sea becomes no salter.
25. Water in Plants and Animals. — Water constitutes the greater part of all plants and animals. The
human body is four-fifths water. In many of the lower
animals the proportion is much greater. From a sun-fish
weighing 30 pounds, only 240 grains of solid matter were
obtained; so that water makes up about.999 of the
weight of such animals. The vegetable substances which
we use for food contain almost as large a percentage
of water.  In potatoes, the fraction is.75; in apples,.80; in turnips,.go; in watermelons,.94; and in cucumbers,.97.
26. Water of Crystallization. — Many salts, in crystallizing from their solutions, unite with a definite quantity
of water, which is then called water of crystallization.
If the salt be heated, the water is driven off, and the crystals fall to pieces; but the chemical properties of the substance are not altered. Many salts part with this water
by mere exposure to the air, and efloresce; that is,
crumble into white powder. Sodic carbonate (carbonate
of soda) is an efflorescent salt. Other salts, on the contrary, like potassic carbonate (carbonate of potash), absorb water from the air, and become moist, or even dissolve; in which case they are said to deliquesce.




20           COMPOUNDS AND ELEMENTS.
27. Uses of Water. -" On the uses of water it is almost
needless to enlarge, for they are universally felt and appreciated. In each of its three physical conditions, the
blessings which it confers on man are inestimable. As
ice, it furnishes in northern lands, for months together, a
solid bridge of communication between distant places: in
the liquid condition, it is absolutely necessary to the existence of vegetable and animal life; in this shape, too,
it furnishes to man a continual source of power in the
flow of streams and rivers; it supplies one of the most
convenient channels of communication between places
widely separated; and further, it is the storehouse of
countless myriads of creatures fitted for use as food: in
the state of vapor, as applied in the steam-engine, it has
furnished a power which has, in late years, done more
than any other physical agent to advance civilization, to
economize time, and to ameliorate the social condition of
men. In each and all of these points, if rightly considered, we must perceive the entire adaptation of this compound to the ends which it was designed by the Creator
to fill.
" Glancing at the physical condition of our planet, we
cannot fail to be impressed with the important effects produced by the movements of water at periods anterior to
the existence of man, as well as in more recent times.
To such causes must we refer the formation of sedirrmentary rocks, and their arrangement in successive strata
upon the surface of the earth: even now, observation
shows that denudation is proceeding at some points, elevation and filling-up at others; whilst the accumulation
of drift, and a variety of other extensive geological
changes, must be traced to the same ever-acting and
widely-operating agency.
" It may further be observed, that there is no form of
matter which contributes so largely as water to the beauty




COMPOUNDS AND ELEMENTS.              2I
and variety of the globe which we inhabit. In its solid
state, we are familiar with it, in the form of blocks of ice,
of sleet and hail, of hoar-frost fringing every shrub and
blade of grass, or of snow protecting the tender plant, as
with a fleecy mantle, from the piercing frosts of winter.
The rare but splendid spectacles of mock suns, or parhelia, are due to the refractive power of floating spicula
of ice upon the sun's rays. In its liquid condition, as rain
or dew, it bathes the soil; and the personal experience
of all will testify to the charm which the waterfall,
the rivulet, the stream, or the lake, adds to the beauty
of the landscape; whilst few can behold unmoved
the unbounded expanse of ocean, which, whether motionless, or heaving with the gently undulating tide, or
when lashed into fury by the storm which sweeps over its
surface, seems to remind man of his own insignificance,
and of the power of Him who alone can lift up or quell
its roaring waves. In vapor, how much variety is added
to the view by the mist or the cloud, which, by their
ever-changing shadows, diversify, at every movement, the
landscape over which they are flitting; whilst the gorgeous hues of the clouds around the setting sun, and
the glowing tints of the rainbow, are due to the refractive action of water and watery vapor upon the solar
rays." *
NITROGEN.
28. PrejSaratzion of Nitrogen.  Pure nitrogen may
be readily prepared by passing a stream of chlorine gas
through strong aqua ammonia. It is well to pass the
nitrogen through a wash-bottle, to remove the white
fumes, which, as we have seen (3), are a compound of
hydrogen and nitrogen. The apparatus used is shown in
* Miller's Elements of Chemistry, Part II. pp. 35, 36.




22           COMPOUNDS AND ELEMENTS.
Figure io. The chlorine is generated in the flask at the
left; the ammonia is put in the next bottle; and the nitroFig. Io.
gen is washed in the third bottle, bybeing made to bubble
up through water.
29. Properties of Nitrogen.- Nitrogen is a colorless
gas, and is a little lighter than air. Its chief characteristic is its inertness. We have already seen (3) that it
neither burns nor allows a taper to burn in it.
30. Niitric Oxide. — Put some bits of copper into a
bottle (Figure I I), and add aquacfortis or nitric acid. A
Fig. II.
I AL A




COMPOUNDS AND ELEMENTS.             23
reddish gas fills the upper part of the bottle, and passes
off through the tube. When collected over water, it is
colorless. The red color was owing to impurities, which
have been absorbed by the water.
Invert a jar of this gas over a piece of well-lighted
phosphorus, and the latter burns almost as brilliantly as
in oxygen, filling the jar with white fumes of phzosphoric
anhydride (phospkhoric acid.)  The experiment proves
the presence of oxygen in the gas in which the phosphorus
was burned.
Pass a mixture of equal parts of this same gas and
hydrogen through a tube containing some heated platinized as6estos, and hold a piece of moistened red litmuspaper at the mouth of the tube. The paper is turned
blue, showing that ammonia has been produced; for ammonia is the only gas that turns red litmus-paper blue.
We have seen (3) that ammonia is a compound of hydrogen and nitrogen; therefore there must have been
nitrogen in the gas mixed with the hydrogen.
The gas is, in fact, a compound of nitrogen and oxygen,
and is called nitric oxide (deutoxide or binoxide of nitrogen), and its symbol is NO.
31. Catalysis. - In the above experiment the platinized asbestos remains wholly unchanged. By its mere
presence, it has made the hydrogen unite with the elements of the gas mixed with it. This remarkable action
by mere presence is called catalysis. It occurs in many
other cases, but is very imperfectly understood.
32. lVascent Stale.- Nitrogen, as we have seen, is a
very inert substance. Indeed, it can be made to combine directly with scarcely any element. In the above
experiment, the hydrogen first seizes upon the oxygen,
forming water, and sets the nitrogen free. At the moment when it is thus set free it has an increased activity,
and readily unites with the hydrogen to form ammonia.




24          COMPOUNDS AND ELEMENTS.
It is found generally true that elements are unusually
active when just liberated from compounds. They are
then said to be in the nascent state.
33. Nitrous An hydride.- If a jar of oxygen be inverted over a jar of nitric oxide, the gases, on mixing,
become of a bright cherry-red color. The compound
formed differs from nitric oxide only in containing more
oxygen. It is called nitrous anhydride (nitrous acid),
and its formula is N203.
34-. nitric Peroxide and Nitric Anhydride. -It is
possible to form two higher oxides of nitrogen, NO2,
nitric peroxide, and N205, nitric anhydride.
The former, at a temperature below 70o, is an orangecolored liquid; and the latter is a white solid, which
eagerly unites with water, forming the well-known aquaforlis, or nitric acid, HNO3. The reaction between
nitric anhydride and water is shown by the following
equation: -
12 (H0O + N205) = HNO3.
35. Nitric Acid.  Nitric acid is a strongly fuming
liquid, colorless when pure, but usually yellowish from
the presence of some of the lower oxides of nitrogen.
It is one of the most corrosive substances known, and
rapidly destroys all animal substances. When diluted, it
stains the skin, wool, feathers, and the like, a bright yellow color, and is often used as a permanent yellow dye
for silk and woollen goods. It acts violently upon tin and
iron filings, especially when they are moistened with
water. Indeed it attacks all the ordinary metals, except
gold and platinum. Its action upon them, however, is
more energetic when it is somewhat dilute.
The action of nitric acid upon the metals is owing to
the readiness with which it parts with some of its oxygen. It first oxidizes them, and then acts upon these




COMPOUNDS AND ELEMENTS.              25
basic oxides (I6), to form salts (I7). During this process, the lower oxides of nitrogen are always given off, as
is indicated by the appearance of red fumes.
Nitric acid may be made on a small scale by heating
potassic nitrate (saltpetre), in a retort with sulphuric
acid (oil of vitriol). The nitric acid distils over, and is
collected in a receiver. The re-action is as follows:2KNO, + H2SO4 - K2SO4 + 2HNO3.
The hydrogen and the potassium change places, giving
rise to potassic sulphate (sulphate of potash) and nitric
acid.
On the large scale, iron retorts, coated with fire-clay on
the inside of the upper part, where they are exposed to
the acid vapors, are employed for the distillation, and
sodic nitrate (soda saltpetre) is substituted for potassic
nitrate, as it is a cheaper salt, and likewise yields 9 per
cent more nitric acid than potassic nitrate.
36. Nitrous Oxide. -A fifth oxide of nitrogen is obtained by gently heating ammonic nitrate (nitrate of ammonia). It is called nitrous oxide, and its symbol is N20.
The reaction is shown by the following equation:(H4N)NO,3- 2H,20 + N0.
The ammonic nitrate, (H4N)NO,, breaks up into water
and nitrous oxide.
N.0 is a colorless gas, and readily gives up its oxygen.
Phosphorus burns in it as brilliantly as in pure oxygen.
A splint of wood with a spark on the end of it bursts into
flame when plunged into the gas. When inhaled, it has
a peculiarly exhilarating effect, and hence is called laugk-,
inggas. It is used by dentists as an anest/etic, since it
makes the patient for the time insensible to pain. Great
care must be taken that the gas when inhaled is perfectly
fure.




26          COMPOUNDS AND ELEMENTS.
37. Ammonia. -We have seen (3) that ammonia is a
compound of hydrogen and nitrogen. It is a colorless
gas, which is greedily absorbed by water, forming the
ordinary aqua ammonia. The eagerness with which it
is taken up by water may be shown by filling a jar with
the gas and opening it under water. The gas is instantly
absorbed, and the water rushes in and fills the bottle. At
a temperature of 32~, water will absorb more than one
thousand times its bulk of ammonia.
Ammonia takes its name from the fact that it was first
obtained firom a salt found in Libya, near the temple of
Fig. I2.           Jupiter Ammon.  It
is now prepared from
the same salt, sal-ammon'iac or ammonic
chloride, which  is
made in large quantities from the waste
" _I, Pi fliquor of gas-works.
The sal-ammoniac is
powdered and mixed
with lime, and the
mixture is heated in
a flask arranged as
shown in Figure I2.
The gas is washed by passing it through a wash-bottle,
and is then conducted into water.
38. Ammonium. —The symbol of ammoni'c chloride
is (H4N)Cl; that of ammonic nitrate is (H4N)NO3.
If we compare these with the symbols.of the potassic
chloride and nitrate, KC1 and KNO3, we shall see that
the group of atoms H4N plays the same part in the compounds as the metal potassium; and this is the case in
a large class of salts. Hence this group of atoms has
come to be considered as a metal, and has received the




COMPOUNDS AND ELEMENTS.            27
name of ammonium. It has not, however, been obtained
in a separate form, since it at once breaks up into ammonia, HN, and hydrogen.
39. Cyanogen. - When carbon and nitrogen are heated
together in the presence of potash, a remarkable compound called potassic cyanide (cyanide of potassium),
KCN, is formed. From this a large number of substances
can be prepared, all of which contain the group of atoms
CN. To this group the name cyanogen (blue-maker) is
given, from its forming a number of blue compounds. It
is remarkable as entering into composition exactly like a
non-metallic element. It can be obtained in a free state
as a colorless gas by heating mercuric cyanide (cyanide
of mercury.) It forms with hydrogen an acid, HCN,
analogous to muriatic acid, HC1. This acid is called
hydrocyanic or prussic acid.
The most important of the blue compounds of cyanogen is Prussian blue, which may be formed by mixing
a solution of either the red or the yellow prussiate of
potash with a solution of green vitriol.
Groups of atoms, like H4N and CN, which play the
part of elements, are called radicals.
40. Thze Chzaracteristics of N'itrogen. —The most
marked features of nitrogen are its inertness (29); the
indirect way in which it enters into combination; and
the great variety, the remarkable nature, and the instability of its compounds.
The great variety of its compounds is shown in the
five which it forms with oxygen:Nitrous oxide,    N2O.
Nitric oxide,    NO.
Nitrous anhydride, N20O.
Nitric peroxide,  NO2.
Nitric anhydride, N205.




28          COMPOUNDS AND ELEMENTS.
These compounds, as we have seen, are widely unlike in
their properties; but in composition they differ only in the
amount of oxygen which they contain.
The remarkable nature of the compounds is illustrated
by ammonium and cyanogen, one of which acts like a
metallic and the other as a non-metallic element.
The instability of the compounds is seen in the readiness with which the oxides give up their oxygen. Nitric
iodide (iodide of nitrogen), which may be prepared by
the action of ammonia on iodine, is so unstable that it
explodes even when touched with a feather.  Nitric
chloride (chloride of nitrogen) is even more explosive,
and is one of the most dangerous compounds known.
CARBON.
41. Properties of Carbon. - Carbon differs from the
elements already described in being a solid when in a
fiee state. It exists in three forms, which in outward
appearance have nothing in common, but which are
identical in their chemical relations. These three allotropfic forms are diamond, graphkite or fzlumbago, and
charcoal. These differ in hardness, color, specific gravity, and the like; but when burnt in oxygen, the same
weight of each produces the same weight of carbonic
acid.
The diamond was first found to be pure carbon by
Lavoisier in I775-76. It occurs crystallized in certain
rocks and gravels in India, Borneo, and Brazil. It is the
hardest of all known bodies; and when cut, has a brilliant
lustre and a high refractive power.
Graphite, pzlumbago, or black lead, is the substance
used in the manufacture of the so-called " lead pencils."
Although very brittle, its particles are very hard, so that
a saw or other instrument used in cutting it is soon
dulled. Mixed with oil it is extensively used to diminish




COMPOUNDS AND ELEMENTS.              29
the friction of machinery. It is the basis of mcst kinds
of slove-poZlish, and of certain paints used to protect ironwork. It is also made into crucibles, which, on account
of their infusibility, are much prized by the chemist.
Carbon, in all its forms, is the most infusible substance
known. Its infzisibility and its allolro-pic states are its
chief characteristics.
42. Carbonic Anhydride (Carbonic Acid). — The
most important compound of carbon is CO,, carbonic
anydride, commonly called carbonic acid. This gas is
readily prepared by the action of dilute muriatic acid on
Fig. I3.
chalk or marble (Figure I3). The reaction is as follows:CaCO, + 2HC1 -  CaCl2 + H20,      CO,.
CaCO., caZcic carbonate (chalk, or marble), is broken
up by the action of the acid. The calcium combines
with the chlorine of the acid, forming caccic cAZoride
(czloride of calcium), CaCl2; one atom of the oxygen
combines with the hydrogen of the acid, forming water;
and CO2 is set free.
We have already seen (i i) that lime-water readily
shows the presence of carbonic acid, by becoming milky
white. The lime-water contains lime, CaO, which com



30          COMPOUNDS AND ELEMENTS.
bines with the carbonic acid, CO2, to form CaCO8
again.
If a lighted taper be plunged into a jar of carbonic
acid, it goes out. We have seen that the same thing
takes place in nitrogen; but the two gases can be distinguished by the lime-water test.
Carbonic acid is about I.5 times as heavy as air, so
that, with an ordinary dipper, it can be dipped out from
one jar and poured into another, like water. It is poisonous when breathed, even though mixed with a large
quantity of air.
43. Carbonic Oxide. — Carbonic oxide, CO, is a gas
formed when carbon burns with a limited supply of oxygen. It is often produced in an ordinary coal-fire, and is
seen to burn with a pale blue flame. It is far more
poisonous than carbonic acid.
CO may be obtained pure from several compounds of
carbon. Thus, if crystallized oxalic acid, C2H204, be
heated with strong sulphuric acid, the latter withdraws
from it one molecule of water, H20, leaving C20,8 which
at once splits up into CO and CO2. The CO2 may be
removed by passing the mixed gases through a solution
of caustic soda.
SULPHUR.
44. Sources of SuljAhur.- Sulphur occurs in nature
both free and combined: it is found free in certain volcanic countries, especially in Sicily and Iceland; it exists
in combination with many metals, forming sulzzides.
These sulphides are the ores from which several of the
metals are commonly obtained. Thus PbS, plumbic
sulphide (galena), ZnS, zincic sulphide (zinc blende),
and CuS, cupric sulphide (sulphide of copper), are the
most productive ores of those metals.
In order to obtain pure sulphur, the mineral, containing




COMPOUNDS AND ELEMENTS.                 3I
the crude substance mixed with earthy impurities, is
heated in earthen pots (Figure I3); the sulphur distils
over in the form of vapor, which is condensed in similar
pots placed outside the furnace. The sulphur thus obtained is refined or purified by a second distillation.
If the vapor of sulphur is quickly cooled below its
melting-point, it solidifies in a crystalline powder, called
flowers of sulphur; just as watery vapor, when cooled
below the freezing point of water, becomes snow. If
Fig. x4.
sulphur is gently heated, it melts, and may be cast into
sticks, and is then known as brimstone, or roll sulphur.
45. Properlies of Sul;hur. - Sulphur is a yellow
solid, and exists in three allotropic forms (I4). The
first is that in which it crystallizes in nature. The other
two are obtained by melting sulphur. If melted sulphur
be allowed to cool slowly, it crystallizes in long, transparent needle-shaped crystals, which are quite different
in form from the natural crystals, and have a specific




32          COMPOUNDS AND ELEMENTS.
gravity of 1.98, while the natural crystals have a specific
gravity of 2.o7.  These transparent crystals become
opaque after an exposure of a few days to the air, owing
to their breaking up into several crystals of the natural
and permanent form. The third allotropic form of sulphur is obtained by pouring melted sulphur at 450o into
cold water. It then forms a soft, tenacious mass, resembling india-rubber, and has a specific gravity of I.96.
This form of sulphur is not permanent. In a few hours
it returns to its ordinary brittle state. These peculiar
modifications are also apparent when sulphur is heated.
It begins to melt at 239~, and forms an amber-colored
limpid liquid; as the temperature rises, it begins to
thicken, and to become dark-colored, so that at about
45o~ it can scarcely be poured from the vessel; heated
still higher, it again becomes fluid, and remains as a dark
thin liquid, till the temperature rises to 8360, when it begins to boil, and gives off a red vapor.
Sulphur is an inflammable substance, and when heated
in the air or oxygen burns with a bluish flame, and with
the suffocating odor so well known in the burning of a
common lucifer match. It is insoluble in water and in
most liquids, but dissolves in carbonic bisulphide (50).
46. Su12phurous Anhydride (SuLzhurous Acid). —
This compound, SO2, as we have seen (x ), is formed
when sulphur is burned in oxygen, or in the air, which is
a mixture of oxygen and other gases. The suffocating
odor which we perceive when a common friction match
is lighted is caused by SO2.
The most important property of SO2 is its power of
bleaching silk, woollen, straw, etc. It is largely used for
this purpose in the arts.
This property may be illustrated by holding a red rose
or other flower in a jar of SO2. The flower quickly
loses its color.




COMPOUNDS AND ELEMENTS.             33
47. SuZihturic Acid. - Sulphuric acid, or oil of vitriol, is the most important and most powerful of all the
acids. It has a very strong attraction for water, and
when the two are mixed, intense heat is developed.
Hence caution is necessary in mixing them, especially in
thick glass vessels. The acid should always be poured
into the water, not the water into the acid. It rapidly
chars all organic matter, and is a valuable drying agent.
Sulphuric acid was first prepared by distilling green
vitriol, or ferrous su/lZhate, whence its name, oil of
vitriol. In this form it is sometimes known as Vordhausen acid, from the name of the city in Saxony where
it was first manufactured. It is a fuming liquid, denser
than the ordinary acid, and is a mixture of this acid with
the szlphzuric anhydride.
This method has long been superseded by a more convenient one, which depends upon the fact that, though
SO2 does not combine with free oxygen and water to
form sulphuric acid, it is capable of taking up the oxygen when the latter is united with nitrogen in the form
of nitrous anycydride, N203. Thus:SO2 -t H20 + N203 _ H2SO4 + 2NO.
Sulphurous anhydride, water, and nitrous anhydride,
yield sulphuric acid and nitric oxide.
The NO formed in this decomposition takes up another atom of oxygen from the air, becoming N20, and
this is again able to convert a second molecule of SO2,
with water, H20, into sulphuric acid, H2SO4; being a
second time reduced to NO, and ready again to take up another atom of oxygen from the air. Hence it is clear that
the NO acts simply as a carrier of oxygen between the air
and the SO2; and a very small quantity of it is therefore
able to convert a very large quantity of sulphurous anhydride, water, and nitrous anhydride, into sulphuric acid.
3




34          COMPOUNDS AND ELEMENTS.
This process is conducted on a large scale in chambers
made of sheet-lead, which are often of a capacity of
50,000 or Ioo,ooo cubic feet. The sulphurous anhydride
is obtained either by burning sulphur in a current of air,
or by roasting a mineral called iron pyrites (ferric bisulphide, FeS2), and is led, together with air, into the
chamber. The N203 is got from sodic nitrate (soda saltpetre), which is decomposed either by the heat of the
burning sulphur, or in a separate furnace. Jets of steam
are also blown into the chamber, and a thorough draft is
maintained by a high chimney. The sulphuric acid, as
it forms, falls to the floor of the chamber, whence it is
continually drawn off. It is then heated, first in open
leaden pans, and then in vessels of glass or platinum (as
lead is attacked by the strong acid), until the excess of
water is driven off, and a sufficiently concentrated acid is
obtained.
So extensively is this acid used, that the quantity
manufactured in South Lancashire (England) alone exceeds 3,000 tolls a week.
This method of making sulphuric acid may be illustrated, on a small scale, by dipping a shaving or cloth in
nitric acid, and then holding it in a jar of sulphurous
anhydride, with a little water at the bottom of the jar.
Red fumes at once appear, which show that the nitric
acid has lost some of its oxygen, having given it up to
the SO2, which thus becomes SO3. If the experiment be
repeated a number of times, the water at the bottom of
the jar will be found to contain sulphuric acid.
48. Suznlphuric Anhydride. - If fuming Nordhausen
acid be gently heated in a glass retort, which is connected with a receiver, kept cool by ice, white fumes
will pass over and solidify into a white silky fibrous
mass. This solid is sulthuric anhydride. It has no
acid properties, and can be moulded in the fingers with



COMPOUNDS AND ELEMENTS.             35
out charring the skin. When thrown on water, the heat
emitted is so intense that it hisses like red-hot iron.
49'. Hydric Sulithide, Sulphuretted Rydrogen, or
Hydrosulizhuric Acid. - Sulphur combines with hydrogen, forming hydric sulPhidce, H2S, a compound analogous in composition to water. It is a gas of a very
offensive odor, and very poisonous. It reddens litmuspaper, and is therefore an acid. It is best prepared by
the action of dilute sulphuric acid on ferrous sulphide,
FeS. Thus:FeS + H2SO4 = H2S + FeSO4.
The hydrogen and the iron change places, forming
hydric sulphide and ferrous sulphate (sulphate of iron,
or green vitriol).
This gas is an invaluable agent in chemical analysis.
50. Carbonic Bisulhicide. — If the vapor of sulphur
be passed over red-hot charcoal, a volatile compound,
CSo, is formed. It is seen to be analogous to carbonic
acid, CO2. It is a very inflammable, colorless liquid, of
an offensive odor, and is called carbonic bisuifPhide (or
bisulthide of carbon). It is of great importance in the
arts, since it dissolves gums, caoutchouc, sulphur, and
phosphorus.
5I.  The Oxygen Group. - The two compounds, H2S
and CS2, are analogous in composition to H20 and CO2,
and it is true in general that for every oxide there is a
corresponding sulphide. Thus we have K20, potassic
oxide (polassa), and K2S, potassic sulZthide (suZlshide
of potassium); BaO, baric oxide (baryta), and BaS,
baric sulizhide (sulithide of barium); A1203, aluminic
oxide (alumina), and Al2S3, aluminic sulthide (sulp hide of aluminium); and so on.
Oxygen and sulphur, then, belong to the same group
of elements, which may be called the oxygen group. To




36          COMPOUNDS AND ELEMENTS.
this group also belong the rare elements, selenium and
tellurium.
It will be noticed that the atomic weight of sulphur,
32, is just double that of oxygen.
CHLORINE.
52. Preparation of Chlorine. - Chlorine, as we have
already seen (i), is prepared by heating a mixture of
muriatic acid and black oxide of manganese, MnO2.
The reaction is shown in the following equation:MnO2 + 4HC1 = MnCl2 + 2H20 + 2C1.
The hydrogen of the HC1 combines with the oxygen of
the MnO2, forming two molecules of water, 2H20.
Half the chlorine of the HC1 unites with the manganese,
to form manganic chloride (chloride of manganese),
MnC12, and the other half is set free.
53. Prop5erties of Chlorine.- Chlorine was discovered by Scheele in I774. It does not occur free in
nature, but is found combined with metals, forming
chlorides, of which rock-salt is the most common.
Chlorine is, as we have seen, a greenish-yellow gas of a
most disagreeable and irritating odor. It is very poisonous when inhaled in any considerable quantity. It is a
very heavy gas, being nearly 2.5 times as heavy as air.
Chlorine has a very strong affinity for the metals. If
these in a finely divided state are brought into contact
with it, they take fire spontaneously, giving rise to metallic chlorides. It has so strong an affinity for phosphorus, that this element will take fire spontaneously
when put into a jar of chlorine. But the most remarkable property of chlorine is its power of combining with
hydrogen to form muriatic acid. When these gases are
mixed in equal volumes, they combine with an explosion




COMPOUNDS AND ELEMENTS.              37
on applying a lighted taper to them, or on exposing them
to the sunlight. This property of chlorine has already
been illustrated in the decomposition of water and ammonia (2, 3).
Another remarkable property of chlorine is its 6beaching power, which depends on its ability to decompose
water. We may enclose a piece of cotton cloth colored
with a vegetable substance in a bottle of dry chlorine,
and no change of color takes place, even after many
weeks. If, however, a few drops of water are added,
the cotton is at once bleached. The chlorine combines
with the hydrogen of the water, and the oxygen, at the
moment of its liberation, when it is in the nascent state
(32), combines with the coloring matters, forming colorless compounds.  Ordinary free oxygen has not this
power, at least to any great extent.
54. Chloride of Linze, or Blecach/zng Powder. - Since
chlorine destroys all organic colors (that is all colors derived from the vegetable and animal kingdoms) it is very
extensively used in bleaching cotton and linen goods and
paper. Cotton fabrics may now be rendered perfectly
white in a few hours; while, by the old method of laying them on the grass in the sun, it required weeks, and
even months, to effect it. It was necessary, moreover,
to have meadow-land suitably situated for the bleaching;
hence most of the cloth manufactured in England was
carried to Holland to be bleached. Besides the diminished expense, the cotton stuffs bleached with chlorine
suffer less injury in the hands of skilful workmen than
those bleached in the sun.
The health of the workmen is greatly endangered by
the use of chlorine in the gaseous state; but it has been
found that the gas is readily absorbed by slaked lime,
and is as readily given up again when the lime is treated
with dilute acid.




38          COMPOUNDS AND ELEMENTS.
When thus combined with lime, the chlorine can be
easily transported. The compound is called chloride of
lime, or bleaching powder.
This powder is made on a large scale by conducting
chlorine into spacious chambers, on the floor of which
slaked lime is spread to the depth of two inches.
In bleaching, the goods are first dipped into a solution
of the bleaching powder, and then passed through dilute
acid. The chlorine is thus set free in the fibres of the
cloth, where it does its work of bleaching without injury
to the workmen.
Chloride of lime is also largely used as a disinfectant.
The chlorine acts upon organic odors in the same way
as upon organic colors; that is, it oxidizes and destroys
them.
55. Hydric Chloride (Hydrochloric Acid). — Hydric
chloride or hydrochloric acid is a colorless gas, somewhat heavier than air, and is very soluble in water. This
solution is the ordinary muriatic acid of the shops. It
may be easily prepared, by placing in a capacious retort
3 parts of fused sodic chloride (chloride of sodium, or common salt) in fragments, and adding slowly, through a bent
funnel, 3 parts of oil of vitriol. If pounded salt be used,
the action of the acid is apt to be too rapid. The retort
is connected with a series of bottles; in the first, a small
quantity of water is placed, to detain any impurities
which might be carried over mechanically with the gas;
the second bottle may contain 4 parts of water, and
should be immersed in a vessel of cold water, as the condensation of the gas is attended with a great disengagement of heat. On applying a gentle heat to the retort,
the acid comes over and is condensed; an easily soluble
sodic sulphate (sulphate of soda) remains in the retort.
For manufacturing purposes, the decomposition is effected
in iron cylinders, like those employed in the manufacture




COMPOUNDS AND ELEMENTS.             39
of nitric acid, and only one half the quantity of sulphuric
acid prescribed above is used: —
2NaC +H2SO4 =-HC1 +Na2SO4.
Sodic sulphate, Na2SO4, remains in the cylinder, whilst
the acid is condensed in a series of salt-glazed stone-ware
jars.
Enormous quantities of muriatic acid are obtained as an
incidental product in the manufacture of soda-ash, which
will be described farther on. More than Iooo tons are
made every week at the soda-ash works in South Lancashire (England) alone.
56. Hydracids.- Hydric chloride, HCl, and hydric
sulphide, H2S, contain each but two elements, and no
oxygen; while nitric acid, HNO., and sulphuric acid,
H2SO4, contain each three elements, one of which is
oxygen. There are, then, two classes of acids: one containing oxygen, and called oxyacids; and the other,
containing no oxygen, called hydracids.
57. Aqua Regia.-When muriatic acid is mixed with
nitric acid, it forms the so-called nitro-muriatic acid.
This acid was called aqua regia (royal water) by the
alchemists, because it dissolves gold, the "king of
metals."  Both platinum  and gold are insoluble in
either acid separately; but when the two acids are
mixed, they decompose each other. Chlorine is set free,
and in its nascent state (32) acts upon the metals, and
dissolves them.
58. Chzlorine Oxyacids. - Chlorine has a very weak
affinity for oxygen; but it forms four oxyacids: zypochZorous acid, HC10; cilorous acid, HC10; chloric
acid, HCO13; and /yperchloric or l5erchloric acid,
HC105. Of these, the hypochlorous and the chloric
form some important salts.




40           COMPOUNDS AND ELEMENTS.
BROMINE.
59. Pro~perties of Bromine. — This element, which
closely resembles chlorine in its properties and compounds, was discovered by Balard, in I826, in the salts
obtained by the evaporation of sea-water. It does not
occur free in nature, and is, like chlorine, found combined with sodium and magnesium as bromides in certain mineral springs.
Bromine is a dark, reddish-black, heavy liquid, being
the only element, except mercury, that exists as a liquid
at the ordinary temperature. Its specific gravity is 2.966,
it freezes at -9~, and boils at I45~. It has a very strong,
irritating smell, resembling that of chlorine, and when
inhaled, acts as a violent poison. It is quite soluble in
water, and this solution bleaches, but more feebly than a
solution of chlorine. Some of its salts are much used in
medicine and in photography.
IODINE.
60. Properties of Iodine. —Iodine also occurs in seawater, combined with sodium and magnesium. It was
discovered in I8I2 by Courtois. At the ordinary temperature it is a dark gray solid, with a bright metallic
lustre. It has a specific gravity of 4.95; it melts at 225~,
and boils at about 350o. Its vapor is of a beautiful deep
violet color, and has a faint chlorine-like smell. Iodine
does not possess such active qualities as either chlorine
or bromine. Its solution does not bleach vegetable colors,
and it is set free from its compounds by both the above
elements. Free iodine forms with starch a remarkable
compound of a rich blue color (I2). Iodine acts as a
violent poison; but, given in small quantities, it is much
used as a medicine. Some of its salts also are used in
medicine and in photography.




COMPOUNDS AND ELEMENTS.             4I
FLUORINE.
6i. Properties of Fluorine. - This element occurs
combined with the metal calcium, as calcic fluoride
(fluoride of calcium) or jfluor-spar. It is remarkable as
forming no compound with oxygen, and as being extremely difficult to prepare in a pure state. Many unsuccessful attempts have been made to obtain fluorine;
but, by the action of dry iodine upon dry argentic fluoride
(fluoride of silver), it appears to have been isolated; and
it is found to be a colorless gas.
62. Hydric Fluoride, or Hydrojffuoric Acid. -When
calcic fluoride (fluor spar) is acted upon by sulphuric
acid, a very corrosive gas is obtained, called hydric
fuoride (izydrofluoric acid). The reaction is shown in
the following equation: —
H2SO4 + CaF2 = CaSO4 + 2HF.
The calcium and the hydrogen change places, forming
calcic sulp/zate (sultphate of lime), CaS04, and hydric
fluoride.
This acid must be prepared in vessels of lead or platinum, since it rapidly attacks glass. It acts violently
upon the skin, producing painful sores, and the fumes
are very poisonous to the lungs. It is used for etching
on glass. The glass is first covered with wax, through
which the design is traced with a sharp point. The
glass is then exposed to the gas, which corrodes it where
the wax has been removed. The solution of the gas in
water is also used for the same purpose.
63. The Chlorine Group. — The four elements just
described form a well-marked group. They are especially remarkable for their gradation of properties. Thus
chlorine is a gas, bromine a liquid, and iodine a solid, at
the ordinary temperature. Chlorine may be easily con



42           COMPOUNDS AND ELEMENTS.
densed into a liquid, and the specific gravity of liquid
chlorine is 1.33, of bromine 2.97, and of iodine 4.95.
Liquid chlorine is transparent, bromine slightly so, and
iodine opaque. The atomic weight and density of bromine are nearly the mean of those of chlorine and iodine,
35.5 + I27 - 8I.25; and in its general chemical de2
portment bromine stands half-way between the other
two elements.
These elements all form powerful acids with hydrogen,
and have a strong affinity for the metals. They all have
a very weak affinity for oxygen.
PHOSPHORUS.
64. Protierties of Phosphorus. — This element does
not occur free in nature, but is found combined with
oxygen and calcium in large quantities in the bodies,
especially the bones, of animals, and in the seeds of
plants. Animals obtain their phosphorus from plants,
plants from the soil, and the soil from the slow disintegration of the oldest rocks.  Phosphorus was accidentally discovered by Brande, in I669; but Scheele,
in 1769, pointed out its existence in the bones, and
carefully examined its properties. It is prepared from
bones, and is used chiefly in the manufacture of lucifer
matches.
Phosphorus is a yellowish, semi-transparent solid, resembling wax. Its specific gravity is 1.83. It melts at
II10, and boils at 550~. In the air it gives off white
fumns, and emits a pale light in the dark, whence its
name, which means lzght-bearer. While emitting this
light, it appears to be undergoing a slow burning. At a
temperature a little above its melting-point, phosphorus
takes fire in the air, and burns with great energy. It




COMPOUNDS AND ELEMENTS.             43
may be set on fire by slight friction, by a blow, and even
by the heat of the hand. Hence it should be handled
with great care, and always be cut under water. Phosphorus has several well-marked allotropic states, the
most important of which is that known as red phzos2phorus. This is much less inflammable than ordinary
phosphorus, and is not poisonous.
65. Compounds of Phosphorus. - Phosphorus combines with oxygen, to form several acids, the most important of which are known as hypopihosphorous acid
and phosphoric acid. From the former are derived salts
(hypophosphites), used in medicine; while the latter furnishes a large class of salts (phosphates and sup]erphosp hates), which are valuable to the farmer as fertilizers.
Phosphorus unites with hydrogen, to form hydric phos-:phide (phosphuretted hydrogen), H3P, a poisonous gas,
with a very offensive odor. When this gas is prepared
by the action of caustic potash on phosphorus, each
bubble of the gas takes fire as it comes into contact with
the air, forming beautiful rings of phosphoric anhydride
(phosphoric acid), which expand as they rise. This
spontaneous combustion is owing to the presence of a
small quantity of a liquid compound of phosphorus and
hydrogen, whose symbol is H2P. Pure phosphuretted
hydrogen does not take fire in this way.
ARSENIC.
66. Properties of Arsenic. — Arsenic closely resembles phosphorus and nitrogen in its chemical properties,
and in those of its compounds, and is therefore to be
counted as a non-metallic element. In physical features,
such as specific gravity and lustre, it bears a greater
resemblance to the metals, with which it was formerly
classed. (See, in Appendix, Chemical Philosophy, ~  9.)




44          COMPOUNDS AND ELEMENTS.
Arsenic is sometimes found in a free state, but more
often combined, chiefly with iron, nickel, cobalt, and
sulphur. One of the compounds of this element with
oxygen, As203, is the well-known poison, wzite arsenic.
67. The Nitrogen Group. — Nitrogen, phosphorus,
and arsenic form a well-marked group. They all form
similar compounds with oxygen and with hydrogen.
Thus we have H8N  (ammonia), H3P (phosphuretted
hydrogen), and H3As (hydric arsenide); N203 (nitrous
anhydride), NO, (nitric anhydride), P203 (phosphorous
anhydride), P205 (phosphoric anhydride), and As2O8
(arsenious anhydride), As2O5 (arsenic anhydride).
BORON.
68. Prof erlies of Boron. -Boron is found in nature
combined with oxygen as boracic acid, and with oxygen
and sodium as borax. In certain volcanic districts in
Tuscany, jets of steam and gas are continually escaping
from the earth.  These steam-jets contain small quantities of boracic acid, which collects in artificial basins
formed for the purpose at the mouth of the jet. By
means-of the heat of natural steam-jets, this solution of
boracic acid is concentrated and crystallized. About
2,000 tons of crude acid are thus prepared and exported
from Tuscany every year.
Boron is remarkable as combining directly with nitrogen at a high temperature.
SILICON.
69. Profperties of Silicon. — Next to oxygen, silicon
is the most abundant element known. It does not, however, occur in a free state, but always combined with
oxygen (for which it has a very strong affinity) as silica.




COMPOUNDS AND ELEMENTS.             45
Silica is found nearly pure in quartz, flint, sand, and in
several minerals, and combined with metals in almost all
known rocks. Its symbol is SiO2.
Silicon can be obtained in three modifications, corresponding to the three states of carbon.
70o. The Carbon Grout. - Carbon and silicon, then,
form a well-marked group, resembling each other closely
in their allotropic states.
SUMMARY.
Chemistry divides substances into two classes: —
Ist, Elements, or substances which cannot be decomposed by any known process. Of these only 65 are
known.
2d, Comnpoounds, or substances made up of elements.
The force which causes elements to combine, and
holds them in combination, is called Alffnity.
Affinity changes the properties of the substances
which it combines.
Affinity always causes substances to combine in fixed
and definite quantities. This law of combination is
called the Law of Definite Protortions.
A4 given element combines with some elements in
preference to others.
Matter is made up of molecules; and molecules are
made up of atoms.
The compounds of nitrogen and oxygen show that the
same elements may combine in more than one proportion, and that in such cases the proportions of the elements in the compounds are always multziples of the
atomic weights of the elements. This law of combination
is known as the Law of Multiiple Proportions.
The symbol of an element is usually the first letter of
its name, a second letter being added to distinguish




46          COMPOUNDS AND ELEMENTS.
names beginning with the same letter. The symbol of
an element always stands for one atom of the element.
The symbol of a comnpound indicates its composition.
It is formed by writing together the symbols of the elements of the compound, with a small figure after each
symbol expressing the number of atoms of that element
found in a molecule of the compound. The symbol
of a compound always stands for one molecule of the
compound.
The chemical changes, or reactions, which substances
undergo, are indicated by equations made up of these
symbols.
The compounds of oxygen with the elements are called
oxides. These oxides are either acid, neutral, or basic.
The oxides of the non-metallic elements are generally
acid; those of the metallic elements are generally basic.
The acid oxides combined with water form acids.
The basic oxides combined with water form bases.
When a metal takes the place of the hydrogen of the
acid, the compound is called a salt.
A hydracid is made up of hydrogen and a non-metallic
element.
The names of binary salts take the ending -ide; those
of ternary salts, the endings -ate or -ite, according as the
name of the acid ends in -ic or -ous.
In general, the name of a binary compound takes the
ending -ide.
Oxygen is the most abundant element, and is usually
prepared from potassic chlorate. It has a wider range
of affinities than any other element.
Ozone is an allotropic form of oxygen, and is more
active than ordinary oxygen.
Hydrogen is the lightest element, and is usually obtained by the action of zinc on dilute sulphuric acid. Its
most important compound is water.




COMPOUNDS AND ELEMENTS.              47
Nitrogen is one of the most inert of elements. It is
remarkable for the indirect way in which it enters into
combination, and for the variety and the nature of its
compounds.
Carbon is an infusible solid, and has three allotropic
states.
Szulzhur is an inflammable solid, forming suliphides
which in their composition resemble oxides. It has
several remarkable allotropic states.
Chlorine is most readily prepared by the action of
black oxide of manganese on muriatic acid. It is distinguished by its color, its odor, and its affinity for hydrogen
and the metals. Its bleaching and disinfecting power is
due to its strong affinity for hydrogen.
Bromine, iodine, and fluorine are elements closely resembling chlorine in their chemical properties.
Pho.?shorus is a very inflammable substance, and is
mainly used for making lucifer matches. It is obtained
from bones.
Phosphorus and arsenic resemble nitrogen in the compounds which they form.
Silicon resembles carbon in its allotropic states.
Boron combines directly with nitrogen at a high temperature.
NVilric acid is remarkable for its oxidizing power.
Sui/phuric acid is the strongest of acids, and is remarkable for its affinity for water.
SulpZhurous acid is a bleaching agent.
NVitrous oxide is used as an anaesthetic.
Carbonic acid is a heavy gas, and is most readily prepared by the action of muriatic acid on marble.
The most important non-metallic suitZhides are hydric
sult hide and carbonic bisultzide.
The most important of the non-metallic chlorides is
muriatic acid.




48         COMPOUNDS AND ELEMENTS.
Cyanogen is a remarkable compound of nitrogen
and carbon, and plays the part of a non-metallic
element.
Ammonium is a remarkable compound of nitrogen and
hydrogen, and plays the part of a metal.
Ammonia, although it is not an oxide, has very powerful basic properties. It is known as the volatile alkali,
and is extensively used in the arts.




THE METALS.
GENERAL PROPERTIES OF THE METALS.
pI. Physical Projperties of the Melals. -The metals
differ widely from one another, both in their physical and
chemical properties. Those metals which are lightest
have the greatest affinity for oxygen, whilst the heavier
metals are oxidized with difficulty.
The following Table gives the specific gravities of the
most important metals: -
Iridium            21.8  Iron                 7.8
Platinum           21.5   Tin                 7.3
Gold               I9.3   Zinc                7.I
Mercury            13.596 Antimony *          6.7
Lead               I  1.3   Chromium          5.9
Silver             Io.5   Aluminium           2.56
Bismuth *           9.8   Strontium           2.54
Copper              8.9   Magnesium           1.75
Nickel              8.8   Calcium             1.58
Cadmium             8.6   Sodium              0.972
Cobalt              8.5   Potassium           o.865
Manganese           8.0   Lithium             0.593
The melting-points of the metals differ even more
widely than their densities, as will appear from the following Table, which is mainly compiled from Miller: —
* See in Appendix the chapter on Chemical Philosohpy, ~~ x9
and 20.
4




50                THE METALS.
Mercury            - 390 Antimony          + 7370
Cadmium           +242  Silver              I873
Tin                 442 Copper              I996
Bismuth             507 Gold                2016
Lead                6I7 Steel        2350 to 2500
Zinc                733 Wrought Iron 2700 to 2850
Some metals can be easily converted into vapor, or
volatilized; thus mercury boils at 662~, while potassium,
sodium, magnesium, zinc, and cadmium can be distilled
at a red heat. Even the more infusible metals, such as
copper and gold, are not absolutely fixed, but give off
small quantities of vapor when strongly heated.
72. _/ketalic Ores. - Only a few of the metals occur
in a free state in nature; in general they are found combined with oxygen, sulphur, or some other non-metal.
These metallic compounds are most variously distributed
throughout the earth's crust; some are known to occur in
only one or two localities, and even then only in minute
quantity, while others are found widely distributed in
enormous masses. Aluminium, iron, calcium, magnesium, and sodium form, when united with oxygen and
silicon, the whole mass of granitic rocks composing our
globe; but it is not from these sources that they can be
obtained for the purposes of the arts. For this object we
employ other combinations, found in smaller quantity,
termed metalZic ores, from which the metals can be more
easily extracted.
The heavy metals and their ores are interspersed
throughout the older rocks, in the form of veins or lodes,
which are cracks or fissures of the rock filled up with
the ore. Other ores, such as ironstone, are found in the
more recent rocky formations, having been deposited in
large masses, probably from aqueous solution.




TBE METALS;                  5r
THE MOST USEFUL METALS.
The most useful metals are iron, lead, cotter, tin, and
zinc.
73. IR ON. - Iron is, of all metals, the most important
to mankind. Its uses were long unknown to the human
race, the age of iron implements being preceded by the
ages of bronze and stone. Pure metallic iron exists only
in very small quantity on the earth's surface, almost entirely occurring in meteoric stones.
The process of obtaining iron from its ores requires an
amount of knowledge and skill which the early races of
men did not possess. The iron of commerce exists in
three different forms, exhibiting very different properties,
and having different chemical constitutions: (I) zwrought
iron; (2) cast-iron; (3) steel.
The first is nearly pure iron; the second is a compound
of iron with varying quantities of carbon and silicon; and
the third a compound of iron with less carbon than is
needed to form cast-iron.
Pure iron in the form of powder may be obtained by
heating the oxide moderately in a current of hydrogen.
The hydrogen combines with the oxygen to form water,
leaving the iron free. It must, however, be kept in an
atmosphere of hydrogen, as finely divided iron takes fire
spontaneously in the air. Iron has a bright white color,
and is remarkably tough, though soft. The pure metal
crystallizes in cubes. Iron which has been hammered
has, when broken, a granular structure; but it becomes
fibrous when the iron is rolled into bars, and the more or
less perfect form of the fibre determines to a great extent
the toughness and the value of the metal. This fibrous
texture of hammered bar-iron undergoes a change when




52                  THE METALS.
exposed to long continued vibration, the iron returning to
its original crystalline condition. Many accidents have
occurred in the breaking of railway axles, owing to
this change from the fibrous to the granular texture.
Wrought iron melts at a very high temperature; but, as
it becomes soft at a much lower point, it can be easily
worked. When hot, it possesses the peculiar property of
welding; that is, the power of uniting firmly when two
clean surfaces of hot metal are hammered together.
Iron and certain of its compounds are strongly magnetic. The metal loses this power when red-hot, but
regains it upon cooling. A solid mass of iron does not
oxidize or tarnish in dry air, at the ordinary temperature;
but if heated, it oxidizes in black scales. When more
strongly heated in the air, or plunged into oxygen gas, it
burns with the formation of the same black oxide (I I).
In pure water, iron does not lose its brilliancy; but, if a
trace of carbonic acid is present, and access of air is permitted, the iron soon rusts.
74. Ifianufacture of Iron. -The oldest method of
manufacturing wrought iron was to heat the ore in a blastfurnace with charcoal or coal, and to hammer out the
spongy mass of iron thus obtained. This plan can only
be economically followed on a small scale and with the
purest ores, and has been superseded by a more complicated method, applicable to all kinds of iron-ore. The
most important ore is an impure carbonate called clay
ironstone. This is first roasted (that is, heated in contact with air) to drive off the carbonic acid, and reduce
the iron to an oxide. It is next smelted in a blast-furnace.   These furnaces (Figure I5) are usually about
fifty feet high, and about fifteen feet in diameter in the
widest part of the cavity CD. The lowest part, F, is
called the crucible, or hearth. IIare the tuyeres, or
pipes through which air is forced by powerful bellows.




THE METALS.                    53
K, K, and M are arched galleries for the convenience
of workmen employed about the  furnace.  When
working regularly, the
furnace is charged from
a door at the end of the
gallery near the top, first  I'
with coal, and then with -
a mixture of roasted ore
and  limestone  broken
into small pieces.  As
the fuel burns away and
the materials gradually
sink, fresh supplies of     i..       __
fuel and of ore are add-    li        i
ed; so that the furnace 
is kept filled with alternate layers of each.
The oxygen of the air                    f
from  the bellows com-                    Li
bines with the carbon of
the fuel, forming carbonic oxide, CO, which
rises through the porous mass, and, taking the oxygen
from the ore, becomes converted into carbonic acid, CO0.
The iron, mixed with the earthy matter of the ore, settles
down into the hottest part of the furnace, where both are
melted. The iron, being the heavier, sinks to the bottom, where it is drawn off at intervals through a Itah-h~ole
in the floor H. The lighter earthy matter, or slag, floats
on the surface of the iron, like oil on water, and flows off
through an opening above the tymp-stone L.  The limestone aids in liquefying the earthy matter, and unites with
it to form the slag.
At this stage the iron is cast-iron.
The properties and appearance of cast-iron vary much




54                  THE METALS.
with the amount of carbon and silicon which it contains-;
for. cast-iron is not a definite chemical compound:of these
elements with iron. The carbon is found in cast-iron,
(I) as scales of graphite, giving rise to mottled cast-iron;
and (2) in combination, forming white cast-iron.
In order to make wrougzht iron from cast-iron, the latter
must undergo the processes of rez'ning and puddling.
These consist essentially in burning out the carbon and
silicon, by exposing the heated metal to a current of air
in a reverberatory furnace. Such a furnace is repreFig. x6.
sented in Figure i6. The ore is put into the hoppers
Hi,'from which it falls into the chamber C, where it is
spread out on the bed cc. The fuel is burned on a
hearth at A, separated from  the ore by the bridge b.
The heated gases rising from the burning fiuel are reverberated, or reflected, by the arched roof of the furnace,
and driven down upon the ore, and then pass off through
the fluef.  When the ore is sufficiently roasted, it is
allowed to fall through openings, dd, into the chamber E. The ore is stirred from time to time, to expose
fiesh surfaces to the action of the air and the flame. The
melted cast-iron becomes first covered with a coat of
oxide, and gradually thickens, so as to allow of its being
rolled into large lumps or balls. During this process, the




THE METALS.                   55
whole of the carbon escapes as carbonic oxide, and the
silicon becomes oxidized to silica, which unites with the
oxide of iron, and forms a fusible slag. Any phosphorus
or sulphur contained in the iron is also oxidized in this
process. The ball is then hammered, to give the metal
coherence, and to squeeze out the liquid slag, and the
mass is afterwards rolled into bars or plates.
75. Steel.-Steel is formed when bars of wrought
iron are heated to redness for some time in contact with
charcoal. The bar is then found to have become finegrained instead of fibrous; the substance is more malleable and more easily fusible than the original bar-iron,
and is found to contain carbon varying in amount from
one to two per cent. Steel has several important properties, especially the power of becoming very hard and
elastic when quickly cooled, which fits it for the manufacture of edge-tools.  These are, however, generally
made of bar-steel, which has been previously fused and
cast into ingots.
A new and very rapid mode of preparing cast-steel is
that known as the Bessemer process. This process consists in burning out all the carbon and silicon in cast-iron,
by passing a blast of atmospheric air through the molten
metal, and then adding such a quantity of pure cast-iron
to the wrought iron thus prepared as is necessary to give
carbon enough to convert the whole mass into steel.
The melted steel is then at once cast into ingots. In this
way six tons of cast-iron can, at one operation, be converted -into steel in twenty minutes. The Bessemer steel
is now largely manufactured for railway axles and rails,
for boiler-plates, and other purposes, for which it is much
better fitted than wrought iron, so that this process bids
fair to revolutionize the old iron industry. It has already
been put into practice on a large scale in England, France,
Belgium, Sweden, and India.




56                  THE METALS.
76. LEAD. — Lead does not occur free in nature. It
is obtained from galena, or plumbic sulphide, PbS. The
galena is roasted in a reverberatory furnace, with the
addition of a small quantity of lime to form a fusible slag
with any silicious mineral matter present in the ore. By
the action of the air, a portion of the sulphide is oxidized
to sulphate, while in another portion the sulphur burns
off, and plumbic oxide is left behind. After a time, the
air is excluded, and the heat of the furnace raised, and
the remaining sulphur burns at the expense of the oxygen
in the oxide already formed, leaving the lead fi-ee.
Lead is a bluish-white metal, and so soft that it may
be scratched with the nail. It is quite ductile and malleable, but has little tenacity or elasticity. It melts at 617~,
and at a higher temperature volatilizes, though not in
quantity sufficient to be distilled.
The surface of the metal remains bright in dry air, but
it soon becomes tarnished in moist air, owing to the
formation of a film of oxide; and this oxidation proceeds
rapidly in presence of a small quantity of weak acid, such
as carbonic or acetic. In pure water freed from air, lead
also preserves its lustre; but, if air be present, plumbic
oxide is formed, and as this dissolves slowly in the water,
a fresh portion of metal is exposed for oxidation.  This
solvent action of water upon lead is a matter of much
importance, owing to the common use of lead waterpipes, and the peculiarly poisonous action of lead compounds upon the system when taken even in minute
quantities for a length of time. The small quantity of certain salts contained in all spring and river waters exerts
an important influence on the action of lead. Thus
waters containing nitrates or chlorides are liable to contamination with lead, while those hard waters containing sulphates or carbonates may generally be brought
into contact with lead without danger, as a thin deposit




THE METALS.                  57
of sulphate or carbonate is formed, which preserves the
metal from further action. If the water contains -much
free carbonic acid, it should not be allowed to come into
contact with lead, as the carbonate dissolves in water
containing this substance.  The presence of lead in
water may easily be demonstrated by acidulating the
water, passing a current of hydric sulphide (sulphuretted
hydrogen) through a deep column of the liquid, and
noticing whether it becomes tinged of a brown color,
from the formation of plumbic sulphide.
Lead pipes lined with tin have been recommended for
water-pipes; but if the lining is not absolutely perfect,
they are more dangerous than ordinary lead pipes. If
from defective. soldering, or cracks, or breaks in the lining, or from corrosive action, the water comes in contact
with the lead, a galvanic action begins, and the lead is
more rapidly oxidized than it would be if not joined with
the tin.
There is the same danger in the use of the metallic
double-lined ice-pitchers. The lining is often made of
dissimilar metals, and the parts are joined by a solder
containing lead. The thin film of silver is soon worn
off upon the interior; galvanic action then promotes
corrosive action, and the water becomes poisonous.
On the whole, the best way of protecting lead-pipes
from oxidation, is by coating them with sulphide of lead,
which is insoluble in water. This can be done by dissolving -one pound of potassic sulphide (sulphide of
potassium)- in two gallons of water, and letting the
solution remain in the pipe twelve hours, or until the
whole inside is thoroughly blackened. This preventive
process is not perfect, but it is very nearly so.
77. COPPER.- -  Copper is -an important metal,
largely used in the arts. It has been known from very




58                  THE METALS.
early times, as it occurs native in the metallic state, and
is moreover easily reduced from its ores. Metallic copper is found in enormous quantity near Lake Superior, in
North America, and other localities. The following ores
are the most important: (I) a compound of copper, sulphur, and iron, known as copter fpyrites, Cu2S + Fe2S3;
(2) the cuprous suip6hide, Cu2S; (3) the carbonate or
malachite; and (4) the red or cuprous oxide, Cu20.
Copper is obtained on a large scale from the carbonate
or oxide, by reducing these ores, together with carbon
and some silica, in a blast-furnace.
Metallic copper has a peculiar deep red color, which
is best seen when a ray of light is several times reflected
from a bright surface of the metal; it is very malleable,
ductile, and tenacious; it melts at a red heat, and is
slightly volatile at a white heat, giving a green tint to a
flame of hydrogen gas which is passed over it; and it is
one of the best conductors of heat and electricity. Copper does not oxidize, either in pure dry or moist air, at
ordinary temperatures, but if heated to redness in the air,
it is soon converted into cupric oxide.
78. Alloys of Copper. -Copper combines with several
of the metals to form what are called alloys.
Brass is an alloy containing about two-thirds of copper
and one-third of zinc. It is harder than copper, and can
be more easily worked. The addition of from one to
two per cent of lead improves the quality of brass for
most purposes. The yellow mezal, used for the sheathing of ships, contains sixty per cent of copper. Bronze,
gun-metal, bell-metal, and speculum-me/al are alloys
of copper and tin in varying quantities. They are all
remarkable for the property of being hard and brittle
when slowly cooled, but of becoming soft and malleable
if, when red-hot, they are cooled suddenly by dipping
into cold water.




THE METALS.                  59
79. TIN;.- The ores of tin - although this metal has
been known from very early times — occur in but few
localities, and the metallic tin is not found in nature.
The chief European sources of tin are the Cornish mines,
where it is found as tin-stone, SnO2. It was probably
from these mines that the Phcenicians and Romans obtained all the tin which they employed in the manufacture of bronze. Tin-stone is also met with in Malacca
and Borneo and Mexico. In order to prepare the metal,
the tin-stone is crushed and washed to remove mechanically the lighter portions of rock with which it is mixed,
and the purified ore is then placed in a reverberatory
furnace, with anthracite or charcoal, and a small quantity
of lime. The oxide is thus reduced, and the liquid
metal, together with the slag, consisting of calcic silicate,
falls to the lower part of the furnace. The blocks of tin,
still impure, are then refined by gradually melting out
the pure tin, leaving an impure alloy behind.
Tin has a white color resembling that of silver; it is
soft, malleable, and ductile, but has little tenacity. When
bent, pure tin emits a peculiar crackling sound. It melts
at 442~, and is not sensibly volatile. Tin does not lose
its lustre on exposure to the air, whether dry or moist, at
ordinary temperatures; but if strongly heated, it takes
fire, and a white powder of stannic oxide is formed.
Owing to its brilliancy, and its power of resisting
ordinary atmospheric changes, tin is largely used for
coating iron, copper, and other metals, which are more
abundant and more easily oxidized.  Tin plate, or sheet
tin, as it is called, is iron thus coated with tin. The thin
sheets of iron are thoroughly cleaned with sulphuric acid,
and then immersed in melted tin for an hour or so.
Copper is tinned by brushing the melted tin over its surface, which must first be made perfectly clean.
Tin is sometimes used for water-pipes; and there is a




60o                 THE METALS.
popular impression that it is never acted upon by water.
In certain localities, however, it oxidizes rapidly, and is
soon rendered worthless. The safety of tin pipes, as
compared with lead, does not consist-in their exemption
from corrosive action, but in the harmlessness of the resultant oxides and carbonates.
80. Alloys of Tin. - Several alloys of tin, besides those
already mentioned (78), are employed in the arts. Britannia metal is an alloy of equal parts of brass, tin,
antimony, and bismuth.  The best pewter is an alloy of
four parts of tin to one of-lead. Common solder contains equal parts of tin and lead, and is more fusible
than lead.
8i. ZINVC.- Zinc is an abundant and useful metal,
closely resembling magnesium  in its chemical character,
but it is much more easily extracted from its ores. The
chief ores of zinc are the sulpzhide or blende, the carbonate or calamine, and the red oxide.  In order to
extract the metal, the powdered ore is roasted, to convert
the sulphide or carbonate into oxide; the roasted ore is
then mixed with fine coal or charcoal, and strongly
heated in crucibles or retorts of peculiar shape; the
zincic oxide is reduced by the carbon, carbonic oxide
gas comes off, and the metallic zinc distils over, and is
easily condensed.
Zinc is a bluish-white metal, with a crystalline structure. It is brittle at the ordinary temperature, but when
heated to between 200~ and 300~, it may be rolled out or
hammered with ease. If more strongly heated, it is
again brittle, and may be broken up in a mortar. Zinc
melts at 7730, and at a bright red heat it begins to boil,
and volatilizes; or if air be present, it takes fire, and
burns with a greenish flame, forming zincic oxide. Zinc
is not acted upon by moist or dry air, -and hence it is




THE METALS.                  6I
largely used in the form of sheets, and is employed as a
protecting covering for iron. The sheets of iron are
plunged into melted zinc, covered with sal-ammoniac,
which keeps the surface of the zinc free from oxide, and
allows the two metals to unite. Iron thus coated with
zinc is said to be galvanized.  German silver is an
alloy of zinc, copper, and nickel.
82. IROON  SAL TS. -The oxides of iron are four in
number: (i) ferrous oxide, FeO, from which the green
or ferrous salts are derived; (2) ferric oxide, Fe2O3,
yielding the yellow ferric salts; (3) the magnetic, or
black oxide,'FeO4, which does not form any definite
salts; (4) ferric acid, H2FeO4, a weak acid, forming
colored salts with potassium. The ferrous oxide colors
glass green, and gives the peculiar tint to common bottleglass. The most important of the ferrous salts are,(I) Ferrous Sulphzate, FeSO4.  This soluble salt,
sometimes called green vitriol, is obtained by dissolving
(I) metallic iron, or (2) ferrous' sulphide,:in sulphuric.
acid, or by the slow oxidation of iron pyrites, FeS2.
(I) Fe + H2So4 - FeSO4 + H2.
(2) FeS + H2SO4 = FeSO4 + H2S.
The solution thus obtained yields, on evaporation, large
green crystals of the salt.  It is largely used in the
manufacture of several black dyes, and is one of the
constituents of writing ink.  Like ferrous oxide, this
salt easily takes up oxygen, producing a new salt called
ferric suljphate.
(2) Ferrous acetate, formed by the action of acetic
acid on iron, is largely used in dyeing and calico-printing.
Of the ferric salts, the chloride, Fe2Cl6, is the most




62                 THE METALS.
important; it forms in brilliant red crystals when chlorine gas is passed over heated metallic iron.
83. LEAD  SAL TS. — Three compounds of lead
and O are known: (i) Litharge, or iplumbous oxide,
PbO, a straw-colored powder obtained by heating lead
in a current of air. It is used in painting and in glassmaking, and with acids forms the important lead salts.
(2) Plumbic oxide, PbO2. (3) Red oxide, or red lead,
a compound of the two last oxides, having the composition, 2 PbO, PbO2. It is obtained by exposing litharge
to the air at a moderate red heat, oxygen being absorbed.
Red lead is used as a paint and in glass-making.
Of the soluble salts of lead, the nitrate, Pb2NO,, is the
most important. This compound is obtained by dissolving the oxide, the carbonate, or metallic lead in warm
nitric acid. Plumbic acetate, or sugar of lead, is also a
soluble salt. Almost all the other lead salts are insoluble
in water. Plumbic carbonate, or while lead, PbCO., is
a substance much used in the arts as a paint. The salt
may be obtained in the pure state by precipitating a cold
solution of the nitrate with an alkaline carbonate, when
it falls down as a white powder. For preparing the salt
in quantity, two plans are employed: the one similar in
principle to that described for the pure salt; and the
other an old and interesting process, known as the Dutch
method. In this process thin sheets of lead are rolled
into a coil, and each coil placed in an earthen pot containing a small quantity of crude vinegar, which, however, does not come in contact with the lead. Several
hundred of these jars and coils are packed on a floor in a
bed of stable manure or spent tan-bark, and then covered with boards, while a second layer of pots similarly
charged is placed above, and this is continued until the
building is filled. After remaining thus for several weeks,




THE METALS.                   63
the coils are taken out, when the greater part of the lead
is found to be converted into white carbonate. It appears
that a lead acetate is first formed, and that the acetic acid
is gradually driven out from its combination by the carbonic acid evolved from the putrefying organic matter,
and thus enabled to unite with another portion of the lead
lying underneath that which was first attacked.
Plumbic sulz'pide, orgalena, PbS, is found native, and
is the chief ore of the metal. It is prepared as a black
precipitate by passing sulphuretted hydrogen gas through
a solution of a lead salt. Galena has a bright bluish-white
metallic lustre. Plumbic sulphate PbSO4, is a white insoluble salt, which is found native, and is prepared artificially by adding sulphuric acid to a soluble lead salt.
Plumbic chloride, PbC12, is prepared by adding muriatic
acid to a strong solution of plumbic nitrate, when a crystalline precipitate of plumbic chloride is formed. It dissolves in about thirty parts of boiling water, separating
out in shining needles on cooling. Plumbic iodide, PbI2,
is precipitated in the form of splendid yellow spangles,
when hot solutions of potassic iodide and plumbic nitrate are mixed and allowed to cool. Plumbic chromate,
PbCrO4, is a yellow insoluble salt, generally known as
chrome yellow, and much used as a paint.
84. COPPER SAL TS. —Copper forms two oxides,
cuprous oxide, Cu2O, and cupric oxide, CuO. Cuprous
oxide imparts to glass a ruby color. Cupric oxide is soluble in acids, and forms a series of salts. The most important of the soluble salts are cupric sultzfhale, CuSO4,
and cujpric acetate, or verdigris. The former is often
called blue vitriol, and is largely manufactured by dissolving copper or its oxide in sulphuric acid. It is used
in calico-printing, and in making Scheele's green, or cupric arseniate, and other paints.




64                  THE METALS.
As many of the vegetable acids act upon copper so as
to form poisonous salts, copper or brass vessels should
never be used for cooking unless they are lined with tin.
85. SALTS OF ZINC.- Zinc forms but one oxide, ZnO, which is much used as a white paint. Its
most important salt is zincic suithate, or white vitriol,
which is used in calico-printing.
86. SAL TS  OF  TIN. - Tin forms two oxides, the
stannous, SnO, and the stannic, SnO2.  Stannous chloride, SnCl2, formed by dissolving tin in muriatic acid, is
termed tin salts in commerce; it is largely manufactured
for the calico-printer and dyer, who use it as a mordant;
that is, to fix the color in the fibre of the cloth, so that it
will not wash out. Polassic stannate (stannate of potash), K2SnO3, formed by boiling stannic oxide with soda,
is used in the same way. Stannic chloride, SnC14, is
also used by dyers, and is prepared for this purpose by
dissolving tin in cold nitro-muriatic acid. Of the sulphides of tin, SnS, stannous sultZhide, and SnS2, stannic
sulphide, are the most important; the former is blackishgray, and the latter a bright yellow crystalline powder,
known as mosaic gold.
NOBLE METALS.
The noble metals are mercury, silver, gold, and tibatinum. They are so called because they do not rust, that
is, combine with the oxygen of the air at ordinary temperatures.
87. M//ER CUR'. - The chief ore of mercury is the
sulphide, or cinnabar, which occurs at Almaden in Spain,
at Idria in Illyria, in California, and also in China and




THE METALS.                   65
Japan. The metal is easily obtained by roasting the ore,
when the sulphur burns off, and the metal volatilizes, and
its vapor is condensed in earthen pipes. Mercury is the
only metal liquid at the ordinary temperature; it freezes
at — 39~; in the solid state it is malleable and possesses
a density of I4.4. It boils at 662~, and gives off a slight
amount of vapor at the ordinary temperature. Mercury,
when pure, does not tarnish in moist or dry air; but when
heated above 700oo, it rapidly absorbs oxygen; and it
combines directly with chlorine, bromine, iodine, and
sulphur. Mercury is largely used in extracting gold and
silver from their ores, and for many other purposes.
Mercury dissolves many of the metals, forming amalgams. The most important of these is the amalgam of
tin and mercury, used for silvering mirrors. " In order
to apply it to the glass, a sheet of tinfoil is spread evenly
upon a smooth slab of stone, which forms the top of a
table carefully levelled, and surrounded by a groove, for
the reception of the superfluous mercury. Clean mercury
is poured upon the tinfoil, and spread uniformly over it
with a roll of flannel; more mercury is then poured on
till it forms a fluid layer of the thickness of about half a
crown; the surface is cleared of impurities by passing a
linen cloth lightly over it; the plate of glass is carefully
dried, and its edge being made to dip below the surface
of the mercury, is pushed forward cautiously; all bubbles
of air are thus excluded as it glides over and adheres to
the surface of the amalgam. The plate is then covered
with flannel, weights are placed upon the glass, and the
stone is gently inclined so as to allow the excess of mercury to drain off; at the end of twenty-four hours it is
placed upon a wooden table, the inclination of which is
increased from day to day until the mirror assumes a vertical position: in about a month it is sufficiently drained
to allow the mirror to be framed." - MILLER.
5




66                  THE METALS.
88. SIL VER. - Silver was known to the ancients.
It is found in the native state, as well as combined with
sulphur, antimony, chlorine, and bromine. It is also
contained in small quantities in galena, and it can be
extracted with profit from the lead prepared from this
ore, even when the lead contains only two or three
ounces of silver to the ton. The method thus adopted for
the extraction of the silver depends upon the fact that
the whole of the silver can be concentrated into a small
portion of lead by crystallization; metallic lead free from
silver separates out in crystals, and a rich alloy is left.
When this reaches the concentration of 300 oz. of silver
to the ton, the alloy undergoes the operation of cupellation, in which the mixture is melted in a furnace on a
porous bed of bone-earth, and a blast of air blown over
the surface. The lead oxidizes, and the oxide (litharge)
fuses, and partly runs away and partly sinks into the
porous bed of the furnace, while the silver remains behind
in the metallic state.
For the extraction of silver from the other ores, a
process termed amalgamadtion is employed, in which
mercury is used to dissolve the metallic silver. The
argentiferous ores of Germany, in which the silver occurs
in combination with sulphur, are roasted in a furnace
with common salt, by which means the sulphide is converted into chloride; the mixture is then placed in casks
made to revolve, and scrap-iron and water are added.
The iron reduces the silver to the metallic state, and
when this is fully accomplished, metallic mercury is
added; this forms a liquid amalgam with the silver (and
gold, if any be present), and, by distilling the mercury
off, the silver is obtained in an impure state. Silver has
a bright white color and a brilliant lustre, which it does
not lose in pure air at any temperature. When melted
in the air, it possesses the singular power of absorbing




THE METALS.                    67
mechanically a large volume (twenty-two times its bulk)
of oxygen; this gas it again gives out on solidifying.
Silver is probably the best conductor of heat and electricity known, and is extremely ductile. Sulphur combines at once with silver, forming a black sulphide; silver
articles long exposed to the air tarnish from this cause.
It is because they contain a small quantity of sulphur that
eggs, mustard, and horseradish blacken silver spoons.
Where coal-gas is used, silver articles not unfrequently
tarnish, owing to the fact that the sulphuretted hydrogen
has not been thoroughly removed in the purification of
the gas.
89. GOLD. —Gold is usually found in the metallic
state. It occurs in veins in the older rocks, and in the
sands of most rivers, and, although generally found in
small quantities, it is a widely diffused metal. In order
to obtain the gold, the detritus or sand which contains
the metal is washed in a cradle or other arrangement, by
means of which the lighter particles of mud or mineral
are washed away, while the heavier grains of gold sink to
the bottom of the vessel. MWhen gold has to be worked
in the solid rock, the mineral is crushed to powder and
then shaken up with mercury, and the gold thus extracted
by amalgamation.
Gold has a brilliant yellow color, and, in thin films,
transmits green light; it is nearly as soft as lead; it can
be drawn out into fine wire, and is the most malleable
of all the metals. It does not tarnish at any temperature, in dry or moist air; nor is it, like silver, affected by
sulphur. It is not acted upon by any single acid (except
selenic), but dissolves in presence of free chlorine and
in nitro-muriatic acid. At high temperatures, gold is
slightly volatile. The gold used for coin is an alloy of
gold and copper, in the proportion of I i parts of gold to




68                 THE METALS.
I of copper. This alloy is harder and more fusible, but
less ductile, than pure gold. The purity of gold is commonly expressed in carats. Pure gold is said to be 24
carats ine; an alloy containing 23 of pure gold is called
23 carats fne; I  of pure gold (the finest usually employed for jewelry), I8 caratsfine; and so on.
go. PLA TINYUM  - Platinum  is a comparatively
rare metal, which always occurs in the native state, and
generally alloyed with five other metals; namely, paZladium, rhodium, iridium, osmium, and ruthenium.
This alloy occurs in small grains in detritus and gravel
in Siberia and Brazil.
The original mode of obtaining the metal was to dissolve the ore in aqua-regia (nitro-muriatic acid), and
precipitate the platinum (together with several of the accompanying metals) with sal-ammoniac, as the insoluble
double chloride of ammonium and platinum, 2NH4
Cl,PtCl4. This precipitate, when heated, yields metallic
platinum in a finely divided or spongy state; and this
sponge, if forcibly pressed and hammered when hot,
gradually becomes a coherent metallic mass, the particles
of platinum welding together, when hot, like iron. A
new mode of preparing the metal has recently been proposed, the ore being melted in a very powerful furnace,
heated with the oxy-hydrogen blow-pipe. In this way a
pure alloy of platinum, iridium, and rhodium is formed,
the other constituents and impurities of the ore being
either volatilized by the intense heat, or absorbed by the
lime of which the crucible is composed. This alloy is in
many respects more useful than pure platinum, being
harder and less easily attacked by acids.
Platinum has a bright white color, and does not tarnish
under any circumstances in the air. It is extremely infusible, and can only be melted by the heat of the oxy



THE METALS.                  69
hydrogen blowpipe.  It dissolves in aqua-regia, but is
not acted upon by the ordinary acids, and hence platinum
vessels are much used in the laboratory. Caustic alkalies,
however, act upon the metal at high temperatures. When
finely divided, metallic platinum has the power of condensing gases upon its surface in a remarkable degree.
When a mixture of oxygen and hydrogen is brought in
contact with spongy platinum, the heat developed by the
condensation of the gases is sufficient to ignite them.
9I. SALTS  OPF iMERCURY:-Mercury forms
two oxides, the mercurous, Hg20, and the mercuric,
HgO, and two corresponding classes of salts. The mercuric sulphide, HgS, is known as cinnabar, or vermilion, much used as a paint. Afercurous chloride, Hg2C12,
or calomel, and mercuric chloride, HgCl2, or corrosive
sublimate, are used in medicine. The bromides and
iodides of mercury are used in photography.
92. SALTS  OF  SIL VER. - Silver forms two
oxides, Ag40, argentic suboxide, and Ag20, argentic
oxide. The latter is the base of the ordinary silver salts.
Argentic nitrate, AgNO3, is the most important soluble
salt of silver. It is obtained in the form of large transparent tabular crystals, on evaporating a solution of
silver in nitric acid. It fuses easily on heating; and when
cast into sticks, goes by the name of lunar caustic. This
salt undergoes decomposition when exposed to the sunlight in contact with organic matter, and a black substance, probably the suboxide, is formed; hence it is
employed in the manufacture of indelible ink for marking linen and other fabrics.
Of the insoluble silver salts, the chloride, AgC1, is the
most important. This salt occurs in nature, and is then
known as horn silver.  It is precipitated as a white




70                 THE METALS.
curdy mass, when a solution of a chloride and a silver
salt are brought together. When exposed to the light,
the white chloride becomes tinted of a purple color,
which increases in shade as the action of light continues.
This coloration arises from a partial decomposition of the
salt, a small quantity of subchloride and free muriatic
acid being formed. In presence of organic matter this
change takes place much more rapidly, and upon this
fact the art of photography depends. Argentic chloride
is easily soluble in a solution of sodic hyposulphite, and
it is for this reason that the latter salt is used for fixing
photographic pictures, that is, dissolving out the unaltered
silver salt, and thus rendering the image permanent.
Argentic bromide, AgBr, is also acted upon by the light,
and is soluble in ammonia and an alkaline hyposulphite.
The iodide, AgI, is a yellow powder, insoluble in water
and ammonia, but dissolved by an alkaline hyposulphite.
The cyanide, AgCN, as well as other salts of silver, is
used in electro-plating.
93. SALTS OF GOLD.-Gold forms two oxides,
the aurous, Au2O, and the auric, Au20,. Neither of
these oxides forms salts with acids, but the latter unites
with bases to form salts called aurates. Auric chloride,
AuC13, obtained by dissolving gold in aqua-regia, and
auric cyanide, Au(CN)8, are the most important salts of
gold, being used in electro-gilding and photography.
94. SAL TS OF PLA TINLUM1 - Platinum forms
two oxides, the platinous, PtO, and the platinic, PtO2.
Plalinic chloride, PtC14, is the most important platinum
compound. It is obtained as a yellowish-red solution,
by dissolving the metal in aqua-regia.  It is used in
electro-platinizing.




THE METALS.                  7I
LESS USEFUL METALS.
The less useful metals are sodium, magnesium, aluminiunm, antimony, bismzut/, and nickel. These are little
used in a metallic state, though their compounds are of
the highest importance.
95. SODJUlV. —This metal was discovered by Sir
H. Davy, by the decomposition of soda with the galvanic
current. It can be procured by reducing the carbonate
in presence of carbon, and is now manufactured in considerable quantities for the preparation of other metals,
especially magnesium and aluminium. Sodium is a
silver-white metal, soft at ordinary temperatures, and
melting at 2070; it volatilizes below a red heat, yielding
a colorless vapor. The compounds of sodium are very
widely diffused, being contained in every speck of dust.
They exist in enormous quantities in the older rocks; but
they are most readily obtained from sea-water, which
contains nearly 3 per cent of sodic chloride (common
salt), or from the large deposits of this substance which
occur in the form of rock-salt.
96. M31A GNE SIUM - This metal occurs in large
quantities in combination with lime and carbonic acid, in
dolomite or mountain limestone, and also in sea-water
and certain mineral springs, as chloride and sulphate.
The metal itself has only recently been prepared in
quantity. It is best obtained by heating magnesic chloride with metallic sodium, sodic chloride and metallic
magnesium being formed. This metal is of a silverwhite color, and fuses at a low red heat. It is volatile,
and may be easily distilled at a bright red heat.  When
soft, it can be pressed into wire, and with care it may be




72                 THE METALS.
cast like brass; although, when strongly heated in the
air, it takes fire, and burns with a dazzling white light,
with the formation of its only oxide, magnesia, MgO.
The light emitted by burning magnesium wire is distinguished for its richness in chemically active rays, and is
therefore employed as a substitute for sunlight in photography. It is coming to be used for purposes of illumination.
97. AL UMAINIUM-.This metal occurs in large
quantities, combined with silicon and oxygen, in felspar
and all the older rocks, and also in clay, marl, slate, and
in many crystalline minerals. Metallic aluminium is
obtained by passing the vapor of aluminic chloride over
metallic sodium. It has recently been manufactured on
a large scale, both in England and France, and from its
lightness (specific gravity 2.6), its tenacity, and its bright
lustre, it has been used for optical purposes as well as for
ornamental work. Some of its alloys, as aluminzium
bronze, promise to become of great value in the arts.
98. ANTlIMONi -- Metallic antimony occurs native,
but its chief ore is the trisulzlhide, Sb2,S. The metal is
easily reduced, by heating the sulphide with about half
its weight of metallic iron, when ferrous sulphide and
metallic antimony are formed. Antimony may also be
reduced by mixing the ore with coal, and heating in a
reverberatory furnace. Antimony is a bright bluishwhite metal. It is very brittle, and can readily be powdered in a mortar. It melts at about a red heat, and may
be distilled at a white heat, in an atmosphere of hydrogen.
Antimony undergoes no alteration in the air at ordinary
temperatures, but rapidly oxidizes if exposed to air when
melted; and if heated more strongly, it takes fire, and
burns with a white flame, giving off dense white fumes of




TIHE METALS.                  73
oxide. Antimony is not attacked either by dilute muriatic
or sulphuric acid; but nitric and nitro-muriatic acid dissolve it easily. The alloys of antimony are largely used
in the arts. Of these, type-metal (an alloy of lead and
antimony) is the most important; it contains from 17
to 20 per cent of the latter metal.
99. BISfU7TH. -This metal is found in small quantities in the native state, but occurs more often as a sulphide; it is easily reduced to the metallic state, and then
exhibits a pinkish-white color. It melts at 5070, and is
volatilized at a white heat. Bismuth does not oxidize in
dry air at the ordinary temperature; but if heated strongly,
it burns with a blue flame, forming an oxide; it also takes
fire when thrown into chlorine gas. Bismuth dissolves
easily in nitric acid. The metal is chiefly used as an ingredient of fsible metal. The alloy of 2 parts of bismuth, I of lead, and I of tin, melts at 2orI; that of
8 parts of bismuth, 5 of lead, and 3 of tin, melts at 212~.
The compounds of bismuth are used in the porcelain
manufacture, in medicine, and as cosmetics.
Both bismuth and antimony closely resemble arsenic
in the compounds which they form. Thus we have
Sb2O8, Sb2Os, and H3Sb; Bi20, and Bi2O5 (67). Hence
bismuth and antimony are now generally classed among
the non-metallic elements of the nitrogen grou-p.
Ioo. VICKEL. - Nickel occurs in large quantities
combined with arsenic, as kupfernickel; also together
with cobalt in speiss; and it is now prepared in considerable quantities for the manufacture of German silver, an
alloy of nickel, zinc, and copper. Nickel is a white,
malleable, and tenacious metal; it melts at a somewhat
lower temperature than iron, and is strongly magnetic,
but loses this property when heated to above 600oo.




74                 THE METALS.
IOI. SAL TS OF SODIUM: -There are two compounds of sodium and oxygen, Na20, sodic oxide, and
Na202, sodic peroxide. Sodic oxide has a strong affinity
for water, with which it combines to form HNaO, sodic
hydrate (caustic soda). This is a white solid, very
soluble in water, very caustic and alkaline, and is largely
used in making soap.
Caustic soda is now manufactured on a very large
scale, by boiling lime and sodic carbonate (carbonate of
soda) with water, and evaporating down the clear solution. The reaction is as follows:CaO + Na2CO3 + H20 = CaCO8 + 2HNaO.
I02o. Sodic Chloride. - Sodic chloride, NaCL, is common salt. It is from this compound that nearly all the
other sodic compounds are prepared.
In Southern Europe, on the shores of the Mediterranean, large quantities of salt are obtained from seawater. The water is allowed to flow into large shallow
pools, called salt-pans, where it is evaporated by the
agency of the air and the sun. Only pure water passes
off in the form of vapor, and the solution grows more
and more concentrated.  After a time, the brine is
pumped into large iron pans, and evaporated by artificial heat until the salt crystallizes.
In many parts of the earth there are salt lakes, often
called seas. The streams flowing into them are more or
less impregnated with salt, which they dissolve from the
soil over which they flow. Such lakes are natural saltpans, for the water which is evaporated from them is
pure, and they consequently become more and more
saturated with salt, till it is finally deposited on the
bottom in solid crystals. The most remarkable of these
lakes is the Great Salt Lake in Utah.
Such salt lakes appear to have existed in all geological




THE METALS.                   75
ages, and by long-continued evaporation to have given
rise to large masses of solid salt, called rock salZ. These
beds of rock salt are found in all parts of the earth. The
most remarkable are at Wieliczka in Poland, and at Cardona in Spain. The former is 500 miles long, 20 miles
broad, and 1,200 feet deep. It has been worked for
several centuries. Some of the galleries excavated in it
are 30 miles long. The bed at Cardona is a "' mountain
of salt," 400 or 500 feet high, and the salt is of the
greatest purity.
Salt is obtained from these beds sometimes by excavation and sometimes by solution. In the latter case, a
hole is sometimes bored down to the bed of salt, often to
the depth of I,200 or I,500 feet. A tube somewhat smaller
than the bore is then introduced, and fresh water allowed
to flow down outside the tube. This water, on reaching
the bed, becomes saturated with salt, and rises in the
tube. Since, however, it is heavier than fresh water, it
will not rise to a level with the latter on the outside of
the tube. If the bore is I,200 feet deep, the brine will
rise within about 200 feet of the top. It must be pumped
up the remaining distance. The solution is then evaporated, and solid salt obtained.
It not unfrequently happens that natural springs occur
in such localities that their waters come into contact with
beds of salt. Such springs are called salt springs, or
brine springs. They sometimes come to the surface;
but oftener they can only be reached by boring, and the
brine brought to the surface by means of the pump. The
water of these natural springs is usually less concentrated
than that of the artificial springs described above. In
England and in this country the salt produced is nearly
all obtained from brine springs.
The most important salt springs of this country are in
Central New York, in Virginia, and in Pennsylvania.




76                 THE METALS.
About 6,ooo,ooo bushels of salt are produced annually
in New York. When the brine is not a saturated solution, it is usually concentrated by partially evaporating it
in large shallow pans by the air and the sun. It is then
further concentrated and crystallized by artificial heat.
Io03. Sodic Carbonate. - Sodic carbonate, Na2CO3,
is known in commerce as soda-ash, and is manufactured
on an enormous scale. It is largely used in glass-making, soap-making, bleaching, and many other processes
illn the arts.
Before the French Revolution, the Continental nations
of Europe derived their soda-ash mainly from  Spain,
where it was made from the ashes of certain marine
plants, which contain a large amount of soda. The sodaash thus obtained was called barilla.
In England, the soda-ash used was mainly obtained
firom the ashes of a sea-weed called kelp, which grows
abundantly on the north and west coast of Ireland, and
on the west coast and the islands of Scotland.
One of the first effects of the war of the French Revolution was to cut off the supply of alkali from Spain.
About this time, a French chemist, Le Blanc, discovered
a process by which sodic carbonate, or soda-ash, could
be obtained from common salt, or sodic chloride, NaCl.
This process became publicly known through a commission appointed, during the first year of the Republic, to
investigate the subject of alkali manufacture.
Le Blanc's method is the same as that now used in the
making of sodic carbonate, which has come to be one of
the most important branches of chemical manufacture.
The process may be divided into two stages: --
(i) Manufacture of sodic sulphate, or salt-cake, from
sodic chloride; called the salZt-cake process.
(2) Manufacture of sodic carbonate, or soda-ash, from
salt-cake; called the soda-ash process.




THE METALS.                   77
(I) Salt-cake Process. —This consists in the decomposition of salt, by means of sulphuric acid. This is
effected in a furnace, called the salt-cake furnace, a section of which is represented in Figure 17. It consists
Fig. I7.
of a large covered iron pan, placed in the centre of the
furnace, and heated by a fire placed underneath; and two
roasters, or reverberatory furnaces, placed one at each
side, on the hearths of which the salt is completely decoimposed. The charge of half a ton of salt is first placed
in the iron pan, and the sulphuric acid allowed to run in
upon it. Hydric chloride (muriatic acid) is evolved,
and escapes through a flue with the products of combustion into towers, or scrubbers, filled with coke or bricks
moistened with a stream of water; the acid vapors are
thus condensed, while the smoke and heated air pass up
the chimney. The reaction is as follows:2NaCl + H2SO4 = Na2SO4 + 2HC1.
After the mixture of salt and acid has been heated for
some time in the iron pan, and has become solid, it is
raked out upon the hearths of the roasters, where the
flame and heated air of the fire complete the decomposition into sodic sulphate and hydric chloride.
(2) Soda-ash Process. - This consists (I) in the
preparation of the sodic carbonate, and (2) in the separation and purification of the same. The first chemical
change which the salt-cake undergoes is its reduction to
sodic sulbzhide, by heating it with powdered coal: —
Na2SO4 + C4 = Na2S + 4CO.




78                  THE METALS.
The second decomposition is the conversion of the sodic
sulphide into sodic carbonate, by heating it with chalk or
limestone (calcic carbonate):Na2S + CaCO,- Na2CO3+ CaS.
These two reactions are, in practice, carried on at
once; a mixture of Io parts of salt-cake, I0 parts of
chalk or limestone, and 7.5 parts of coal, being heated in
a reverberatory furnace, called the ballingfurnace, until
it fuses, and the decomposition is complete, when it is
raked out into iron wheelbarrows to cool. This process
is generally called the black-ash process, from the color
of the fused mass.
The next operation consists in the separation of the
sodic carbonate from the insoluble calcic sulphide and
other impurities. This is easily accomplished by lixiviation, or dissolving the former salt out in water. On
evaporating down the solution, for which the waste heat
of the balling furnace is used, and calcining the residue,
the soda-ash of commerce is obtained.
No less than 200,000 tons of common salt are annually
consumed in the alkali works of Great Britain, for the
preparation of nearly the same weight of soda-ash, the
value of which is about $Io,ooo,ooo.
Io4. Bicarbonate of Soda. -The salt known as bicarbonate of soda, HNaCO3, is obtained by exposing the
crystallized sodic carbonate in an atmosphere of carbonic
acid. It is a white crystalline powder, used in medicine
and for making effervescing drinks; also in bread-making, as a substitute for yeast.
Io5. Other Sodic Salts. - Sodic nitrate (soda sal/pe/re), NaNO8, is found in northern Chili in large beds.
It is used in making nitric acid, and as a manure.
Sodic sulphate (sulphate of soda), Na2SO4, is familiarly known as Glauber's salts.




THE METALS.                  79
Sodic hyposulpzhite (hyposulphite of soda) is used in
photography (92).
Sodic borate, or borax, is considerably used in the arts,
especially as a fl7ux in soldering. It dissolves the oxide
formed upon the surfaces to be united, and thus keeps
them clean and bright.
Sodic silicate (silicate of soda) is called soluble glass,
and is used to some extent as a paint or varnish for fixing
fresco colors, and for preserving stone-work, and quite
largely in calico printing and dyeing.
io06. SAL TS OF MA GNVESIUJl. - Magnesium
has but one oxide, MgO, or magnesia. The most important salt of this oxide is the magnesic sulphate or
Episom salts, used in medicine.
Io7. SAL TS OF AL UiTINVIUM  - The only oxide of aluminium is alumina, A1203. It occurs native in
a nearly pure and crystalline state as corundum, ruby,
safpphire, and emery. Alumina is largely used as a mordant in dyeing and calico-printing, as it has the power of
forming insoluble compounds, called lakes, with vegetable coloring-matter, and thus fixes the color in the pores
of the cloth so that it cannot be washed out (85).
The soluble aluminic sulphate, A123SO4, is prepared on
a large scale for the use of the dyer, by decomposing clay
by the action of sulphuric acid. The solid mixture of
silica and aluminic sulphate thus obtained goes by the
name of alum-cake. The most useful compounds of
alumina are, however, the alums, a series of double salts,
which aluminic sulphate forms with the alkaline sulphates.  Common potash alum  has the composition
KA12SO4. It may be prepared by dissolving the two
sulphates together, and allowing the compound salt to
crystallize, but it is usually obtained from the decomposi



So                  THE METALS.
tion of a shale or clay containing iron pyrites, FeS2.
This substance gradually undergoes oxidation when the
shale is roasted (taking oxygen from the air), producing
sulphuric acid, which unites with the alumina of the clay,
and, on the addition of a potassic compound, alum crystallizes out. A salt called ammonium alum, and containing H4N, instead of K, is at present prepared on a
large scale; the ammonia liquor of the gas-works, together with sulphuric acid, being added to the burnt
shale, instead of a potash salt.
There are a great many other alums known, in which
Fe2O3, Cr203, or Mn2O3, oxides of iron, chromium, and
manganese, are substituted for the alumina in common
alum.  Clay is an alunmiinic silicate resulting from the
disintegration and decomposition of felspar by the action
of air and water. Kaolin or porcelain clay is the purest
form of clay, containing no iron or other impurities.
There are many very beautifully crystalline minerals, as
garnet and mica, consisting of aluminic silicates combined with silicates of other metals.
IoS. Glass, Porcelain, and Earthen-ware. - The
silicates of the alkalies are soluble in water and noncrystalline; those of the alkaline earths (Ba, Sr, and Ca),
are soluble in acid and crystalline; while compounds of
the two are insoluble in water and acids, and do not assume a crystalline form. Such a compound, when fused,
is termed a glass. There are four different kinds of glass
used in the arts, differing in their chemical composition,
and exhibiting corresponding differences in their properties: (I) Crown or window and plate glass, composed
of silicates of soda and lime; (2) Bohemian glass, consisting of silicates of potash and lime; (3) flint glass or
crystal, containing silicates of potash and lead; and (4)
common green bottle-glass, composed of silicates of soda,
lime, iron, and alumina. The first and third of these




THE METALS.                     8I
kinds of glass are easily fusible, while the second or potash glass is much less fusible; the addition of plumbic
oxide increases the specific gravity and lustre of the glass
as well as its fusibility. The common glass articles of
household use are generally made of flint glass, while for
chemical apparatus a soda-lime glass is to be preferred.
The potash-lime glass is much employed where an infusible or hard glass is needed.  The fourth kind of glass
is an impure mixture of various silicates, employed for
purposes in which the colors and fineness of the glass are
not of consequence.
In the preparation of all the fine qualities of glass,
great care is requisite in the selection of pure materials,
as well as in the processes of manufacture. Generally
the materials are melted together with a quarter to
a half their weight of cullet, or broken glass of the
same kind.  After the glass articles have been blown
or cast, they must be annealed, that is, made less brittle by being very slowly heated and as slowly cooled in
an oven arranged for the purpose.
Certain metallic oxides have the power of coloring
glass when they are added in small quantity. Thus ferrous oxide produces a deep green color (bottle-glass),
while the oxides of manganese impart a purple tint to
glass. Advantage is taken of this in the preparation of
colorless glass, for as it is difficult to obtain materials
perfectly free from iron, which imparts a green color, a
small quantity of black oxide of manganese is added to
the mixture, and the violet color thus produced neutralizes the green, and a nearly colorless glass is the result.
The addition of arsenious oxide effects the same end by
oxidizing the ferrous to ferric oxide. The colors of precious stones are imitated by adding certain oxides to a
brilliant lead glass called paste; thus the blue of the sapphire is given by a small quantity of cobaltic oxide,
6




82                 THE METALS.
while cuprous oxide imparts a ruby-red color, and ferric
oxide a yellow color resembling topaz.
The various forms of porcelain and earthen-ware
consist of aluminic silicate or clay in a more or less pure
state, covered with some substance which fuses at a
high temperature, and forms a glaze, giving a smooth
surface and binding the material closely together, and
thus filling up the pores of the baked clay. For the
manufacture of porcelain the finest kaolin or China clay
is used, while for common earthen-ware an inferior clay
may be employed. The glaze used for porcelain is generally finely powdered felspar, the biscuit, or porous
ware, being first dipped into a vessel containing this substance suspended in water and then strongly heated.
The articles thus coated can be used for chemical purposes, as this glaze withstands the action of acids. For
earthen-ware the so-called salt glaze is used; obtained
by throwing some common salt into the furnaces containing the strongly heated ware. The salt is volatilized and
undergoes decomposition on the heated surface, depositing a fusible silicate upon it, and rendering the ware
impervious to moisture.
Io9. SALTS OF A NTIMON'Y - Antimony has
two oxides, Sb203, and Sb2Os, and two corresponding
sulphides and chlorides. The most important of its salts
is tartar-emetic, or tartrate of antimony and z5otask,
used in medicine.
IIo. SAL TS OF BISMUTH. - Bismuth forms
two oxides, analogous to those of antimony. The most
important of the salts is the nitrate, Bi3NO., which is
easily procured by dissolving the metal in nitric acid.
III. SALTS  OF  JVICKrEL.     There are two




THE METALS.                  83
oxides of nickel, NiO, and Ni208. The former of these
gives rise to salts which have a peculiar apple-green
color. The latter is a black powder, prepared by adding
a solution of bleaching-powder to a soluble nickel salt.
The most important soluble salt is the nitrate, NizNO3.
METALS NOT USED IN A FREE STATE, BUT
VALUABLE FOR THEIR SALTS.
There are certain metals which are not used in a free
state, but which form salts of considerable importance.
These metals are potassium, calcium, strontium, barium,
manganese, chromium, and cobalt.
I I 2. PO TASSIU/M.  This metal was discovered
in the year 80o7, by Sir Humphrey Davy, who decomposed potash by means of a powerful galvanic current.
Before this time the alkalies and alkaline earths were
supposed to be elementary bodies. The metal is now
prepared by heating together potash and carbon to a high
temperature in an iron retort.
Potassium is a bright, silver-white metal, which can be
easily cut with a knife at the ordinary temperature; it is
brittle at 320, and melts at I44~.  It rapidly absorbs
oxygen when exposed to the air, and becomes converted
into a white oxide.
The original source of potassic- compounds is in the
felspar of the granitic rocks, as these contain from.02 to.o03 of this metal. Up to the present time, no cheap and
easy mode has been found of separating the potash from
the silicic acid with which it is combined in felspar.
Plants, however, are able slowly to separate out and
assimilate the potash from these rocks and soils; so that,
by burning the plant and leaching the ashes with water,
soluble potash-salt is obtained.




84                 THE METALS.
This is the crude potassic carbonate, called, when
purified by crystallization, pearlash. It is the substance
from which most of the potassic compounds are obtained.
The most important compounds of potassium are
caustic potash, HKO, potassic carbonate (carbonate of
potash), K2CO3, and potassic nitrate, or saltsetre,
KNOW. This last compound readily parts with its oxygen, and is therefore extensively used in making gunpowder and fireworks.
Gunpowder consists of an intimate mixture of saltpetre, charcoal, and sulphur. When the gunpowder is
ignited, the sulphur and charcoal burn at the expense of
the oxygen in the saltpetre, while the nitrogen is set free.
It is to the expansive force of the large volume of gases
suddenly set free in a confined space, that the destructive
power of gunpowder is due.
Potassic chlorate, KC108, gives up its oxygen even
more readily than the nitrate, and is used, as we have
seen, in the preparation of oxygen (io). It is also used
in making fireworks and percussion caps.
II3. CAL CIUAl  - Calcium  forms a considerable
portion of the rocks of which the earth is composed, and
occurs in very large quantities, forming whole mountain
chains of chalk, gypsum, and limestone. The metal is
obtained by the decomposition of the chloride by the electric current, or by heating the iodide with sodium. It is
a light, yellow metal, which easily oxidizes in the air.
When heated in air, it burns with a bright light, forming
lime, CaO, the only oxide of calcium.
Lime is prepared on a large scale for building and
other purposes, by heating limestone (the carbonate) in
kilns by means of coal mixed with the stone; the carbonic acid escapes, and quicklime or caustic lime remains. Pure lime is a white, infusible substance, which




THE METALS.                   85
combines with water very readily, giving off great heat,
and falling to a white powder called calcic hydrate, or
slaked lime. The hydrate is slightly soluble in water,
I part of it dissolving in 730 parts of cold, but only in
I,300 parts of boiling water, and forming lime-water,
which, like the hydrate, has a great power of absorbing
carbonic acid from the air. It is indeed partly owing to
this property that the hardening or setting of mortars
and cements made from lime is due. Mlbortar consists of
a mixture of slaked lime and sand. A gradual combination of the lime with the silica occurs, and this helps
to harden the mixture.  Hydraulic cement, which
hardens under water, is prepared by carefully heating an
impure lime containing clay and silica; a compound
silicate of lime and alumina appears to be formed on
moistening the powder, which then solidifies, and is not
acted upon by water. Lime is largely used in agriculture, its action being, (I) to destroy the excess of
vegetable matter contained in the soil; and (2) to liberate the potash for the use of the plants from heavy
clay soils by decomposing the silicate.
Calcic carbonate (carbonate of lime) CaCO, occurs
most widely diffused, as chalk, limestone, coral, and
marble; many of those enormous deposits being made
up of the microscopic remains of minute sea-animals.
The carbonate is almost insoluble in pure water; but
readily dissolves when the water contains carbonic acid,
and is deposited again, in crystals, as the gas escapes.
In this way enormous masses of crystalline limestone are
formed. Water charged with carbonic acid and calcic
carbonate makes its way through the roof of limestone
caverns, and, as the carbonic acid gradually escapes, the
calcic carbonate is deposited in dependent masses, like
icicles, termed stalactites; while the water, falling on
the floor of the cavern before it has parted with all its




86                  THE METALS.
carbonic acid and dissolved limestone, deposits a fresh
portion of the crystalline matter, and thus a new growth,
or stalagmite, gradually rises to meet the stalactite
which hangs from the roof. In this way a natural pillar
of limestone is formed.
Calcic sulphcate, CaS04, occurs in nature, combined
with 2H20, as gypsum  or alabaster. It is soluble in
400 parts of water, and is a very common impurity in
spring water, giving rise to a hardness which cannot be
removed by boiling. Gypsum, when moderately heated,
loses its water, and is then called pclaster of Paris; this,
when moistened, takes up two atoms of water again and
sets to a solid mass, and is therefore much used for
making casts and moulds.
Calcic chloride (chloride of calcium), CaC12, is
formed when limestone or marble is dissolved in muriatic acid; if the solution be then evaporated, colorless
needle-shaped crystals are obtained. When these are
dried, they form a porous mass which takes up moisture
with great avidity, and is much used for drying gases.
I 14. STR ONITIU. - This element occurs in much
smaller quantities than calcium, being found in only a
few minerals. It likewise occurs in minute quantities in
certain spring waters. The metal has a yellowish-white
color, and is prepared by the action of a current of electricity on the fused chloride.  It resembles calcium
closely in its properties. When heated in the air, it
burns, forming the oxide strontia.
The native salts of strontium, the carbonate and sulpjhate, are insoluble, and serve for the preparation of the
remaining salts. The nitrate, Sr2NO3, and the chloride,
SrC12, are soluble in water. These are the only salts of
this metal which are employed in the arts. They are
used for the preparation of red Jires, as the volatile




THE METALS.                  87
salts of strontium have the power of coloring the flame
crimson.
I I 5. BARIUM. - Barium compounds occur somewhat more widely dispersed than those of strontium, the
two most common barium minerals being the sulphate,
or heavy spar, and the carbonate, or witherite. The
metal barium has not yet been obtained in the coherent
state; but the metallic powder may be prepared in the
same way as calcium and strontium, which it closely resembles in its properties.
The most important barium compounds are the chloride and the nitrate, used as tests for sulphuric acid, and
for giving a green color to the flame in fireworks.
I6. C/HROMAIU2iL. - Chromium  is a substance
whose compounds do not occur very widely distributed,
or in large quantities. They are, nevertheless, much
used in the arts as pigments, many of them having a fine
bright color. The chief ore of this metal is a compound
of the oxides of chromium and iron, called chrome ironstone, found in America, Sweden, and the Shetlands.
A compound of chromium, lead, and oxygen, called
plumnbic chromate (chromate of lead), is also found.
Pure chromium appears to be the most infusible of all
the metals, as it cannot be melted at a temperature
sufficient to fuse and volatilize platinum.
Chromium forms three oxides: chromous oxide, CrO,
chromic oxide, Cr203, and chromic peroxide, CrO3,
which, dissolved in water, has a strong acid reaction,
and may then be called chromic acid. It neutralizes
bases, and forms yellow or red salts, called chromates.
The most common of these are known as the chromate
and bichromate of 5otash, K2CrO4 and K2Cr207. The
former is a yellow salt, and the latter a red salt, which




88                 THE METALS.
is made on a large scale, and used in the preparation of
the various chrome pigments.
The chief of the insoluble chromates is  liumbic
chromate, PbCrO4, or chrome yellow, obtained by precipitating a potassic chromate by a soluble lead salt,
and largely used for dyeing and other purposes.
117. COBAL 7'.-Cobalt is never found in a free
state except in small quantities in meteoric iron. It is
almost as infusible as iron. It is of a reddish-gray color,
hard, and strongly magnetic. It is not used in a metallic
state, but many of its compounds are remarkable for the
beauty of their colors, and are used as pigments. It
forms two oxides, CoO and Co2O3. The zafre of commerce is a very impure oxide of cobalt, mixed with two
or three times its weight of sand. It is used for coloring
glass.  ThSenard's blue, or artificial ultramarine, is a
compound of cobaltic and aluminic oxides.
I I8. VAIVNGANVE SE. -Manganese occurs in nature
as an oxide, and it can be obtained, though with difficulty, in the metallic state, by heating the oxide very
strongly with charcoal. The metal is of a reddish-white
color; it is brittle, and hard enough to scratch glass. It
decomposes water at the ordinary temperature with evolution of hydrogen; it cannot be preserved in the air
without undergoing oxidation, and must be kept under
naptha, or in a sealed tube; it is slightly magnetic, and,
like iron, combines with carbon and silicon. Metallic
manganese is not used in the arts; but an alloy of this
metal and iron is now made on a large scale, and used
in the manufacture of steel. Some of its oxides are used
for evolving chlorine from muriatic acid, and also for
giving glass a purple color.
Manganese forms several well-marked oxides: (I) man



THE METALS.                  89
ganous oxide, MnO, a basic body, furnishing a series of
salts; (2) manganic oxide, Mn)O3, which also forms
salts, but of a much less stable character; (3) black
oxide, MnO2, a neutral substance, occurring as an ore
of manganese; (4) and (5) two acid oxides, which give
rise to salts known as manganates and permanganates.
Black oxide of manganese is found in many parts of
Europe; but the most productive mines are in Thuringia
and Moravia. More than I8,ooo tons are used annually
in England in the manufacture of bleaching powder.
THE RARER METALS.
The other metallic elements are very rare substances,
and as yet are of very little practical importance.
i g9. Cadmiium (Cd) is a white metal resembling tin,
and is found in small quantities in the ores of zinc. It
is remarkable for forming very fusible alloys. For example, an alloy of I5 parts of bismuth, 8 of lead, 4 of tin,
and 3 of cadmium, melts at about I400 F. The sulphide
is a valuable yellow pigment, and the iodide is used to
some extent in photography.
I2o. Iridium (Ir) is the heaviest of the metals. An
alloy of iridium and osmium is very hard, and is used
for the points of gold pens. It forms three oxides, which
readily pass one into another, giving rise to the variety
of tints which characterize the solution of its salts. It is
because of these changes of color that the metal is called
iridium, from iris, the rainbow.
I2I. Tungsten, or woifranium (W), forms with steel
an alloy of remarkable hardness. WO,, or tungstic acid,
combines with sodium to form sodic tungstate (tungstate of soda), Na2WO4, which is used in calico-printing,
and in combination with starch to render linen and
cotton fabrics incombustible.




90                 THE METALS.
122. Uranium (U) forms an oxide, UO, which gives
a peculiar yellow color to glass, and also renders it
dfuorescent.
The other metals are of too little use or interest to be
mentioned here.
SUMMARY.
The metals are seldom found in a free state, but
usually combined with other elements as ores. Their
separation from these ores is called reduction.
The most useful metals are iron, lead, copper, tin,
and zinc.
The noble metals are gold, silver, mercury, and platinum.
The less useful metals are sodium, magnesium, aluminium, antimony, bismuth, and nickel.
The metals not used in a free state, but valuable for
their salts, are potassium, calcium, strontium, barium,
manganese, chromium, and cobalt.
Among the rarer metals, cadmium, iridium, tungsten,
and uranium are of some interest.
Among the most important metallic compounds may
be mentioned: salt, soda-ash, soda saltpetre, caustic soda,
bicarbonate of soda, pearlash, saltpetre, caustic potash,
lime, alum, glass, porcelain, green vitriol, blue vitriol,
white vitriol, litharge, red lead, and white lead.




CHEMISTRY OF THE ATMOSPHERE.
COMBUSTION.
123. Composition of the Atmosp5here.-We live at
the bottom of an aerial ocean called the atmosphere,
which is some fifty miles in depth. This atmosphere
contains free oxygen; as may be shown by inverting a
jar of it over a jar of nitric oxide. The gases, on mixing, become cherry-red (33).
Burn a piece of phosphorus in a jar of air over water.
The jar is filled with dense white fumes, which are soon
absorbed by the water, which rises and partially fills the
jar. Introduce now some nitric oxide into the jar while
still over the water, and the gas shows no trace of red
color. The free oxygen then can be removed from the
air by burning phosphorus in it. After all the oxygen
has combined with the phosphorus, and the compound
formed has been absorbed by the water, the jar is found
to be about one-fifth filled with water; showing that
about one-fifth of the air is oxygen.
The gas remaining in the jar is found to be almost
pure nitrogen.
Besides the oxygen and nitrogen, there is a small
quantity of carbonic anhydride (carbonic acid); as may
be shown by passing a large volume of air through limewttater. There is also watery vapor, which is continually condensed in the form of rain and dew. A trace
of ammonia, and of nitric acid, is also found; and to




92     THE CHEMISTRY OF THE ATMOSPHERE.
these are to be added the exhalations continually rising
from the earth. The whole quantity of these minor ingredients, with the exception of watery vapor, does not
amount to more than one part in a thousand. The proportions of oxygen and nitrogen are almost invariable,
while those of the other ingredients are continually fluctuating.
It must be borne in mind that the atmosphere is not a
chemical compound, but merely a mixture of these different gases. "Indeed, we may regard the globe as surrounded by at least three separate atmospheres, - one of
oxygen, one of nitrogen, and one of aqueous vapor, - all
existing simultaneously in the same space, yet each entirely distinct from the other two, and only very slightly
influenced by their presence."
The following Tables are from Miller: —
Composition of the Atmosphere.
Oxygen....    20.61
Nitrogen....  77.95
Carbonic Acid.04
Watery Vapor (average).....             I.40
I00.00
Composition in Tons.
Oxygen....   I,233,0oI   billions of tons.
Nitrogen....  3,994,593
Carbonic Acid..     5,287,,,.
Watery Vapor..    54,460o, 
124. The Products of the Burning of a Candle or
Coal-Gas are Carbonic Acid and Water.-When a
lighted taper is held to a candle, or to a jet of coal-gas,
the latter takes fire. In what does its burning consist?




THE CHEMISTRY OF THE ATMOSPHERE.    93
Invert a bottle for a short time over the candle or gasburner; then remove it, pour in a little lime-water, close
the mouth of the bottle with the hand, and shake it. The
lime-water becomes milky-white; showing that carbonic
acid has been produced by the burning.
If the candle or gas be burnt under a tin funnel connected with a long glass tube (which must be kept cold),
moisture will collect on the inside, and, after a short time,
will trickle down, and drop from the end of the tube.
When potassium is put into water, it burns with a rosecolored flame.  If the liquid from the tube be tested
with a bit of potassium, it proves to be water, which
is therefore another product of the burning.
Fig. i8.
No other substance is produced, except in very minute
quantities, by the burning of the candle or the gas.
125. The Candle, in Burning, removes Oxygen from
the Air.- Arrange a candle, so that it can be covered
with a bell-jar, over the water-trough; then light it, and
cover it with the jar. It soon ceases to burn, and the
water rises in the jar. The burning, then, removes something from the air.
Put a lighted candle into air from which the oxygen
has been removed, and it is at once extinguished; showing that it cannot burn without oxygen. It must then be
oxygen which it removes from the air when it burns.




94     THE CHEMISTRY OF THE ATMOSPHERE.
I26. A1? ordinary Combustion consists in the Combination of the Oxygen of the Air with the burning
Substance. — We have seen that carbonic acid, CO2,
and water, H20, are the products of the burning of a
candle. Of the three elements in these products, the 0,
as we have seen, comes from the air; the C and H exist
in the candle.
The force, then, which causes the candle to burn, is
affinity, and the burning is the combination of the oxygen of the air with the elements of the candle.
Experiments similar to those which we have tried with
the candle, will show that any ordinary combustible substance removes oxygen from the air when it burns, and
that it cannot burn without oxygen. We conclude, then,
that all ordinary combustion is the combination of the
oxygen of the air with the burning body.
I27. W~hy a Draft is necessary in Stoves and Furnaces. -We see now why our stoves and furnaces must
have a draft. As fast as the oxygen is taken from the
air by the burning fuel, this air must be removed, and a
fresh supply must take its place.  In other words, a
stream of air must be kept constantly flowing over or
through the fuel.
We see, also, how the fire can be regulated by means
of the draft. If the doors or dampers through which
the air is admitted be partially closed, the supply of air
will be diminished, and the burning will therefore be
retarded.
I28. Combustibles and SutVorters of Combustion. -
Any substance, as coal-gas, which can be made to burn,
is called a combustible; while any substance, as air or
oxygen, in which it can burn, is called a supporter of
combustion. These terms are convenient, though, strictly
speaking, the one substance is no more a combustible or
a supporter of combustion than the other. Since the




THE CHEMISTRY OF THE ATMOSPHERE.         95
burning of coal-gas consists in the combination of the gas
with oxygen, the oxygen in reality burns, as well as the
gas; and, on the other hand, the gas is as much a supporter of the combustion as the oxygen. The burning
must of course take place where the gases come together.
A jet of oxygen would appear to burn in an atmosphere
of coal-gas, just as a jet of coal-gas appears to burn in an
atmosphere of oxygen.
Fit a cork to one             Fig. I9
end of a lamp chimney, and let the tip               I 
of a gas-burner pass
through it, as represented in the figure. 
Allow the gas to es-  //
cape for some time,
and then light it at the                  i
top of the chimney.
It will burn quietly,
and the chimney will
evidently be filled
with coal-gas. Fill a gas-bag with oxygen, and fasten
to the bag a bent glass tube drawn out into a fine jet.
Force the oxygen through the tube in a gentle stream,
and introduce the end of the tube through the flame into
the chimney. As it passes the flame, the oxygen takes
fire, and burns brightly in the coal-gas; the oxygen apparently becoming the combustible body, and the coalgas the supporter of combustion.
In both the flames which we have here, it will be seen
that gases are burning where they come together; — the
coal-gas and the oxygen of the air, where they meet at
the top of the chimney; the oxygen from the bag and the
coal-gas, where they meet at the end of the tube inside
the chimney.




96     THE CHEMISTRY OF THE ATMOSPHERE.
129. Oxygen must be Heated before it will combine
with ordinary Combustibles. - The jet of coal-gas has
no disposition to burn until a lighted taper is applied
to it. The oxygen of the air is at all times in contact
with wood and coal, yet they do not burn unless they are
first kindled. When even as inflammable a gas as hydrogen is mixed with oxygen, it does not burn unless
ignited with a taper or an electric spark. "At the ordinary temperature of the air its chemical affinities are
dormant; and, although endowed with forces which are
irresistible when in action, it awaits the necessary conditions to call them forth. One of the grandest works of
ancient art which have come down to us, is the colossal
statue of the Farnese Hercules. The hero of ancient
mythology is represented in an erect form, leaning on his
club, and ready for action; but at the moment every one
of the well-developed muscles of his ponderous frame is
fully relaxed, and the figure is a perfect ideal of repose,
yet a wonderful embodiment of power. Here in this
antique we have most perfectly typified the passive condition of oxygen, the hero of the chemical elements.
Raise now the temperature to a red heat, and in a moment all is changed. The dormant energies of its mighty
powers are aroused, and it rushes into combination with
all combustible matter, surrounded by those glorious
manifestations of light and heat which every conflagration presents." - COOKE.
130. Combustion is Self-sustaining.- It is not necessary to arouse any large amount of oxygen to activity
in order to insure the continuance of the combustion.
When, for instance, a lighted match is held to the wick
of a candle, it excites but a few molecules of oxygen to
activity. These few rush into combination with the elements of the candle, and by so doing develop sufficient
heat to awaken the activity of more oxygen, which in




THE CHEMISTRY OF THE ATMOSPHERE.         97
turn enters into combination and develops more heat.
In this way a supply of active oxygen is maintained until
the candle is consumed.
The slowness of combustion depends upon the fact,
that the oxygen is mixed with the inert nitrogen in such
proportions as generally to " restrain the awakened energies of the fire-element within the narrow limits which
man appoints."
I31. zThe Poitn of Igniz'ion. - Different substances
begin to burn at very different temperatures. This is
well illustrated in the kindling of a coal-fire. Shavings
are put into the grate first, then kindling-wood, then
charcoal, and finally hard coal. The shavings are lighted
by means of a match. Tile match is a bit of dry, soft
wood, one end of which is covered with sulphur and
tipped with phosphorus. It is a well-known fact, that
when two bodies are rubbed together, heat is developed.
On striking the match, sufficient heat is developed by the
friction to ignite the phosphorus, which takes fire at a
temperature of about I500 Fahrenheit. The phosphorus
in burning develops heat enough to ignite the sulphur,
which burns at a temperature of about 500~. The burning sulphur develops heat enough to ignite the wood of
the match; the match, to ignite the shavings; the shavings, the kindling-wood; the kindling-wood, the charcoal; and the charcoal, the hard coal, which requires
the temperature of a full white heat to set it on fire.
132. The Products of Combustion are not always
Gaseous. - In the burning of coal-gas and of a candle,
the products are wholly gaseous, and in the burning of
wood they are mainly gaseous; but when metals, as copper and iron, burn in oxygen, the products of their combustion are solid.
I33- Magnesium and some other Metals will burn in
the Air. -A magnesium wire will burn brightly in the
7




98     THE CHEMISTRY OF THE ATMOSPHERE.
air (96). Calcium, also, burns readily in the air ( I 3), as
aluminium (97) does, if pulverized and strongly heated.
It will be noticed that all these elements are rare in
their free state. Many of the rare metals, as potassium,
sodium, magnesium, and calcium, are as combustible as
carbon; but they differ from carbon in giving rise to
solid products while burning.
I34. Oxygen is not the only Sulpporter of Combustion. - If a piece of gold-leaf or Dutch foil be dropped
into a jar of chlorine, it vanishes in a flash of light (53)Here the burning consists in a combination with chlorine.
Tin and copper foil and pulverized antimony will also
burn in chlorine. Many metals will burn in the vapor of
sulphur; the burning being then a combination of the
metal with sulphur.
I35. Thze Materials of the Earth's Crust are chiefy
Chemical Comn5ounds. - We have seen that when marble is acted upon by muriatic acid (42) we obtain carbonic acid, C02, and calcic chloride, CaCl. The calcium,
carbon, and oxygen of these compounds must come from
the marble, or calcic carbonate, CaCOa.
We find, then, in marble two very combustible substances, calcium and carbon, combined with oxygen.
Limestone has the same composition. Calcium, then,
which is a very great rarity in a free state, is a very
abundant element in nature.
It has been found that the rocks and solid matter of the
earth are made up chiefly of such combustible elements
as potassium, calcium, magnesium, aluminium, and carbon, combined with oxygen. Many of the rarest and
most costly metals, then, are the most abundant in nature.
The fact that they are so rare in a free state is due to their
extreme combustibility. It is very difficult to separate
them from oxygen, and no less difficult to keep them
separate.




THE CHEMISTRY OF THE ATMOSPHERE.         99
I36. The Present M]aterials of the Earth are Products of Combustion. - We see, then, that water, the
most abundant of liquids, is made up of the very combustible elements, hydrogen and oxygen; while the solid
materials of the earth are composed chiefly of the very
combustible elements, potassium, magnesium, calcium,
aluminium, carbon, and silicon, in combination with
oxygen. These materials are the products of combustion. There must have been a time when these elements
existed together in a free state. Then, by some means
unknown to us, the mass took fire; and the conflagration
raged until all the materials were consumed. There was
more oxygen than was needed for the combustion; and
this is now found in the air in a free state. Oxygen was
the most abundant of all the elements, since it alone
makes up half the weight of the solid earth, eight-ninths
the weight of the water, and one-fifth the weight of the
atmosphere.
The diagram below (from Cooke) illustrates what has
been said of the composition of the earth. It will be
seen, that, of the 65 elements, I3 alone make up at least.99 of its known mass, while the other 52 do not constitute altogether more than.oI.
Silicon.
Oxygen.
Aluminium.
Magnesium.
Calcium.
K Na Fe C
_ S H C1 N I 52 others.




I00    THE CHEMISTRY OF THE ATMOSPHERE.
SLOW COMBUSTION.
I37. Partially Active Condition of Oxygen. —We
have seen (II, I2) that, besides its active and passive
states, oxygen exists in a third, or intermediate, condition, in which it is partially active. In this form it plays
a very important part in nature. It acts silently and
slowly, taking months, and even years, to accomplish its
work; but the results " far surpass in true grandeur those
dazzling displays of power which the fire-element manifests when fully aroused."
138. Decay. - When wood, or any other organic substance (that is, any compound of vegetable or aninmal
origin) is exposed to moist air, it decays. It first becomes rotten, and then slowly disappears. This decay
consists in a gradual union of the substance with oxygen;
in other words, a slow  combustion. A  log of wood
which rots in the forest undergoes the very same change
as one which is burnt on the hearth; the sole difference
being, that, while the latter burns up in a few hours, the
former is consumed only after the lapse of many years.
Wood, like other vegetable compounds, consists mainly
of carbon, hydrogen, and oxygen. When it burns on the
hearth, its carbon and hydrogen combine with the oxygen
of the air, forming carbonic acid and water, which pass
off in the smoke. The hydrogen is more combustible
than the carbon, and therefore burns first, leaving the carbon in the form of glowing coals. These are consumed
in their turn, gradually smouldering away, until nothing
is left but a little ashes.
Quite the same process is going on with the decaying
log in the forest. In decay, as in burning, the hydrogen
of the wood unites with the atmospheric oxygen sooner
than the carbon does; hence, in this stage of its decay,
the wood becomes darker, and more like charcoal. At




THE CHEMISTRY OF THE ATMOSPHERE.   IOI
length, both the hydrogen and the carbon are burnt; and
the log is slowly converted into carbonic acid and water,
leaving only a handful of earth as the ashes of this lingering combustion. Even the h/eat generated in this
form of burning is found to be precisely the same as in
ordinary combustion; the only difference being that, in
the latter case, it is all set free in a few hours, while in
the former it is so slowly developed that it escapes our
notice.
I39. Causes of Decay. - Green wood decays much
sooner than dry wood. Indeed, if wood be kept perfectly dry, it will not decay for ages. In the dry climate
of Egypt, wooden mummy-cases have been preserved
for more than three thousand years.
The decay of the green wood is due to the presence of
what are called alcbuminozs substances. The most important of these is vegetable albumen, and it is essentially the same thing as the albumen (or white) of an
egg. We have said that most vegetable substances are
made up of carbon, hydrogen, and oxygen; but these
albuminous compounds, which form only a small part of
the bulk of plants, contain an additional element, nitrogen. We have seen that the compounds of nitrogen are
generally very unstable, and these albuminous substances
are peculiarly so. In the presence of moisture they soon
putrefy, or break up into simpler compounds. The
oxygen of the air takes no part in this process, but, by
contact with the putrefying substance, it is, in some mysterious way, awakened to the state of partial activity
mentioned above. It is thus enabled to attack and consume the wood and all the other organic compounds
present. The decay, or slow combustion, once begun, is
self-sustaining; fresh portions of oxygen being continually
roused to activity by the process itself, precisely as in
ordinary burning (I30).




102    THE CHEMISTRY OF THE ATMOSPHERE.
When  the nitrogenized vegetable compounds are
burnt, the nitrogen passes off in a free state; when
they decay, combined with hydrogen as ammonia.
I40. Rusling.- The slow  combustion of metals is
called rusting, and the oxide formed is called rust. All
the familiar metals, except silver, gold, and platinum, are
tarnished on exposure to the air; that is, they become
covered with a film of rust, or oxide.
That heat is developed by rusting, as by other kinds of
slow combustion, is shown by the fact that if a large pile
of iron-filings be moistened and exposed to the action of
the air so that they rust rapidly, the temperature rises
perceptibly.
A remarkable case of heat developed by rusting occurred in England during the manufacture of a submarine electric cable. The copper wire of the cable was
covered with gutta-percha, tar, and hemp, and the whole
enclosed in a casing of iron wire. The cable, as it was
finished, was coiled in tanks filled with water: these
tanks leaked, and the water was therefore drawn off,
leaving about i63 nautical miles of cable coiled in a mass
30 feet in diameter (with a space in the centre 6 feet in
diameter) and 8 feet high. It rusted so rapidly that the
temperature in the centre of the coil rose in four days
from 663 to 79~, though the temperature of the air did
not rise above 66~ during the period, and was as low as
59~ part of the time. The mass would have become even
hotter, had it not been cooled by pouring on water.
I4I. Spontaneous Combustion.-When charcoal which
has been finely pulverized for making gunpowder is exposed in large heaps, the oxygen of the air combines
with it slowly at first; but, as the heat developed accumulates, the oxidation becomes more rapid, until in some
cases the mass takes fire and burns.
So too, when cotton or tow, which has been used for




THE CHEMISTRY OF THE ATMOSPHERE.    I03
wiping machinery, and has become saturated with oil, is
laid aside in heaps, it begins to oxidize slowly; but the
heat developed makes the combustion more and more
rapid, until sometimes the heap bursts into a flame.
This rapid combustion, developed gradually from slow
combustion, is called spontaneous combustion.
I42. Respiration. - The albuminous or nitrogenized
compounds, which form but a small part of the plant,
make up almost the entire bulk of the animal, so that
animal substances are even more prone to decay than
vegetable. And this decay is not confined, as we might
suppose, to dead animal matter, but is constantly going
on in the living animal. The only difference is, that in
the latter case the loss from decay is continually repaired,
while in the former case it is not. The materials for the
repair of the living body are furnished by the food.
This food is mainly made up of three classes of substances: (I) non-nitrogenized, as starch and sugar;
(2) nitrogenized, as lean meat; and (3) fatty substances, as butter.  All three kinds are absolutely necessary to the life of man. They are all contained in
milk, which may be regarded as " the type of animal
food." It contains sugar, which belongs to the first of
the above classes; caseine, or curd, which belongs to the
second; and butter, which belongs to the third.  Bread
also contains all three kinds of food; being made up of
(I) starch, (2) gluten (the most important nitrogenized
constituent of wheat and other grain), and (3) a small
quantity of oil. A man cannot live for any length of
time on any one kind of food, as starch or butter, or on
any mixture of kinds of food, which does not contain all
three classes of substances.
The different classes of food serve different purposes
in the body. The nitrogenized and a part of the fatty
substances supply the waste which results from the action




104    THE CHEMISTRY OF THE ATMOSPHERE.
of the varied machinery of the body. They renew the
muscles, sinews, and nerves, which are constantly wearing out. On the other hand, the non-nitrogenized substances, as starch and sugar, probably take no part in
repairing the machinery, but merely furnish fuel to keep
up the heat of the body. To produce heat they must
be burnt up, and we shall see that the process is another example of slow combustion.
Starch and sugar make up by far the greatest part of
this fuel, and in fact of our food generally. They are
almost identical in composition, and starch can readily
be converted into sugar. When taken into the stomach,
starch undergoes this change, and the sugar then readily
dissolves in the water present.  The solution is absorbed by the veins, and becomes mingled with the
blood, which carries it to the heart. By the heart, which
is made up of two force-pumps, the blood is forced
through the lungs. These are composed of millions of
little membranous bags or air-cells, closely packed together, and all connected by means of tubes with the
windpipe, and thus with the nose and mouth. The
membrane of the cells is very thin, so that they are easily
compressed. The whole mass of the lungs is also very
elastic, and by the action of muscles they are alternately
expanded and contracted as we breathe. When they expand, the air from without rushes in and fills the cells;
and when they contract, this air is forced out again.
We have said that the blood charged with sugar is
forced through the lungs. The tube, or artery, which
conveys it, divides and subdivides, until it is reduced to
very small capillary tubes, which form a delicate network
on the surfaces of the air-cells. The walls of these capillaries are very thin, and the oxygen of the air readily
passes through them, by a process called osmose, and
mingles with the blood. At the same time, and in the




THE CHEMISTRY OF THE ATMOSPHERE.    I05
same way, carbonic acid is given out by the blood, and
mixes with the air. The blood, holding in solution both
sugar and oxygen, now goes back to the heart; and by
the second force-pump it is sent to all parts of the body.
In the mean time, the sugar is burnt up by the oxygen
which was absorbed in the lungs.
" Sugar, like wood, consists of carbon, hydrogen, and
oxygen. The last two are present in the proportions to
form water, so that sugar may be said to be composed of
charcoal and water. Of these two substances the charcoal only is combustible. This, during the circulation of
the blood, is slowly burnt up by the dissolved oxygen,
and converted into carbonic acid, which remains in solution until it is discharged, when the blood returns again
to the lungs, or else escapes through the skin." *
Respiration, then, is a kind of combustion, in which
"the fuel is sugar, and the smoke carbonic acid and
aqueous vapor." The presence of carbonic acid in the
air, from the lungs, may be proved by breathing through
a glass tube into lime-water, which soon becomes milky.
The presence of the watery vapor may be shown by
breathing upon any cold substance.
The weight of carbonic acid breathed out by a fullgrown man, in a day, varies from I to 3 pounds, or from
9 to 27 cubic feet; and the weight of carbon burnt is
from 5 to 15 ounces. The amount of heat produced is
of course the same as would be set free by burning the
same weight of charcoal in a stove. The temperature of
the body is thus kept above that of the air; the heat
* Cooke's "Religion and Chemistry." The greater part of
~~ I35-I37 and 140-I42 has been condensed from the 3d and 4th
Lectures in this admirable series. We cannot too strongly commend the book to teachers. They will be certain to draw from
it, for the purposes of oral instruction, far more largely than our
limits have permitted here.




io6    THE CHEMISTRY OF THE ATMOSPHERE.
of the blood, even in the coldest climate, being maintained at 96~.
" In regulating the temperature of his body, man follows instinctively the same rules of common sense which
he applies in warming his dwellings. In proportion as
the climate is cold, he supplies the loss of heat by burning more fuel in his lungs, and hence the statements of
arctic voyagers, who have told us that twelve pounds
of tallow-candles make only an average meal for an
Esquimaux, are not inconsistent with the deductions of
science."
I43. Slow and Rapid Combustion of Sugar. —We
may compare the rapid combustion of sugar in air with
its slow combustion in the body, by the following experiment: Take 2 ounces of pulverized sugar, or the
average quantity burnt in the body of a man in an hour,
and mix it with 52 ounces of pulverized potassic chlorate.
We have then the sugar and the solidified oxygen of the
chlorate mingled as in the blood; but the oxygen is passive, and will not combine with the sugar, until roused
to activity. A single drop of sulphuric acid let fall upon
the mixture serves to awaken its dormant energy; and
the mass is consumed in an instant, with intense evolution of heat and light. The amount of heat concentrated
in this momentary burst of flame is no greater than would
have been generated in the blood in the course of an
hour.
"The splendid displays of combustion arrest our attention by their very brilliancy, while we overlook the
silent yet ceaseless processes of respiration and decay,
before which, in importance and magnitude, the greatest
conflagrations sink into insignificance. These are but
the spasmodic efforts of nature; those, the appointed
means by which the harmony and order of creation are
preserved."




THE CHEMISTRY OF THE ATMOSPHERE.   IO7
I44. The Daily Consumption of Oxygen in VNature.
-"Faraday has roughly estimated that the amount of
oxygen required daily, to supply the lungs of the human
race, is at least one thousand millions of pounds; that
required for the respiration of the lower animals is at
least twice as much as this, while the always active processes of decay require certainly no less than four thousand millions of pounds more, making a total aggregate
of seven thousand millions of pounds required to carry
on these processes of nature alone. Compared with this,
the one thousand millions of pounds which, as Faraday
estimates, are sufficient to sustain all the artificial fires
lighted by man, from the camp-fire of the savage to the
roaring blaze of the blast-furnace, or the raging flames of
a grand conflagration, seem small indeed.
Amount of Oxygen required Daily.
Whole population..,ooo,ooo,ooo
Animals.                      2,000,000,000
Combustion and fermentation. I,ooo,ooo,ooo
Decay and other processes.. 4,000,000,000
Oxygen required daily.. - 8,000,00o,000 lbs.
" How utterly inconceivable are these numbers, which
measure the magnitude of nature's processes, - eight
thousand millions of pounds of oxygen consumed in a
single day!  When reduced to tons, the number is
equally beyond our grasp; for it corresponds to no less
than 3,57I,428 tons. If such be the daily requisition of
this gas, will not the oxygen of the atmosphere be in time
exhausted? It is not difficult to calculate approximately
the whole amount of oxygen in the atmosphere. It is
equal to about I,r78,I58 thousand millions of tons; a
supply which, at the present rate of consumption, would
last about nine hundred thousand years."




Io8    THE CHEMISTRY OF THE ATMOSPHERE.
THE GROWTH OF PLANTS.
I45. The Embryo Plant in the Seed.-How  do
plants grow? How does the tiny seed become the leafy
herb? How does the little acorn develop into the giant
oak? We shall get the best answer to these questions by
tracing a plant through its whole growth.
The seed is formed in the flower, the essential parts of
which are the stamens and the Pistil. The slamens
bear the anthers, and these contain the pollen. The
pistil is in the centre of the flower. It encloses in its
ovary the ovules, which, when ripened, become seeds.
In the ripe seed we find the embryo, which is a miniature plant with stem and leaves. How has this embryo
been formed?
At a certain time a little cavity is formed in the centre
of the ovule within the pistil. This cavity is called the
Fig. 20.   embryo sac, and is marked s in Figure
20. Within this sac, at its upper end,
F    s.... we see a minute body or vesicle, v.
This is the first germ of the embryo;
but in order that it may begin its de-'t/,  fill    velopment, it must be acted upon by
the pollen. This we see in the form
of small grains, a, resting on the top
of the pistil. It has fallen from the'//r\  anthers, and lodged here; and now it
sends out a very fine and delicate tube,
S     the pollen-tube, which pierces the tissue of the pistil, and extends itself
until it reaches the vesicle, v. Its contact with this microscopic particle of
matter has the mysterious power of making it begin to
grow, and thus form the embryo.
The vesicle is at first a single cell; that is, a memn



THE CHEMISTRY OF THE ATMOSPHERE.    IO9
branous globule, filled with liquid, in which minute particles can sometimes be discerned. After it has been
acted upon by the pollen-tube, it enlarges somewhat, and
a partition forms across its interior, dividing it into two
cells. Each of these grows and divides in like manner,
and thus a cluster of cells is formed. After a time the
mass begins to take a definite shape. One end becomes
the radicle, or the beginning of the root of the plant;
and the other divides into two parts, which develop into
the cotyledons, or seed-leaves. It is now a perfect embryo, a miniature plant, with root, stem, and leaves, but
still shut up in the seed.
I46. The Plantlet. -The growth of the plant in the
seed, and out of the seed, is essentially the same process.
The same division and multi-           Fig. 2.
Fig. 2x.
plication of cells continues, and
all the parts of the plant are. 
formed by the clustering or ag- _l
gregation of these cells. The    j
cells are too minute to be dis- 1   __
tinguished with the naked eye,
but the microscope shows them
in every portion of the plant.
Figure 21 shows a thin slice of     lil.
a rootlet, cut crosswise and
lengthwise, as it appears when
highly magnified. We see that the whole structure is
cellular; that is, made up of cells crowded together.
A single cell is represented in Figure 22. The natural
shape of the cell is spherical; but when cells are clustered or crowded together, they compress one another
into the shape in which we see them in these figures.
Where they are not thus squeezed, they are generally
found to be spheres, more or less perfect. They vary
in size, from about the thirtieth to the thousandth of an
inch in diameter.




I IO    THE CHEMISTRY OF THE ATMOSPHERE.
At first the cells are all alike in shape and in texture; but they are greatly modified in both respects in
Fig 22.   forming the varied tissues of the plant.
They may be lengthened out into tubes,
as in the fibres of cotton, which  are
I   single cells thus drawn out.  The soft,
thin membrane which encloses them may
become hard and thick, as in the shell of
a walnut or the tough wood of an oak.
They may be closely crowded together, and nearly
filled up with solid matter; or they may be loosely
interlaced, and form vessels to contain the vegetable
juices. Their contents are as varied as their structure,
and, seen through the transparent walls, give rise to all
the manifold colors of leaf and flower and fruit.
Figure 23 (from Wood's "Class-book of Botany")
shows a few of the varied forms which cells assume. At
the top we have wood-cells from the fibre of flax. Below
Fig. 23.
are represented the many-sided cells of the pith of elder;
stellate (star-shaped) cells of the pith of the rush spherical cells of the houseleek; and wood-cells of the oak.
I47. Organic Structure.- This cellular structure is
the characteristic of organic beings; that is, plants and




THE CHEMISTRY OF THE ATMOSPHERE.    III
animals, as distinguished from  inorganic things, or
minerals; and hence it is called organic structure. The
cell is " the simplest form of organic life," whether vegetable or animal. Cells are the units of which the most
complicated organic tissues are made up. They are essentially different, then, from the particles into which an
inorganic or mineral substance may be divided. Each
of these particles has all the properties of the mass from
which it was separated; and if we divide it into yet
smaller particles, the same will be true of those; and so
on indefinitely. But if we cut a cell in two, the halves
do not have the properties of the whole; they are not
smaller units, but the fragments of a unit.
148. The Food of Plants. — Plants get their food
from the earth and the air, but much the greater part
from the air. We know that there are plants which
flourish in the most barren soil, or even upon the naked
rock, and that some live and grow suspended in the air,
and having no contact with the earth. Even those which
demand a rich soil are indirectly indebted to the air for
what they draw from the earth. The soil owes its fertility to the decomposition of organic matter; and this
organic matter was originally produced by plants which
had no rich soil to draw from, but were dependent
mainly upon the air.
The atmosphere, then, is the storehouse from which
plants directly or indirectly obtain nearly all their food.
The portion which is purely of earthy origin is always
insignificant, and often it is nothing at all. In fact, plants
give to the earth far more than they get from it. This
is illustrated by the accumulation of vegetable organic
matter in the soil wherever vegetation is undisturbed
from year to year.  In uncultivated fields and in primeval forests we often find a great depth of rich mould.
The more rank and luxuriant the vegetation, the more




I 112    THE CHEMISTRY OF THE ATMOSPHERE.
rapidly this deposit increases, showing that the plants
not only restore to the soil all that they have drawn from
it, but are continually transferring fresh matter from the
aerial storehouses to the earth.
But while the soil is enriched by undisturbed vegetation, it is impoverished by agriculture. The farmer
carries away the crop from the field, with all that it has
taken from both the earth and the air. The land cannot
yield in this way year after year, unless he follows the
example of nature, and restores to the soil an equivalent
for what he removes. This he can do by the use of
manure.
i49. The Earthy Portion of the Plant. - If we burn
wood or any other vegetable substance, almost all of it is
dissipated into air. But a little ashes will remain; and
these represent the earthy or inorganic portion of the
plant. They consist mainly of alkaline chlorides, potash,
soda, silica, metallic phosphates, calcic and magnesic
carbonates, and ferric and manganic oxides. These are
dissolved in the water which soaks through the soil and
which is taken up by the roots of the plant. Much of
the water is evaporated through the leaves, but the substances which it held in solution remain behind, and
thus gradually accumulate in the tissues of the plant.
Since the plant must obtain from the soil the inorganic
materials it needs, it is evident that it will flourish only
in a soil containing those materials. This explains why
certain plants thrive only in certain situations. A locality
may be fertile for some species of vegetation and barren
for others. The pines, which need little alkaline matter,
will flourish in a sandy soil containing little alkali; but
the maples and elms, which require a good deal of potash, cannot live in such a soil.
We have said that the farmer, who carries away the
produce of the field with all that it has drawn from the




THE CHEMISTRY OF THE ATMOSPHERE.    I I3
soil, must restore in the form of manure an equivalent for
what he removes, or the field will soon become impoverished.
"A medium crop of wheat takes from one acre of
ground about I2 pounds; a crop of beans, about 20
pounds; and a crop of beets, about i i pounds of phosphoric acid, besides a very large quantity of potash and
soda. It is obvious that such a process tends continually
to exhaust arable land of the mineral substances useful to
vegetation which it contains, and that a time must come,
when, without supplies of such mineral matters, the land
would become unproductive from their abstraction....
In the neighborhood of large and populous towns, for
instance, where the interest of the farmer and marketgardener is to send the largest possible quantity of produce to market, consuming the least possible quantity on
the spot, the want of saline principles in the soil would
very soon be felt, were it not that for every wagon-load
of greens and carrots, fruit and potatoes, corn and straw,
that finds its way into the city, a wagon-load of dung,
containing each and every one of these principles locked
up in the several crops, is returned to the land, and
proves enough, and often more than enough, to replace
all that has been carried away from it." — BOUSSINGAULT.
This renewal of fertility is sometimes attained by letting the field lie falZow, or uncultivated, for one or more
years. The inorganic materials of the soil are mainly
furnished by the gradual disintegration of the rocks; and
while the field lies fallow this process is going on, under
the influence of the oxygen and carbonic acid of the air,
aided by the rains and changes of temperature. In this
way, fresh portions of the rocks or of their ruins are
rendered soluble and thus fitted for the nourishment of
plants.
8




II4    THE CHEMISTRY OF THE ATMOSPHERE.
An allternation of crops may answer the same purpose
as letting the field lie fallow. For instance, wheat and
potatoes may be raised on the ground in alternate years.
The wheat requires a large amount of silica and alkaline
matter, while the potatoes take up no silica. The renewal of the soluble silica in the soil therefore goes on,
while the potatoes are growing, as it would if the field
were fallow.
Some soils abound in silicates so readily decomposed,
that in every one or two years a sufficient supply for a crop
of wheat becomes soluble. In Hungary there are large
districts where wheat and tobacco have been raised alternately upon the same soil for centuries, the land never
receiving back any of the mineral matter which is carried away with the crops. On the other hand, there are
fields in which the amount of soluble silica required for
a single crop of wheat is not separated from the insoluble
masses in the soil in less than three or four years.
I50. Thze Organic Portion of the Plant.  When
we burnt the vegetable matter, much the greater part
of it passed off into the air. This was the organic portion of the plant. It was taken from the air, and the
burning has given it back in the very form in which the
plant found it there.
We have learned that all the vegetable tissues, however varied in their texture and consistency, are almost
entirely made up of the same kind of cells. The substance of which these cells are made is called cellulose,
or woody fibre; and it is a compound of carbon, hydrogen, and oxygen, C 12H2000. We have also learned that
the plant contains small quantities of alburninous compounds (I39), which, in addition to the elements just
named, contain nitrogen. These four elements, then,
are essential to the growth of the plant. and must be contained in its food.




THE CHEMISTRY OF THE ATMOSPHERE.    I 15
I5I. The Plant gets Hydrogen and Oxygen from
Water. - The hydrogen and the oxygen of the cellulose
are obtained from the water which the plant takes in,
not only through its roots, but through its leaves. It will
be noticed that water contains hydrogen and oxygen in
the same proportions as cellulose does.
152. The Plant gets Carbonfrom  Carbonic Acid.We have learned that carbon is a solid, and insoluble in
water. Even if it were reduced to the finest powder and
mixed with the water, it could not be taken up by the
plant, since nothing but liquids and gases can pass
through the walls of the cells. It must, then, be furnished
to the plant in some liquid or gaseous compound, like
the carbonic acid, which, as we have seen, is one of the
gases mixed in the atmosphere.
Now if a leafy plant be placed under a glass vessel
and set in the sunshine, and a stream of carbonic acid
be made to pass slowly over it, it is found that a part of
the carbonic acid is removed and replaced by oxygen.
The plant absorbs the carbonic acid, decomposes it, retains the carbon, and exhales the oxygen.
We conclude, then, that it is from the carbonic acid
in the atmosphere that plants get their carbon. In the
leaves, under the influence of sunlight, the carbonic acid
is decomposed, the carbon stored away in the plant, and
the oxygen given back to the air.
Since carbonic acid is soluble in water, it is probable
that plants also obtain a part of their carbon through the
roots. Plants which live under water must get all their
carbon from the gas dissolved in the water.
I53. The Plant gets Nitrogen from  Ammonia.We have learned (I23) that there is ammonia in the atmosphere, and (37) that this gas is very soluble in water.
Hence it is washed out of the air by the rain, and, thus
dissolved in water, is taken up by the roots of plants.




I I6    THE CHEMISTRY OF THE ATMOSPHERE.
I54. The Growth of Plants is a Chemical Process
carried on in the Leaf by the Sunlig'ht. —We have
seen that the plant takes in water, carbonic acid, and
ammonia; that it decomposes these substances; and
that from their elements it elaborates all the organic
compounds which enter into its own structure.  The
leaf is the laboratory in which this chemical process is
conducted, and since it is only in sunshine or bright daylight that the work goes on, it is evident that the sunlight
is the agency by which it is accomplished.
" The sun's rays, acting on the green parts of the leaf,
give to them the power of absorbing water, carbonic acid,
and ammonia, and of constructing from the materials thus
obtained the woody fibre, starch, sugar, and other compounds of which the plant consists. We have analyzed
the woody fibre, and we know that it is composed of
charcoal and water. Nineteen ounces of wood contain
nine ounces of charcoal and ten ounces of water. Moreover, the amount of charcoal required to make nineteen
ounces of wood is contained in thirty-three ounces of carbonic acid. If, then, we add together thirty-three ounces
of carbonic acid and ten ounces of water, and subtract
from this sum twenty-four ounces of oxygen, we shall
have just the composition of wood. This is what the
sun's light accomplishes in the leaves of the plant. It
decomposes the carbonic acid, and unites its carbon to
the elements of water to form the wood."- COOKE.
What is here stated to be true of wood is equally true
of other vegetable products. If in their production carbonic acid and water alone take part, we have such
substances as woody fibre, starch, sugar, and gum; and
these make up nine-tenths of all vegetable structures. If
the ammonia is likewise employed in the process, we
have nitrogenized products, like albumen and caseine.
The force which the sunbeam exerts in the decomposi



THE CHEMISTRY OF THE ATMOSPHERE.    I I7
tion of carbonic acid in the leaf is very remarkable, since
it overcomes the intense affinity of oxygen for carbon.
"In order to decompose carbonic acid in our laboratories, we are obliged to resort to the most powerful
chemical agents, and to conduct the process in vessels
composed of the most resisting materials, under all the
violent manifestations of light and heat, and we then succeed in liberating the carbon only by shutting up the
oxygen in a still stronger prison; but under the quiet
influences of the sunbeam, and in that most delicate of
all structures, a vegetable cell, the chains which unite
together the two elements fall off, and, while the solid
carbon is retained to build up the organic structure, the
oxygen is allowed to return to its home in the atmosphere. There is not in the whole range of chemistry a
process more wonderful than this.  We return to it
again and again, with ever increasing wonder and admiration, amazed at the apparent inefficiency of the
means, and the stupendous magnitude of the result.
When standing before a grand conflagration, witnessing
the display of mighty energies there in action, and seeing
the elements rushing into combination with a force which
no human agency can withstand, does it seem as if any
power could undo that work of destruction, and rebuild
those beams and rafters which are disappearing in the
flames? Yet in a few years they will be rebuilt. This
mighty force will be overcome; not, however, as we
might expect, amidst the convulsion of nature, or the
clashing of the elements, but silently, in a delicate leaf
waving in the sunshine." - COOKE.
I55. Plants ptrzfy the Air for t/e Respiration of
Anzimals. -We have learned (I44) that by the various
forms of combustion going on in nature, eight thousand
millions of pounds of oxygen are daily removed from the
atmosphere; and that an immense amount of carbonic




I IS    THE CHEMISTRY OF THE ATMOSPHERE.
acid is pouring back into the air as one of the chief
products of this combustion. The atmosphere, then, is
continually losing the element which is essential to the
support of animal life, and receiving in its place a gas
which, even when largely diluted with air, is a deadly
poison to animals.
But we have also learned that during the daytime
plants are constantly drinking in this carbonic acid, and
giving out an equal bulk of pure oxygen. They are thus
purifying the air for the respiration of animals. They
breathe in what animals breathe out, and breathe out
what animals breathe in; so that the air is kept in a
fit state to sustain both forms of organic life.
An Oriental fable narrates that a nightingale and a
rose-tree were once imprisoned in a cage of glass, and
long lived together there, happy in each other's society.
But at last the rose-tree withered and died; and the bird
soon pined away, and perished with grief at the loss of
its beloved companion. The fancy of the poet is in perfect harmony with the facts of science, and prettily illustrates the dependence of animals upon plants for the very
breath of life.
I56. Plants prepafre Food for Animals. -We have
seen that the plant draws its food directly from the earth
and the air. It has the power of forming organic compounds out of inorganic matter. The animal, on the
other hand, has no such power. It can elaborate its tissues only from organic matter, which it receives readymade from the vegetable kingdom. It may get this
matter either directly from the plant, as when it eats
vegetable food, or, indirectly, as when it eats animal
food; but in either case the origin is the same. By
the process of digestion the organic compounds originally prepared by the plant are converted into bones,
muscles, nerves, or whatever else enters into the struc



THE CHEMISTRY OF THE ATMOSPHERE.    I I9
ture of the animal. In this process they do not undergo
any radical change, but merely "become parts of more
finely organized tissues." We find in the blood albumen
and caseine, having precisely the same composition as
when prepared from potatoes, and the substance of the
muscles does not differ essentially from the gluten of
wheat-flour.
I57. The Relations of Plants and Animals to each
other and to the Air. - The plant, then, is a producer
of organic materials; the animal, a consumer of these
materials. " While the plant is a true apparatus of reduction, the animal is a true apparatus of combustion, in
which the substances it derived from the vegetable are
burnt, and restored to the atmosphere in the form of carbonic acid, water, and ammonia, ready to be again absorbed by the plant and to repass through the phases of
organic life. Our bodies are furnaces, - furnaces continually burning, - whose fuel is our own flesh, and the
smoke of whose fires is the food of the plant....
"When the foundations of the globe were laid, there
were collected in the atmosphere all the essential elements of organized beings.  From  this inexhaustible
storehouse the plant absorbs water, carbonic acid, and
ammonia, which were placed there for its use, and which
have been made to serve as its nourishment and food.
It is the special office of the plant to elaborate from
these few mineral substances, and a small amount of
earthy salts, all the materials of organized beings. The
animal receives these crude materials already prepared,
and builds with them its various tissues; but no sooner
are the cell-walls finished, and the structure ready to discharge its vital functions, than it is consumed by almost
the very act which gave it life.  The carbonic acid,
water, and ammonia are restored to the atmosphere, and
the cycle is complete." - COOKE.




120    THE CHEMISTRY OF THE ATMOSPHERE.
NATURAL VEGETABLE PRODUCTS.
I58. Starch. - Starch has already been mentioned as
one of the most important products of vegetable growth.
Its chemical composition is precisely the same as that of
woody fibre, C12H2010. It consists of round or oval
granules, varying considerably in size in different vegetables. The largest are about maXth, and the smallest
less than l~Ith of an inch in diameter. In the potato
(Figure 24) they are considerably larger than in wheatFig. 24.            Fig. 25.
flour (Figure 25). These granules consist of concentric
layers, formed one after another, about a nucleus or
centre. Lines, indicating these layers, can sometimes be
seen on the surface of the larger grains, as in those of
potato starch in the figure. Since the grains from the
same kind of plant are tolerably uniform in size and
shape, while they vary much in different species, the
microscope will show to what plant starch-grains belong. Adulterations of arrowroot, and of other starchy
substances, may thus be detected.
Starch is heavier than water, and is insoluble in cold
water, alcohol, or ether. If, however, it be placed in
water at I500, the grains swell up and burst, forming
a paste or jelly. When long boiled in water, starch
is converted into the soluble dextrine (i62).
The test for starch is iodine, with which it forms a
compound of a deep blue color (60). Bromine gives
starch a brilliant orange tint.




THE CHEMISTRY OF THE ATMOSPHERE.    12I
Starch is the form in which food is stored    Fig. 26.
up in the plant for future use. In the seed, it
furnishes the material for the growth of the
embryo, before it can draw its nourishment
from the earth and the air.  It sometimes
surrounds the embryo, as in the seed of the
onion (Figure 26); and sometimes it is
found in the cotyledons, or seed-leaves, of
the embryo itself, as in the seed of the bean (Figure 27).
When the seed germinates, the             Fig. 27.
starch is dissolved, and converted
into dextrine, and this into sugar,
which is even more soluble. It is
then dissolved in the sap, which
conveys it wherever it is needed
for the growth of the infant plant.
Several forms of starch are extensively used as articles of food. Arrowroot is obtained
from the roots of a tropical plant, which is cultivated in
the West Indies, especially in Bermuda and Jamaica, and
to some extent in the East Indies and in Africa. Tapioca
is also made from the roots of plants which grow in the
West Indies, South America, and Africa.  Sago is extracted from the pith of several species of palm-tree, in
India and the islands of the Indian Archipelago. Cornstarch, maizena, and farina, and various other preparations of the kind, are made from the starch of Indian
corn, wheat, etc. Potatoes yield fromn I2 to 27 per cent
of starch; peas and beans from 33 to 36 per cent; wheatflour, 56 to 72 per cent; rye-meal, 6I per cent; maize,
8I per cent; rice, 83 to 85 per cent.
Starch is also used in large quantities for laundry purposes; in the manufacture of cotton cloth, as a sizing for
the thread; and in the making of dextrine and grape,
sugar (I6I, 162).




I22    THE CHEMISTRY OF THE ATMOSPHERE.
I59. Sugar. - Sugar, like starch, is a vegetable product, prepared for the future growth of the plant. It is
found, dissolved, in varying proportions, in the juices of
all plants. In ripe fruits it is quite abundant; pears containing 6 per cent; peaches, I6- per cent; and cherries,
I8 per cent. In rye-meal there is about 32 per cent of
sugar; in wheat-flour, from 4 to 8 per cent; in beet-root,
from 5 to 8 per cent; and in dried figs, more than 60
per cent.
There are many kinds of sugar, of which the two most
important are cane-sugar and graspe-sugar.
I6o. Cane-Sugar. - Cane-sugar, C12H220m1, is found
in the juices of many plants. It is mostly prepared from
the juice of the sugar-cane; but on the Continent of
Europe, it is largely made from beet-juice. In tropical
regions, it is also manufactured from the juice of the
date-palm; and in the Northern United States it is
obtained in considerable quantities from the sap of the
rock or sugar maple.
In the manufacture of sugar from sugar-cane, the juice
is first extracted from the canes by pressure, then mixed
with a small quantity of slaked lime, and heated nearly
to boiling. The lime serves to neutralize the acid in the
juice, and also to remove the albuminous matter, which,
if left in the sugar, would soon cause it to ferment and
spoil. The juice is next evaporated in open pans to a
thick syrup, which is allowed to cool and crystallize, and
is then drained in perforated casks. The liquid drained
off is known as molasses.
By this process, raw or brown sugar is obtained.
This is refined by dissolving it in water, adding albumen
(usually from ox-blood), and heating it. The albumen
separates most of the impurities from the solution, which
is then filtered through bone-black to remove the coloring
matter. It is then boiled down in vacuum pans, large




THE CHEMISTRY OF THE ATMOSPHERE.    123
vessels from which the air is partially exhausted by
pumps, in order that the evaporation may be carried on
at a lower temperature than in open pans. By this process there is a saving of fuel, while the quantity of sugar
obtained is increased. The concentrated syrup is crystallized in conical moulds, with an opening at the bottom
for drainage, and thus becomes loaf-sugar.
When sugar crystallizes very slowly, it forms the large
and very hard crystals seen in rock-candy. In making
loaf-sugar, the syrup is frequently stirred, to prevent the
formation of these large crystals.
If cane-sugar be heated to about 4000, it loses two
atoms of water, and is converted into caramel, a dark
brown substance, much used for coloring brandy and
other spirits.
The manufacture of sugar from the sugar-cane, and
other sources, is now one of the largest branches of
human industry, but its importance is of comparatively
modern date. Sugar was known to the Greeks and
Romans only as a medicine or a curiosity. For several
centuries after the Augustan age, we find scarcely any
mention of it; and, even so late as the seventh century,
Paul of AEgina describes it as " India salt, resembling
common salt in color and consistency, but honey in taste
and flavor." The sugar-cane appears to have been introduced into Europe by the Saracens, who cultivated it in
Rhodes, Cyprus, Crete, and Sicily, in the ninth century.
In the fifteenth century, it was transplanted into Madeira
and the Canary Isles, whence it was probably brought to
America. It became known in England in the fourteenth
century; and, in I329, it was sold in Scotland at one
ounce of silver (equal to four dollars of our money) a
pound. It did not become an article of ordinary consumption until the beginning of the seventeenth century.
Since that time its use has very rapidly increased, and it




124     THE CHEMISTRY OF THE ATMOSPHERE.
seems destined to an indefinite extension. "' It is so nutritious, wholesome, and agreeable, that there never can
be a limit to its use, except in a prohibition or an inability to buy it. Men and nations differ widely in respect
to most kinds of food, sauce, and drinks. Neither wheat,
rice, flesh, nor potatoes can command unanimous favor.
No article of housekeeping, save sugar, can be named,
which is so universally acceptable to the infant and the
aged, the civilized and the savage."
The annual production of sugar throughout the world
is estimated at more than 5,000 millions of pounds, of
which nearly 88 per cent is cane-sugar; about 7 per cent,
beet-sugar; 4 per cent, palm-sugar; and about I per cent,
maple-sugar.  According to Chambers's Encyclopmdia
(I867), the yearly consumption for each inhabitant,
in several great countries, is as follows: Russia, It  lbs.;
Austria, I  lbs.; France, 4 lbs.; Belgium, 6 lbs.; Great
Britain, 30 lbs.; United States, 40 lbs.
i6I. Grape-Sugar.- Grape-sugar, or glycose (less
properly spelled glucose), C12H24012, is found in the juice
of grapes, plums, cherries, figs, and many other fruits,
and may often be seen in a crystalline form on raisins
and dried figs. It likewise occurs in honey.
It is manufactured on a large scale, in Europe, from
starch. A mixture of starch and water, at a temperature
of about 130~, is made to flow gradually into a vat, containing boiling water, acidulated with one per cent of
sulphuric acid. In about half an hour, the starch is converted into sugar. The sulphuric acid is neutralized
with chalk, forming a deposit of calcic sulphate; and the
clear solution of sugar is then boiled down and crystallized. Instead of starch, in this process, paper, flax,
cotton and linen rags, sawdust, or any other form of
woody fibre, may be used. The woody fibre is first converted into starch, and then into sugar.




THE CHEMISTRY OF THE ATMOSPHERE.    I25
Glycose is largely used in Europe for confectionery,
for adulterating cane-sugar, and for the manufacture of
beer and spirits.
I62. Dextrine. - Dextrine, or British gum, C12H20010,
is obtained by heating starch to about 400~; or by subjecting the starch to the long-continued action of dilute
acids, at a high temperature. It is often used instead of
gum-arabic in calico-printing, and for stiffening certain
goods. It is also applied to the back of postage-stamps
and other adhesive labels.
WVhen wheaten bread is baked, a small quantity of
starch is converted into dextrine on the outside of the
crust, forming a brownish glazing.
I63. Cellulose and Gun- Cotton. - Cellulose, or woody
fibre, C12H200,1O has already been described (I50). It is
insoluble in water, alcohol, or ether, but dissolves in an
ammoniacal solution of cupric oxide (oxide of copper).
Gun-cotton, or nitro-cellulose, is made by the action
of strong nitric acid upon cellulose. Cotton wool is immersed, in small portions at a time, in a mixture of equal
volumes of strong nitric and sulphuric acids. It does not
undergo any apparent change; but, on being washed and
dried, it is found to be very inflammable. Six atoms of
its hydrogen have been replaced by NO2, so that its composition is now represented by Cl2H14 (NO2)6010.
The use of gun-cotton, as a substitute for gunpowder,
has been proposed, for the following reasons: —
(i) The explosive force of gun-cotton is, weight for
weight, greater than that of gunpowder. (2) The products of the combustion of gun-cotton, being chiefly carbonic acid and nitrogen, are not so apt to foul the gun.
(3) When moistened, it becomes inexplosive, and only
requires drying to render it again explosive.
The reasons which render the general adoption of this
substance doubtful are, — (I) its liability to explode on




126    THE CHEMISTRY OF THE ATMOSPHERE.
percussion; (2) the possibility of its spontaneous decomposition when kept for a length of time.
A variety of gun-cotton, containing a smaller proportion of NO2, dissolves readily in a mixture of ether and
alcohol, and yields a solution termed collodion. This is
largely used for the purpose of forming a thin coating on
glass to receive silver salts, upon which the photographic
image is formed.
I64. Vegetable Parchment. —When paper is immersed for a short time in a mixture of two volumes of
oil of vitriol and one of water, and thoroughly cleansed
by repeated washings with water, and finally with ammonia, it is changed into a substance resembling parchment, and often called vegetable parchment.
" The alteration which takes place in the paper is of a
very remarkable kind. No chemical change is effected,
nor is the weight increased; but it appears that a molecular change takes place, and the material is placed in a
transition state between the cellulose of woody fibre and
dextrine."
Vegetable parchment is now extensively used instead
of parchment for legal and other documents. In some
respects it is preferable to the old kind, for insects attack
it less.
I65. Vegetable Acids. - The acids of vegetable origin
are almost innumerable. We shall describe here only a
few of the most important.
Tartaric acid, C4H.O6, is found, either free or combined with potash or lime, in tamarinds, grapes, pineapples, and many other vegetables. It is usually seen in
the form of colorless crystals, which have an agreeable
acid taste, and are soluble in water and alcohol. It is
used in large quantities in calico printing and dyeing,
and also in medicine, especially for making effervescent
draughts. Some of its more important compounds are




THE CHEMISTRY OF THE ATMOSPHERE.    127
the familiar substances, Rochelle salts, cream of tartar,
and tartar-emetic.
Citric acid, C6H807, is usually prepared from lemons.
It is also contained in gooseberries, currants, raspberries,
strawberries, and other fruits. It is a crystalline solid,
readily soluble in water, and has an intensely sour taste.
It is used in silk-dyeing, in calico-printing, and in
medicine.
]/i2alic acid, C4H605, is one of the most abundant of
these vegetable acids. It is found in apples, from which
(Latin, malum) it takes its name; in currants, barberries,
rhubarb, and many other fruits and plants. It forms
needle-shaped crystals, which are very soluble in water
and alcohol. It is not used in the arts or in medicine.
Oxalic anhydride, C208, is not known in a free state.
It is found in the juice of wood-sorrel (oxalis acetosella,
from which it takes its name), and of many other plants,
in combination with potash or lime. It forms a compound with water, H2C204, which is oxalic acid. This
is a crystalline substance, and is very poisonous. It is
much used in cotton-printing and straw-bleaching, and is
prepared in very large quantities by the action of caustic
potash on sawdust. Crude potassic oxalate (oxalate of
potash) is thus formed, which, by means of lime, is converted into the insoluble calcic oxalate (oxalate of lime),
and this is decomposed by sulphuric acid.
Tannic acid and tannin are the names given by
chemists to a number of compounds of C, H, and 0,
which are characterized by a well-marked astringent
taste. They are soluble in water and alcohol, and form
precipitates with most metallic oxides. Ferric salts yield
black, or nearly black, precipitates, which are the basis of
the ordinary writing inks. Tannic acid also precipitates
gelatine (or glue); and it is by a similar process that it
converts the gelatinous tissue of raw hides into tanned




128    THE CHEMISTRY OF THE ATMOSPHERE.
leather. The bark and leaves of most forest trees, such
as the oak, elm, willow, horse-chestnut, and pine, and of
many fruit-trees, as the pear and plum, contain considerable quantities of tannin. Coffee and tea likewise contain modifications of this compound; but the tannin in
coffee, unlike that from  all the other plants we have
named, does not form the black salt with iron. A drop
of tea on a knife-blade becomes inky at once, but a drop
of coffee does not.
I66. NVatural Fats and Oils. -The natural oils and
fats (fats being merely solid or semi-solid oils) are all
compounds of organic acids, called the fatty acids, with
a base called glycerine (i67), and they are found in
both plants and animals. Cocoa-nut oil, p5alm oil, and
nutmeg fbuler are examples of vegetable fats.
The vegetable oils are divided into the fixed oils,
which cannot be distilled without decomposition, and the
volatile oils, which bear distillation without change.
The fixed oils are divided into drying and non-drying
oils. The former become dry and solid from oxidation,
when spread out thin and exposed to the air; while the
latter remain unaltered. The chief drying oils are those
of linseed, hemp, poppy, and walnut, all much used in
paints and varnishes; and the most important non-drying
oils are olive oil, almond oil, and colza oil, which are extensively used in making soap, candles, and illuminating
oils, in wool-dressing, and for many other purposes.
Castor oil seems to form a connecting link between these
two classes of oils, as it gradually becomes hard by long
exposure to the air.
The volatile or essential oils are believed to constitute
the odorous principles of plants. Most of them are nearly
colorless when fresh, but darken on exposure to light and
air. When long exposed to the air, they absorb oxygen,
and become resins. They are largely used in the manu



THE CHEMISTRY OF THE ATMOSPHERE.    I29
facture of perfumery; for flavoring confectionery and
liquors, and for various other purposes in the arts; and
in medicine.
I67. Soap. - When the oils or fats are boiled with an
alkali, they undergo the remarkable change called saponzfication. The fat is decomposed into a fatty acid and
glycerine (I66). The acid combines with the alkali to
form soap, and the glycerine passes into solution. If the
alkali be soda, a hard soap is formed; if _5otash, a soft
soap. The soaps, then, like the fats, are true salts.
Fats may also be separated into acid and glycerine by
distillation with steam, at a temperature between 5000
and 600~.
Glycerine (CH,606O), is a colorless viscid liquid, of a
sweet taste (whence its name, which is from a Greek
word, meaning sweet), soluble in water and alcohol, but
nearly insoluble in ether. It is used in medicine, in
making copying-ink, and as a lubricating agent.
The most important of the fatty acids are oleic, stearic,
and palmic, or palmitic. They are used on a large scale
in the manufacture of candles.
I68. Wax. -The various forms of vegetable wax resemble in many respects the fixed oils, but are quite
different from them in chemical composition. They are
solid or semi-solid substances; easily broken when cold,
but soft and pliable when moderately warm, and melting
below  2I2~.  They are insoluble in water and cold
alcohol, but dissolve readily in ether; they burn with a
bright flame, and are not volatile. They are found as
exudations on leaves and fruits, where they form the
glaucous surface, which repels water. Some fruits, as
the bayberry, are thickly coated with wax.
I69. Gums and Resins.- In the strict sense, a gzm
is a substance which dissolves in water, forming a mucilage; but is insoluble in ether, alcohol, and oils. A resin,
9




I30    THE CHEMISTRY OF THE ATMOSPHERE.
on the other hand, is insoluble in water, and soluble in
ether, alcohol, and oils.  Gum arabic and gum senegal
are products of different species of acacia, and are extensively used in the arts.  Gum tragacanth is the product
of a shrub which grows in Persia and Asia Minor. It is
only partially soluble in water, forming a white paste
instead of a mucilage. It is used for paste and cement,
and also for stiffening woven fabrics. Dextrine is now
much used as a substitute for these and other gums (I62).
The resins are divided into the hard resins, the soft
resins, and the gum-resins. The hard resins are brittle
at ordinary temperatures, and are easily pulverized. The
most important are copal, the varieties of lac, mastic,
and sandarach. They are much used for varnishes and
for other purposes in the arts. The soft resins are easily
moulded by the hand, and some of them are semi-fluid,
in which case they are called balsams.  They consist
essentially of hard resins dissolved in oils. On exposure
to the air, they are oxidized and converted into hard
resins. Under this head are placed turibentine, Canada
balsam, etc. The gum-resins are the milky juices of
certain plants, solidified by exposure to the air. They
consist of a mixture of gums, resins, and essential oils.
Caoutchouc, or india rubber, is the most important of
the gum-resins.  It is obtained from  several quite different kinds of trees. The original india rubber of the
East Indies is the product of a species of fig-tree. Guttapercha is the dried milky juice of a tree found in Malacca
and the neighboring islands. The applications of these
two gum-resins in the arts are almost innumerable, and
are continually increasing. Many valuable medicines are
obtained from gums and resins. Amber is a fossil resin.
I70. Vegetable Alkaloids. -A great variety of alkaline compounds, known as alkaloids, are produced by
plants. They are mostly formed in the bark and in the




THE CHEMISTRY OF THE ATMOSPHERE.    131
leaves. Among them are some of the most active poisons
and some of the most valuable medicines, as morphine,
strychnine, and quininze.  Tea and coffee owe their
peculiar effects to the same alkaloid, theine.  Opium is
remarkable for the great number of these compounds
which it contains. The narcotic power of tobacco is due
to a highly poisonous alkaloid called nicotine.
I7I. Proteine Bodies. - Under the term  proteine
bodies have been included the most important nitrogenized products of plants, as albumen, caseine, and.fbrine. They all have essentially the same composition,
containing about 53.6 per cent of carbon, 7.I of hydrogen, I5.6 of nitrogen, 22.1 of oxygen, and a varying
quantity of sulphur not exceeding i.6 per cent. They
are found in animals as well as in plants, and there are
several similar compounds found only in animals.
The froteine bodies form the most essential articles of
food for animals, since, as we have learned, nitrogenized
compounds are indispensable to the repair of the machinery of the body. And for these, as for all other constituents of their food, animals are directly or indirectly
dependent on plants.
SUMMARY.
The atmosphere contains oxygen, nitrogen, carbonic
acid, and watery vapor, with traces of ammonia and
nitric anhydride.
Ordinary combustion, decay, and respiration are chemical processes, differing from one another mainly in the rapidity and the completeness with which they take place.
The division of substances into combustibles and suSpporters of combustion is convenient, though merely con



132    THE CHEMISTRY OF THE ATMOSPHERE.
ventional; since combustion consists in the chemical
union of two or more elements, and, in reality, one of
the elements is just as combustible as another.
The present materials of the earth, being mainly compounds of hydrogen and carbon with oxygen, and of the
metals with oxygen, chlorine, and sulphur, must be regarded as products of combustion.
The rusting of the metals is a process of slow combustion.
The products of combustion, decay, and respiration
are chiefly carbonic acid, water, and ammonia.
The growth of plants is a chemical process, carried on
in the leaf by the agency of the sunbeam. In growing,
plants remove from the air carbonic acid, water, and
ammonia. These compounds are broken up; the oxygen
in part given back to the air; and the other elements,
with the remaining oxygen, re-arranged so as to form
the various vegetable compounds.
By removing the products of combustion, and restoring oxygen, plants purify the air for the respiration of
animals.
Animals derive all their food, directly or indirectly,
from plants; while plants derive their food, directly or
indirectly, from the air.
Most of the natural vegetable products are compounds
of carbon, hydrogen, and oxygen; but some contain
nitrogen in addition to these, and are, therefore, called
nitrogenized compounds. Of the former class, the most
important are starch, sugar, dextrine, the vegetable acids,
the fats and oils, wax, the gums and resins, and the vegetable alkaloids; of the latter class, the proteine bodies,
including albumen, caseine, and fibrine. The latter are
the most essential articles of food for animals, since the
nitrogenized products make up almost the entire bulk of
the animal structure.




DESTRUCTIVE DISTILLATION AND,
ITS PRODUCTS.
I72. WVhen vegetable substances are heated in closed
vessels, so as to exclude the oxygen of the air, they are
broken up into a number of compounds, which vary with
the temperature to which they have been exposed.
When vegetable matter burns or decays, these organic
compounds, as we have seen, are broken up by the affinity of oxygen brought to bear upon them from without;
while in the other case they are broken up by the internal action of heat. In the first case, new compounds
are formed by the addition of new material; in the
second case, by subdivision, without any addition of new
material.  The first process is called combustion; the
second, destructive distillation.
I73. The Preparation of Charcoa. — We have a
very simple case of destructive distillation in the preparation of charcoal. This process may be illustrated by
putting pieces of dry wood into a flask, closed with a
cork, through which a glass tube passes.  This tube
passes into a cold glass bottle, and thence to a jar over
water.  Heat the flask, and the wood turns black.
The jar fills with an inflammable gas. Hold a cold
glass vessel over the flame of this gas, and moisture
collects upon it, showing that water is a product of the
burning of this gas.  Carbonic acid also is found to
be produced. This gas obtained from the wood must,




134         DESTRUCTIVE DISTILLATION.
therefore, be a compound of hydrogen and carbon. A
part of the carbon of the wood combines with hydrogen,
to form the inflammable gas; while the greater part remains behind as a black solid. This black residue is
charcoal, a form of carbon. If the heating is continued,
a liquid product is also obtained.
One way of preparing charcoal is to place billets of
wood in an iron cylinder, which is closed air-tight and
heated to dull redness. The volatile products are driven
off and allowed to escape through a flue, and the solid
charcoal remains behind.
A ruder method is practised in the country, where
wood is plenty. A stake is set in level ground, and
brushwood heaped about its base. Wood is then stacked
round the stake, so as to form a mound some 20 or 30
feet in diameter. This mound is then covered, first with
leaves or turf, and then with earth, leaving only a small
opening at the bottom, through which the wood is set
on fire. When the fire is well under way, the mound is
covered more deeply and allowed to burn slowly out.
This requires about a month. The burning of a part of
the wood furnishes heat for charring the rest.
I74. The Products of the Distillation of Wood. —
When hard wood, as beech, is subjected to destructive
distillation in a retort, and the volatile products are
condensed in a suitable vessel, four principal classes of
substances are formed: (I) gases; (2) a watery fluid;
(3) a dark resinous fluid; (4) charcoal.
(I) This product is a mixture of inflammable gases,
the most important of which are the two hydrocarbons
(or compounds of hydrogen and carbon), marsh-gas,
H4C, and oleftant gas, H2C.
(2) This product is an acrid liquid, known as f5yroligneous acid, or wood vinegar, which is used in the
manufacture of acetic acid.




DESTRUCTIVE DISTILLATION.           I35
(3) This product is wood tar, a thick liquid, insoluble
in water, but soluble in alcohol. Its chief use formerly
was for tarring and calking ships, but recently it has
become an important source of illuminating and lubricating oils. These oils will be described hereafter.
(4) This product is the charcoal remaining in the
retort. It is used chiefly as fuel and in reducing metallic ores.
175. Ingredients of Wood Tar. — When beech-wood
tar is distilled, a light oil passes over first, called euziion,
or wood naphAtza. It is now often sold under the name of
benzole, and used as a burning-fluid, for removing oilstains from clothes, and for countless other purposes. It
burns with a brilliant white flame, free from smoke; but
its extreme inflammability makes it a dangerous liquid
for lamps.
After this light oil has distilled over, a heavy oil follows. It contains various ingredients, the chief of which
are creosote and j5araffne.
I76. Creosote. — This is an oily, colorless liquid, with
a peculiar smoky odor. It has remarkable antiseptic (or
preservative) properties. A piece of flesh steeped in a
very dilute solution of it dries up into a mummy-like
substance, which refuses to decay. Meat, as tongues or
hams, may be almost instantly cured by dipping it into
a solution containing one part of creosote to Ioo parts of
water or brine. It is this substance which imparts to
wood-smoke its property of preserving meat. It is a
compound of carbon, hydrogen, and oxygen.
177. Paraffine. - This is a pearly-white, tasteless, and
odorless solid. The most corrosive acids and alkalies
have no effect upon it. Hence its name, from jiarum,
little, and affnis, from which affinity is derived.
It burns with a bright white flame, without smoke. It
is now much employed as a material for candles, which




I36         DESTRUCTIVE DISTILLATION.
for purity and lustre are not surpassed by even the best
wax candles.
Unsized paper, after having been soaked in paraffine,
may be kept for weeks in concentrated sulphuric acid
without undergoing the slightest alteration. Hence it is
an excellent coating for the labels of bottles in which
acids are kept.
I78. Asphalt.-Asphalt, or pitch, is the residue left
after distilling tar. It is used for varnishes, and as a
material for making lamp-black.
79. Slow Destructive Distillation. - When vegetable substances decay with a partial or complete exclusion of air, we have a kind of slow destructive distillation.
Hydrocarbon gases, which in some places escape from
the earth in large quantities, are one of the products of
this process; the well-known coal-oils are another; and
coal is a third. The gas obtained by stirring the mud
in marshes and at the bottom of stagnant pools is formed
in this way, and is made up chiefly of marsh-gas, H4C,
and carbonic acid, CO2.
I8o. The Formation of Mineral Coal. —In tropical
swamps where vegetation is rank, vast masses of vegetable matter accumulate, and gradually decay under water.
In some cases the land at the bottom of these swamps is
slowly sinking; and the bed of peat, as it sinks with it,
becomes covered with mud and sand, which numerous
streams are washing down upon it. This goes on, year
after year and century after century, until the bed is
buried hundreds of feet beneath the surface. The vegetable matter, thus sunk in the earth and subjected to
enormous pressure, gradually undergoes a process of internal combustion similar to that which takes place under
water. In many cases the decomposition is hastened by
the agency of the internal heat of the earth. It is probable that the vast beds of coal found in various parts of




DESTRUCTIVE DISTILLATION.          137
the earth have been thus formed. All this coal is the
remains of an ancient vegetation, and it undoubtedly required millions upon millions of years to complete its
conversion into coal.
I8i. Hard and Soft Coals. - The mineral coals may
be conveniently divided into hard, or anthracite, and
soft, or bituminous coal, and there are several varieties
of each.
The main differences between the two are these: hard
coal is almost pure carbon, while soft coal contains also
considerable hydrogen and some oxygen; hard coal still
retains the cellular structure of the wood, which is clearly
seen under the microscope, while in soft coal this cellular
structure is almost entirely wanting; hard coal burns
without flame, soft coal with flame.
182. Products of the Distillation  of Bituminous
Coal. - The products obtained by the destructive distillation of coal are still more numerous than those obtained
from wood. Wood, containing much oxygen and comparatively little nitrogen, furnishes compounds which
contain much acetic acid and little ammonia, and which,
therefore, have an acid reaction. Coal, on the other
hand, contains much nitrogen and little oxygen, and
gives products rich in ammonia, and having consequently an alkaline reaction.
When coal is distilled at high temperatures, an abundance of an inflammable gas is obtained, and also a large
amount of liquid products, which are then called tars.
When coal is distilled at a low temperature, little gas
is obtained, and the liquid products are then called oils.
183. The Comtiosition of Coal-tar. - Coal-tar has
been found to contain three classes of substances:
(i) Acid oils.
(2) Alkaline oils.
(3) Neutral oils.




138          DESTRUCTIVE DISTILLATION.
(I) The most important and abundant ingredient of
the acid oils is carbolic acid, C6H60. It is analogous to
creosote, and has even more powerful antiseptic properties. It is one of the most valuable disinfectants
known, and both the acid and the compound which it
forms with lime are now much used for this purpose.
It is also largely employed in dyeing silk and woollen
goods. The dye-stuff is prepared by heating carbolic
acid moderately with nitric acid, and is called picric
acid. On evaporating this liquid, yellow scaly crystals
are obtained. Like all the tar colors, its dyeing qualities, when in solution, are most intense. Silk and woollen goods put into the solution, even when cold, assume
a rich yellow color, far surpassing that of other dyes.
(2) The alkaline oils constitute but a small fraction
of the tar. Their most important ingredients are ammonia and aniline, C8HTN.
Aniline is an oily substance which, when acted upon
by compounds which readily part with oxygen, furnishes
a complete series of the most brilliant dyes. The preparation of these rich dyes from aniline is one of the
most interesting discoveries of modern times, and has
caused almost a revolution in the arts of dyeing and
calico-printing. It is still more surprising when we consider that these brilliant colors are obtained from what
was until recently a disagreeable waste product of the
gas-works. When first prepared, they were worth their
weight in gold; now, they can be bought at a comparatively moderate price.
Their dyeing qualities are so intense, that a little material goes a great way; so that, notwithstanding their
high price, they are more economical than other dyes.
(3) The neutral oils are the coal-oils proper. They
contain a great variety of compounds, both liquid and
solid, the latter being held in solution. Of the liquids,




DESTRUCTIVE DISTILLATION.          I39
6enzole, toluole, and cumole are the most important; and
of the solids, parajfne and napZhthaline.
I84. Benzole and Nitro-6enzole. - Benzole is a very
important compound, as it is the material from which
aniline is usually prepared. The symbol for benzole is
C6H6. When mixed with concentrated nitric acid, it
loses one atom of H, and takes one of NO2 in its place,
and becomes nitro-benzole, C6H5NO2.
Nitro-benzole is the artificial oil of bitter almonds,
and is much used in the art of perfumery. Its most important use, however, is in the preparation of aniline.
When heated with acetic acid (C2H402) and iron filings,
it loses two atoms of oxygen and takes up two of hydrogen, and is converted into aniline, CA6HN.
185. Toluole and Canzole. — Toluole, C7H8, and
cumole, C9H12, are the chief ingredients of the wellknown illuminating or lamp oils obtained from coal.
I86. XNaphthaline. - Naphthaline is a beautiful, pearlywhite solid. It is inflammable, but burns with a smoky
flame and a disagreeable odor. Brilliant red and blue
colors, rivalling those prepared from aniline, have lately
been obtained from this solid.
When vegetable matter is distilled at a high temperature, benzole and naphthaline are formed in great abundance, with but small quantities of toluole, cumole, and
paraffine. When, on the other hand, the distillation is
conducted at a low temperature, toluole, cumole, and
paraffine are formed in large quantities, with but little
benzole and naphthaline.
COAL-OILS.
I87. At the beginning of the present century, the
means of lighting our dwellings consisted, in the main,
of poor tallow candles and dim and dirty oil-lamps. On




I40         DESTRUCTIVE DISTILLATION.
the continent of Europe, whale-oil and other animal oils
were costly, and resort was had to natural tar and bituminous slate, in order to obtain illuminating oils. For
more than twenty years past, lamp-oils have there been
extensively prepared from wood, rosin, and bituminous
matter.
In Great Britain and in this country the manufacture
of coal-oils is of much more recent growth, because the
extensive whale-fisheries supplied all the wants of the
market.
The manufacture of coal-oil was introduced into this
country in I853, and was at first confined to those districts where bituminous coal could be mined at a cheap
rate.
Soon after this manufacture was established in this
country, and after the value of coal-oils came to be fully
recognized, attention was drawn to tetroleum, or rockoil, as a ready means of supplying these oils cheaply. On
examination, this oil was found to be analogous, in its
composition and its properties, to that obtained by the
destructive distillation of soft coal and other bituminous
substances.
I88. Thze Orzgin of Petroleum. -All scientific men
are agreed that the petroleum found in the earth results
from the decomposition of organic matter, and nearly all
are agreed that it results mainly from the decomposition
of vegetable matter. It is, however, a disputed point,
whether it results from the original decomposition of the
vegetable substances, or from the action of the internal
heat of the earth on the bituminous coal at a subsequent
period.
It is probable that the petroleum now found in the
earth is the product both of the original decomposition
and of subsequent distillation. Petroleum is, however,
rarely found in contact with bituminous strata of any




DESTRUCTIVE DISTILLATION.           I4I
kind. It is more often found in fissures in sand rocks;
rocks in which no oil could ever have been generated,
since whatever organic matter they might have contained
was too much exposed to atmospheric oxygen to admit
of its being bitumenized, or made bituminous. It is not
only impossible that the oil could have originated in these
sand rocks, or in the sandy shales which underlie them
in the oil region in Western Pennsylvania; but it is most
probable that the oil ascended from still lower rocks in
the form of vapor, which condensed in the cavities above.
Since, then, petroleum is seldom found where it originated, but, ordinarily, in cavities of rocks higher up, it
seems probable that it is mainly the product of distillation.
The chemical conditions essential to the generation of
oil have evidently existed over a very wide area; but the
oil is found only where fissures exist in the rocks. These
fissures serve two purposes: one, to give space for the
formation and expansion of the hydrocarbon vapor; the
other, to furnish receptacles for the condensed oils.
These fissures must connect with the sources of the oil.
If they have any outlets at the surface of the earth, by
which the more volatile portions of the oil may escape as
gas, the oil within them becomes thicker and heavier.
Hence, as a general rule, the oil found near the surface
is heavy, the cavities containing it being likely to have
outlets. It may, of course, happen that a deeply-seated
fissure has such an outlet.
I89. How Petroleum  is obtained.- The oil is obtained by piercing one of these cavities by a well. It
often happens that the upper part of the cavity is filled
with pent-up uncondensible gases. In this case, if the
well happens to pierce the lower part of the cavity, the
expansive force of the confined gases will drive the oil
from the well in a continuous stream. Oil is often forced




I42         DESTRUCTIVE DISTILLATION.
from a new well with such velocity, that it rises in a jet
a hundred feet high.
It sometimes happens that the lower part of the cavity
is filled with brine, upon which the oil floats. If, in this
case, the well pierces the lower part of the cavity, brine
is the first product. After a time the salt-well may
change to an oil-well.
COAL - GAS.
90o. The MJanufacture of Coal- Gas. — The idea of
turning hydrocarbon gases to the practical purposes
of illumination occurred at about the same time to
Murdock, in England, and Lebon, in France. This was
in I790; but for a long time there was a strong popular
feeling against the new light. In England, it was not
until I8I2 that Parliament consented to charter a company for its manufacture. Even then the enterprise was
looked upon as so visionary, that the act of incorporation
was said to be granted in order to make a great experiment of a plan of such extraordinary novelty. In
December, 1813, Westminster Bridge was first lighted
with gas. From this time gas-lighting made the most
rapid progress in England; and now the consumption of
gas in London alone amounts to more than seven billions
of cubic feet annually. To make this gas, eight hundred
thousand tons of coal are required; while the length of
the main pipes in the streets of the city is more than two
thousand miles.
Paris was first lighted with gas in I820. There, as in
England, strong prejudices had to be overcome.
The most essential parts of the apparatus used in the
making of coal-gas are represented in Figure 28.
Of course, it is only soft or bituminous coal that can
be used for making gas. This coal is distilled in long




DESTRUCTIVE DISTILLATION.              I 43
iron retorts, seen at the left of the figure. When charged
with coal, these retorts are closed air-tight. They are
i 11iii,
Il                     a
then heated to a very high temperature by the furnaces
beneath.




I44         DESTRUCTIVE DISTILLATION.
The gaseous and volatile compounds, formed by the
distillation of the coal, pass up through pipes (one of
which may be seen leading from each retort) into a long
horizontal pipe, M, called the /hydraulic main. This is
half full of water, into which the pipes from the retorts
dip.  The gas readily escapes from the pipes by bubbling up through the water; but, of course, it cannot
return through the water.
The gas is carried from the hydraulic main through a
pipe into a tank, T, called the tar cistern. By this time
the more condensible gases have become liquid, and
collect in the smaller vessel into which the pipe passes,
and from which they overflow into the larger tank.
From the latter they are drawn off at intervals. These
condensed products are coal-tar and a liquid highly
charged with ammonia, called ammoniacal lizuor.
The uncondensed gases pass on through the series of
upright pipes at C, called the condenser. Here they
become still further cooled, and all the remaining condensible gases are reduced to the liquid state.
After leaving the condenser, the gas still contains, besides the compounds fit for illuminating purposes, the
noxious compounds carbonic acid and hydric sulphide
(49). These are removed in the purifer, P. It consists of a chamber with several perforated shelves, which
are covered with slaked lime. In passing over this lime,
the carbonic acid and hydric sulphide are absorbed, while
the purified gas passes along into the gasometer, G.
This gasometer consists of a large sheet-iron bell-jar,
which dips into a cistern of water. The latter is deep
enough to allow the bell to be completely submerged,
and filled with water. The bell is counterpoised with
weights, and rises as the gas enters it.
From the gasometer the gas passes out, by the pipe
at the right, into the streets and houses of the city.




DESTRUCTIVE DISTILLATION.          145
ILLUMINATION.
I9I. Nature of Flame. — We know  that coal-gas
burns with flame, while the solid carbon burns without
flame. All combustible gases burn with flame.
We have seen that wood, when heated in a closed tube,
gives off an inflammable gas; and the same is true of
wax or tallow heated in the same way. Every solid
which appears to burn with flame can thus be converted
into an inflammable gas by means of heat. When these
solids begin to burn, the heat developed is sufficient to
generate this inflammable gas. It is this gas, and not
the solid, which burns with flame.
Flame, then, is gas burning.
I92. A  Solid and Heat are necessary to Illumination. - The oxy-hydrogen flame (22) develops intense
heat, but scarcely any light. If, however, a cylinder of
lime be held in this flame, we get the brilliant calcium,
or Drummond light.
We see, then, that a solid and an intense heat are
necessary to illumination.
I93. These two Conditions arefufilled in the Burning of Coal- Gas. - Illuminating gas, as we have seen,
is a compound of carbon and hydrogen. If we hold a
cold glass rod in a gas-flame, it becomes blackened with
soot, showing that there is free carbon in the flame. We
therefore conclude that the hydrogen of the gas combines
with the atmospheric oxygen first. In doing so, it develops great heat.
In the manufacture of charcoal, the delicate cells of
the wood are preserved intact; showing that the carbon, at the high temperature to which it is exposed
in the process, has no disposition to melt. Its infusibility is its most marked characteristic (4I).
Io




146         DESTRUCTIVE DISTILLATION.
When the hydrogen of coal-gas combines with the
oxygen of the air, the carbon is set free in a solid state.
As the hydrogen consumes all the oxygen in the nearest
layer of air, the carbon must delay a moment in the flame
before it can get at oxygen to unite with. This finely
divided solid thus becomes heated white-hot, and gives
out light. This condition lasts but an instant. The next
instant the carbon combines with atmospheric oxygen,
and passes off as a colorless gas. As fast, however, as
the carbon is consumed, a fresh supply is set free, and
thus the light is constantly kept up.
The value, then, of coal-gas for illumination depends
upon a most delicate adjustment of affinities.
Were the affinity of carbon for oxygen a little stronger
than it now is, the carbon would burn at the same time
with the hydrogen, and there would be no light in the
flame. On the other hand, were the affinity of carbon
for oxygen less than it is, the carbon would not burn at
all, but, after developing light, would pass away from the
flame in the form of soot.
194. Bunsen's Lamp. -The fact that carbon must
Fig. 29.   remain an instant in the flame in the
solid state to develop light, is illustrated
by Bunsen's burner. It is shown in Figure 29, and consists of a brass tube, near the
bottom of which are four round holes,
through which the air can pass into the
tube. A second tube opens into the inside
of the brass tube from  the bottom, just
on a level with these holes. The coal-gas
passes into the larger tube, through this
second tube. The air passes in through the holes at
the same time, and the two gases become intimately
mixed before they reach the top of the tube. Upon
lighting the mixture as it escapes from the tube, it burns




DESTRUCTIVE DISTILLATION.          I47
with scarcely any light, but a good deal of heat. If we
close the holes at the bottom of the tube, the gas burns
with the ordinary luminous flame.  In the first case,
there is an excess of oxygen mixed with the coal-gas,
so that there is enough to combine with the carbon as
soon as it is set free, before it becomes sufficiently heated
to develop light. In the second case, the carbon cannot
get at the oxygen to combine with it, until it has passed
through the burning layer of hydrogen, and thus become
intensely heated.
I95.'The Best Shaje for a Gas-Flame. -From
what has been said, it is evident that the light of the
flame is developed only at the surface, in the burning
layer of hydrogen. The ordinary gas-burner is so made
that the flame will be flat, in order that it may have as
much surface as possible. The greater the surface, the
greater the light developed.
I96. The Argand Burner. — A sheet of paper will
evidently present to the air just as much surface when it
is bent round till the two edges meet, as when it is flat;
while in the second case it is in a more compact form.
So the ordinary gas-flame will present just as much surface, if its edges are bent round till they meet. In the
Argand burner, this form is given to the flame, by supplying the gas through a circle of small holes in a hollow brass ring. A current of air passes up through this
ring, furnishing oxygen to the inner surface of the flame.
I97. The Bude Light. - If the interior of the ring of
an Argand burner be closed, the flame becomes of a dull
red color. Since no oxygen is supplied to the inner
surface of the flame, the combustion is imperfect, and
develops but a low degree of heat.
If, on the other hand, a stream of pure oxygen be supplied to the interior of the cylindrical flame, the flame
diminishes in size; but the light becomes very intense,




I48         DESTRUCTIVE DISTILLATION.
and of a pure white color. The increased supply of oxygen increases the energy of the combustion of the hydrogen, and the intensity of the heat developed by it. In the
first case, the carbon is heated only to a dull redness,
while in the second case it is raised to a full white heat.
I98. A Burning Candle is a miniature Gas-:Factory. — We have seen that wax or tallow, when heated
in a flask, is converted into an inflammable gas. This
gas, in burning, produces water and carbonic acid;
hence it must contain hydrogen and carbon, which are the
main ingredients of coal-gas. This gas is in fact identical
with coal-gas. The heat of the burning match converts
some of the wax of the candle into gas, which takes fire,
and in burning develops sufficient heat to convert more
of the wax into gas; and thus the supply is kept up.
199. The Flame of a Candle consists of three distinct Parts. — In the flame of a candle there are three
distinct parts: (I) the dark central zone, or supply of
Fig. 30.  unburnt gas surrounding the wick; (2)
the luminous zone, or area of incomplete combustion; and (3) the nonluminous zone, or area of complete
combustion. If we put one end of a
small glass tube (see Figure 30) into
the dark central zone, the unburnt gas
will pass up the tube, and may be
ignited at the other end. In the luminous part of the flame, as in the case
of the gas-flame (I93), the gas is not
completely burnt, and carbon is separated in the solid state; and it is this carbon heated
white-hot which renders the flame luminous. In the
outer zone the supply of oxygen is greater; all the carbon
is at once burnt to carbonic acid, and the flame here
becomes non-luminous.




DESTRUCTIVE DISTILLATION.          I49
SUMMARY.
Vegetable compounds may be broken up by destrucfive distillation.
In the preparation of charcoal, wood is decomposed
into carbon and a number of volatile compounds.
When these volatile products are cooled and condensed, we obtain: (I) permanent gases; (2) a watery
fluid; (3) a dark resinous fluid.
(I) The permanent gases are chiefly marsh-gas, H4C,
and olefant gas, H2C.
(2) The chief ingredient of the watery fluid is pyrolizgneous acid, or wood vinegar.
(3) The dark liquid is wood tar.
The most important ingredients of wood tar are wood
naphtha, creosote, jSaraffne, and asShaft.
Mineral coal has probably been formed by the gradual
decomposition of vegetable matter buried in the earth, and
thus excluded from the air; the decomposition in many
cases being hastened by the internal heat of the earth.
When the volatile products were allowed to escape
freely, anthracite coal was formed; when they could not
escape, bituminous coal was formed.
The volatile products often escaped into large cavities
in the rocks, and on condensing gave rise to the celebrated rock-oil, or j5etroleum.
In some cases, this oil may have been formed by the
decomposition of the vegetable matter at a temperature
too low for its conversion into vapor, and may afterwards
have been distilled by the internal heat of the earth.
The products of the destructive distillation of bituminous coal are more numerous than those of the distillation of wood. They are less rich in compounds containing
oxygen, but richer in those containing nitrogen.




150         DESTRUCTIVE DISTILLATION.
When the coal is distilled at a high temperature, a
large amount of gas is obtained, and the liquid products
are then called tars. When the coal is distilled at a low
temperature, only a small amount of gas is obtained, and
the liquid products are called oils.
When the gas obtained by the distillation of coal is
purified, it forms the well-known illuminating gas.
The most important ingredients of coal-tar are carbolic
acid, ammonia, aniline, benzole, toluole, cumole, para/ine, and nap hthaline.
The aniline colors are prepared chiefly from benzole.
Only gases burn with flame. Solids that appear to
burn with flame are first converted into a gas by heat,
and this gas burns with flame.
The two conditions essential to illumination are the
presence of a solid and intense heat.
The illuminating gases are all hydrocarbons, or compounds of hydrogen and carbon.
The hydrogen has the stronger affinity for oxygen, and
burns first. The carbon is set free in a solid state, and
delaying for an instant in the intense heat of the flame,
before combining with oxygen, becomes luminous.
The light of the flame is increased (I) by increasing
the surface of the flame, as in the ordinary gas-flame,
and that of the Argand burner; and (2) by increasing
the intensity of the combustion of the hydrogen, as
in the Bude light.
The heat of the flame is increased by mixing oxygen
with the gas before it burns, so that the carbon and hydrogen may burn together, as in the Bunsen burner.
The burning candle or oil-lamp is a miniature gasfactory.
The candle flame consists of three parts: (I) an inner
zone of unburnt gases, surrounded by (2) a luminous
zone of incomplete combustion, outside of which is (3) a
non-luminous zone of complete combustion.




FERMENTATION.
200. Causes of Fermentation. - Complex organic
compounds are often broken up into simpler compounds
by the agency of growing plants. This process is called
fermentation, and the organisms which effect it are
calledferments. Different ferments give rise to different
products, as alcohol, vinegar, etc.  Most of these ferments are plants, but one at least is an animal; and this,
strange to say, cannot live in contact with free oxygen,
but flourishes in an atmosphere of hydrogen. In order
that the ferment should grow, it must be supplied with
proper food, especially with ammoniacal salts and alkaline phosphates.  These are contained in the albuminous matter generally present in the liquid about to be
fermented. In order that the fermentation should go on
well, the temperature should be from 7o0 to I00oo; at
much higher, as at much lower temperatures, the vitality
of the ferment is destroyed.
In many cases, spontaneous fermentation sets in without the apparent addition of any ferment: thus wine,
beer, milk, etc., when allowed simply to stand exposed
to the air, become sour or otherwise decompose. These
changes are, however, not effected without the presence
of vegetable or animal life, and are true fermentations.
The spiorules, or seeds of these living bodies, are always floating in the air, and on dropping into the liquid
begin to propagate themselves, and in the act of growing
evolve the products of the fermentation. If the liquid




I 2               FERMENTATION.
be left only in contact with air which has been passed
through a red-hot platinum tube, so that the living
sporules are destroyed; or if the air be simply filtered
by passing through cotton-wool, so that the sporules are
prevented from coming into the liquid, it is found that
the liquid may be preserved for any length of time without undergoing the slightest change.
The principal forms of fermentation are -
(I) The alcoholic fermentation, producing chiefly alcohol and carbonic acid.
(2) The acetous fermentation, producing acetic acid.
20o. Alcoholic Fermentation. - Sugar, if dissolved
in presence of yeast (which is a plant and a ferment),
undergoes fermentation, evolving mainly alcohol and
carbonic acid:
C12H24012  4C2H60 (alcohol) + 4CO2.
About 6 per cent of the sugar undergoes a different
change, part being used as nourishment for the yeast,
and part forming glycerine and other compounds. The
alcoholic fermentation is best effected at a temperature
between 77~ and 86~.
When the cereal grains are used for making alcohol,
the starch of the grain is first converted into sugar. This
change may be brought about by the action of sulphuric
acid, as already explained (I6I); but, practically, it is
usually effected by means of diastase.
202. The Formation of Diastase in Growing Plants,
-We have learned that the seed contains a supply of
starch which is the food of the embryo plant until it is
able to derive its sustenance from the earth and the air.
We have learned, too, that this starch must be converted
into sugar, in order that it may be dissolved in the sap of
the plant and carried where it is needed for the purposes
of growth. Let us now see how the starch is changed to




FERMENTATION.                   153
sugar. The seed contains more or less of the nitrogenized compound, gluten (I42). This, under the influence
of heat and moisture, begins to putrefy, and    Fig. 31.
a portion of it is converted into the ferment
diastase.  This has so powerful an action
upon starch, that one part of it, at a temperature of I500, is sufficient to convert 2000 parts
of starch into dextrine and then into sugar.
We can now understand how a seed, like
the acorn (Figure 3I), germinates. If we
cut the acorn open, we see the radicle (at the
right in the figure), and the two thick cotyZedons, or seed-leaves, containing
the starch and gluten. In the moist
warm soil the acorn absorbs a little     X
water, and the gluten is thus
changed into diastase, which converts some of the starch into
sugar.  The radicle absorbs                   i
this sugar, and uses it to make
woody fibre.  It is thus enabled to thrust out a little root
and begin to draw food
from the earth, as well
as from the starch in the 1:
seed. It next sends out
the plumule, a little stem
with its first leaves
unfolding  to  the:
air and light.  It              has now  the means of
deriving its nour-              ishment both from  the
earth and the air, and is no longer dependent upon the
seed, which soon withers and perishes. Both root and
stem are now rapidly developed (145-I54), and thus at
length the acorn becomes the mighty oak.




I54               FERMENTATION.
203. Brewing. — The brewer avails himself of this
natural change in the germinating seed, and calls into
action on a larger scale the chemical influence of diastase.
The grain commonly used for the purpose is barley.
This is first moistened in heaps, and spread out in a dark
room to heat and sprout. When the gluten has begun to
be transformed into diastase and the starch into sugar, so
that the germ is about to burst from the envelop of the
seed, the growth is arrested by heating the grain, and
thus killing the embryo plant.
The malt, as the barley is now called, is next bruised,
and soaked in warm water in the masz-tu6. The water
dissolves first the sugar which has already been formed
in the seed, and then the diastase. The latter acts upon
the rest of the starch of the seed, and of any raw grain
which may be added to the malt, converting it into sugar,
so that little, except the husk of the grain, is left undissolved; and the liquor, or worn, has a decidedly sweet
taste.
The wort is now heated to boiling, to stop the action
of the diastase, and to coagulate the albumen which has
been dissolved out of the grain. At the same time, hops
are added to the wort; and these, besides giving a bitter
aroma to the liquid, help to clarify it. The boiled liquor
is then filtered, and drawn off into shallow vessels, where
it is cooled down to about 60~. Yeast is now added, and
the mixture is allowed to ferment for six or eight days.
This fermentation is never allowed to continue until
all the sugar is converted into alcohol. From one-half
to three-fourths of it is decomposed; and the rest is left
to give a sweet taste to the beer, and also to keep it
from souring in the cask.
The liquor is next put into casks, where it goes through
a second and much slower fermentation, which is essential to its preservation. When this fermentation is com



FERMENTATION.                   I55
pleted, the cask must be closed tight, to exclude the air,
the oxygen of which would cause acetouzs fermentation.
During this second fermentation, the carbonic acid is
generated, to which the liquor owes its sparkling effervescent character.
204: The Distillation of Spirits. - When fermented
liquors are boiled, the alcohol they contain rises in the
form of vapor, mingled with steam. If the boiling be
performed in a close vessel, and the vapors be led by a
pipe into a cold receiver, they condense into a liquid,
containing a large percentage of alcohol. This process
is called distillation, and the apparatus for carrying it
on is called a still.
If the alcoholic liquor thus obtained be re-distilled, or
rectzifed, a spirit may be obtained, containing go per
cent of alcohol and io of water. This is the strongest
commercial alcohol. If this be mixed with calcic chloride, which has a strong affinity for water (I I3), and then
be re-distilled, pure or absolute alcohol may be obtained.
We have seen that, in making beer, the fermentation
of the wort is checked before all the sugar is converted
into alcohol. But, in the manufacture of spirits from
grain, the fermentation is prolonged until all the sugar is
transformed into alcohol and carbonic acid. To leave
any of it unchanged, would not only involve a loss of
spirit, but, during the subsequent distillation, might injure the flavor of the spirit obtained.
The alcohol obtained from the fermentation of sugar is
sometimes called wine alcohol, or vinic alcohol, to distinguish it from a large number of similar compounds,
known to chemists as alcohols. Its symbol is C2H60.
205. Ether. —When equal weights of strong alcohol
and oil of vitriol are boiled in a retort, a colorless, fragrant, and highly volatile liquid passes over, called ether,
or suljZhuric ether, CHloO.  It is called sulZ5huric




I56               FERMENTATION.
ether, to indicate its origin, and to distinguish it from
other analogous compounds called ethers.
When poured on the hand, ether produces a strong
sensation of cold, owing to the rapidity with which it
evaporates, rendering heat latent.  It is very inflammable, and burns with a white flame. Its vapor forms
explosive mixtures with air or oxygen. It dissolves oils,
fats, and resins far more readily than alcohol does. It
also dissolves sulphur, phosphorus, and iodine. When
inhaled in sufficient quantity, its vapor is an anesthetic,
and was the first substance used for that purpose by
physicians.
Acetic ether is obtained by distilling a mixture of
alcohol, sulphuric acid, and acetic acid. It is used in
medicine. If nitric acid be used, we get nitric ether,
which is well known under the name of sweet spirits
of nitre. Several of the ethers exist in a natural state
in fruits, giving them their peculiar flavors.
206. Acetic Acid. —If alcohol, diluted with water,
be mixed with a ferment, as yeast, and exposed to the air
at ordinary temperatures, it is soon converted into acetic
acid, or vinegar. The alcohol absorbs 2 atoms of oxygen, forming water and acetic acid:C2oH60 + 02 - 20 + C2H402 (acetic acid).
This process constitutes what is commonly called the
acetous fermentation.  Since the alcohol is oxidized, it
is in a certain sense a combustion that takes place. It is,
however, brought about by the influence of a ferment,
known as the vinegar-.plant, or mother of vinegar.
There are a great many methods of making vinegar on
the large scale; but, for the most part, they are only different devices for exposing to the air as large a surface as
possible of the alcoholic mixture. In one process, the
liquid is allowed to trickle down through vats, filled with




FERMENTATION.                 I57
flat pieces of wicker-work, piled one upon another.
These are first watered with vinegar, or liquid partially
converted into vinegar, and thus become covered with
the germs of the vinegar-plant. Air is admitted through
holes in the bottom of the vats, and passes out at the top,
after giving up a part of its oxygen to the alcohol. Heat
is produced by the oxidation, and this causes an upward
draught, and quickens the circulation of air through the
vats.
In another process, the weak alcoholic liquor trickles
down through perforated casks, filled with beech shavings, which have been thoroughly scalded to remove all
soluble matter. Air is admitted by holes around the
lower part of the cask, and passes out at the top.
When vinegar is purified, and concentrated by distillation, it constitutes the acetic acid of commerce. This
is prepared on a large scale from -pyroligzneous acid,
or wood vinegar (I74), which is obtained by the destructive distillation of wood.
207. JBread-making. —  The making of bread in the
ordinary way, by means of leaven or yeast, is an example
of alcoholic fermentation.
When the grain of wheat is ground in a mill, and then
sifted, it is separated into two parts, the bran and the
/lour. The bran is the outside harder part of the grain,
which is not ground so readily, and, when ground, makes
the flour darker. Both the bran and the flour consist
mainly of gluten, starch, and water.
If the flour be mixed with water enough to moisten
it thoroughly, the particles cohere and form a doug'h,
which can be kneaded or moulded with the hand. It
is the gluten of the flour which gives the tenacity to
the dough.
A little leaven or yeast is added to the flour, either
before it is mixed with water into a dough or in the




I58               FERMENTATION.
course of this process; and the dough is then placed for
some hours in a warm atmosphere, in order that it may
rise. This rising is a fermentation, caused by the leaven
or yeast. Leaven is the primitive ferment, and is simply
a piece of moistened, dough which has begun to putrefy.
When brought in contact with a fresh portion of flour
and water, it very quickly acts as a ferment, and develops
fermentation in the whole mass. Yeast, as has been
stated, is one of the vegetable growths which are ferments (200, 20I).
The leaven or yeast soon begins to act on the gluten,
starch, and sugar of the flour, and a portion of the sugar
is converted into carbonic acid and alcohol in every part
of the dough. The bubbles of gas, thus disengaged in
the mass, form innumerable cavities, and make it light
and porous.
The spongy dough is now put into a hot oven, where
the fermentation and swelling are at first increased by the
heat; but when the whole has been heated to about 2I2~0,
the fermentation is suddenly arrested, and the mass becomes fixed in the form it has then attained. In the baking, some of the water is dissipated from the dough, the
starch and gluten are partially boiled, and some of the
starch is converted into dextrine. The brown, glossy
appearance of the crust is due to this formation of dextrine (I62). Most of the alcohol is driven off by the
heat; but a large amount of water (about 45 per cent of
the weight of the bread) remains in the loaf after the
baking.
There are various methods of making bread without
fermentation, most of which depend on the liberation of
carbonic acid from one of its compounds, by means of an
acid. Bicarbonate of soda and muriatic acid are the materials sometimes used. Cream of tartar, which is a
compound of tartaric acid (I65), is often used as the acid.




FERMENTATION.               159
The salt and acid are usually mixed with the dough, and
the carbonic acid there set free; but in the manufacture
of the so-called aerated bread, water charged with the
gas is used in making the dough.
SUMMARY.
Fermentation is the breaking up of complex organic
compounds into simpler ones, by the agency of certain
plants called ferments.
The alcoholic fermentation takes place in sugar, and
produces alcohol and carbonic acid.
In making alcoholic liquors from grain, the starch
of the grain is converted into sugar, by the action of
diastase, as in the germination of seeds. The sugar is
then converted into alcohol by the use of a ferment, as
yeast.
The alcohol of fermented liquors may be separated
from the water, and concentrated by distillation.
By the action of acids upon alcohol, important compounds called ethers are obtained.
The acetous fermentation takes place in alcohol, which
undergoes oxidation, producing vinegar, or acetic acid.
The making of bread with yeast is an example of
alcoholic fermentation.








APPENDIX.
CHEMICAL PHILOSOPHY.
ATOMS AND MOLECULES.
I. Molecular and Atomic Constitution. —The astronomer
finds that the universe is made up of stars, or suns, each of
which is probably, like our own sun, the centre of a solar system nade up of planets. These solar systems are the larger
units, or individuals, of the universe; and the planets are the
smaller units of which these systems are composed. Some of
these smaller units, as Venus and Mars, are simple; others, as
the Earth and Jupiter, are complex, being made up of a planet
and one or more moons. We now believe that all the bodies
about us are made up of units analogous to these. The physicist
finds matter to be made up of separate and distinct masses, or
units, which lie calls molecules. He cannot see these even with
the aid of the microscope; but he is as certain of their existence
as the astronomer is of his planets and solar systems.  The
chemist pulls these molecules in pieces, and finds that they are
made up of smaller units, which he calls atoms or comjpound
radicals, according as they are simple or complex. He believes
that in most cases the molecules of the elements, as well as of
compounds, are made up of two or more atoms; the only difference being, that in the one case the atoms are all alike,
while in the other they are not. Thus a molecule of hydrogen
is believed to be made up of two atoms of hydrogen; while a
molecule of water is made up of two atoms of hydrogen and one
of oxygen. When a molecule of water is broken up, it ceases to
be water, and becomes hydrogen and oxygen. Hence we may
II




I62                     APPENDIX.
define a molecule as the smallest mass of a substance which can
exist by itself; and an atom as the smallest mass of any substance
which can exist in a molecule.
The molecules of a body are bound together by cohesion, and
the atoms by affnity. The state of a body depends upon the
strength of the cohesive force. When this force binds the molecules together firmly, they form a solid; when very weakly, a
liquid; and when not at all, a gas. The molecules of a solid, as
a general rule, tend to arrange themselves in regular order, so
as to build up symmetrical forms called crystals. These crystals
have usually the same form for the same substance, but very
different forms for different substances.
It is probable that the atoms when bound together by affnity
tend to arrange themselves with equal regularity; but as yet we
are ignorant of the mode of arrangement. Indeed, the number
of atoms in the molecules of many substances is as yet a matter
of mere hypothesis.
2. Molecular Weight. - When the molecules of any body are
so far apart that the cohesive force exerts no constraint upon
them, the substance is called a true gas. When the molecules
are still somewhat under the restraint of cohesion, but not
bound together by it, the substance is called an imperfectgas,
or vapor. Now there are two characteristics of all true gases,
which throw light upon their molecular constitution. " First,
all true gases obey the same law of compressibility. Second!y,
equal volumes of all true gases expand equally on the same increase of temperature." The repulsive force, then, which acts
among the molecules, and tends to keep them apart, or to separate them, is the same for all true gases. This has led to the
conclusion that equal volumes of all trtue gases have the same
number of molecules. We can therefore readily find the molecular wezght (that is, the relative wezght of their molecules) of all
those substances which can by heat be converted into true gases,
by weighing equal volumes of these gases under the same pressure and temperature.
There are, however, many substances which cannot be
brought into a gaseous state.  To determine the molecular
weights of these substances, we must find their atomic constitu



APPENDIX.                       I63
tion, and the atomic weights of their elements. Suppose, for
instance, that we do not know the molecular weight of water,
but do know that a molecule of water contains two atoms of
hydrogen and one of oxygen, and that the atom of hydrogen
weighs I and the atom of oxygen i6. The molecular weight of
water must then be i6 +- 2 or I8.
In finding the molecular weight of different substances, they
are all compared with hydrogen, whose molecular weight is assumed to be 2. The following table gives the molecular weights
of several gases, all of which contain hydrogen; also the relative
weight of the hydrogen in each molecule: —
Molecular Weight of           Molecular Weight of
Weight. Hydrogen.             Weight. Hydrogen.
H              2        -     H2S            34        2
HC1           36.5      I     H3N            I7       3
HBr           8I        I     H3P            34       3
HI           128        I     H3As           78       3
H20           I8        2     H4C2           28       4
H4C           I6        4
3. Atomic Weights. -When any element forms a number of
compounds which can be brought into the gaseous state, we find
its atomic weight by first finding the molecular weight of these
compjounds, and then analyzing these comnzounds, so as /o find the
wezght of the common element in each molecule, or, what amounts
to the same thing, in equal volumes of the gases.
Thus, in the above table, it is found that when HC1 is decomposed, it gives half its own volume, or, in other words, half its
own number of molecules, of hydrogen. Hence a molecule of
HCl contains haZf a molecule, or one part by vweight, of hydrogen. The same is found to be true of HBr and HI. Water gas
is found on analysis to give its own volume, or, in other words,
its own number of molecules, of hydrogen. Hence each molecule
of water contains a *whole molecule, or two jarts by weight, of
hydrogen. The same is found to be true of HS. Again, H3N
gives one and a half its ozvn volme of hydrogen. A molecule of
ammonia, then, contains one and a half molecules, or three parts
byweight, of hydrogen. The same is true of H3P and H3As.
Again, H4C (marsh-gas) gives twice its own volume of H; and




164                    APPENDIX.
each of its molecules must therefore contain two molecules, or
four pSarts by weight, of H.
In this way, it is found that oneparl by wezigt' is the smallest
quantity of hydrogen found in a molecule of any of its compounds. Hence I is taken as the atomic weight of hydrogen;
and since the molecular weight of hydrogen has been assumed
as 2, each of its molecules must contain 2 atoms.
In a similar way, it has been found that the molecular weight
of nitrogen is 28, and its atomic weight I4. "1 This method of
investigation can be extended to a large number of the chemical
elements, and the conclusions to which it leads are evidently
legitimate, and cannot be set aside until it can be shown that
some substance exists whose molecule contains a smaller mass
of any element than that hitherto assumed as the atomic weight,
or, in other words, until the old atom has been divided."
This method is, however, applicable only to those elements
which form a number of gaseous or volatile compounds. In
other cases, the number of atoms in a molecule is a matter of
inference merely. Whenever analogous elements, as iodine,
bromine, fluorine, and chlorine, combine with the same element,
we infer that the molecules formed have the same atomic constitution, especially if the compounds have the same crystalline
form and similar chemical relations. Of course, if we know the
atomic constitution of a compound, and the atomic wezght of one
of its elements, we can find the atomic weight of its other elements.
Suppose, for instance, we know that the molecule of baric
chloride contains one atom of barium and two of chlorine, and
that the atomic weight of chlorine is 35.5, we find on analysis
that baric chloride contains 137 parts by weight of barium to 7I
of chlorine, 7I = 35.5 X 2 =the weight of two atoms of chlorine.
Hence the weight of the one atom of barium must be I37.
" Nevertheless, it is true in very many cases that our conclusion in regard to the number of atoms which a molecule may
contain is more or less hypothetical, and hence liable to error
and subject to change. This uncertainty, moreover, must extend to the atomic weights of the elements, so far as they rest
on such hypothetical conclusions."




APPENDIX.                      I65
Experiment, however, has shown that it is generally true that
the elementary atoms have the same speczfic heat; that is, if
we take of different elements quantities proportionate to their
atomic weights, and which therefore contain the same number
of atoms, the same amount of heat wvill raise them all the same
number of degrees in temperature; in other words, it takes just
as much heat to raise I atom of hydrogen I degree in temperature as it does to raise I atom of nitrogen, oxygen, or any other
element I degree.
Hence, when we are in doubt as to the atomic weight of any
element, we can sometimes settle the question by its speczjfc heat.
QUANTIVALENCE AND ATOMICITY.
4. Quantivalence. -When the atoms of different elements
replace one another in a compound molecule, it is found that
while in some cases' atom of an element may replace I of
another, in other cases it may replace 2, 3, or 4 atoms of another.
Thus, when hydric chloride and argentic nitrate act upon each
other, we have the following change:AgNO3 + HCI = AgCl + HNO3.
Here I atom of Ag changes place with I of H.
When Zn acts upon H2SO4 we have
H2SO4 + Zn = ZnSO4 + H2.
Here I atom of Zn replaces, and is equivalent to, 2 atoms of H.
Again, in the reaction between water and phosphorous chloride, we have -
3H20 or H8H303 + PC13- H3PO3 + 3HC1.
Here I atom of P replaces, and is equivalent to, 3 atoms of H.
" This relation of the elements to each other is called by Hofmann quantivalence; and selecting here, as in the system of
atomic weights, the hydrogen atom as our standard of inference,
the atoms of different elements are called univalent, bivalent,
trivalent, or quadrivalent, according as they are, in the sense
already indicated, equivalent to I, 2, 3, or 4 atoms of hydrogen.




I66                    APPENDIX.
These terms are very appropriate, since they are all derived from
the same root as our common English word equzivalent, which
best expresses the fundamental idea which underlies the whole
subject."
The quantivalence, whenever important, may be indicated by
a Roman numeral placed over the atomic symbols; thus, -
I   II   II   IV
C1,  O,  N,  C.
5. Atomicily. - "The quantivalence of an element is shown,
not only by its power of replacing hydrogen atoms, but also by
its power of replacing any other atoms whose quantivalence is
known. Moreover, what is still more important, the quantivalence of an element is shown not only by its replacing power,
but also by what we may term its atom-yfxing tower; that is, by
its power of holding together other elements in a molecule.
We may take as examples the molecules of four very characteristic compounds; namely, hydrochloric acid, water, ammonia,
I    II   II       IV
and marsh-gas," whose symbols are HCl, H20, H3N, and H4C.
" By these symbols it appears that, while the univalent atom of
chlorine can hold but I atom of hydrogen, the bivalent atom of
oxygen holds 2, the trivalent atom of hydrogen 3, and the quadrivalent atom of carbon 4 atoms of the same element."
"The quantivalence of the chemical elements, especially as
indicated by their atom-fixing power, is by no means always the
same. That of the univalent elements alone is constant. They
always combine with single atoms..... But the other elements
frequently exhibit, under different conditions, an unequal atomII        IV   III       V
fixing power. Thus we have SnC12 and SnC14, PC13, and PC15,
III       V
NH3 and NH4C1.  Each element, however, has a maxzinum
power, which it never exceeds. This we shall call its atomicity;
and we shall distinguish the elements as monads, dyads, triads,
etc., according to the number of univalent atoms they are able at
most to bind together. Thus nitrogen is a pentad, although it
is commonly trivalent; and lead is a tetrad, although it is
usually bivalent."
The prevailing quantivalence of an element is a more charac



APPENDIX.                      I67
teristic property than its atomicity. The former is generally
well established, while the latter is frequently still in doubt.
6. Qualntivalence of Radicals. - "Vhen in the molecule of
any compound the dominant or central atom is united to as many
other atoms as it can hold of that kind, the molecule is said to
be saturated. Thus HC1, H20, H3N, and I-4C are all saturated
I II
molecules. On the other hand, the molecules CO, PC13, and
II
SnC12 are not saturated; for they can combine directly with more
oxygen or chlorine, forming thus the saturated molecules CO2,
PC15, and SnC14." It will be seen that CO, PC1,3, and SnC12 are
bivalent radicals, since they can each hold the equivalent of two
atoms of hydrogen. The CO can hold an additional atom of
oxygen, and PCI3 and SnCl2 can each hold two additional atoms
of chlorine. The quantivalence of an atom of C is 4, and that
of an atom of O is 2; and the difference of these is 2, the quantivalence of the radical CO. In general, the quantivalence of a
binary radical is the dzference of the quantivalences of its elementary atoms. Thus, the quantivalence of N is 5, and that of 02 is
4; and that of the radical NO2 is I. The quantivalence of SO2
is 2, that of S being 2, and that of 02 being 4. The quantivalence of PO is 3, that of P being 5, and that of O being 2.
The quantivalence of C102 is I. This radical illustrates the
way in which elements often seem to combine. The 2 atoms of O
unite with each other, and thus neutralize 2 of their equivalents,
leaving 2 unsaturated. Now I of these is neutralized by the
C1, leaving I unsaturated. Thus C102 becomes a univalent.
CHEMICAL TYPES.
7. Types of Chemical Compounzds. - " There are three modes
or forms of atomic grouping to which so large a number of substances may be referred, that they are regarded as molecular
types or patterns, according to which the atoms of a molecule
are grouped together..... The three compounds, hydroI    II        III
chloric acid, water, and ammonia, HC1, H20, and H3N are
generally taken as the representatives of these types; and substances are said to belong to the type of hydrochloric acid, to




i68                   APPENDIX.
the type of water, or to the type of ammonia, as the case may
be.... It will be noticed that in the first of these types a single
univalent atom or radical is united to another single univalent
atom; that in the second, a bivalent atom binds together two
univalent atoms, or their equivalents; that in the third a trivalent atom binds together three univalent atoms, or their equivalents."
8. Condensed Types. — " In the same way that a bivalent atom
may bind together two univalent atoms or their equivalents, so
also it may serve to bind together two molecules; and, in like
manner, a trivalent atom may bind together three molecules into
a more complex molecular group; and thus are formed what are
called condensed types."
9. Metallic Chlorides. -All the metallic chlorides, fluorides,
bromides, iodides, and cyanides may be considered as belonging
to the muriatic acid type. In those of the monad metals, there
is no condensation, or soldering together of molecules. Thus
we have —
HC1 (muriatic acid).
AgC1 (argentic chloride).
Here one atom of hydrogen in a molecule of HC1 may be regarded as replaced by an atom of a univalent metal.
The chlorides, etc., of the bivalent metals may be regarded as
formed by the soldering together of 2 molecules of HC1 by a
bivalent atom which replaces the H. Thus, —
HCI (two molecules of muriatic acid).
Ca    =   Cl2 (calcic chloride).
The chlorides, etc., of the trivalent metals may be regarded as
3 molecules of HCl, soldered together by a trivalent atom, which
has replaced the H. Thus, —
HCl I
HC1. (three molecules of muriatic acid).
HC J
C1l
Au C1  = AuCl3 (auric chloride).
C1




APPENDIX.                      I69
The chlorides, etc., of the quadrivalent metals may be regarded as four molecules of HC1, soldered together by a quadrivalent atom which replaces the H. Thus, -
HCI
HCl  (four molecules of muriatic acid).
HC1 J
C1
C1
Pt C1    = PtC14 (platinic chloride).
C1
The symbol of alumiz'c chloride is A12C16. Here, although
Al is quadrivalent, A12 is only sextivalent, not octivalent. Two
atoms of C1 seem to combine with each other, and thus neutralize 2 of their 8 equivalents. There are several cases like this.
Chromium, iron, manganese, uranium, and some other metals
are both bivalent and quadrivalent. When quadrivalent, they
combine like aluminium. Thus we have -
Cr2C16, chromic chloride.     Mn2Cl6, manganic chloride.
Fe2Cl6, ferric chloride.     [ U2C16, uranic chloride.
As bivalents, they form the following chlorides: —
CrCl2, chromous chloride.     MnC2, manganous chloride.
FeC12, ferrous chloride.     | UC12, uranous chloride.
The bivalent mercury forms the two chlorides, HgCl2, mercuric chloride, and Hg2Cl2, mercurous chloride. In the last, the
2 atoms of Hg combine with each other, and thus neutralize
2 of their 4 equivalents, leaving the other 2 to be neutralized by
the C12. The bivalent copper is like mercury in this respect.
Io. Bases. - The bases belong to the water type, and may be
regarded as made up by replacing a part of the H of the H20
by an equivalent of a metallic element. In the bases of the
univalent metals, I atom of H is replaced by I of the univalent
metal. Thus, -
HHO =H20.
KHO = potassic hydrate.




170                   APPENDIX.
The bases of the bivalent metals are of a condensed type, 2
molecules of H20 being soldered together by a bivalent atom,
which replaces an atom of H in each. Thus, -
H2H202  2H20
CaH202 = calcic hydrate.
The bases of the trivalent metals are also condensed in type,
3 molecules of H20 being soldered together by a trivalent atom.
Thus, -
H3H303 = 3H20.
AuH303 = auric hydrate.
The quadrivalent aluminium forms a base by soldering together 6 molecules of H20 with 2 trivalent atoms. Thus, -
H6H60 = 6-H20.
A12H606  aluminic hydrate.
It will be seen that this hydrate is analogous to the aluminic
chloride already explained. In the same way, chromium, iron,
manganese, and uranium, as quadrivalents, form the hydratesCr2H606, chromic hydrate.
Fe2H606, ferric hydrate.
Mn2H606, manganic hydrate.
U2H606, uranic hydrate.
As bivalents, they form the bases -
CrH202, chromous hydrate.
FeH202, ferrous hydrate.
MnH202, manganous hydrate.
UH202, uranous hydrate.
Mercury also forms two bases, HgH202 and Hg2H202, corresponding to its two chlorides.
ii. Basic Oxides. -Basic oxides belong to the water type,
and may be regarded as formed by replacing all the H of one or
more molecules of H20 by an equivalent of metal.




APPENDIX.                      17 I
In the un'valent oxides, 2 equivalents of H are replaced by
2 univalent atoms. Thus, -
H20 = water.
Ag20 = argentic oxide.
In the bivalent oxides, 2 equivalents of H are replaced by I
bivalent atom. Thus, -
H20 = water.
CaO = calcic oxide.
In the trivalent oxides, 6 equivalents of H are replaced by
2 trivalent atoms, which bind together 3 molecules of H20.
Thus,
H603 = 3H20.
Au203 = auric oxide.
A1203, alumninic oxide, Fe2O3, ferric oxide, Cr203, chromic oxide,
Mn2O3, manganic oxide, and U203, uranic oxide, are formed in
the same way as the trivalent oxides; 2 of the metallic equivalents in each case being neutralized by the metal itself, as in
their chlorides and hydrates. All these metals, except Al, form
regular bivalent oxides, whose names take the ending -ous. Hg,
besides its bivalent oxide, HgO, forms a mercurous oxide, Hg20.
i2. Acids. -The oxyacids belong to the water type, and may
be regarded as formed by replacing a pbart of the H of one or
more molecules of H20 by an equivalent of a non-metallic element or radical.
Nitrous acid is formed by replacing 3 atoms of H in 2 molecules of H20 by I of the trivalent N. Thus, —
HH302 = 2H20.
HNO2 = nitrous acid.
Nitric acid may be formed by replacing I atom of H in I
molecule of H20 by the univalent radical NO2. Thus, -
HHO = H20.
HNO20 = HNO3 (nitric acid).




172                    APPENDIX.
In ckhorous acid, I atom of H is replaced by the univalent radical C10. Thus, -
HHO=- H20.
HC1OO = HC102.
If the atom of H be replaced by the univalent C102, we get
HC103, chloric acid.
When 2 molecules of water are soldered together by the bivalent 0, we get H2SO02 or H2SO3, sulszhurous acid. If the
bivalent SO2 solders the 2 molecules of H20, we get H2SO202
or H2SO4, suilhuric acid.
When 3 molecules of H20 are soldered by the trivalent P or
As, we get H3PO3, jhhosp2horous acid, and H3AsO3, arsenious
acid. If the 3 molecules of H20 are soldered by the trivalent
PO or AsO, we get H3PO4, pjhosjphoric acid, or H3AsO4, arsenic
acid.
Boracic acid, HBO2, is formed by replacing 3 atoms of H in 2
molecules of H20 by the trivalent B.
Silicic acid, H4SiO4, is formed by replacing 4 atoms of H in
4 molecules of H20 by the quadrivalent Si.
Carbonic acid, H2CO0, is formed by replacing 2 atoms of H in
2 molecules of H20 by the bivalent CO.
I3. Anhydrides. — The anhydrides belong to the water type,
and are formed by replacing all the H of one or more molecules
of H20 by an equivalent of a non-metallic element or radical.
Thus,HHO = H20.
I   I
NO2 NO20 =N206 (nitric anhydride).
H20 = water.
COO = CO2 (carbonic anhydride).
Ii
SO20 = SO3 (sulphuric anhydride).
H3H303= 3H20.
III III
POPOO3 = P205 (phosphoric anhydride).
I4. Salts.- When the H of a base is replaced by a nonmetallic element or radical, or the H of an acid by a metallic
element or radical, a salt is formed. Thus, —




APPENDIX.                      I73
KHO gives KC10 (potassic hypochlorite).
NaHO gives NaNO20 =NaNO03 (sodic nitrate).
CaH202 gives CaSO202 = CaSO4 (calcic sulphate).
CaH202 gives CaCO02  CaCO3 (calcic carbonate).
Again, -
HNO3 gives KNO3 (potassic nitrate).
H2SO4 gives CuSO4 (cupric sulphate).
H3PO4 gives K3PO4 (potassic phosphate).
The nitrates of the metals are analogous to the chlorides,
with NO3 in place of the C1. The sulhhates are analogous to
the oxides, with SO4 in place of the 0. Thus, -
KC1       KNO3 (potassic nitrate).
CaC12    Ca2NO3 (calcic nitrate).
A12C16   A126N03 (aluminic nitrate).
K202      K2SO4 (potassic sulphate).
CaO       CaS04 (calcic sulphate).
A1203    A123SO4 (aluminic sulphate).
The chlorates are like the nitrates; and the carbonates like
the suZl}hates, with C03 in place of SO4.
The sztrphides are like the oxides.
I5. Substitution. —"  When cotton-wool is dipped in strong
nitric acid (rendered still more active by being mixed with twice
its volume of concentrated sulphuric acid), and afterwards
washed and dried, it is rendered highly explosive; and, although no important change has taken place in its outward
aspect, it is found on analysis to have lost a certain amount of
hydrogen, and to have gained from the nitric acid an equivalent
amount of nitric peroxide, NO2, in its place."
C12H20010 (cotton) becomes C12H14(NO2)6010 (gun-cotton).
Under the same conditions, glycerine undergoes a like change,
and is converted into the explosive nitro-glycerine.
C6H1606 (glycerine) becomes C6H1o(NO2)606 (nitro-glycerine).




I 74                    APPENDIX.
So also the hydro-carbon, naphtha, called benzole, is changed
into nitro-benzole.
C6H6 (benzole) becomes C6H5(NO2) (nitro-benzole).
"The last compound is not explosive, and the explosive
nature of the first two is, in a measure, an accidental quality,
and is evidently owing to the fact, that into an already complex
structure there have been introduced, in place of the indivisible
atoms of hydrogen, the atoms of a highly unstable radical, rich
in oxygen. The point of chief interest for our chemical theory
is that this substitution does not alter, at least profoundly, the
outward aspect of the original compound. Every one knows
how closely gun-cotton resembles cotton-wool. In like manner, nitro-glycerine is an oily liquid, like glycerine; and nitrobenzole, although darker in color, is a highly aromatic, volatile
fluid, like benzole itself. Products like these are called substitution jroducts; and they certainly suggest the idea that each
chemical compound has a certain definite structure, which may
be preserved even when the materials of which it is built are, in
part, at least, changed. If, in the place of firm iron girders, we
insert weak wooden beams, a building, while retaining all its
outward aspects, may be rendered wholly insecure. And so the
explosive nature of the products we have been considering is not
at all incompatible with a close resemblance, in outward aspects
and internal structure, to the compounds from which they are
derived."
I6. Isomorphism. -" Closely associated with the facts of the
last section, which find their chief manifestation in substances
of organic origin, are the phenomena of isomorpkhism, which are
equally conspicuous among artificial salts and native minerals.
There seems to be an intimate connection between chemical
composition and crystalline form, and two substances which,
under a like form, have an analogous composition, are said to
be isomorthous."  The following minerals are isomorphous:Calcite, or calcic carbonate,      CaCO3
Magnesite, or magnesic carbonate, MgCO3
Chalybdite, or ferrous carbonate,    FeCO,
Diallogite, or manganous carbonate, MnCOa




APPENDIX.                       I75
"The most cursory examination of these symbols will show
that they differ from each other only in the fact that one metallic
atom has been replaced by another. It is not, however, every
metallic atom which can thus be put in without altering the
form. This is a peculiarity which is confined to certain groups
of elements, which for this reason are called grou zs of isomor5hous elements. Moreover, as a rule, there is a close resemblance between the members of any one of these groups in all
their other chemical relations. These facts, like those of the
last section, tend to show that the molecules of every substance
have a determinate structure, which admits of a limited substitution of parts without undergoing essential change, but which
is either destroyed or takes a new shape when, in place of one
of its constituents, we force in an unconformable element. A
well-known class of artificial salts called the alzms affords even a
more striking illustration of the principles of isomorphism than
the simpler examples we have chosen."
I7. Isomerismn, A4llorojpism, and Polymorpkism.-" We should
infer from the doctrine of chemical types that the same atoms
might be grouped together in different ways, so as to form different molecules, which, in their aggregation, would present
essentially distinct qualities. Hence we should expect to find
distinct substances having the same composition, and, in fact,
our science, organic chemistry especially, is rich in examples of
this kind. Such substances are said to be isomeric, and the
phenomenon is called isomerism."  Thus, common sugar and
gucm arabic have exactly the same composition, C12H22011, and
are isomeric.
When, however, the differences are not sufficiently great to
justify a distinct name, the two bodies are said to be different
allotroz'ic states of the same substance, and the phenomenon is
called allotropism. Thus, there are three varieties of tartaric
acid which differ in their action on polarized light, but which
are in almost every other respect identical.
Sometimes a substance crystallizes in fundamentally different
forms, as calcic carbonate in the minerals calcite and aragonite.
This phenomenon is called jpolymorp1hism, and is invariably
accompanied by a marked difference of properties.




I76                    APPENDIX.
Differences of this kind, even more marked, are found among
elementary substances, and give strong grounds for believing
that these elements may be really composite.
ELECTRICAL RELATIONS OF THE ELEMENTS.
I8. When the electric current is passed through any compound
liquid which is a conductor of electricity, the liquid is decomposed; its atoms, or radicals, travelling in opposite directions
towards the two poles. Thus, when the current is sent through
muriatic acid, the hydrogen atoms go towards the negative pole,
or cathode, and the chlorine atoms towards the positive pole, or
anode. There are certain elements and radicals which, like
hydrogen, always go towards the negative pole; and certain
others, like chlorine, which always go towards the positive pole.
The former are called electro-j5ositive, and the latter electro-negative elements. There are other elements which in some of
their compounds are electro-positive, while in others they are
electro-negative. The electrical relations of the elements are
best shown by grouping the elements in series, so that each
member of the series shall be electro-positive when in combination with the elements which follow it, and electro-negative
when combined with those which precede it. It is found that
the non-metals are always negative when combined with the
metals, which are then positive. The electrical relations of the
metals show that hydrogen, although a gas, and the lightest
substance known, is really a metal. It is the one gaseous metal,
as mercury is the one liquid metal.
CLASSIFICATION OF THE ELEMENTS.
Ig. The Metals. -The electrical relations of the elements, as
well as their formation of bases and acids, show that there is a
fundamental distinction between metals and non-metals. "The
characteristic qualities of a metal, with which every one is more
or less familiar, are the so-called metallic lustre, that peculiar
adaptability of molecular structure known as malleability or
ductility, and the power of conducting electricity or heat. These
qualities are found united and in their perfection only in the true




APPENDIX.                        I77
metals, although one, or even two of them, are well developed
in several elementary substances, which, on account of their
chemical qualities, are now almost invariably classed among
the non-metals; as, for example, selenium, tellurium, arsenic,
antimony, boron, and silicon."
20. Scheme of Classification. -m  The classification of the elementary atoms which has been adopted in this book is shown
in the table on page i8o. The atoms are classed, in the first
place, in six families, according as in their usual condition they
are equivalent to one, two, three, four, five, or six atoms of
hydrogen. These families are subdivided into groups, separated
by bars in the table, of closely allied elements. The atoms of
any one of these groups are isomorfpous, and they are arranged
in the order of their weights, which is found to correspond also,
in almost every case, with their electrical relations. Each group
forms a very limited chemical series; and not only the weights
and the electrical relations of the atoms, but also many of the
physical qualities of the elementary substances vary regularly as
we pass from one end of the series to the other. The order of
the variation, however, is not always the same; for while, in
some cases, the lightest atoms of a series are the most electronegative, in other cases they are the most electro-positive."
DOUBLE DECOMPOSITION.
21. The salts, both binary and ternary, are ordinarily formed
by a double transfer of elements, as shown in the following
equation: -
I        II        II
H2SO4 + BaH202 = BaSO4  211H20.
Such a double transfer of elements is called double decomposilion.
The change which takes place is usually called simply a reac0ioZt.
On mixing any two solutions, such a change will always take
place, when an insoluble or volatile compound would thereby be
formed.
In working out the following reactions, it must be borne in
mind that it is always the metals which change places; and that
12




I78                    APPENDIX.
they must always be in equivalent quantities. It is better in all
cases to indicate by the proper mark the combining power of
the elements which are to replace each other. Before beginning
to work the problems of the next section, the student should be
able to read and explain all the equations given below, and
especially to give the reason for the number of molecules used
in each case. If more molecules than one are used in any case,
it is always in order that the combining units of the elements
which replace each other may be equal.
I        It        I        II
H2S   + Pb2NO3=2HNO3 +PbS.
I       II       II        I
2HNO3+ BaH202 = Ba2NO3-+ 2H20.
I       III       I        III
3H2S  +2AsC13 =6HC1  +As2S3.
III       I       III        I
BiCla  +3KI   =-BiJ3   +3KC1.
I      II        II
2HC1 +Pb2NO=-2HNO3+ PbC12.
I        II      I          I
2AgNO3 + C aC 12 = C a2NO3 + 2AgC 1.
II       II       It        II
CaSO4 + Ba2NO3 — Ca2NO3+ BaSO4.
PROBLEMS.
I. Show the reaction between plumbic nitrate and sodic
hydrate.
Pb2NO3+ 2HNaO=PbH202 + 2NaNO3;
that is, plumbic nitrate filus sodic hydrate gives plumbic hydrate
thlfs sodic nitrate.
2. Plumbic nitrate and sulphuric acid.
3. Cupric sulphate and potassic hydrate.
4. Manganic sulphate and sodic hydrate.
5. Zincic sulphate and potassic hydrate.
6. Cobaltic nitrate and sodic hydrate.
7. Manganic sulphate and ammonic carbonate, (H4N)2CO8.
8. Baric nitrate and ammonic carbonate.
9. Calcic sulphate and ammonic carbonate.
Io. Strontic nitrate and calcic sulphate.




APPENDIX.                      I79
II. Aluminic sulphate and ammonic hydrate.
I2. Ferrous nitrate and ammonic hydrate.
I3. Hydric chloride and argentic nitrate.
I4. Hydric chloride and plumbic nitrate.
i5. Hydric chloride and mercurous nitrate.
I6. Hydric sulphide and argentic nitrate.
17. Hydric sulphide and plumbic nitrate.
iS. Hydric sulphide and mercurous nitrate.
19. Argentic nitrate and potassic iodide.
20. Potassic iodide and plumbic nitrate.
21. Potassic iodide and mercurous nitrate.
22. Stannous chloride (SnC12) and hydric sulphide.
23. Stannic chloride (SnC14) and hydric sulphide.
24. Bismuthic chloride and hydric sulphide.
25. Stannous chloride and potassic hydrate.
26. Auric chloride and hydric sulphide.
27. Mercuric chloride and hydric sulphide.
28. Platinic chloride and potassic iodide.
29. Auric chloride and potassic iodide.
30. Cupric sulphate and hydric sulphide.
3I. Mercuric chloride and potassic iodide.
32. Cupric sulphate and potassic iodide.
33. Aluminic chloride and ammonic hydrate.
34. Baric chloride and ammonic carbonate.
35. Calcic chloride and ammonic carbonate.
36. Baric chloride and sodic hydrate.
37. Strontic chloride and calcic sulphate.
38. Argentic nitrate and ammonic hydrate.
39. Argentic nitrate and sulphuric acid.
40. Cadmic chloride and hydric sulphide.
If additional problems are desired, they can be easily prepared
by the teacher.
The Table on the following page is from Professor Cooke's
" First Principles of Chemical Philosophy." All the direct quotations in this chapter are from the same book, our great indebtedness to which has already been acknowledged in the Preface.




TABLE.
UNIVALENTS.                     TRIVALENTS.
Metals. |                                        - E
o.~    0  Metals.   o.. [   o'
1-                     -
Hydrogen    I.  H-H        I   Gold        197.0 Au-Au   III
Lithzkzm     7.oj L'-i  I     Non-Metals.
Sodium      23.0 Na-Na   I,,
Potassium         K 39. I K-K  Boron        II.O0  B?,,
Rubidium    85.4 Rb-Rb,,   Nitrogen    14.0 N-N  IIIorV
Cwesium    I33.0  Cs-Cs,,   Phosphorus 3.o0 P2-P2,,
Silver     Io8.o Ag-Ag,,   Arsenic       75.olAs2-As2 0.
ThZlium   204.  Ti-Ti I or III Antimony  I22.0 Sb2-Sb2,,
Bismuth   210.0 Bz2-Bi2,,
Non-Metals.                                    - 2 
Fluorine    19.  F-F       I         QUADRIVALENTS.
Chlorine    3551 Cl-Cl,,       Metals.
Bromine    8o.o Br-Br 
Iodine     I27o  I-I            Aluminium  27.4  Al?    IV._   7_0 - _   _   Chromium   52.2  Cr? IIorIV
Cerium      92.0  Ce,,
BIVALENTS.             Uranium    I20.0  U?.______. __-   R ut/henium  1044 Ru?,,
Metals.                      Osmzium    199.2  Os,
Calcium     40.0  Ca      II   Rhodium    104.4  R,,
Strontium   87.6   Sr,    ridium     I96.0  Ir
Barium     I37-.0  Ba,   Palladium  io6.6 Pd?
Lead       207.0  Pb   IIorIV Platinum   197.4  P1?,
Magnesium  24.0  Mg       II   Titanium    5o.o  Ti  IV
Zinc        65.2  Zn,,   Tin        I8.  Sn?,,
Indizm      72.0  In,   Zirconium   89.6 Zr?,,
Cadmium   112.0  Cd,,   Thorium    23I.5 Th?,,
Glucinum     9.3  G?9,I    Non-Metals.
rtrium      61.7   r?
Erbium       112.6  E?         Carbon      I2.0  C       IV
Lan/hanum  93.6  La             Silicon     28.0  Si,,
Didymium n 95.0  D                   QUINTIVALENTS.
Manganese  55    Mn  IIor IV
Iron        56.o  Fe,,       Metals.
Nickel      58.8  Nt              iobium    94.            V
Cobalt      58S.  Co                i Tanalum   IS2.0  Ta_ 9,,
Copper      634  Cu       IITa 
Mercury   200.0  Hg        1,         SEXTIVALENTS.
Non-Metals.                      Metals.
Oxygen      I6.o   0              Ma
Sulphur    32.0   S   II orVI Molybdenum 96.0o Mo?    VI
Seleniutm    794   Se          Tungsten  I84.0  W?,,
Tellurium  128.o  Te,   Vanadiun  137.0  V?,




NOTES ON EXPERIMENTS.
APPARATUS.
The following list includes all the apparatus needed for the
more important experiments in this book: —
I. Pneumatic trough. - Gases which are not absorbed by
water, or but slightly so, can be collected by first filling the
vessel with water, and inverting it with its mouth under water.
The tube through which the gas is escaping is introduced under
the mouth of the jar, and the gas rises and fills the jar.
For collecting gases in this way, a pneumatic trough is useful
and almost indispensable. This apparatus consists of a vessel
deep enough to allow of filling and inverting under the water
any of the jars ordinarily used. A shelf perforated with holes
extends across the vessel about an inch under the surface of the
water. After the jar is filled with water and inverted, it is set
upon the shelf over one of the holes. The delivery tube (which,
except the part passing through the cork, may be of rubber) is
then passed into this hole, and the jar filled. It is convenient
to have a shelf large enough to hold several jars, after they have
been filled with gas.
The best pneumatic trough is made of soapstone or copper;
but any vessel which will hold water and has a perforated shelf
will answer the purpose. The teacher can easily provide himself with such a trough at little expense.
2. Two glass cylinders: one, I inch in diameter and 5 inches
deep; the other, IA inches in diameter and 7 inches deep. These
should have ground mouths and be provided with ground-glass
plates for covers.




I82                     APPENDIX.
3. Two two-quart glass jars, with ground mouths and ground
plates for covers.
4. Two nipper-taps. A nipper-tap is a convenient substiFig. 32.               tute for a stop-cock.
By means of it a
rubber tube can be
pinched close. The
best kind is shown
<_F:      >j<(full size) in Fig-ure
32. The tube is com—.. —----------  -      pressed by a spring.
5. One two-gallon india-rubber gas-bag. This may be closed
with a rubber cork, through which passes a short glass tube,
connected with a second glass tube by a short piece of rubber
tubing, which may be closed with a nipper-tap. Such an arrangement is cheaper than a stop-cock, and better, since gases
sometimes corrode the latter.
6. A bottle generator. This consists of a wide-mouthed pint
bottle, closed with a rubber cork, through which pass two tubes;
one, large and straight, and passing nearly to the bottom; the
other, small, and bent at right angles, passing only through the
cork. An ordinary cork will answer, but rubber corks are
always to be preferred for chemical apparatus. They cost more
at first, but they last much longer, and make perfectly tight
joints.
7. Three half-pint flasks. One, at least, of these should have
a rubber cork through which passes a bent delivery-tube.
8. An iron lamp-stand with three rings.
9. A lamp. A Bunsen's lamp is much to be preferred where
gas is to be had; otherwise, an alcohol lamp.
Io. A wooden retort-holder with two clamps.
II. A hydrogen generator. The most convenient apparatus
for preparing hydrogen is the self-regulating generator shown
in Figure 33. It consists of a glass vessel closed with a metallic
cap. A bell-shaped glass vessel, open at top and bottom, is fastened to this cap by an air-tight joint. A tube closed by a stopcock passes through the cap into the bell-shaped vessel.  A
copper bucket' perforated with fine holes is hung from a hook




APPENDIX.                      I83
inside this vessel. This bucket is filled with    Fig. 33.
shreds of sheet zinc or bits of granulated zinc.
The outer vessel is filled about two-thirds full
of dilute sulphuric acid (the ordinary oil of i
vitriol diluted with about ten parts of water).
The metallic cap with the bell-glass attached
is then put in its place, and the stop-cock
opened.  The air is first driven out, and the
dilute acid coming in contact with the zinc
begins to act upon it, and hydrogen is given
off in abundance.  When sufficient hydrogen
has been obtained, the stop-cock is closed, the
hydrogen generated collects in the upper part
of the bell-glass, and drives the acid out. As soon as the acid
is driven out, the action ceases until the stop-cock is opened
again, and the hydrogen allowed to escape. By means of rubber
tubing, the hydrogen can be conveyed friom the generator to the
jar or vessel in which it is to be collected. When hydrogen
is to be burned, the greatest care must be taken that all the air
is driven out of the apparatus before the gas is collected.
I2. A chlorine tube. This is a glass-tube, 3 of an inch in
diameter, and i$ inches long, closed at one end. The other end
should be provided with a rubber cork, through which passes a
glass tube drawn out to a fine jet inside. This should be connected with a small glass funnel by means of a short piece of
rubber tubing, which may be closed by a nipper-tap.
13. Two small beakers.
I4. Two evaporating dishes.
15. A U-tube (Figure 5). One end of the tube should be
closed, and near this closed end two platinum wires should
pass through the sides so as nearly to meet within. These
wires should terminate outside in loops.  It is not necessary
that the U-tube should be tubulated at the bend, as represented
in the figure, or fastened to a stand, since it may be held in the
clamp of the retort-holder.
I6. A chalk cup. This is a cylinder of chalk, about Ist inches
in diameter and 2 inches high, hollowed out at the top.
I7. Awash-bottle. This is like No. 6. The rubber tube which




I84                      APPENDIX.
is delivering the gas should be connected with a glass tube small
enough to pass down through the straight glass tube to the
bottom.
I8. A nitric-oxide bell and jar. The bell is half the capacity
of the jar, and the mouths of both are ground, so as to fit together air-tight.
I9. An asbestos tube.
20. A half-pint tubulated retort.
21. A dozen 5-inch test-tubes.
22. Half a pound of glass tubing, i of an inch in diameter.
23. 4 feet of rubber tubing, i of an inch in diameter.
The following additional apparatus will be needed for experiments with the oxy-hydrogen blowpipe:Two 25-gallon gas-bags, with stop-cocks and tubing.
An oxy-hydrogen jet.
A copper flask for making oxygen.
EXPERIMENTS.
I. (~ I, Exp. I.)  Use bottle generator (No. 6 in list of apparatus above). The end of the long tube must be kept beneath
the surface of the acid. The acid is diluted with 2 or 3 parts of
water. The hydrogen may be collected in the small glass cylinder (No. 2); but the gas which first comes off must not be collected, as it is mixed with air, and therefore explosive.
2. (~ I, Exp. 2.) Use flask (No. 7) with rubber cork. Pour
in strong muriatic acid first, so that none of the dry manganese
may stick to the flask. Use only a small quantity of the materials, as the chlorine is very disagreeable if it escapes into the
room. It is well to have a large jar filled with water, ready to
receive any chlorine that may come off after the small cylinder
has been filled. It will be well also to let the gas which first
comes off pass into this jar until the air is expelled from the
flask. The flask should be supported on the ring of the lampstand (No. 8), and should be separated from the flame, either by
a sand-bath or, better, by a piece of fine wire gauze.
3. (~ I, Exp. 3.)  Use the smaller glass cylinder (No. 2).
Let the hydrogen pass in first until it is half full, and then fill




APPENDIX.                      I85
the remainder with chlorine. Close the cylinder under water
with the glass plate, bring it near the lamp, remove the glass
plate, and quickly put the mouth of the cylinder into the flame.
The explosion is not very violent with these small quantities.
Never attempt to use large quantities, and be careful to keep the
mixed gases out of direct sunshine.
Another way of per-                 Fig. 34.
forming the experiment
is to use two cylinders of
the smaller size (No. 2),
filling one with hydrogen
and the other with chlorine. Cover them with the
glass plates, and  place
therm together, mouth to
mouth, as represented in
Figure 34.  Then with-  __
draw  the  glass plates,  
keeping the mouths of -
the  cylinders  together,
shake the cylinders to mix the gases, and open them over a.
burning lamp, as shown in Figure 35.
4. (~ 2, Ext. i.)  The              Fig. 35.
sodium used must be pure,
else there is danger of an
explosion.  The smaller
cylinder (No. 2) must be
used  and  held  in the
clamp of the retort-holder    
(No. io).  The sodium
may be first thrown upon
the water, and then thrust
under the cylinder by means of a perforated metallic cup, which
may be made out of a thimble by punching a few holes through
the top, and fastening a wire round it for a handle.
5. (~ 2, Exp. 2.) The water may be saturated with chlorine
by putting it in a wash-bottle (No. I7), and allowing the chlorine to pass through it as long as it is taken up by the water.




I 86                   APPENDIX.
The delivery-tube of the bottle should be connected with a jar
over the water-trough, in order that no chlorine may escape into
the room. The chlorine water thus prepared may be put in the
larger cylinder (No. 2), inverted in a soup-plate of water, and
set in the sunshine.
6. (~ 2, Exp. 3.) Fill one of the jars (No. 3) with oxygen,
and let it stand over the trough long enough to drain. Burn the
hydrogen as it escapes from the generator (No. ii) through a
glass tube bent at right angles and drawn out to a fine jet; and
hold the jar of oxygen over the flame.
Glass tubing may be bent by heating it red-hot in the flame
of the lamp. A tube may be drawn out to a fine jet by heating
the middle red-hot, and then quickly pulling the ends apart. It
may be cut by scratching it a little on one side with a threecornered file, and then bending it over the thumb-nails, held
close together on the side opposite the scratch.
7. (~ 3, Exj5. I.) Fill chlorine tube (No. I2) with chlorine
over the water-trough. Close the mouth while under water with
the thumnb, invert it, and insert the cork. Pour a little strong
ammonia into the funnel, and let it drop slowly into the tube by
means of the nipper-tap, to the depth of half an inch. Close
the nipper-tap, and pour off the ammonia from the funnel; and
then fill the funnel with water, and let it run into the tube, care
being taken to keep water in the funnel all the time, so that no
air may get into the tube.
In this and all other cases where chlorine is to be used, it will
be best to prepare it beforehand, and keep it in a gas-bag till
wanted. On its way fiom the generating flask to the gas-bag,
it should be passed through a wash-bottle containing a small
amount of water. The gas is washed to remove any muriatic
acid which may be in it, and which would corrode the bag.
8. (~ 6, ExP. I.) Fill the bent tube in the first place with
water, close it with the thumb, and invert it over water. Then
allow a little hydrogen to pass into it from the generator, and
also some oxygen from a gas-bag which has been previously
filled with this gas. With a little care, one can readily get the
right proportions. The tube should not be more than twothirds full of the mixed gases, and a considerable excess of one




APPENDIX.                      187
gas should be used, so that enough may be left for testing.
After putting the gases into the tube, close it with the thumb,
raise it from the water, and tip it so that the gases may pass into
the closed arm; then pour out a little of the water, and again
close it with the thumb. Connect the outer coating of a charged
Leyden jar with one of the platinum loops, by means of a wire
or chain, and bring the knob of the jar in contact with the other
loop. After the spark has passed, again fill the open arm with
water, close it with the thumb, and tip the tube so as to transfer
the remaining gas to the open arm, and there test it.
9. (~ IO, Ex5p. I.) As explosions sometimes occur in the
manufacture of oxygen, care should be taken that the chemicals
are pure; and it would be well to test each purchase by putting
some of the potassic chlorate in an iron spoon and heating it
over a spirit lamp until it is melted; then stir into it with an
iron wire some of the black oxide of manganese; and if these
materials are not good, an explosion will take place, and a
whitish mass with red spots in it will be left in the spoon. If,
however, the chemicals are pure, there will be no explosion, and
the melted mixture will soon dry up, leaving a dark gray residuum. If the bubbles come over too violently, remove the
lamp for a few minutes until they come more moderately.
A glass flask may be used; but as it is liable to break, a copper flask may perhaps be found cheaper in the long run, especially if one has to make oxygen often.
Io. (~ ii, Exh. I.) Use glass jar (No. 3). The charcoal may
be fastened to a piece of wire and ignited in the flame of a lamp.
It is well to have the other end of the wire attached to a copper
or wooden disk, which serves to cover the jar while the charcoal
is burning.
Lime-water may be made by putting a small quantity of
slaked lime into a jar (No. 3) of water, stirring it thoroughly,
and allowing it to settle. The clear liquid may then be poured
off into a bottle, and kept for use.
ii. (~ II, Ex5p. 2.) Fill a jar (No. 3) with oxygen, and let it
stand to drain. Put a piece of sulphur in the chalk cup (No.
I6), ignite it by touching it with a red-hot wire, and invert a
jar of oxygen quickly over it. The jar should be kept closed




I SS                    APPENDIX.
with the plate until it is inverted, and brought just over the sulphur. The chalk cup should stand in a shallow dish of water,
so that the mouth of the jar may dip under the water and prevent the SO2 from escaping into the room.
I2. (~ ii, Exp. 3.) The phosphorus may be burnt in the
same way as the sulphur. As phosphorus is a very inflammable
substance, and as burns from it are very slow to heal, great
caution must be exercised in using it. The sticks must always
be cut under water, and it must be carefully dried, by pressing
it between pieces of unsized paper, before it is burnt; else it will
fly about in a very disagreeable and dangerous manner. It
should always be lighted by touching it with a heated wire,
never by holding it in the flame of a lamp.
13. (~ ii, Exp. 4.)  The watch-spring' should be either
straightened out or formed into a spiral, and fastened to a disk
of copper or wood, as above described. Water should be left in
the bottom of the jar to the depth of two inches or so, that the
melted globules of iron may not burn into the jar.
I4. (~ 12, Exp. i.) Ozone may be most easily prepared by
pouring a little ether into a jar (No. 3), and then when the air
in the jar has become saturated with the vapor of ether, stirring
the air with a glass rod heated nearly to redness.
I5. (~ 20, Ex.p. I.) In making hydrogen, use the hydrogen
generator (No. ii).
I6. (~ 2I, Exp,. I.) Mix the gases in the gas-bag, letting each
gas pass in separately. The quantities can be estimated nearly
enough by the eye. Fasten an ordinary clay tobacco-pipe to
the gas-bag, hold the mouth of the pipe in soap-suds, and
press out the mixed gases in a gentle stream. For obvious
reasons, the nipper-tap should be closed before the bubbles
are lighted.
I7. (~ 28, Ext. I.)  Fill the bottle generator (No. 6) onethird full with strong ammonia, and connect the large tube with
a rubber bag filled with chlorine. Connect the delivery-tube
with the wash-bottle (No. I7), and the delivery-tube of the washbottle with the larger cylinder (No. 2). Force the chlorine
through the apparatus by compressing the bag. Care must be
taken not to force an excess of chlorine through the ammonia,




APPENDIX.                       189
lest the very explosive nitric chloride (page 28) be formed.
There is little danger, however, if sironzg ammonia is used.
i8. (~ 30, ExS. I.) Use the bottle generator (No. 6). First
pour in water enough to cover the bits of copper (brass or nickel
will do as well), and then pour in gradually strong nitric acid.
The gas is very poisonous, and should not be allowed to escape
into the room.
I9. (~ 30, ExP. 2.) The management of the experiment is the
same as in the burning of phosphorus in oxygen (I2).
20. (~ 30, Ext. 3.) The gases may be mixed in a gas-bag.
It is not necessary that the proportions should be exact.
21. (~ 33, Ex6p. I.) Use nitric-oxide bell and jar (No. I8).
Fill the bell with oxygen, and the jar with nitric   Fig. 36.
oxide. The jar should be closed with a plate and
set on the table, and the bell of oxygen set on the
plate covering the jar (Figure 36). When the experiment is to be tried, the plate should be drawn
out, and the mouths of the bell and jar allowed
to come together.
22. (~ 36, Exit. I.) Use tubulated retort (No.
20). Only a small quantity of the ammonic nitrate    L   X
need be used. The retort must not be heated too         ___
much, lest the gas should come off with explosive         -
violence.
23. (~ 37, Ext. I.) Gases, like ammonia and muriatic acid,
which are absorbed by water, must be collected over mercury.
For the experiments of this book we think a mercury-trough
a needless luxury. An evaporating dish of Berlin porcelain
answers every purpose. One five inches in diameter is large
enough to use with the cylinders mentioned above. It should
be set in a shallow dish of strong glass or earthen ware, to prevent loss of mercury in case of accident.  It should then be
filled nearly full of mercury. The cylinder to be used is next
filled with mercury to the brim. The ground-glass cover is then
placed on the mouth of the cylinder and held firmly with the
right hand, the cylinder inverted, and its mouth plunged beneath
the mercury in the evaporating dish. It is well to put the cylin



Igo90                   APPENDIX.
der in a strong dish when you are filling and inverting it, to
save any mercury which may be spilled. After the cylinder is
filled and inverted over the mercury in the dish, the plate is
slipped from its mouth, and the cylinder is securely fastened in
the clamp of a retort-stand, so that its mouth is held about A or
i of an inch above the bottom of the dish.
To fill the cylinder with ammonia gas, a little aqua ammonia
is put into a flask provided with a delivery-tube, and gently
boiled. To the delivery-tube is attached a piece of rubber tubing to connect it with the cylinder. A short piece of glass tubing with its end slightly turned up must be fastened to the end
of the rubber tube, so that the gas may be introduced into the
cylinder through the mercury. On first boiling the aqua ammonia, a large amount of air passes over from the flask. The
ammonia gas must not be collected until this has all passed
over. To determine when this has taken place, put the glass
tube at the end of the rubber tube into a vessel of water; when
heat is first applied to the flask, bubbles of gas will rise from
the end of the tube through the water as long as any air comes
over. When the air is all over, the ammonia gas is absorbed
by the water as fast as it comes over, and no bubbles rise to the
surface. After the air ceases to come over, plunge the end of
the glass tube into the mercury, and introduce it under the
mouth of the cylinder. The gas will rise into the jar and displace the mercury.
When the cylinder is filled with
Fig. 37.
ammonia, close it with a glass
plate, and remove it to a vessel of
water; then open the mouth of
i K.~         the jar under the water (Figure 37).
24. (~ 43, Exi. I.)  The oxalic
acid may be heated with sulphuric
/i  acid in a flask, and the solution
of soda put in a wash-bottle.
25. (~ 45, Exfp. I.)  In both experiments, the sulphur should be
-~-' —- I~ -— ~ —-- heated cautiously, that it may not




APPENDIX.                       I9I
take fire. Figure 38 shows the needle-         Fig. 38.
shaped crystals which may be obtained
by the first experiment.
26. (~ 53, ExPj..)  With the aid of
an air-pump, phosphorus may be burnt
in chlorine in the following manner:
Place the chalk cup, with a bit of phosphorus in it, on the bottom of the nitric- \
oxide jar (No. I8), and cover the jar          -
with a well-fitting glass plate which has
in its centre a round hole, a of an inch in diameter. This hole is
closed with a rubber cork, through which passes a glass tube
connected with a second glass tube by a short piece of rubber
tubing provided with a nipper-tap. Connect the jar with the
air-pump by rubber tubing, and exhaust the air. Close the
nipper-tap, and connect the jar with a gas-bag filled with chlorine. Open the nipper-taps, and let the chlorine pass into the
jar, until the pressure within is nearly but not quite equal to that
outside. The phosphorus will soon take fire. If the jar were
filled full of chlorine, the heat of the burning phosphorus would
expand the chlorine, and force out some of it into the air.
27. (~ 60.) The color of iodine vapor may be shown by heating a few grains of iodine in a flask over the lamp.
28. (~ 65, ExP. I.)  Use tubulated retort (No. 20). Fill it
nearly full of water, put in a small piece of phosphorus, and let
the mouth of the retort dip under water. Heat the retort until
the water in it boils, and then drop in a stick of caustic potash
through the tubulature. The water is boiled first in order to
drive out the air from the retort, so that the hydric phosphide
may not take fire inside, and thus cause an explosion.
29. (~ I23, Exp. I.) The process is the same as in the experiment in ~ 33, using air instead of oxygen.
30. (~ 123, EXp. 2.) Observe the precautions given in ~ I2.
3I. (~ I42, EXp. I.)  The sugar and the potassic chlorate
should be pulverized separately, and then mixed carefully. Put
the mixture on an earthen dish, and let one drop of sulphuric
acid fall upon it from the end of a long glass rod. The experiment is brilliant, even with much smaller quantities.








QUESTIONS FOR REVIEW AND
EXAMINATION.
TiTe numbers refer to tke sections of/Se book.
THE NON-METALLIC ELEMENTS. — I. Describe the experiments with muriatic acid. What products are obtained? The
test for each? How may they be united again? 2. Describe
the experiments with sodium and chlorine water. What are
obtained? How is the oxygen tested? If hydrogen be burnt
in oxygen, what is the product? What does this show? 3. Describe the experiment with ammonia. What new gas is obtained, and how is it tested? What does ammonia contain?
4. Define compounds and elements.  Give examples of each.
How many elements? 5. What two classes of elements? What
are symbols? What is the symbol of gold? of iron? Explain.
6. What is affinity? What are its three characteristics? Illustrate each. 7. What are molecules? atoms? Why so called?
What is said of the atoms of an element? What of the molecules of a compound? What is this theory called? What is the
atomic constitution of muriatic acid? of water? of ammonia?
8. What symbols do compounds have? What is indicated by
these symbols? Illustrate. 9. What are atomic weights? The
atomic weight of H? of O? of N? of Cl? How is the relative
weight of the elements in a compound shown by the symbol?
Io. Describe the preparation of 0 from KC103. What is a reaction? Express this reaction by an equation, and explain in
full.  ii. Describe experiments with charcoal, sulphur, and
phosphorus. What product in each case? How may Fe be
burnt in 0? What product? What properties of 0 do these
exDeriments illustrate? I2. What is ozone? Why so called?
I 




I94 QUESTIONS FOR REVIEW AND EXAMINATION.
How obtained? How tested? 13. What are allotropic states?
14. What are oxides?  How  named?  15. What are acid
oxides? anhydrides? acids?  Illustrate.  Explain the names
and symbols of acids.  I6. What are basic oxides? bases?
How named? Illustrate. What are alkalies?  17. What are
neutral oxides? I8. What is a salt?  How named? Illustrate.
I9. What are binary compounds? ternary compounds?  20.
How is H prepared? Express the reaction in an equation, and
explain it. 2I. What are the properties of H? Illustrate by
experiments. 22. Describe the oxy-hydrogen blowpipe, and the
experiments with it. What is the lime light? 23. The properties of H20? What is said of its solvent power? 24. What is
said of rain water? spring water? mineral waters? hard and soft
water? sea water? 25. What is said of H20 in plants and
animals? 26. What is water of crystallization? Efflorescence?
Deliquescence? 27. Give some account of the uses of H20. 28.
How is N prepared? 29. The chief characteristic of N? 30.
How is NO prepared?  What experiments with it? 3I. Define
catalysis. 32. What is meant by the nascent state? 33. What
is N203? How prepared? 34. What is NO.2? N2O5? HNO3?
35. The properties of HNO3? How made? Illustrate by an
equation. Explain the action of HNO3 on metals? 36. What
is N20?  How made?  Its properties and uses?  37. What
is H3N? When absorbed by water, what does it form? How is
it prepared? 38. What is ammonium? Why is it considered a
metal? 39. What is CN? How obtained? For what remarkable? What are some of its compounds? What are radicals?
40. What are the characteristics of N? Illustrate each. 4I. Describe the allotropic forms of C. 42. What is CO2? Its properties? How prepared? Explain. How tested? 43. What is
CO? Its preparation? Properties? 44. What are the sources
of S? How is it purified? 45. Describe the allotropic forms of
S. Its properties? 46. What is SO2? Properties and uses? Illustrate by experiment. 47. What is H2SO4?  Ways of making
it? Explain in full. 48. What is SO3? Properties? 49. What
is H2S? Preparation? Properties and uses? 50. What is CS2?
How made? Properties? 5I. What elements belong to the O
group? Why thus classed? 52. How is C1 prepared? Explain




QUESTIONS FOR REVIEW  AND EXAMINATION.  I95
the reaction.  53. Properties of Cl?  Explain its bleaching
power. 54. Describe the old and new methods of bleaching.
How is bleaching powder made? For what else is it used?
55. How is muriatic acid made? Explain the reaction. 56.
What are hydracids? oxyacids?  57. What is aqua regia? Why
so called? Explain its action on gold. 58. Give the names and
symbols of the C1 oxyacids. 59. Give the history and properties of Br. 60. Where is I found? Its properties? 6I. Properties of F?  How  prepared?  62. What is HF?  How made?
Uses? 63. What elements in the C1 group? What is said of
them? 64. Give the history and the sources of P. Its properties? Uses? 65. What is said of the compounds of P? 66.
What is said of As? 67. What elements in the N group? Why
thus grouped?  68. How is boracic acid obtained?  For what
is B remarkable?  69. What is SiO2?  What is said of Si?
70. What is said of the C group?
THE METALS.-7I. What are some of the heaviest metals?
some of the lightest? What is said of the melting-points of the
metals?  72. What are ores? veins, or lodes?  73. What is Fe?
Explain the symbol. What three forms of Fe in commerce?
How is Fe made fibrous? How does it sometimes lose this texture? Explain welding. 74. Describe the blast-furnace. How
is cast-iron made?  How converted into wrought iron?  Describe the reverberatory furnace. 75. How is steel made? Its
properties? Describe the Bessemer process. 76. What is Pb?
How obtained? Properties? What is the action of 1120 on
Pb? What is said of lead pipes lined with tin? How are lead
pipes best protected from water action? 77. What are the chief
ores of Cu? Properties of Cu?  78. What are some of the
alloys of Cu? Their composition?  For what are they remarkable? 79. What is SnO2? Where found?  How is Sn obtained
from it? Properties of Sn? Uses? What is said of tin water
pipes? 80. What alloys of Sn are mentioned? 8i. Chief ores
of Zn? How reduced?  Properties and uses of Zn? Its alloys?
82. Give the names and symbols of the iron oxides. What is
FeSO4, and how is it made? Its uses? What other salts of Fe
are mentioned? 83. The names and symbols of the lead oxides?
What is PbCO3?  How is it made?  Explain.  What is the




I96 QUESTIONS FOR REVIEW AND EXAMINATION.
chemical name and symbol of chrome yellow? 84. What are the
oxides of Cu? What are the chief cupric salts? 85. What oxide
of Zn? What salt is mentioned? 86. What is SnO? SnO2?
WVhat is a mordant? What salts of Sn are used as mordants?
87. The chief ore of Hg?  How reduced?  Properties of Hg?
Uses? What are amalgams? Describe the silvering of mirrors. 88. Sources of Ag? Explain cupellation and amalgamation. Properties of Ag? What is said of the compound of Ag
and S? 89. Where is Au found? How is it obtained? Properties? go. Where and in what state is Pt found? HIow is it
obtained from the ore? Its properties and uses? 9I. Give the
names and symbols of the oxides of Hg. What is calomel?
corrosive sublimate? vermilion? 92. What two silver oxides?
Their symbols? What is AgNO3? AgCl? What silver salts
are used in photography?  For what is AgCN used?  93. What
is Au20? Au203? What salts of gold are mentioned? Their
uses? 94. What is PtO? PtO2? PtCI4? 95. How was Na discovered? How obtained now?  Properties?  What is said of
its compounds?  96. Where is Mg found?  How obtained?
Properties and uses? 97. The sources and preparation of Al?
Its properties? 98. What is Sb? Its chief ore? How reduced?
Properties?  Alloys?  99. State the sources, properties, and uses
of Bi. How is it now classed? Ioo. Name the properties and
uses of Ni. IOI. What is Ia2O? Na2O2? HNaO? Its properties
and uses? How made? State the reaction.  I02. Give the
chemical name and symbol of common salt. How is salt obtained from sea water? How are salt lakes formed? What is
said of rock-salt? of salt springs?  Io3. What is Na2CO3? Its
uses? How was it formerly made? Give the history of the
modern method?  Describe the process in full. Io4. How is
HNaCO3 made? Its commercial name? Uses? Io5. What is
the chemical name and symbol of soda-saltpetre?  Its uses?
What is Na2SO4?  Mention other sodic salts.  io6. What is
MgO? Epsom salts?  Io7. What oxide has Al?  Its sources
and uses? What is alum-cake?  Give an account of the alums.
What is clay? kaolin?  108. What is glass? Describe the four
kinds. Give an account of glass-making. What is porcelain,
and how is it made? Io9. What two oxides of Sb? Its chief




QUESTIONS FOR REVIEWV  AND EXAMINATION.  I97
salt? IIO. What are the Bi oxides? What is Bi3NO3? III.
What two oxides of Ni? II2. How was K discovered?  How is
it now prepared? Its properties? What is pearlash, and how
is it made?  What are the chief potassic compounds?  What is
said of gunpowder? of KC1O,?  II3. Where does Ca occur?
How is the metal obtained? What is CaO? Its preparation,
properties, and uses?  What is mortar? hydraulic cement?
What is said of CaCO,? of CaSO4? of CaCI2?  II4. Give an
account of Sr and its compounds. I15. What is said of Ba and
its compounds? II6. The chief compounds of Cr and their
uses?  II7. Describe Co.  What compounds are mentioned?
II8. Give an account of Mn. What oxides has it? Which is
the most important? Its uses? II9-I22. What is said of Cd?
of Ir? of W? of U?
CHEMISTRY OF THE ATMOSPHERE. - I23. Prove that the air
contains free 0. What are its other constituents? Is it a comnpound of these gases? I24. What are the products of the burning of a candle?  Prove this. I25. Prove that the candle takes
o from the air. 126. What is all ordinary combustion?  127.
Why is a draft needed in a stove? 128. What is a combustible?
A supporter of combustion?  What is true of these terms?  I1lustrate by an experiment. 129. What is necessary to make 0
unite with a combustible? 130. Show that combustion is selfsustaining. I3I. Show that the point of ignition is dififerent for
different bodies. I32. When are products of burning gaseous,
and when solid?  I33. What is true of Mg?  Give other examples of the kind. I34. Show that 0 is not the only supporter of
combustion. I35. WMhat is true of the earth's crust? 136. Show
that the materials of the earth are the results of burning. 137.
What three states of O? What is said of the third?  I38. What
is decay? Describe the process, and explain in full. 139. Explain the causes of decay. I40. What is rusting? Show that it
develops heat. I4I. Define and illustrate spontaneous combustion. I42. What is said of decay in animals? What three kinds
of food? What does milk contain? What does bread? What
purpose does each kind of food serve in the body? How is the
body heated? Describe and explain in full. I43. What experiment illustrates the burning of sugar? I44. Give facts concern



198  QUESTIONS FOR REVIEW  AND EXAMINATION.
ing the daily consumption of 0. I45. Describe the formation
of the embryo plant in the seed. 146. Give an account of the
growth and structure of the plantlet. I47. What are organic
beings? What is organic structure? I48. Explain how plants
get their food. I49. Of what does the inorganic portion of the
plant consist?  Why are manures necessary in agriculture?
Why are fields allowed to lie fallow?  Explain the principle of
the alternation of crops. I5o. Give an account of the organic
portion of the plant. ISI-I53. How does the plant get H and
O? C? N? N? I54. Show that the growth of plants is a chemical
process, and how it is carried on. I55. Show that plants purify
the air for animals to breathe. I56. Show that plants prepare
food for animals. I57. What is said of the relations of plants
and animals? I58. Give a full account of starch. I59. What is
sugar?  What two kinds?  I6o. What is the symbol for canesugar? From  what is it obtained? Describe its manufacture
from the cane, and the refining process. Give some facts in the
history of sugar. I6I. What names has C12H24012? In what is
it found? I-Iow may it be made? Its uses? i62. What are the
sources and uses of dextrine?  I63. What is the symbol of cellulose?  How is gun-cotton made?  What is said of it? What
is collodion?  Its uses?  I64. Describe the manufacture of
vegetable parchment. Its uses? I65. What is said of C4H606?
of its compounds? What is C6H807? C4H605? C20,? H2C204?
Give an account of tannic acid and tannin. I66. What is the
composition of fats and oils? What two classes of oils?  Give
some account of both. I67. What is soap? How do hard and
soft soap differ? The composition and uses of glycerine? I68.
What is said of wax? I69. How do gums and resins differ?
Mention the chief examples of each. I70. Give some account of
vegetable alkaloids. 171. Describe the proteine bodies? Why
are they important?
DESTRUCTIVE DISTILLATION  AND  ITS  PRODUCTS. - I72.
What is destructive distillation? I73. Describe the preparation
of charcoal. I74. What are the products of the distillation of
wood? I75. Describe wood naphtha. I76. What is creosote?
Its uses? I77. Give an account of paraffine. I78. What is asphalt, and for what is it used? 179. What is slow destructive




0QUESTIONS FOR REVIEW AND EXAMINATION. I99
distillation? I80. Explain the formation of mineral coal. 181.
What two kinds of coal? How do they differ? 182. How do the
products of the distillation of soft coal and of wood differ? I83.
What is found in coal-tar? What are the uses of carbolic acid?
Of aniline and its compounds? I84-I86. What is said of benzole
and nitro-benzole? of toluole and cumole? of naphthaline?
I87. Give the history of the coal-oil manufacture. I88. Explain
the probable origin of petroleum. I89. How is petroleum obtained? I90o. Give the history of coal-gas. 191. What is flame?
I92. What are the two conditions of illumination? I93. Explain the burning of coal-gas.  I94. Describe and explain
Bunsen's lamp.  I95. What is the best shape for a gas-flame?
i96. Describe the Argand burner. I97. Explain the Bude
light. I98. Show that a burning candle is a miniature gasfactory. I99. Analyze the candle-flame.
FERMENTATION. -200. State the nature and causes of fermentation. Explain apparent cases of fermentation without a
ferment.  What two kinds of fermentation?  20I. Explain
the alcoholic fermentation. How is it brought about in grain?
202. Explain the formation of diastase in plants. 203. Describe
in full the process of brewing. 204. Describe the distilling and
rectifying of spirits. 205. What is ether? Its properties and
uses? Name other ethers. 206. Explain the acetous fermentation. Describe methods of making vinegar. 207. Describe and
explain bread-making. How may bread be made without fermentation?








INDEX.
f    For concise statements of the leading topics of the book, see the SUMMARIES,
which will be readily found by means of the Table of Contents. The references in this
Index are only to the fuller treatment of subjects in the body of the work.
A.                        Alums, 79, I75.
Amalgamation, 66.
Amalgams, 65.
Acid, acetic, 156.                            Ammonic chloride, 26.
boracic, 44.                            Ammonia, 6, 9, 23, 44, IT5, 190.
carbolic, i38.                                      preparation of, 26.
carbonic, II, 29.                                   produced by decay, o02.
chromic, 87.                            Ammonium, 26.
citric, I27.                            Anmesthetics, 25, I56.
hydrochloric (see muriatic).            Anhydride, carbonic, II, 29, 91.
hydrocyanic, 27.                                    nitric, 24, 9I.
hydrofluoric, 4I.                                   nitrous, 24, 33.
hydrosulphuric, 35.                                 phosphoric, II, I3, 23.
hypophosphorous, 43.                                sulphuric, 13, 34.
malic, 127.                                         sulphurous, II, I3, 32.
muriatic, 3, 9, 38, 77.                 Anhydrides, 23, I72.
nitric, 24.                             Aniline, I38.
nitrous, 24, 33.                        Animal heat, 104.
Nordhausen, 33.                         Animals, food of, I3I.
oxalic, I27.                            Antimony, 72.
phosphoric, II, I3, 23, 43.                         salts, 82.
picric, 138.                            Apparatus, list of, I8S.
prussic, 27.                            Aqua ammonia, 23.
pyroligneous. 134, 157.                       regia, 39, 67.
sulphuric, I3, 33.                      Argand burner, I47.
sulphurous, I, I3, 32.                 Argentic salts, 69.
tannic, 127.                            Arrowroot, 121.
tartaric, I26, I75.                     Arsenic, 43.
tungstic, 89.                           Asphalt, I36.
Acids, 23, 171.                               Atmosphere, composition of, 9I.
fatty, 228.                            Atoms, 9, i6i.
vegetable, I26.                        Atomicity, I66.
Affinity, 8.                                  Auric salts, 70.
characteristics of, 8.
Alabaster, 86.
Albumen, I3I.                                                     B.
Albuminous  substances, lox, 103, x14,   Balsams, 230.
ii6, I3I.                                   Barilla, 76.
Alcohol, I55.                                 Barium, 87.
Alkalies, 14.                                           salts, 87.
Alkaloids, vegetable, I30.                    Bases, I4, I69.
Allotropic states, 13, x75.                   Bell-metal, 58.
Allotropism, I75.                              Benzole, I35, I39, I74.
Alternation of crops, I 14.                   Bessemer process, 55.
Alum-cake, 79.                                Bismuth, 73.
Alumina, 79.                                             salts, 82.
Aluminium, 72, 98.                            Bleaching, 37.
salts, 79.                                  powder, 37.




202                                   INDEX.
Blende, 6o.                                  Collodion, I26.
Blowpipe, the oxy-hydrogen, 16.              Combustibles, 94.
Boracic acid, 44.                            Combustion, nature of ordinary, 94.
Borax, 44, 79.                                             self-sustaining, 96.
Boron, 44.                                                 spontaneous, 102.
Brass, 58.                                                 supporters of, 94.
Bread, composition of, 103.                  Compounds, 6.
making of, I57.                                    binary, I5.
Brewing, 154.                                              molecules of, 9.
Brimstone, 31.                                             ternary, I5.
Britannia metal, 6o.                         Copper, 57.
Bromides, 40                                          alloys of, 58.
Bromine, 40.                                          salts, 63.
Bronze, 58.                                  Corn-starch, 121.
aluminium, 72.                       Corrosive sublimate, 69.
Bude light, the, 147.                        Cream of tartar, I27.
Bunsen's lamp, 146.                          Creosote, 135.
Butter, Io3.                                 Crops, alternation of, II4.
Crystals, i62.
c.                        Cumole, I39.
C.-~~~ ~           Cupellation, 66.
Cadmium, 89.                                 Cupric salts, 63.
Calamine, 60.                                Cyanogen, 27.
Calcic carbonate, 85.
chloride, 86.                                             D.
sulphate, 86.
Calcium, 84.                                 Decay, a slow combustion, ioo.
burns in air, 98.                          causes of, 10I.
Calomel, 69.                                 Deliquescence, I9.
Candle, a gas-factory, 148.                  Dextrine, 120, 125, 136.
products of burning, 92.             Diamond, the, 28.
Candle-flame, analyzed, I48.                 Diastase, 152.
Cane-sugar, 122.                             Distillation, destructive, 133.
Caoutchouc, 130.                                                      of coal, I37.
Caramel, 123.
~~~~~~~~~~~~Carbolic acid, I39wood, 134.
Carbolic acid, 38.,,    slow, 136.
Carbono, 28.                                              of spirits, I55.
anld oxygen, I46.                   Double decomposition, I77.
Carbonic acid, II, 29, 9I, 105, 115, 117.    Draft in stoves and furnaces, 94.
bisulplhide, 35.                   Drummond light, the, i6.
group, 45.
oxide, 30.
Caseine, 103, 13I.                                              E.
Catalysis, 23.
Cellular structure, 109.                     Earth, the crust of the, 98, 99.
Cellulose, II4, I25.                         Earthen-ware, 8o.
Chalk, 84, 85.                               Efflorescence, I9.
Charcoal, 11, I33.                           Elements, 7.
Chlorides, metallic, I68.                               classification of the, I76.
Chlorine, 4, 36, 4I-                                    electrical relations of, 176.
group, 4I.                         Epsom salts, 79.
nascent state of, 39.               Ether, I55.
oxyacids, 39.                       Eupion, I35.
preparation of, 36, I84, i86.
supports combustion, 98.                               F.
Clhrome yellow, 63, 88.
Chromium, 87.                                Farina, 121.
salts, 87.                       Fats, 128.
Cinnabar, 64, 69.                            Fermentation, acetous, I56.
Clay, 80.                                                   alcoholic, I52.
Coal, I36.                                                  causes of, i5i.
Coal-gas, 142.                               Ferments, 152.
Coal-oils, 138.                              Ferric chloride, 6i.
Coal-tar, I37.                                      sulphate, 6i.
Cobalt, 88.                                  Ferrous acetate, 6i.
compounds, 88.                                sulphate, 6I.
Coffee, alkaloid in, 130.                    Fibrine, I3I.
tannin in, 128.                       Flame, nature of, I45.




INDEX.                                     203
Fluorine, 4T.                                Isomerism, 175.
Fluor-sp-r, 41.                              Isomorphism, I74Food, IC3.
of animals, 131.                                         K.,, plants,  I.                        Kaolin, 8, 82.
Furnace, the blast, 52.                      Kaolin, 8, 8.
the reverberatory, 54.              Kupfernickel, 73.
G.                                           L.
Galena, 56, 63.                              Laughing gas, 25.
Garnet, 8o.                                  Lead, 56.
Gas, imperfect, I62.                                black, 28.
true, I62.                                     red, 62.
Gelatine, 127.                                      salts, 62.
German silver, 6i, 73.                              sugar of, 62
Glass, 80.                                          white, 62.
soluble, 79.                          Leaven, I58.
Gluten, 103.                                 Lime, 84.
Glycerine, i28, 129, I73.                           chloride of, 37.
Glycose, 124.                                       light, i6.
Gold, 67.                                    Limestone, 84, 98.
salts, 70.                             Litharge, 62.
Grape-sugar, I24.                             Lixiviation, 78.
Graphite, 28.                                Lunar caustic, 69.
Growth of plants, I08, I52.                  Lunrs describe, 6 04
Gtiin-resins,  130.                          Lungs, described, 1o4.
Gumn-resins, I30.
Gutms, I29.
Gun-cotton, I25, I73.                                           M.
Gunpowder, 84.
Gutta-percha, I30.                           Magnesia, 72, 79.
Gypsum,  84, 86.                             Magnesium, 71.
burns in air, 97.
salts, 79.
H.                        Maizena, 121.
Malacllhite, 58.
Heart, description of the, 104.              Manganese, 88.
Heat, animal, I04.                                        black oxide of, ii, 89.
produced by decay, JoI.                Manures, use of, 11I2, II3.,, rusting, 102.            Marble, 84, 85, 98.
Hydracids, 39.                               Marsh-gas, I36.
Hydrates, I4.                                Mercury, 64.
Hydraulic cement, 85.                                  salts, 69.
Hydric chloride (hydrochloric acid), 38.               trough, 189.
fluoride (hydrofluoric acid), 41.    Metallic veins or lodes, 50.
phosphide (phosphuretted hydro-    Metals, 49, 176.
gen), 43, 191.                             fusible, 73, 89.
sulphide (sulphuretted hydrogen),            noble, 64.
35.                                        melting-points of, 49.
Hydrocarbons, 134.                                   most useful, 51.
Hydrogen, 3, 5, I5.                                  ores of, 50.
a metal, I76.                             specific gravity of, 49.
generator, 182.                   Mica, 80.
preparatiou of, 15.               Milk, composition of, I03.
Mirrors, silvering of, 65.
Molasses, 122.
IMolecules, 9, 161.
Ignition, point of, 97.                      Monads, dyads, triads, etc., 166.
Illu,ination, 145.                          Mordants, 64.
India-rubber, I30.                           Morphine, I3.
Mortar, 84.
indel, I2, 69.                          Mosaic gold, 64.
Iodine, 1~2, 40.~                 M Muriatic acid, 3, 9, 38, 77.
Iridium, 89.
Iron, 5I.                                                       N.
manufacture, 5N.
pyrites, 34, 6I.                       Naphthaline, I39.
salts, 61.                             Nascent state, 23.




204                                  INDEX.
Neutrals, 14.                               Porcelain, 80.
Nickel, 73.                                  Potash, caustic, 84.
salts, 82.                           Potassic carbonate, 84.
Nicotine, I3I.                                       chlorate, 84, Io6.
Nipper-tap, the, i82.                                cyanide, 27.
Nitric acid, 24.                                     nitrate, 84.
chloride, 28, 189.                    Potassium, 83, 93.
iodide, 28.                           Problems, I78.
oxide, 22, 33.                        Prussian blue, 27.
Nitro-benzole, I39, 174.                    Putrefaction, ioI.
NYtro-cellulose, 125.
Nitrogen, 6, 21.
group, 44, 73.
properties of, 22, 27.            Quantivalence, 165.
Nitro-glycerine, I73                        Quinine, 131.
Nitrous oxide, 25.
R.
Radicals, 27, I6i, I66.
Oils, 128.                                  Reaction,  I.
Opium, I3I.                                 Rectifying of spirits, 155.
Organic structure, Iio.                     Resins, 30o.
OsmIose, i04.                               Respiration, Io3.
Oxides, acid, I3.                           Rochelle salts, 127.
basic, 14, 170.                     Rusting of metals, Io2.
names of, I3.
neutral, 14.
Oxyacids, 39.                                                  S.
Oxygen, 5, Io.
and carbon, 146.                   Sago, 12r.
daily consumption of, o07.          Sal-ammoniac, 26.
group, 35.                          Salt, 74.
making of. 187.                          rock, 75.
nascent state of, 37.                    springs, 75.
partially active state of, ioo.     Saltpetre, 84.
properties of, II.                           soda, 78.
sulphur burned in, I87.            Salts, 14, 172.
Ozone, I2, 100.                             Scheele's green, 63.
way of making, I88.                  Silica, 44.
Silicon, 44.
Silver, 66.
P.                              salts, 69.
Soap, 129.
Paraffine, 135.                             Soda, bicarbonate of, 78.
Parchment, vegetable, I26.                        caustic, 74.
Parhelia, 21.                               Soda-ash, 76.
Pearlash, 84.                               Sodic berate, 79.
Petroleum, I40.                                    carbonate, 76.
Pewter, 60.                                       chloride, 74.
Phosphorus, II, 25, 42, 9I.                        hyposulplhite, 79.
caution in using, I88.                nitrate, 78.
burned in chlorine, i9I.              silicate, 79.
properties of, 42.                    sulphate, 78.
Photography, 70.                                   tungstate, 89.
Plants anld auilials, -I9.                  Sodium, 5, 71.
earthy portion of, 112.                       salts, 74.
food of, 111.                         Solids, liquids, and gases, i62.
growth of, IoS, II6, 152.             Specific heat of atoms, i65.
organic portion of, 114.              Speiss, 73.
prepare food for animals, IIS.        Spirits, distillation and rectification of,
purify the air for animals, II7.        I55.
structure of, i09.                   Stalactites, 85.
Platinum, 68.                               Stalagmites, 86.
salts, 70o.                       Stannic salts, 64.
Plumbago, 28.                               Starch, 103, 120.
Plumbic salts, 62.                                  converted into sugar, 124.
Pneutnatic trotugh, the, i8I.                       kinds of, I2I.
Polymorphistm, I75.                         Steel, 55




INDEX.                                     205
Strontium, 86.                                                  V.
salts, 86.
Strychnine, I3I.                             Verdigris, 63.
Substitution, 173.                           Vermilion, 69.
Sugar, composition of, 105.                  Vinegar, I56.
fermentation of, I52.                          wood, 134.
kind3 of, I22.                        Vitriol, blue, 63.
rapid combustion of, Io6, 19I.                green, 33, 35, 65Sulphides, 30.                                       oil of, 33.
Sulphur, II, 18, 30, 35.                             white, 15, 64.
in eggs, etc., 67.
properties, 31.
supports combustion, 98.                              W.
Sulphuretted hydrogen, 35.
Sulphiuric acid, 33.                         Water, 5, 9, 17.
Sulphurous acid, 32.                                 as food of plants, IS.
Sunlight, an agent in growth of plants,              kinds of, i8.
II6.         nt'           in plants and animals, 19.
Symbols of compounds, 9.                             lead pipes for, 56.
Sy lebols of compounds,  9.              of crystallization, I8.
tin pipes for, 59.
uses of, 20.
T.                        Wax, 129.
Weights, atomic, Io, I63.
Tannin, I27.                                           molecular, I62.
Tapioca, 1I2.                                Welding, 52.
Tartar-emetic, 82, 127.                      Wolfranium, 89.
Tartaric acid, I26, 175.                     Wood, composition of, Ioo, II6.
Tea, alkaloid in, I31.                               distillation of, I34.
tannin in, I28.                                naphtha, 135Theine, I3:.                                         tar, I35.
Tin, 59.                                             vinegar, 134, r57.
alloys of, 6o.                          Woody fibre, 114, 125.
salts, 64.                                            converted into sugar, 124.
water-pipes, 59.
Tobacco, T3I.
Toluole, 139.                                                   Y.
Tungsten, 89.
Type-metal, 73.                              Yeast, I52, I54, I58.
Types, chemical, 167.                        Yellow metal, 58.
condensed, i68.
Z.
U.                        Zaffre, 88.
Zinc, 60.
Uranium, go.                                       salts, 64.
Cambridge: Electrotyped and Printed by John Wilson and Son.








APPARATUS.
The articles in the List on pages I8I-I84 can be furnished
at the following prices:No. 2, (cylinders and ground-glass plates),...... $2.50
No. 3, (jars and ground-glass plates),.....         3.00
No. 4.....................70
No. 5...................  4.0
No. 6,...................oo
No 7...................  I.00
No. 8...................  2.00
No. 9, Bunsen's lamp, $i.50; alcohol lamp,... i.oo
No. 1,........oo00
No. II,... 5.00
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No. 20...................50
No. 2I....... 63
No. 22, Half a pound of tubing, 4 and 4 of an inch in
diameter..30
No. 23.................... 8o
Two 25-gallon gas-bags, with stop-cocks and tubing,.. 35.00
An oxy-hydrogen jet.......... 8.oo
A copper flask for making oxygen.........      7.00
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