HAND-BOOK
OF
INORGANIC ANALYSIS;
ONE HUNDRED AND TWENTY-TWO EXAMPLES,
ILLUSTRATING THE MOST IIMPORTANT PROCESSES FOR DETERMINING
TIIFE
ELEMENTARY COMPOSITION
OF
MIINERAL SUBSTANCES.
BY FRIEDRICH WOHLER,
PROFESSOR OF CHEMISTRY IN THE UNIVERSITY OF G6TTINGEN.
EDITE D
BY A. W. HOFMANN, Pii.D., F.R.S,,
PROFESSOR IN THE ROYAL COLLEGE OF CHEMISTRY.
LONDON:
WALTON AND MABERLY,
UPPER GOWER STREET, AND 1VY LANE, PATERNOSTER ROW.
1854.




LONDON:
Printed by Schulze and Co., 13, Poland Street.




CONTENTS.
PAGE
PREFACE.......     vii
1. CHLORIDE OF SODIUM......  1
2. CHLORIDE OF SILVER.       2
3. SULPHATE OF SODA...                           3
4. TARTRATE OF POTASSA AND SODA.5. SULPHATE OF SODA AND OXIDE OF AMMONIUM..  5
6. SULPHATE OF POTASSA AND MAGNESIA....      7
7. CARBONATE OF POTASSA AND MAGNESIA..  8
8. EPSOM-SALT AND GLAUBER'S-SALT..           9
9. PHOSPHATE OF SODA AND OXIDE OF AMMONIUM... 10
10. PHOSPHATE OF MAGNESIA AND OXIDE OF AMMONIUM.     11
11. THE CHLORIDES OF POTASSIUM, SODIUM AND MAGNESIUM.. 13
12. BITTER-SPAR AND DOLOMITE....                   14
13. BONE-EARTH....... 15
14. HEAVY-SPAR, CELESTINE, AND GYPSUM...          17
15. ALUMINA-ALUM...... 18
16. IRON-AMMONIA-ALUM.....      19
17. ALUMINA-CHROME-ALUM...... 20
18. PHOSPHORIC ACID AND ALUMINA...      21
19. ALUMINA AND SESQUIOXIDE OF IRON..... 23
20. PHOSPHORIC ACID AND SESQU1OXIDE OF IRON..              24
21. SPECULAR IRON, Fe203, AND BROWN IRON-ORE, Fe203, 3 HO.. 25
22. MAGNETIC IRON-ORE...                              26
23. SPATHIC IRON-ORE. 28
24. BOG-IRON-ORE..                                          30
25. SULPHATE OF COPPER.....         32
26. COPPER-PYRITES..27. ZINC-BLENDE..                                      34
28. CALAMINE......             36
29. SULPHATE OF IRON WITH THE SULPHATES OF COPPER AND ZINC.. 37
30. BRASS..                                      -
31. OXIDES OF MANGANESE, IRON, AND ZINC.... 39
32. CADMIUM AND ZINC....
33. GALENA........ 40
34. WHITE LEAD.....              41
35. PYROMORPHITE......          42




V                             CONTENTS.
PAGE
36. SILVER AND LEAD..                     44
37. SILVER AND COPPER.....     45
38. GOLD AND COPPER......     47
39. GOLD AND SILVER.... -
40. AMALGAMS....     49
41. MIXTURES OF PROTOXIDE OF MERCURY, MINIUM, AND CINNABAR. 51
42. TIN AND COPPER.....         52
43. TIN AND LEAD...... 53
44. BISMUTH, LEAD, AND TIN..
45. SCHWEINFURT GREEN...... 55
46. ARSENIC AND LEAD                                                    56
47. ARSENIC AND TIN....
48. TARTAR-EMETIC.                                         58
49. ANTIMONY AND LEAD.. 59
50. BOURNONITE...                             60
51. ZINKENITE...... 61
52. BERTHIERITE......     62
53. RED SILVER-ORE...... 63
54. TIN AND ANTIMONY......     65
55. ARSENIC AND ANTIMONY.....66
56. ARSENIC, ANTIMONY AND TIN.....     69
57. FAHL-ORE....... 71
58. GERMAN SILVER (ARGENTAN).....     76
59. COPPER-NICKEL...                             78
60. SPEISS COBALT...                                     82
61. COBALT-GLANCE...... 84
62. MANGANESE AND COBALT, OR NICKEL                                     87
63. IETEORIC 11RON..                                     88
64. BIStUTH AND COPPER                                                  9...  90
65. PLATINUM-ORE..                                         91
66. PLATINUIM-RESIDUES...                   95
67. PALLADIUM..... 99
68. TELLURIUMORE......    100
69. MESOTYPE........ 103
70. LIEVRITE...                                    105
71, OLIVINE........ 106
72. DATOLITE.......    108
73. FELDSPAR...                              -
74. AUGITE, M.ORNBIENDE, GARNET, IDOCRASE, EPIDOTE..    112
75. BERYL....... 113
76. TOPAZ.......    115
77. ZIRCON........ 116
78. CERITE.......    118
79. ORTHITE.....                 10
80. THORITE......   124
81. APATITE......    -
82. TRIPHYLLINE...                    126
83. FLUOR-SPAR...... 127
84. SPHENE (TITANITE)....                    129
85. TITANIC IRON      e.                130




CONTENTS.                                  V
PAGE
86. RUTILE..132
87. CbLUMBITE....    134
88. WOLFRAM.... 138
89. SCHEELITE......    141
90. MOLYBDATE OF LEAD... -
91. MOLYBDFNITE......    144
92. BROWN IRON-ORE, CONTAINING VANADIUM.... 145
93. VANADATE OF LEAD......    146
94. CHROME-IRON-ORE... 147
95. CHROMATE OF LEAD......    149
96. PITCH-BLENE....... 151
97. SELENIFEROUS DEPOSIT FROM THE SULPIIURIC-AC1D CHAMBERS.    154
98. SELENIDE OF LEAD.... 156
99. SILVER ASSAY.                                                     158
100. IRON ASSAY....
101. WET ASSAY OF IRON......    159
102. CAST-IRON....... 161
103. ASH OF THE REFINING-HEARTH.....    165
104. GLASS........168
105. CLAY........    169
106. COMMON LIMESTONE, HYDRAULIC LIMESTONE, MARL... 170
107. IODIDE, BROMIDE AND CHLORIDE OF SODIUM...    172
108. CRUDE COMMON SALT......173
109. INCRUSTATIONS FROM SALT-PANS....    175
110. MINERAL WATERS, WELL-WATERS, SALINE SPRINGS... 176
111. SOILS.......    180
112. ASHES OF PLANTS.......184
113. GUANO.......    188
114. OXALATE AND PHOSPHATE OF LIME..... 194
115. ALKALIMETRY.......    196
116. VALUATION OF MANGANESE-ORES..... 203
117. CHLORIMETRY......    204
118. ANALYSIS OF NITRF...... 206
119. GUNPOWDER.......    208
120. HYDROCYAN IC ACID...... 209
121. FERROCYANIDE OF POTASSIUM.....    210
122. EXAMINATION FOR ARSENIC IN CASES OF POISONING... 211
EQUIVALENT WEIGHTS OF THE ELEMENTS....    231
EQUIVALENT WEIGHTS OF COMPOUND BODIES... 233
INDEX........    237
ADDENDA: PURIFICATION OF TELLURIIM. SEPARATION OF NICKEL FROMI ZINC. 240








PREFACE.
THIS collection of examples for practice in Chemical
Analysis, is designed chiefly for the use of the laboratory.
It is drawn up under the impression that it is easier for
most minds to obtain a clear insight into general relations
and laws by the study of special cases, than, inversely,
to acquire a knowledge of individual cases by first directing the attention to general rules.  An endeavour has
been made to arrange the book in such a manner as still
to leave enough to demand the reflection of the student
and the explanations of the teacher; the latter also must
point out the authority for the individual methods here
given, if such information should at any time be required.
DR. FRIEDRICH W6IHLER.
The Editor of the English Translation fully concurs
with the views which have led the Author to the publication of this volume. General statements, general instructions, will always remain more or less unintelligible to the




Viii                   PREFACE.
student, as long as he fails to have a sufficient number
of facts at his disposal, by means of which he is enabled to
test, in special cases, the correctness of the general rule.
The safest plan of construction in Natural Science, will
always be found in following the mode in which the truths
of Nature have been elaborated, i. e., in proceeding from
the study of individual phenomena to the recognition of
the law.
The Editor, for many years engaged in laboratory teaching, has often felt the want of a collection of examples
similar to that of Professor Wbhler, a translation of which
he now offers to the English student. IIe may state that
the English version is nothing more than a faithful representation of the German work, with the exception that the
hydrogen scale of equivalents has been substituted for the
oxygen scale adopted in the German Edition, and that the
formulae have been written in the symbols generally used
in England.
A. W. H.
ROYAL COLLEGE OF CHEMISTRY,
NOV. 23, 1853.




HANDBOOK
OF
INORGANIC ANALYSIS.
(QUANTITATIVE.)
1. CHLORIDE OF SODIUM.
NaC1.
PERFECTLY pure crystallized common salt is strongly
heated, to expel adhering moisture, weighed, dissolved il
water, the solution slightly acidified with nitric acid, heated,
and the chlorine precipitated by nitrate of silver, the liquid
being at the same time violently agitated by stirring.
When the chloride of silver has completely separated,
leaving the liquid clear, it is filtered off and washed (with
as little exposure to light as possible), first with hot water
acidified with nitric acid, in order that it may not pass
through the filter, and subsequently with pure water.
When the precipitate has been perfectly dried it is removed
as completely as possible from the filter, and fused, in a
B




2                CHLORIDE OF SILVER.
weighed porcelain crucible, over the spirit-lamp. The filter
is completely incinerated by itself; the ashes are placed
upon the cooled chloride of silver, and heated, first with a
little nitric acid, in order to oxidize the reduced silver, and
afterwards with a few drops of hydrochloric acid; the
excess of acid having been expelled, the chloride of silver
is again heated to fusion, allowed to cool, and weighed.
100 parts of AgC1 contain 24'73 chlorine (and 75'27
silver).
For the determination of the sodium, another weighed
portion of chloride of sodium is carefully moistened, in a
weighed platinum crucible, with concentrated sulphuric
acid; after some time, a gentle heat is applied until all the
chlorine has been expelled in the form of hydrochloric acid,
when the excess of sulphuric acid is carefully evaporated,
and the residual sulphate of soda finally heated to redness,
a fragment of carbonate of ammonia being placed in the
crucible, to decompose any acid salt.  From the weight of
the sulphate of soda, that of the sodium is calculated.
2. CHLORIDE OF SILVER.
AgCl.
In order to determine the composition of chloride of
silver, a weighed quantity of pure silver is dissolved in
dilute nitric acid, the solution precipitated with dilute
hydrochloric acid, and the precipitated chloride of silver
treated as in No. 1.
Or a weighed portion of fused chloride of silver may be
heated with a spirit-lamp, in a bulb-tube, through which a
stream of hydrogen is passed until it is completely reduced
to metallic silver, which is then weighed.




ROCIHELLE-SALT.                   3
3. SULPHATE OF SODA.
NaO, S03 + 10 HO.
For the determination of the water, a weighed quantity
of the salt is gradually and carefully heated in a platinum
crucible, until the whole of the water is expelled, to ensure
which, the heat is finally raised to ignition.
The sulphuric acid is determined by dissolving the salt
in water and precipitating with chloride of barium. The
liquid is then warmed, and must not be filtered until the
sulphate of baryta has completely separated. The clear
liquid is then poured upon the filter, without the precipitate, which is stirred up with hot water, again allowed to
subside, the clear liquid being poured upon the filter, and
the precipitate once more treated in the same way before it
is thrown upon the filter, in order that none may pass
through the pores of the paper. When perfectly washed,
it is dried, separated as much as possible from the filter,
the latter being completely incinerated, and its ashes added
to the precipitate, which is then ignited and weighed.
100 parts of sulphate of baryta contain 34"29 of sulphuric
acid, or 13'71 of sulphur.  The amount of soda is determined by difference.
4. TARTRATE OF POTASSA AND SODA.*
Seignette-salt; Rochelle-salt, (I(O, NaO, T + 8 HO).
The estimation of the water requires the cautious application of heat for a long period. The salt fuses even below
* Prepared by saturating a hot mixture of water and powdered
tartar with carbonate of soda, filtering, and crystallizing.
B2




4                   ROCIlELLE-SALT.
1000, and enters into ebullition at 120~, but does not lose
the whole of its water till heated to 215~.
To determine the bases, the salt is ignited, the alkalies
dissolved out of the carbonaceous mass by dilute hydrochloric acid, and the filtered solution evaporated to dryness;
the mixed chlorides are heated to dull redness in a covered
platinum crucible and weighed. They are then dissolved
in a little water, and the solution mixed with a moderately
concentrated solution of bichloride of platinum. The solution, with the suspended precipitate, is evaporated to
dryness on the water-bath, the dry mass digested for some
time with alcohol, and the potassio-chloride of platinum
collected upon a filter which has been dried at 1000, and
weighed.  The filtrate, which contains the sodio-chloride
of platinum, must still have a distinct yellow colour. The
platinum-salt is washed with alcohol, dried at 100, and
weighed. 100 parts correspond to 16'03 of potassium, or
1933,of potassa.
The amount of the chloride of sodium may be ascertained
by deducting the weight of the chloride of potassium from
that of the mixed chlorides. It is safer, however, to control
this result by direct determination, for which purpose the
filtered liquid is carefully evaporated to dryness, and the
mass strongly ignited in a covered platinum crucible; in
order to ensure the complete decomposition of the chloride
of platinum, the ignition should be repeated, with addition
of a few crystals of oxalic acid. From the cooled mass, the
chloride of sodium is extracted with water.
When, as is frequently the case, the two alkalies are
present as sulphates, together with an excess of acid, the
greater portion of the latter is expelled by careful evaporation, and the saline mass afterwards ignited in a covered
platinum crucible, into which small fragments of carbonate




SULPHATE OF SODA-AMMONIA.               5
of ammonia are from time to time introduced.  The joint
weight of the neutral salts thus obtained is then determined.
In order to convert these sulphates into chlorides, the
mass is moistened with water, mixed with pure chloride of
ammonium, and heated in a covered crucible until the
excess of the latter salt is expelled; this operation is
repeated until the weight is constant, when the chlorides
are separated by means of bichloride of platinum.
Or the solution of the sulphates may be precipitated by
a solution of pure acetate of baryta, the precipitate filtered
off, the filtrate evaporated to dryness, and the residue
ignited. From the carbonized mass, water dissolves the
alkalies as carbonates, which are converted into chlorides
by treatment with hydrochloric acid.
5. SULPHATE OF SODA AND OXIDE OF AMMONIUM.*
NaO, SO3; nNH40, SO3 + 4 HO.
To determine the amount of soda, a weighed portion of
the salt dried at 500 is gradually and carefully heated to
redness in a platinum crucible, a fragment of carbonate of
ammonia being held in the latter, at the end of the
operation, to complete the removal of the excess of sulphuric acid. From the weight of sulphate of soda obtained,
that of the soda is calculated.
The sulphuric acid is determined in another weighed
portion of the salt, which is dissolved in warm water and
* To prepare this salt, two equal portions of dilute sulphuric
acid are taken, the one neutralized with carbonate of soda, then
mixed with the other, ammonia added to neutralization, and the
solution evaporated to the crystallizing point.




6            SULPHATE OF SODA-AMIMIONIA.
precipitated by chloride of barium. From the weight of
the sulphate of baryta, after filtering, washing and igniting,
the amount of sulphuric acid is calculated.
The quantity of the ammonia may be estimated according to two different methods.
a. The weighed salt is dissolved in the smallest possible
quantity of water, and the solution mixed with excess of
an alcoholic solution of bichloride of platinum, which
precipitates the ammonia in the form of ammonio-chloride
of platinum.  When the precipitate is completely separated, it is filtered off, washed with alcohol, dried, and carefully ignited (see p. 4). From the weight of the residual
platinum, that of the oxide of ammonium is calculated.
100 parts of platinum correspond to 26'37 of oxide of
ammonium. In order to ascertain that the platinum does
not contain any sulphate of soda or chloride of sodium
which may have been precipitated by the alcohol, it is
washed with water and again weighed.
5. By distilling the weighed salt with a moderately concentrated solution of soda, the ammonia is evolved, and
may be combined with hydrochloric acid. This is best
effected in a small flask furnished with a funnel-tube by
which the solution of soda is introduced, and a long condensing-tube, the end of which dips into moderately-strong
hydrochloric acid. The liquid is retained in ebullition until
one-half has distilled over. The hydrochloric solution is
carefully evaporated to dryness in a weighed dish, over a
water-bath, and the residue of chloride of ammonium
weighed; or it may be converted into ammonio-chloride of
platinum, which is then treated as above.
After determining the soda, the ammonia and the sulphuric acid, the quantity of the water may be ascertained by
difference.  It may also be controlled by mixing a weighed




SULPHATE OF POTASSA-MAGNESIA.               7
portion of the powdered salt, in a platinum crucible, with
an excess of freshly-burnt lime, free from water and carbonic acid; the mixture is covered with a layer of lime,
the whole weighed, and very strongly ignited over a spiritlamp. The loss of wreight represents the joint amount of
the ammonia and water.
6. SULPHATE OF POTASSA AND MIAGNESIA.*
KO, SO3; MgO, SO3 + 6 HO.
This salt loses all its water at 133~.  The stlphuric acid
is determined by precipitation by chloride of barium (see
No. 3).
For the estimation of the magnesia, another weighed
quantity of the salt is dissolved in water, mixed with chloride of ammonium, subsequently with ammonia, and thle
magnesia precipitated as phosphate of magnesia-ammonia
by adding phosphate of soda. The precipitation is not
complete till after the lapse of twelve hours, when the precipitate is collected on a filter and washed with a mixture
of 3 parts of water and 1 part of caustic ammonia, in
which it is perfectly insoluble.  After drying, it is ignited,
being thus converted into  2 MgO, PO5 which contains
36'44 per cent of magnesia. The potassa may be determined by difference. If a direct estimation be required, as
is frequently the case, especially in the analysis of minerals,
the salt is dissolved in water, and the sulphuric acid and
magnesia precipitated by a hot saturated solution of hydrate of baryta. The excess of baryta is removed from
the filtered liquid by adding a mixture of ammonia and
* This salt is easily obtained in crystals, by mixing a boiling
saturated solution of 1 part of sulphate of potassa, with a saturated
solution of 1- part of sulphate of magnesia.




8          CARBONATE OF POTASSA-MAGNESIA.
carbonate of ammonia, the filtrate saturated with hydrochloric acid, evaporated, the chloride of potassium feebly
ignited and weighed.
If both potassa and soda be present, they are separated
as in No. 4.
From the mixed precipitate of magnesia and s-ulphate of
baryta, the former is dissolved by diluted sulphuric acid,
and afterwards precipitated and determined as above.
Another method consists in mixing the solution of the
double sulphates of magnesia and the alkalies with freshly
precipitated carbonate of baryta, and passing washed carbonic acid through the mixture for a considerable time.
The sulphate of baryta which is then produced is filtered
off, the solution evaporated to dryness, and the mass heated
nearly to redness.  A  mixture of carbonate of baryta,
magnesia, and alkaline carbonate is thus obtained, from
which the latter may be extracted with water, converted into
chloride, and weighed.
7. CARBONATE OF POTASSA AND MAGNESIA.*
KO, C02; 2(MgO, C02) + 9 HO.
When ignited, this salt loses - of its carbonic acid, and
the whole of its water, leaving a mixture of carbonate of
potassa and magnesia, which may be separated by water,
and quantitatively determined, the potassa for this purpose
being converted into chloride of potassium. The magnesia
should not be washed longer than is necessary, since it is
not entirely insoluble in water.
* Obtained in crystals on mixing a solution of chloride of magnesium with a saturated solution of bicarbonate of potassa.




EPSOM-SALT-GLAUBER'S-SALT.             9
The total quantity of carbonic acid contained in the
salt is deterlnined by expelling it in an apparatus arranged
for the quantitative determination of carbonic acid.  The
amount of water may then be inferred by difference.
The joint weight of the water and carbonic acid may be
determined by fusing a quantity of vitrified borax in a platinum crucible, weighing when cool, introducing the salt,
again weighing, and fusing over the spirit-lamp until all
the carbonic acid is evolved, and the fused borax becomes
clear. The loss of weight expresses the joint amount of
water and carbonic acid.
S. EPSOM-SALT AND GLAUBER'S-SALT.
MgO,O,  3 + 7HO and NaO, SO3 + 10 HO.
One hundred parts of pure sulphate of magnesia give, bv
the method described in No. 6, 45'28 parts of phosphate
of magnesia. A specimen of Epsom-salt adulterated with
Glauber's-salt will give a proportionally smaller quantity of
the phosphate.  Since 4552S parts of 2 AMgO, PO5 correspond to 100 parts of crystallized sulphate of magnesia, a
specimen of the latter which yields, for example, only 40
parts of 2 MgO, PO5, would contain only 88'3 per cent of
true Epsom-salt, and 11' 7 per cent of Glauber's-salt.
In order to test Epsom-salt for Glauber's-salt, the specimen is mixed with powdered charcoal, dried, and heated in
a crucible to bright redness. If sulphate of soda be present, water will dissolve out of the cold mass sulphide of
sodium, which, when treated with hydrochloric acid, is converted into chloride of sodium, with evolution of sulphuretted hydrogen.
Or the solution of the salt to be tested may be precipi



10           PHOSPHATE OF SODA-AMMONIA.
tated by hot saturated baryta-water, filtered, the excess
of baryta precipitated from the solution by a mixture of
ammonia and carbonate of ammonia, and the filtrate evaporated, when, if any Glauber's-salt have been present, carbonate of soda will be left.
9. PHOSPHATE OF SODA AND OXIDE OF AMMONIUM.*
NaO, NH40, HO, PO5 + 8 HO.
A weighed quantity of the salt is gradually and cautiously heated in a platinum crucible, the heat being finally
raised to ignition, and continued till the salt is in a state of
tranquil fusion. The ammonia and water are thus expelled,
their joint amount being indicated by the loss of weight.
The fused residue is NaO, PO5.
The determination of the ammonia is effected as in
No. 5, with another portion of the salt.
In order to determine the phosphoric acid, the salt is
dissolved in water and mixed with chloride of ammonium,
ammonia and sulphate of magnesia, the precipitate being
treated as in No. 6.  The ignited 2 MgO, PO5 contains
63'55 per cent of phosphoric acid.
For the direct determination of the soda, a weighed
quantity of the salt is dissolved in water, and the phosphoric acid precipitated by acetate of lead. From the
filtered liquid, the excess of oxide of lead is removed by
a mixture of ammonia and carbonate of amimolia, the' Six parts of crystallized phosphate of soda are dissolved, with the
aid of heat, in 2 parts of water, and in this solution 2 parts of
chloride of ammonium are dissolved. The filtered liquid deposits
crystals of the new salt which are purified by solution in hot ammoniacal water and recrystallization.




PHOSPHATE OF MAGTNESIA-AMMONIA.             1 1
solution heated to ebullition, filtered, evaporated to dryness and the residual acetate ignited, with access of air,
until the carbonate of soda is colourless.
As a control for the determination of the phosphoric
acid, the phosphate of lead may be decomposed by heating
with dilute sulphuric acid, and the phosphoric acid precipitated from the filtrate by sulphate of magnesia, as directed
above.
10. PHOSPHATE OF MAGNESIA AND OXIDE OF
AMMONIUM.-*
2 MgO, NH40, PO5 + 12 HO.
By ignition, the salt is converted into 2 MgO, PO5.
The ammonia is determined by dissolving the salt in
the smallest possible quantity of hydrochloric acid, mixing
the solution with bichloride of platinum and alcohol,
and treating the ammonio-chloride of platinum, as in
No. 5.
In order to separate and determine the phosphoric acid
and magnesia, the ignited salt is fused in  a platinum
crucible, over a spirit-lamp, with 4 parts of carbonate of
potassa and soda.t The mass is digested with water, the
residual magnesia washed, ignited and weighed.
* Prepared by precipitating a solution of sulphate of magnesia to
which much chloride of ammonium has been added, by phosphate
of soda, and washing the precipitate with dilute ammonia.
t Consisting of equivalent proportions of (KO, CO2 and NaO, CO2,
or 13 parts of the fdrmer, and 10 of the latter. Also easily obtained
by igniting Seignette-salt free from lime, dissolving, and evaporating
to dryness.




1 2       PHOSPHATE OF MAGNESIA-AMMONIA.
The alkaline solution is neutralized with acetic acid, and
the phosphoric acid precipitated by acetate of lead. The
precipitate is filtered off, washed, dried, detached as far as
possible from the filter, which is incinerated in a porcelain
crucible, in which the precipitate is then gently ignited and
weighed. Since its composition is variable, the quantity of
the phosphoric acid cannot be calculated from it. In order
to determine this acid, the precipitate is dissolved in warm
dilute nitric acid, and the oxide of lead separated by sulphuric acid, alcohol being afterwards added to complete
the precipitation.
The sulphate of lead is filtered off, washed, ignited and
weighed.  From the amount of this precipitate, that of the
phosphoric acid may be calculated.
The phosphate of magnesia and ammonia may also be
dissolved in acetic acid, the phosphoric acid precipitated
by acetate of lead, the excess of oxide of lead removed
from the filtrate by adding a mixture of ammonia and
carbonate of ammonia, heating, and filtering.  The solution, which contains acetate of magnesia, is evaporated,
and the residue ignited, until the magnesia is perfectly
white.
Another method of separating phosphoric acid and magnesia consists in dissolving the ignited salt in a little
hydrochloric acid, boiling the solution for some time in
order to convert the phosphoric acid into the tribasic form,
and mixing it, first, with solution of sesquichloride of iron,
and afterwards, with excess of acetate of ammonia; if the
solution be now boiled for some time, all the phosphoric
acid and iron are precipitated, and the magnesia remains
in solution.  The filtered liquid is evapoirated to dryness,
the residue heated till all ammoniacal salt is expelled and
moistened with sulphuric acid to convert the magnesia




CHLORIDES OF POTASSIUM, SODIUM, ETC.       13
into sulphate. The excess of acid is expelled by heat,
and the residual salt gently ignited; from the weight of
this residue that of the magnesia, and consequently of the
phosphoric acid, is calculated.
11. THE CHLORIDES OF POTASSIUM, SODIUM AND
MAGNESIUM.
In the analysis of minerals which are decomposed by
hydrochloric acid, there is frequently obtained, after the
separation of the other constituents, a mixture of the abovementioned chlorides.  The solution, if containing, as is
generally the case, ammoniacal salts, is evaporated to dryness, and the mass gently ignited in a platinum crucible
until the latter are volatilized. The magnesia and alkalies
are then separated according to one of the following
methods:
I. The mass is moistened with a concentrated solution
of carbonate of ammonia, dried and ignited, during which
operation, a fragment of carbonate of ammonia is held
within the partially closed crucible. This process is repeated until a constant weight is obtained. A mixture of
magnesia and alkaline chlorides is left, from which the
latter may be extracted by water. This method is more
difficult of execution in proportion as more alkaline chlorides are present.
II. The residue containing the three chlorides is mixed,
in a platinum crucible, with some water and a quantity of
finely-powdered oxide of mercury; the mixture is digested
for some time, dried, and ignited in a covered crucible,
when all the chloride of magnesium is decomposed and
converted into magnesia.




14           BITTER-SPAR AND DOLOMITE.
1II. The chlorides are dissolved in a little water, and the
solution boiled for a long time with freshly precipitated
carbonate of silver, when all the chloride of magnesium is
decomposed.  The precipitate is filtered off, washed, and
the precipitated carbonate of magnesia dissolved out with
dilute hydrochloric acid.
IV. The solution of the bases is mixed with some salammoniac and ammonia in excess, and the magnesia precipitated by phosphate of ammonia (see No. 6). From the
filtrate the ammonia is expelled by evaporation, and the
excess of phosphoric acid precipitated by acetate of lead as
a compound of phosphate and chloride of lead. The excess
of oxide of lead is precipitated by a mixture of ammonia
and carbonate of ammonia; the liquid digested, and the
precipitate filtered off. The alkalies are then obtained
by evaporation.- This method appears to be the most accurate.
If the three bases are combined with nitric acid, the
solution is evaporated, the mass treated, in a platinum
crucible, with carbonate of ammonia, and ignited. From
the residual mixture of magnesia and alkaline carbonates,
the latter are extracted by water.
Should they be in the form of sulphates, the process
indicated in No. 4 must be adopted.
12. BITTER-SPAR AND DOLOMITE.
CaO, CO2; MgO, CO,.
The mineral dried at 1000 is dissolved in dilute nitric
acid, the solution afterwards heated, in order to oxidize any
protoxide of iron, and, after cooling, neutralized with am



BONE-EARTH.                   15
monia and rapidly filtered from any precipitate of sesquioxide of iron. The lime is then precipitated by oxalate of
ammonia. When the precipitate has subsided, after being
digested for some time, it is filtered off, washed, dried and
ignited; it is then moistened with carbonate of ammonia,
again dried, and gently heated. It is weighed as carbonate
of lime. Or. it may be moistened with concentrated sulphuric acid, the excess of acid being expelled by evaporation
and subsequent ignition, and weighed as sulphate of lime.
After the filtered liquid has been mixed with excess of
ammonia, the magnesia is precipitated by phosphate of soda,
and the precipitate treated as in No. 6.
The quantity of carbonic acid contained in the mineral
may be determined by loss. It may also be ascertained
directly by means of the apparatus arranged for the quantitative determination of carbonic acid.
13. BONE-EARTH.
3 CaO, PO5 with 3 MgO, PO, and CaO, CO2.
A mass of white burnt bone is dissolved in dilute nitric
acid, the solution digested for some time to expel all the
carbonic acid, and the phosphates of lime and magnesia
precipitated by ammonia. When the precipitate has separated, the solution, which contains the lime previously in
combination with carbonic acid, is rapidly filtered, and the
precipitate thoroughly washed with ammoniacal water.
From the filtrate, the lime is precipitated by oxalate of
ammonia, and the precipitate treated as in No. 12.
The precipitate of phosphates of lime and magnesia is
dissolved in the smallest possible quantity of hydrochloric




16                   BONE-EARTH.
acid, and the lime precipitated by neutral oxalate of potassa.
The mixture is digested for some time at a gentle heat, to
promote the separation of the precipitate, and the clear
supernatant fluid is then cautiously neutralized with carbonate of potassa, in order to precipitate the oxalate of lime
dissolved by the liberated oxalic acid; as soon as it has
completely separated, the precipitate is filtered off.  From
the filtrate, which contains all the phosphoric acid and
magnesia, the latter is precipitated by ammonia as phosphate of magnesia-ammonia, which is treated as in No. 6.
From the liquid filtered from this precipitate, which must
contain free ammonia, the phosphoric acid is precipitated
by sulphate of magnesia.
Bone-earth may also be analyzed in the following manner.
The finely-powdered substance is heated for a long time,
nearly to boiling, with an excess of dilute sulphuric acid,
the greater part of the water is then evaporated, and the
mass mixed with twice its volume of absolute alcohol,
which dissolves the phosphoric acid. The mixture is filtered,
and the sulphates washed with alcohol. -From these the
sulphate of magnesia and a part of the sulphate of lime are
extracted with water, and separated as in No. 12. The sulphate of lime remaining undissolved is ignited and weighed.
The phosphoric acid solution is mixed with water, the alcohol
evaporated, and the phosphoric acid then precipitated by
sulphate of magnesia and ammonia as in No. 6.
A third method, based upon the insolubility of phosphate of binoxide of tin in nitric acid, is as follows: The
weighed bone-ash is heated in a flask, with moderately
strong nitric acid, and several times its weight of pure tin
(tin-foil), the weight of which must be accurately known;
the contents of the flask are heated to ebullition, diluted
with water, and the binoxide of tin, which contains the




HEAVY-SPAR-CELESTINE-GYrSUM.            17
whole of the phosphoric acid, is filtered off, washed, dried,
ignited and weighed. The difference between the weight
of this precipitate and that of the binoxide of tin which
should be furnished by the amount of metal employed, is
due to phosphoric acid. The separation of the lime and
magnesia contained in the solution is effected as in No. 12.
14. HEAVY-SPAR, CELESTINE, AND GYPSUM.
BaO, S03.-SrO, S03.-CaO, SO3 + 2HO.
The water in gypsum is determined by ignition. Gypsum in fine powder is entirely converted into carbonate by
heating with a solution of carbonate of soda; but the sulphates of baryta and strontia are only partly converted.
Hence these salts, in a state of fine, powder, must be
fused in a platinum crucible with three times their weight
of carbonate of potassa and soda. The mass is then treated
with boiling water, and the earthy carbonate filtered off at
a boiling heat, and washed.
The filtered solution is carefully neutralized with hydrochloric acid, the sulphuric acid precipitated by chloride of
barium, and the precipitate treated as in No. 3.
The earthy carbonates are dissolved in dilute nitric acid,
taking care to obtain a nearly neutral solution, which is
then evaporated to perfect dryness in a flask capable of being
closed. The saline mass is treated with about twice its
volume of absolute alcohol, with which it is allowed to
digest, in the closed flask, for a long time, being constantly shaken, but not heated. The alcohol dissolves the
nitrate of lime only. The mixture is filtered, and the two
undissolved nitrates washed with absolute alcohol in a
closely covered funnel.
c




18                  ALUMINA-ALUI.
The alcoholic solution is diluted with water, the greater
part of the alcohol evaporated, and the lime precipitated, as
in No. 12, by oxalate of ammonia.
The mixture of nitrates of baryta and strontia is dissolved in a little water, and the baryta precipitated by
freshly-prepared hydrofluo-silicic acid, previously mixed with
an equal volume of alcohol.  The silico-fluoride of barium
is collected on a weighed filter, washed with weak spirit,
and dried.
The filtrate containing the strontia is mixed with sulplhuric acid, evaporated to dryness, the sulphate of strontia
ignited, and weighed.
If baryta and lime only are to be separated, the solution
is largely diluted, the baryta precipitated by sulphuric acid,
and the lime separated from the filtrate by oxalate of
ammonia, after previously neutralizing with ammonia.
For the separation of baryta and strontia, neutral chromate of potassa may also be employed, which precipitates
all the baryta as chromate; the latter is washed, dried,
ignited and weighed.  It is necessary, however, that the
solution should be perfectly neutralized and largely diluted.
The strontia may afterwards be precipitated by neutal carbonate of ammonia.
15. ALUMINA-ALUM.
KO, SO3; A1203, 3 S03+ 24 H-O.
A weighed quantity of the pure salt is dissolved in water,
and the sulphuric acid precipitated by chloride of bariunm.
From the solution filtered from the sulphate of baryta,
the alumina is precipitated, together with the excess of
baryta which has been added, by a mixture of carbonate of




IRON-AMMONIA-ALUM.                  19
ammonia and free ammonia. After gently heating for some
time, the precipitate is filtered off, the solution evaporated,
and the saline mass heated till all the chloride of ammonium is volatilized. The gently-ignited residue is chloride
of potassium.
The precipitate containing alumina and baryta is dissolved in dilute hydrochloric acid, and the baryta precipitated by sulphuric acid.
From the solution filtered from the sulphate of baryta,
the alumina is precipitated by carbonate of ammonia, or
better, by sulphide of ammonium, either of which effects a
more complete precipitation than caustic ammonia.
The precipitated hydrate of alumina is well washed, for
which purpose hot water is to be preferred, and strongly
ignited in order to expel the water.
The water contained in the alum is determined by loss.
It may also be estimated directly by exposing the salt for
a very long time to a gradually increasing heat, which n~ist
finally be raised to dull redness.
16. IRON-AMMONIA-ALUM.*
NH4O, SO3; Fe203, 3 SO3 + 24 HO.
At a strong red heat, this salt is entirely decomposed,
leaving pure sesquioxide of iron.
The determination of ammonia is effected as in No. 5;
that of sulphuric acid according to No. 3.
* Powdered red or brown iron-stone is digested with concentrated
sulphuric acid; the white sulphate thus produced is dissolved in
water, the solution mixed with sulphate of ammonia, filtered and
allowed to crystallize.
c2




20               ALUMINA-CHROME-ALUM.
In order to control the determination of the sesqluioxide
of iron, another portion of the salt is dissolved in water, and
the sesquioxide precipitated by ammonia. The precipitated
hydrate is washed, dried and ignited.
17. ALUMINA-CHROME-ALUM.*
Cr20.
KO, SO3; 1203, 3 S03 + 24 HO
The sulphuric acid is precipitated by chloride of barium
as in No. 3.
The alumina, sesquioxide of chromium, and excess of
baryta are precipitated from the filtrate by carbonate of
ammonia mixed with caustic ammonia. After long standing, the precipitate is filtered off and thoroughly washed.
The filtrate is evaporated, the residue heated to expel
chloride of ammonium, and the residual chloride of potassium gently ignited in a covered crutcible.
The mixed precipitate is dried, ignited, and fused with
about twice its weight of carbonate of soda and the same
quantity of nitre, in a porcelain crucible, when all the
chromium is converted into chromate of potassa; this is
* Three parts of finely-powdered bichromate of potassa are mixed
with 15 parts of water, and 1 part of concentrated sulphuric acid
is gradually added, so that no evolution of heat may ensue; sulphurous acid gas is then passed through the solution, which is kept
cool, so that its temperature may not rise above 400, until the odour
of the gas begins to be perceptible. After some time, octohedra of
pure chrome-alum are formed, which may be set aside. The motherliquor is mixed with an equal volume of a solution of common alum,
saturated at 400, when the salt in question separates in yellowish
octohedra.




PHOSPHORIC ACID AND ALUMINA.           21
extracted with water, and the residue of alumina and carbonate of baryta carefully washed.
The solution of alkaline chromate is carefully mixed
with excess of hydrochloric acid and some alcohol, and
heated until it has a pure emerald-green colour. The sesquioxide of chromium is precipitated from the hot solution
by caustic ammonia, washed, dried, ignited and weighed.
The mixture of alumina and carbonate of baryta is dissolved in hydrochloric acid, the baryta precipitated by sulphuric acid, and afterwards the alumina by sulphide of
ammonium (see No. 15).
18. PHOSPHORIC ACID AND ALUMINA.
I. The ignited and weighed alumina containing phosphoric acid is dissolved in concentrated hydrochloric acid,
and tartaric acid added to the solution until it gives no
precipitate with excess of ammonia. Chloride of ammonium and sulphate of magnesia are then added, the precipitated phosphate of magnesia-ammonia being treated as
in No. 6. It generally contains a little alumina which
may be separated by redissolving the precipitate, adding
tartaric acid, and reprecipitating by ammonia.
II. The alumina containing phosphoric acid, after precipitation by ammonia, is dissolved in solution of caustic
soda, the phosphoric acid precipitated from the diluted
solution as phosphate of baryta, by chloride of barium, or
baryta-water, caustic soda again added, the mixture heated
nearly to the boiling-point, and filtered.  The filtrate,
containing alumina, is acidified, and the alumina precipitated, as directed in No. 15.
The baryta-precipitate is dissolved in hydrochloric acid,




22 2PHOSPHORIC ACID AND ALUMINA.
the baryta precipitated by sulphuric acid, and afterwards
the phosphoric acid by ammonia and sulphate of magnesia.
III. The freshly-precipitated alumina is dissolved in the
smallest possible quantity of caustic soda, the solution
diluted, heated to ebullition, and a solution of silicate of
soda added as long as any precipitate of silicate of alumina
is produced. Lastly, in order to precipitate the whole of
the silicic acid, a concentrated solution of sal-ammoniac is
added, the solution again boiled and filtered. From the
filtrate, the phosphoric acid is precipitated by ammonia and
sulphate of magnesia.
T1he silicate of alumina is decomposed by concentrated
hydrochloric acid, the mass evaporated to dryness on the
water-bath, the residue moistened with hydrochloric acid,
the alumina-salt extracted with water, and the alumina
precipitated by carbonate of ammonia.
IV. The weighed alumina containing phosphoric acid is
dissolved in concentrated nitric acid, and the solution
heated with about the same quantity (accurately weighed)
of pure tin (tin-foil). The mixture is diluted with water,
heated until boiling, and the binoxide of tin which has combined with the whole of the phosphoric acid is filtered off',
washed, and ignited.  The difference between the weight
of this precipitate and that of the binoxide of tin which
should have been furnished by the metal employed,
represents the phosphoric acid.  The alumina is then
precipitated from the solution by sulphide of ammonium.




ALUMINA ANb SESQUIOXIDE OF IRON.         23
19. ALUMINA AND SESQUIOXIDE OF IRON.
The mixture of the two is dissolved in hydrochloric acid,
the greater part of the excess of acid evaporated, the solution
mixed with an excess of pure solution of potassa and heated
nearly to the boiling-point. The alumina is thus dissolved,
the sesquioxide of iron being left behind of a dark brown
colour. The solution is filtered off, acidulated with hydrochloric acid, and the alumina precipitated by sulphide of
ammonium.
The sesquioxide of iron, which contains some potassa, is
dissolved in hydrochloric acid, and re-precipitated by ammonia.
This method of separation is unsafe, and, unless repeated more than once, incomplete. It is better to heat
the acid solution to ebullition, to add sulphite of soda, in
order to reduce the sesquioxide of iron to the state of protoxide, to neutralize with carbonate of soda, and afterwards
to boil with excess of caustic soda until the precipitate is
black and pulverulent.
The solution is then filtered off, slightly acidulated with
hydrochloric acid, and the alumina precipitated by sulphide
of ammonium.
Another method of separation consists in heating the
previously ignited precipitate to bright redness, in a little
porcelain boat placed within a porcelain tube through
which a stream of dry hydrogen is passed. The precipitate is allowed to cool in the stream of gas, and weighed.
The amount of the sesquioxide of iron may be inferred from
the loss of weight, and the result controlled by dissolving
out the reduced iron with very dilute nitric acid, and
weighing the residual alumina.




'24    PHOSPHORIC ACID AND SESQUIOXIDE OF IRON.
20. PHOSPHORIC ACID AND SESQUIOXIDE OF IRON.*
In order to separate phosphoric acid from sesquioxide of
iron, the compound is ignited with at least an equal weight
of carbonate of potassa and soda (No. 10), the resulting
mass exhausted with water, the solution supersaturated with
hydrochloric acid and then with ammonia, and the phosphoric acid precipitated by sulphate of magnesia.
The residual sesquioxide of iron retains some alkali.
Or the sesquioxide of iron containing phosphoric acid
is dissolved in hydrochloric acid, precipitated by ammonia,
and digested with excess of sulphide of ammonium (without
previous filtration), until all the sesquioxide is converted
into sulphide of iron.   When the liquid is no longer
green, but of a pure yellow colour, it is filtered off, and
the phosphoric acid immediately precipitated by sulphate
of magnesia.
For the accurate quantitative separation of a small quantity of phosphoric acid from a large quantity of sesquioxide
of iron, the latter is dissolved in hydrochloric acid, and
the solution heated to ebullition with sulphite of soda till
its colour has changed to a bright green, when all the sesquioxide of iron is converted into protoxide.  The solution
is boiled till it no longer smells of sulphurous acid, neutralized with carbonate of soda, and, in order to produce
a little sesquioxide of iron, mixed with a very little chlorinewater, the quantity of which must be regulated according
to the amount of phosphoric acid which is present. The
* For analyses for practice, the phosphate of sesquioxide of iron
is prepared by precipitating sesquichloride of iron with phosphate of
soda. Or a mixture of phosphates may be prepared by precipitating
a solution containing sesquichloride of iron, chloride of calcium,
chloride of magnesium, and chloride of manganese.




SPECULAR  IRON.  BROWN IRON-ORE.          2 5
solution must now be mixed with an excess of acetate of
soda, when phosphate of sesquioxide of iron separates as a
white precipitate. Chlorine-water is then added, drop by
drop, until the liquid has assumed a reddish colour, when it
is boiled, so that the precipitate may collect, and be filtered.
From this precipitate the phosphoric acid is separated by
sulphide of ammonium, as directed above.
Or it may be dissolved in hydrochloric acid, boiled with
sulphite of soda, and afterwards with excess of caustic soda,
till the precipitate is converted into black proto-sesquioxide
of iron, which is filtered off. The solution is acidified, and
the phosphoric acid precipitated as above.
21. SPECULAR  IRON, Fe2O3, AND BROWN IRON-ORE,
Fe203, 3 HO.
For the determination of the water, weighed fragments
of the iron-stone are heated to redness, for a long time, in
a platinum crucible. If the mineral decrepitates, it must
first be finely powdered.
In order to determine the oxygen, the fragments of
ignited iron-stone or of specular iron are heated to redness
in a weighed bulb-tube of very infusible glass (the bulb
being as small as possible), through which a stream of dry
hydrogen, free from arsenic, is transmitted as long as any
water is formed. The reduction must be effected at the
highest temperature of the spirit-lamp, for otherwise the
reduced iron, even when cool, may reoxidize and sometimes
inflame in the air. It is safer to reduce the oxide in a
small porcelain boat, placed in a tube of porcelain, which
is heated by a charcoal fire.
The reduced iron is dissolved in hydrochloric acid.




2 6              MAGNETIC IRON-ORE.
Silicic acid, which is often contained in brown iron-stone,
is then left undissolved, and may be weighed.
22. MAGNETIC IRON-ORE.*
FeO, Fe203.
To determine the amount of oxygen which is combined
with the iron, the proto-sesquioxide is reduced by hydrogen,
as in No. 21.
If the substance contain only proto-sesquioxide of iron,
the whole of the iron may be determined by dissolving in
hydrochloric acid, heating with some chlorate of potassa,
to convert all the protochloride into sesqluichloride, and
adding ammonia to precipitate the sesquioxide of iron,
which is washed, dried, ignited and weighed.
If other constituents be present, the total amount of
iron may be determined as follows: The substance is dissolved in an excess of hydrochloric acid, the protochloride
converted into sesquichloride by addition of chlorate of
potassa, and all free chlorine expelled by boiling.  The
solution is then diluted with water until the flask is more
than half-full; a weighed strip of bright sheet-copper is
placed in the solution, the flask closed by a cork furnished
with a narrow glass tube, and the liquid heated to ebullition. It is retained at this temperature until the darkbrown colour originally observed has changed to a pale
yellowish-green.  The whole of the iron is now contained
in the solution as protochloride, in consequence of the
formation of subcliloride of copper.  The orifice of the
little tube is closed air-tight, and the solution allowed
* Smithy-scales have a similar composition.




MAGNETIC IRON-ORE.                27
to cool somewhat.  The flask is then filled with hot water,
the liquid poured off from the undissolved copper, which is
to be washed, first with dilute hydrochloric acid, then
repeatedly with water, dried, and weighed.-The atomic
weight of copper is to that of iron as the quantity of
copper dissolved is to that of the iron sought.
In order to determine directly the amount of protoxide
and sesquioxide of iron present in a substance, it must be
dissolved in hydrochloric acid. The following is the method
adopted: The compound is dissolved in an excess of concentrated hydrochloric acid, in a flask filled with carbonic
acid, and afterwards closed; the flask is then nearly filled
up with water, previously boiled, and a weighed strip of
copper introduced; the closed flask is placed in water,
which must be gradually heated to boiling, the subsequent
process being conducted and the result calculated as
directed above.
Or the weighed substance is placed in a flask closed with
a cork, and furnished with tubes for ingress and egress,
and with a funnel-tube passing to the bottom of the flask,
which is to be filled with carbonic acid. Hydrochloric acid
is then added through the funnel-tube, and the solution
assisted by heat, whilst carbonic acid is allowed to stream
through the apparatus. The solution is afterwards diluted,
through the funnel-tube, with boiled water, and a milky mixture of carbonate of baryta with water gradually added; this
precipitates the whole of the sesquioxide of iron, while the
protoxide remains in solution.  When the supernatant
liquid has become clear, it is decanted through the egresstube, the precipitate again mixed with water, and after the
clear liquid has been again decanted, quickly thrown upon
a filter, and rapidly washed, air being excluded, with water
which has been previously boiled and allowed to cool.




28                SPATHIC IRON-ORE.
The iron precipitate is dissolved in dilute hydrochloric
acid, the baryta separated by sulphuric acid, and the sesquioxide of iron precipitated by ammonia.
The solution, which contains the protoxide of iron, is
mixed with hydrochloric acid and chlorate of potassa, and
concentrated by evaporation; the baryta is then precipitated
by sulphuric acid, and afterwards the sesquioxide of iron by
ammonia.
23. SPATHIC IRON-ORE.
FeO, CO, frequently containing MnO, CO2,-CaO, CO2,
and MgO, CO2.
I. The best method of analysis, which is especially
applicable where but little manganese is present, is the
following: A weighed portion of the powdered ore, previously dried, is dissolved in hydrochloric acid, with the
aid of heat, nitrate or chlorate of potassa being added
from time to time, so that the whole of the protoxide of iron
is sure to be converted into sesquichloride. The solution,
which must still be acid, so that chloride of ammonium
may be formed, is diluted, and gradually neutralized with
dilute ammonia, until it has acquired a dark brown-red
colour, and a small quantity of hydrated sesquioxide of
iron is precipitated. The whole of the sesquioxide of iron
is then separated by neutral succinate of ammonia, while
protoxide of manganese, lime and magnesia remain in
solution.  The precipitated succinate of sesquioxide of iron
is rapidly filtered off, washed with cold water, dried, and
gradually heated to redness in a porcelain crucible, with
free access of air, till it is converted into pure sesquioxide
of iron.




SPATIIC IRON-ORE.               29
The filtrate is feebly acidulated with hydrochloric acid,
evaporated to dryness, and heated till all ammoniacal salts
are expelled.
The residue is then dissolved in a small quantity of
water, with addition of hydrochloric acid, the solution
saturated with chlorine, and the manganese precipitated as
hydrated sesquioxide by addition of ammonia. The liquid
is rapidly filtered off, so that no carbonate of lime may be
precipitated, and the manganese-precipitate washed, dried,
and ignited, when it is converted into proto-sesquioxide.
The lime and magnesia in the filtrate are separated as
in No. 12.
Or the manganese may be precipitated by sulphide of
ammonium, the sulphide of manganese rapidly filtered off,
and dissolved in hydrochloric acid.  When all the sulphuretted hydrogen has been expelled by evaporation, the
solution is heated with carbonate of soda, when the manganese is precipitated as carbonate, which, after ignition,
leaves the proto-sesquioxide.
From the solution filtered from the sulphide of manganese, the lime and magnesia are precipitated as in
No. 12.
II. The acid solution is largely diluted with water, and
carbonate of soda gradually added (drop by drop, when the
solution is neutral), with constant stirring, until all the
sesquioxide of iron is precipitated. The other bases remain
dissolved in the free carbonic acid. The manganese is then
best precipitated by hypochlorite of soda, in the cold.
III. When a larger quantity of manganese is present, the
solution, which must contain the iron entirely in the form
of sesquichloride, and must not be too acid, is gradually
mixed with carbonate of baryta, which precipitates the sesquioxide of iron only.  When a slight excess of carbonate of




30                  BOG-IRON-ORE.
baryta has been added, and the solution well stirred, it is
filtered.  The washed precipitate is dissolved in dilute
hydrochloric acid, the baryta precipitated by sulphuric
acid, and the sesquioxide of iron by ammonia.
From the solution which contains the other three bases,
the dissolved baryta is first precipitated by sulphuric acid,
and the solution treated as in No. 12.
IV. The diluted solution, obtained as in I, is neutralized
with carbonate of soda till it has a dark brown-red colour,
mixed with a saturated solution of acetate of soda, and
heated to ebullition, when the whole of the sesquioxide of
iron is precipitated.
The filtrate is neutralized with carbonate of soda, mixed
with hypochlorite of soda (containing bicarbonate of soda),
and allowed to stand, in a closed vessel, for twenty-four
hours, when the manganese is precipitated as hydrated
sesquioxide, which is ignited and weighed as proto-sesquioxide.
From the filtered liquid the lime and magnesia are
separated as above.
24. BOG-IRON-ORE.
Fe203 with MnO, A1203, CaO, MgO, SiO3, PO, AsO5.
If the amount of iron only is to be determined, the
process with copper may be employed, as in the case of
magnetic iron; or the ore may be subjected to the dry
assay. The complete analysis is effected in the following
manner:
I. The mineral, dried at 100~, is ignited, and the water
determined.
II. Another portion, which has not been ignited, is




BOG-IRON-ORE.                   31
coarsely powdered, and dissolved in hydrochloric acid;
the solution is evaporated to perfect dryness on the waterbath, the mass dissolved in warm dilute hydrochloric acid,
and the sand and silicic acid removed by filtration.  The
latter may, after ignition and weighing, be separated from
the sand by boiling with carbonate of soda.
III. The hydrochloric solution is boiled with an alkaline
sulphite, until it no longer smells of sulphurous acid, to
reduce the sesquichloride of iron to protochloride, and the
arsenic acid to arsenious acid, which is then precipitated
by sulphuretted hydrogen, as tersulphide of arsenic; sometimes mixed with a little sulphide of copper.
IV. The solution is boiled till the sulphuretted hydrogen
is completely expelled, precipitated by carbonate of soda,
mixed with an excess of caustic soda, and boiled until the
precipitate becomes pulverulent.
V. The solution is filtered off.  It contains all the alumina and part of the phosphoric acid, which are separated
as in No. 18.
VI. The precipitate, consisting of proto-sesquioxide of
iron, carbonate of protoxide of manganese, carbonate and
phosphate of lime and magnesia, is dissolved in hot nitric
acid; the solution is neutralized, as far as possible, with carbonate of soda, mixed with acetate of soda, and boiled,
when all the phosphoric acid and sesquioxide of iron are
precipitated. In order to separate these, the precipitate is
treated as in No. 20.
VII. The filtrate contains the protoxide of manganese,
lime, and magnesia, which are separated as in No. 23.




32              SULPHATE OF COPPER.
25. SULPHATE OF COPPER.
CuO, SO 3+ 5 HO.
For analysis, the salt is purified by recrystallization.
To determine the water, a weighed quantity of the dry
salt, in the state of fine powder, is heated to about 200~,
until it has become perfectly white, and has ceased to lose
weight.
It is then dissolved in water, and the sulphuric acid precipitated by chloride of barium, as directed in No. 3.
For the determination of copper, another weighed portion
of the salt is dissolved in from 50 to 100 times its weight
of water, in a dish or a wide-mouthed flask; the solution
is heated until boiling, and the oxide of copper precipitated
by caustic potassa, which should not be added in too large
excess.  The brownish-black  precipitate is filtered off,
washed with hot water, dried and weighed.
To determine the amount of oxygen in the oxide of
copper, a freshly-ignited portion is introduced into a
weighed bulb-tube, and its weight carefully ascertained;
a stream of dry hydrogen, free from arsenic, is then passed
through the tube, the bulb of which is heated to redness
with a large spirit-lamp flame. When no more aqueous
vapour is perceptible, and the oxide is completely reduced
to the metallic state, it is allowed to cool in the stream of
gas, and weighed as soon as the hydrogen in the tube has
been replaced by atmospheric air.
26. COPPER-PYRITES.
Cu2S, Fe2S3.
The powdered mineral is introduced into a flask, placed
obliquely, and gradually mixed with concentrated nitric




COPPER-PYRITES.                 33
acid, added in small portions at a time; the contents of
the flask are then heated until either the whole is dissolved,
or the metals have passed into solution together with a portion of the sulphur, and the unoxidized sulphur has separated in the form of a yellow powder, or in fused drops of
a clear yellow colour. The solution is diluted with water,
and decanted from any undissolved sulphur, which is well
washed, dried in a porcelain crucible, at a gentle heat, and
weighed. It is then burnt in order to ascertain whether it
contains any metal or quartz, &c.  Should the sulphur be
separated in a pulverulent state, it must be collected on a
weighed filter, washed, and dried at a very gentle heat.
From the filtered solution, that portion of the sulphur
which has been converted into sulphuric acid is precipitated
by chloride of barium, and the sulphate of baryta treated
as in No. 3. Protracted washing with hot water is necessary, since the precipitate has carried down some'nitrate of
baryta.
In order to avoid this, the mineral may be dissolved in
concentrated hydrochloric acid, with gradual addition of
nitric acid, or of chlorate of potassa.
The excess of baryta having been removed from the
liquid filtered from the sulphate of baryta by means of
sulphuric acid, a slow stream of sulphuretted hydrogen
is passed through the filtrate, until the odour of the gas is
distinctly perceptible. The precipitated sulphide of copper
is thrown, as rapidly as possible, upon a dried and weighed
filter, and well washed with water containing sulphuretted
hydrogen.
It is then dried in the funnel at 200, weighed, a
portion of it introduced into a weighed bulb-tube, which
is afterwards again weighed, and heated in a stream of
hydrogen until it no longer loses any sulphur.  It is thus
D




34                  ZINC-BLENDE.
converted into Cu2S, which contains the same amount of
copper as the protoxide.  The weight obtained is calculated upon the whole quantity of sulphide of copper.
Or the filter with its contents may be allowed to dry
in the funnel, the precipitate detached, and thrown into
a beaker; the filter is then completely incinerated, the ash
added to the sulphide of copper, and the latter oxidized
with aqua-regia till the sulphur separates of a pure yellow
colour. From the filtered solution, the protoxide of copper
is precipitated at a boiling heat by caustic potassa, ignited
and weighed.
The solution filtered from the sulphide of copper, containing the iron in the form of protoxide, is heated nearly
to boiling, in a flask, concentrated if necessary by evaporation, and treated at the same time with chlorate of potassa
in small portions, until all the protoxide of iron is converted into sesquioxide, which is then precipitated by
ammonia, washed, dried and ignited.
Notwithstanding the solubility of oxide of copper in
caustic ammonia, this reagent will not effect its complete
separation from sesquioxide of iron, since the latter carries
down with it a considerable quantity of oxide of copper
which cannot be extracted by ammonia.
27. ZINC-BLENDE.
ZnS.
The solution is effected just as in the case of copperpyrites. The mineral must be very finely powdered, and
very concentrated acid must be employed.
After the sulphuric acid which is produced has been
precipitated by chloride of barium, and the excess of




ZINC-BLENTDE.                 35
baryta has been removed, the solution is saturated with
sulphuretted hydrogen, in order to precipitate any copper
and cadmium which often occur in small quantities in this
mineral. The precipitate, after being filtered off and
washed, is dissolved, together with the filter, in nitric acid,
the solution mixed with excess of potassa, and afterwards
with as much hydrocyanic acid as is required to dissolve
the precipitate. From this solution, containing the cadmium and copper in the form of double cyanides, the
cadmium is precipitated by sulphuretted hydrogen, while
the copper is left in solution. This solution is then boiled
with aqua-regia, and the oxide of copper precipitated from
the hot solution by potassa. For the method of treating
the sulphide of cadmium, see Zinc and Cadmium.
The first filtrate, which contains the zinc and generally
a little iron, is heated to ebullition, and mixed, first with
some hypochlorite of soda to peroxidize the iron, then
with excess of ammonia, until all the oxide of zinc is
redissolved, and the, sesquioxide of iron precipitated; the
latter is then washed and ignited. It cannot be obtained
by this method perfectly free from oxide of zinc.
From the filtrate, the zinc is precipitated by sulphide of
ammonium. The precipitate should not be filtered off
until it has separated from the liquid; it is washed with
water containing a little sulphide of ammonium, and digested (together with the filter), while yet moist, with
concentrated hydrochloric acid, the solution filtered off, and
the oxide of zinc precipitated, at the boiling-point, by carbonate of soda. The precipitate is washed, dried, ignited,
and weighed as pure oxide of zinc.
Sesquioxide of iron may be more completely separated
from oxide of zinc by means of succinate of ammonia, as
described in No. 23, or by carbonate of baryta (No. 23, III.)
D 2




36                    CALAMINE
If, as has been proposed, the solution were mixed with
acetate of soda, so as to convert the iron and zinc into
acetates, and treated with sulphuretted hydrogen, not only
zinc, but iron also would be precipitated.
28. CALAMINE.
ZnO, CO2.
Common calamine generally contains small quantities of
protoxides of iron, manganese, lead and cadmium, together
with lime, magnesia and silicic acid.
It is dissolved in hydrochloric acid, the solution evaporated to dryness, the mass digested with concentrated
hydrochloric acid, diluted, heated, and the silicic acid
filtered off.
The solution, which must be acid, is saturated with
sulphuretted hydrogen, which precipitates the lead and
cadmium.
This precipitate is oxidized with concentrated nitric acid,
a little sulphuric acid being also added, evaporated to dryness, and the sulphate of cadmium separated from the
sulphate of lead by water. (See Lead and Bismuth.)
The filtrate is boiled, to expel the sulphuretted hydrogen,
and treated with chlorate of potassa to peroxidize the iron.
Prom the solution, which must still contain free chlorine,
the sesquioxides of iron and manganese are precipitated by
excess of caustic ammonia, and separated as in No. 23.
The zinc is precipitated from the filtered solution, as
sulphide, by addition of sulphide of ammonium, and the
precipitate treated as in No. 27. The solution is rapidly
filtered off, with as little exposure to air as possible, and




SULPHATE OF RON.  BRASS.            37
the lime precipitated by oxalate of ammonia; the magnesia
is afterwards separated by phosphate of soda.
If a specimen of calamine consist of carbonate and
silicate of zinc, their relative quantities may be approximately determined by igniting the finely-powdered mineral,
and digesting it with a mixture of carbonate of ammonia
and free ammonia, which dissolves the oxide of zinc previously in combination with carbonic acid, leaving the
silicate untouched.
29. SULPHATE OF IRON WITH  THE SULPHATES OF
COPPER AND ZINC.
FeO, SO3 with CuO, S03,-ZnO, SO3 and HO.
The aqueous solution is strongly acidified with hydrochloric acid, and the copper precipitated by sulphuretted
hydrogen. (See No. 25.)
The iron and zinc are then separated and determined as
in No. 27.
Or the solution may be treated with hypochlorite of soda
to peroxidize the iron, afterwards neutralized with carbonate of soda till it has become of a dark red colour,
mixed with acetate of soda, and boiled until all the sesquioxide of iron is precipitated. With the latter, however,
a small quantity of zinc is usually precipitated by this
method.
30. BRASS.
The alloy is dissolved in hydrochloric acid with gradual
addition of nitric acid, the solution diluted, and the copper
precipitated by sulphuretted hydrogen. (See No. 25.)




38                      BRASS.
The excess of sulphuretted hydrogen is expelled from
the filtrate by boiling, and the oxide of zinc precipitated
from the hot solution by carbonate of soda. (See No. 27.)
Oxide of zinc cannot be entirely separated from oxide of
copper by even a very large excess of caustic potassa.
Too little zinc is usually obtained by the above process,
because a portion is carried down with the sulphide of
copper. The separation is more completely effected by
neutralizing the diluted solution of the alloy with ammonia,
and digesting with a slight excess of solid hydrate of
potassa until it has lost its colour and ammoniacal odour.
The oxide of copper is then filtered off, and washed with
hot water. From the alkaline solution, the zinc is precipitated by sulphide of ammonium.
The brass sometimes contains traces of tin, It is then
dissolved in hot nitric acid, which leaves the binoxide of
tin (containing a little copper) untouched.
In order to detect a small quantity of lead which frequently occurs in brass, the sulphide of copper precipitated
by sulphuretted hydrogen is oxidized with fuming nitric
acid, the mass dried, and treated with water, which leaves
the sulphate of lead undissolved. Should this contain
sulphur, it must be burnt off.
Or the brass may be dissolved in nitric acid, a little
sulphuric acid added, the solution evaporated to dryness,
and the mass treated with water.
If the brass be placed in a little porcelain boat, and
heated to redness in a porcelain tube through which a
rapid stream of hydrogen is passed, all the zinc may be
volatilized.




CADMIUM AND ZINC.                39
31. OXIDES OF MANGANESE, IRON, AND ZINC.
The solution, which must contain the iron in the form
of sesquioxide, is mixed with carbonate of soda until a
permanent precipitate begins to appear; it is then boiled
with acetate of soda, when all the sesquioxide of iron is
precipitated.
The filtrate is mixed with acetic acid, and the zinc precipitated by sulphuretted hydrogen.
The manganese may be precipitated, after neutralization,
with an alkaline hypochlorite, or by boiling with an alkaline carbonate.
32. CADMIUM AND ZINC.
The alloy of the two metals is dissolved in hydrochloric
acid, the solution, which must be decidedly acid, is largely
diluted, and saturated with a slow stream of sulphuretted
hydrogen, which precipitates all the cadmium in the form
of a yellow sulphide. The latter is thrown upon a weighed
filter, and dried at 1000 till of constant weight.
It is more accurate to dissolve the sulphide of cadmium
in hydrochloric or nitric acid, and to precipitate the oxide
of cadmium from the solution, as white carbonate, by
means of carbonate of soda. The precipitate is washed,
dried and ignited, when it is converted into the brown
oxide. Previously to the incineration of the filter, the
precipitate should be detached, as far as possible.
The filtrate is boiled to expel the sulphuretted hydrogen,
and the zinc precipitated from the hot liquid by carbonate
of soda.




40                      GAINA.
Another method consists in precipitating the cadmium
from the solution containing the two metals, by carbonate
of baryta.
An approximative separation of the two metals may be
also effected by mixing the solution with an excess of ammonia till the precipitate is completely redissolved, adding
a saturated solution of sulphurous acid, and boiling till the
excess of the latter is expelled. The cadmium is then
precipitated as a white, crystalline, double sulphite of
ammonia and oxide of cadmium, while the zinc remains
in solution.
33. GALENA.
PbS.
The finely-powdered mineral, placed in a capacious dish,
is gradually moistened with fuming nitric acid until it is
entirely converted into white sulphate of lead; a few drops
of sulphuric acid are added, to ensure complete conversion,
the mass ignited and weighed.
If the residue, previously to ignition, be treated with
water, and filtered, only traces of lead are found in the
solution.  If the galena contain copper, iron or silver,
they will be detected in the solution, the two first by ammonia and the silver by hydrochloric acid.
If the galena be oxidized with more diluted nitric acid,
the residue consists of a mixture of sulphate of lead and
sulphur, while the solution contains nitrate of lead, from
which the lead may be precipitated by sulphuric acid, or,
more completely, by oxalate of ammonia, after neutralization. By igniting the dried residue, the sulphur is volatilized, and sulphate of lead remains.




WHITE LEAD.                 41
When boiled with a solution of carbonate of soda, the
sulphate of lead is converted into carbonate, which, after
washing, is completely dissolved by nitric acid.
Sulphate of lead is dissolved to a great extent by a mixture of tartrate of ammonia and free ammonia. From this
solution it may be completely precipitated by sulphide of
ammonium as black sulphide of lead, or by chromate of
potassa, in the form of yellow chromate of lead.
34. WHITE LEAD.
2 (PbO, CO2) + PbO, HO
frequently mixed with BaO, SO,,-CaO, S03, —CaO, CO2,
or PbO, S03.
Pure white lead is perfectly soluble in dilute nitric acid.
The oxide of lead may be determined by ignition, after
drying at 100~. In order to estimate the water, a specimen,
which has been dried at 100~, is ignited in a tube to which
a weighed chloride-of-calcium-tube is attached.  The carbonic acid, which is expelled at the same time, is determined by loss. White lead sometimes contains a small
quantity of basic acetate of lead, indicated by the odour of
acetone which is perceived when the specimen is ignited.
White lead adulterated with chalk is likewise dissolved,
with exception of traces of impurities, by nitric acid. From
the diluted solution, the lead is precipitated by sulphuretted hydrogen, the sulphide of lead collected upon a
weighed filter, washed, dried at 100~, and weighed.-From
the solution, after neutralizing with ammonia, the lime is
precipitated by oxalate of ammonia.
If heavy-spar be present in the specimen, it is left behind




42                   PYROMORPHITE.
on treatment with nitric acid. After washing and igniting,
it is weighed and analyzed as in No. 14.
Gypsum would also be in great measure left behind on
dissolving in nitric acid. It may, however, be entirely dissolved and separated from any heavy-spar present at the
same time, by boiling with a large quantity of dilute nitric
acid. The amount of gypsum present may be inferred
from that of the sulphate of baryta obtained by precipitating the solution with chloride of barium.
Sulphate of lead would also be left undissolved by dilute
nitric acid. After washing, it becomes black when treated
with sulphide of ammonium; it is soluble in tartrate of
ammonia mixed with free ammonia. In a mixture of sulphate of lead and sulphate of baryta, the former may be
converted, by digestion with sulphide of ammonium, into
sulphide of lead, which can be transformed into chloride
by treatment with concentrated hydrochloric acid, and may
then be dissolved out by water.
35. PYROMORPHITE.
3 (3 PbO, P05) + PbCl.*
In many varieties, the chloride of lead is replaced by
chloride of calcium, in others, a part of the phosphoric
acid is replaced by arsenic acid.  The green  varieties
contain traces of sesquioxide of iron and sesquioxide of
chromium or chromic acid.
* May be artificially obtained in crystals, by fusing in a porcelain
crucible an intimate mixture of 1 part of fused phosphate of soda,
and 7 parts of chloride of lead; the mass is very gradually heated
to about the fusing-point of the latter; it is then allowed to cool,
and the liquid portion decanted from the crystals.




PYROMORPHITE.                  43
Those specimens which are free from lime are finely
powdered, and dissolved in caustic potassa. The lead is
precipitated from the solution by sulphide of ammonium,
the precipitate collected upon a weighed filter, dried at
100~, and weighed.
The filtered solution is acidified with hydrochloric acid,
which precipitates any sulphide of arsenic, to be treated as
directed in the article upon copper-nickel (No. 59).
The liquid filtered from the sulphide of arsenic is con.
centrated by evaporation, supersaturated with ammonia,
and the phosphoric acid precipitated by sulphate of magnesia.
The chlorine is determined in another portion, by dissolving in nitric acid, and precipitating by nitrate of
silver.
For the determination of lime, the mineral is dissolved
in nitric acid, and the lead precipitated from the diluted
solution by sulphuretted hydrogen. The solution filtered
from the sulphide of lead is neutralized with ammonia, and
the lime precipitated by oxalate of ammonia. The filtrate
is concentrated by evaporation, mixed with ammonia, and
the phosphoric acid precipitated by sulphate of magnesia.
Those specimens which are free from lime, but which
contain arsenic acid, may be analyzed in the following
manner. The mineral, in a state of very fine powder, is
digested with moderately dilute sulphuric acid, the greater
part of the water evaporated, the mass mixed with alcohol,
and the sulphate of lead thrown upon a filter and washed
with spirit of wine. The filtrate is evaporated to expel the
alcohol, and a stream of sulphuretted hydrogen passed
through it, while it is heated to about 50~. It is afterwards allowed to cool while the gas is still passing, and,




44                 SILVER AND LEAD.
when saturated with sulphuretted hydrogen, set aside in a
closed vessel for twenty-four hours, after which the precipitated pentasulphide of arsenic is filtered off.
The filtered solution is treated with ammonia which precipitates the iron as sulphide, occasionally mixed with a
small quantity of sesquioxide of chromium.
The phosphoric acid is precipitated from the flltrate,
after concentration, by sulphate of magnesia and ammonia.
In order to separate the sesquioxide of chromium, the
mineral is digested with a mixture of concentrated hydrochloric acid and alcohol, the solution filtered, evaporated
to expel the alcohol, and the sesquioxide of chromium
precipitated from the hot solution by ammonia. It still
contains a little phosphoric acid.
36. SILVER AND LEAD.
I. By cupellation.
II. The solution of the two metals in nitric acid is
diluted with much water, heated nearly to the boiling-point,
and the silver precipitated as chloride of silver by hydrochloric acid. (See No. 1.)
The filtered solution is allowed to cool, the greater part
of the acid neutralized with ammonia, and the lead precipitated by sulphuretted hydrogen.
III. The diluted nitric solution of the two metals is mixed
with dilute hydrocyanic acid which precipitates the silver
as cyanide. When this has accumulated, leaving the solution clear, it is collected upon a filter which has been dried
at 120~, washed, dried at that temperature, and weighed.
From the filtrate, after neutralizing the larger excess of




SILVER AND COPPER.                45
acid, the lead may be precipitated by sulphuretted hydrogen, or if the solution be concentrated by evaporation, by
sulphuric acid in the presence of alcohol.
IV. Another method consists in precipitating the solution
of the two metals by a slight excess of carbonate of soda,
and digesting the precipitate with cyanide of potassium,
which dissolves the silver in the form of a double cyanide,
leaving the carbonate of lead untouched. Since, however,
it contains some alkali, it must be dissolved in nitric acid,
and precipitated by sulphuretted hydrogen or sulphuric
acid. From the solution containing the silver, the latter
may be precipitated as cyanide by nitric acid.
V. The solution of the lead and silver in nitric acid
is neutralized with an alkali, mixed with an alkaline formate, and heated to boiling, when all the silver is precipitated in the metallic state.
37. SILVER AND COPPER.
(Silver-coin.)
The alloy is dissolved in moderately strong nitric acid,
the silver precipitated from the hot solution by dilute
hydrochloric acid with violent agitation, and the chloride
of silver treated as in No. 1.
The oxide of copper is precipitated from the filtrate by
caustic potassa at a boiling-heat, washed, dried, ignited
and weighed, the filter being completely incinerated apart
from the precipitate.
If the alloy contain gold also, it is left behind by the
nitric acid as a brown powder. If it be present in very
small quantities-as, for example, in all old silver coins



46               SILVER AND COPPER.
the small insoluble residue is filtered off, thoroughly washed,
the filter incinerated, and the ash fused before the blowpipe with carbonate of soda, when the gold appears in
small globules.
In order to prepare pure silver, it is precipitated from
the solution by hydrochloric acid or chloride of sodium,
in the form of chloride which is well washed and fused
in a porcelain capsule. A fragment of zinc is placed upon
the fused mass, and some dilute hydrochloric acid poured
over it. After twenty-four hours, the chloride of silver
is completely reduced; the spongy masses of silver are
rinsed out, rubbed to a fine powder under water, and
digested with dilute hydrochloric acid, to remove any zinc.
It is then thoroughly washed and fused with borax to a
reguline mass.
Or the dry chloride of silver may be mixed with an
equal quantity of anhydrous carbonate of soda, and the
mixture introduced into a crucible, the bottom  and sides
of which are coated with as thick a layer as possible of
carbonate of soda.  The crucible is then heated for a
length of time to low redness, and afterwards to the fusingpoint of silver.
Another plan is to mix the chloride of silver with ~
its weight colophony, to heat gently until the resin is
perfectly carbonized, and, after adding some borax, to raise
the heat until the silver fuses.
It is less effective to boil the chloride of silver, which
must be freshly precipitated, with strong solution of potassa,
which converts it into black oxide; or with potassa and
solution of sugar, which reduces it to the metallic state.
The original solution containing copper may also be
mixed with ammonia in excess, and the silver precipitated
by a plate of copper; or sulphurous acid gas may be




GOLD AND SILVER.                  47
passed into the ammoniacal solution, and the silver thus
precipitated in the metallic state.
38. GOLD AND COPPER.
(Coins.)
I. The alloy is dissolved in a mixture of hydrochloric
and nitric acids, care being taken that none of the latter
shall remain undecomposed after the solution is effected;
the liquid is heated with oxalic acid, which precipitates all
the gold in the metallic state. It is washed, dried, transferred to a porcelain crucible, the filter completely incinerated, and the gold, together with the ashes, ignited and
weighed. From the filtrate the copper may be precipitated
by sulphuretted hydrogen, or by potassa at a boiling,
heat.
II. The gold is first precipitated by a solution of pure
protosulphate of iron, and the copper is afterwards separated from the solution, either by sulphuretted hydrogen,
or by a piece of bright iron placed in the liquid, which
must not be too acid, and should be heated nearly to
boiling.  The precipitated copper is washed, dried, and
ignited in air, when it is converted into oxide.
39. GOLD AND SILVER.
I. From an alloy containing less than about 15 per cent
of silver, aqua-yregia dissolves all the gold, while the whole
of the silver is left as chloride; for this purpose, however,
the metal must be employed in a very thinly laminated
state. The solution is evaporated, to expel as much of the
nitric acid as possible; and diluted with water, to effect




48                 GOLD AND SILVER.
the complete separation of the chloride of silver. From
the solution the gold is precipitated by oxalic acid, or by
protosulphate of iron.
II. If the alloy contain more than 80 per cent of silver,
pure nitric acid dissolves the whole of the silver, and leaves
the gold.  Here also the alloy must be thinly laminated.
The silver is precipitated by hydrochloric acid. The gold
is well washed, and dissolved in aquza-regia, to ascertain if
ally trace of silver be left in it.
III. When the quantity of silver present in the alloy is
between 15 and 80 per cent, it cannot be entirely extracted
by nitric acid, neither can all the gold by dissolved out by
aqua-regia, since the metal becomes covered with a thick
layer of chloride of silver. Such an alloy should be fused
in a porcelain crucible with 3 times its weight of pure
lead. From this alloy, nitric acid then dissolves all the
lead and silver, leaving pure gold.
From the solution filtered from the gold, the silver is
precipitated by hydrocyanic acid; or, after diluting largely,
and heating nearly to boiling, by hydrochloric acid.
IV. Silver and gold in alloys of these metals may also be
separated (parted) by concentrated sulphuric acid, whatever
may be the relative proportion of the two metals. The thinly
laminated alloy is heated with the acid in a capacious dish,
until all evolution of gas ceases, and the acid begins to evaporate. The sulphate of silver which is produced is then dissolved in the requisite quantity of hot water, and the solution
decanted from the gold, which, for greater certainty, is once
more heated with a small quantity of sulphuric acid; afterwards thoroughly washed, ignited and weighed.
V. All such alloys may be also conveniently analyzed by
fusion with bisulphate of potassa.




AMALGAMS.                      49
40. AMALGAMS.
The following amalgams may be analyzed by heating
very gradually in a porcelain crucible, finally raising the
heat to redness, till the mercury is entirely volatilized, and
the tin or copper oxidized. To ensure complete oxidation,
the mass is ultimately moistened with concentrated nitric
acid, and again ignited. The amalgam of silver leaves the
latter in the metallic state.  In order to estimate the mercury also directly, the following method is adopted:
I. AMAIGAM OF COPPER.* —The amalgam  is dissolved
in aqua-regia, the solution neutralized, though not completely, with potassa, mixed with formiate or sulphite of
potassa or soda, and allowed to stand for some time at
a temperature between 50~ and 60~. All the mercury is
thus precipitated as subchloride.   Above 60~, metallic
mercury would also be separated. The subchloride of
mercury is collected upon a filter, which has been dried at
100~ and weighed, and its weight determined after drying
at 1000~.
From the filtered solution the oxide of copper is precipitated, at a boiling heat, by caustic potassa.
II. AMALGAM OF TIN  (amalgam  for mirrors).-This is
dissolved in aqua-regia, the solution mixed with ammonia
in slight excess, afterwards with an excess of sulphide of
ammonium, and digested for a long time in a closed vessel.
The bisulphide of tin which is formed dissolves in the sul* This amalgam, which is semi-fluid at 100~, but solid and crystalline at the ordinary temperature, is obtained when copper, which
has been precipitated by iron, is moistened with nitrate of suboxide
of mercury, and triturated in a warm mortar with mercury, added by
degrees, until the amalgam has the consistence of butter.
E




50                     AMALGAMS.
phide of ammonium, and the black sulphide of mercury
separates; it is collected upon a weighed filter, washed
with weak sulphide of ammonium, and dried at 1000.
From the solution in sulphide of ammonium the bisulphide of tin is precipitated by dilute hydrochloric acid,
filtered off, washed, dried, and roasted, together with the
filter, in a porcelain crucible, with free access of air. A
gentle heat is at first applied, which is gradually increased,
till the whole of the precipitate is converted into white
binoxide of tin; a fragment of carbonate of ammonia is
held in the ignited crucible at the end of the operation.
If it be desired to determine the mercury alone, it may
be precipitated from the solution of the amalgam in aqzaregia by means of protochloride of tin, as in the case of
the amalgam of silver.
III. AMALGAM OF SILVER.* -The amalgam is dissolved,
by the aid of heat, in nitric acid, so that the solution
may contain the whole of the mercury in the state of
protoxide; the acid solution is diluted with water, and the
silver precipitated by an excess of hydrochloric acid.
The solution filtered from the chloride of silver is concentrated by evaporation, with addition of some -strong
hydrochloric acid, to decompose all the nitric acid. The
mercury is then precipitated by sulphuretted hydrogen, and
the precipitate dried at 100~.
Or the solution containing the mercury may be mixed
with an acid solution of protochloride of tin, and heated
nearly to boiling, when all the mercury is precipitated
in the metallic state, either as a greyish-black powder, or
* May be obtained in crystals by allowing a small quantity of
mercury to remain in a moderately diluted solution of nitrate of
silver, or by placing a thick bright copper-wire in the mixed solutions
of nitrate of silver and of suboxide of mercury.




PROTOXIDE OF IIMERCURY, MINIUIM, CINNABAR.   51
in minute globules.  The clear liquid is decanted from
the metal, and concentrated hydrochloric acid poured over
it, when it unites, especially on heating, into larger globules,
which may be washed, and dried in a weighed vessel over
sulphuric acid.
Another method consists in neutralizing the solution
of the amalgam with potassa, and adding excess of cyanide
of potassium, or hydrocyanic acid and potassa; from the
solution of the double cyanides thus formed, the cyanide
of silver is precipitated by nitric acid, dried at 100~ upon
a weighed filter, and the mercury then precipitated by
sulphuretted hydrogen.
41. MIXTURES OF PROTOXIDE OF MERCURY, MINIUM,
AND CINNABAR.
By digesting with dilute nitric acid, the protoxide of
mercury is extracted, together with a portion of the protoxide of lead, the remainder of the lead being left behind
in the form of brown binoxide, mixed with the cinnabar.
This residue is well washed upon a weighed filter.
From the solution, which must contain an excess of
nitric acid, the lead is precipitated by an excess of sulphuric acid, and the mercury then separated by sulphuretted
hydrogen or protochloride of tin, the solution having been
previously freed from nitric acid by evaporation with concentrated hydrochloric acid.  (See Amalgams.)
The mixture of cinnabar and binoxide of lead is treated,
upon the filter, with a warm mixture of dilute nitric acid
and a little oxalic acid, which dissolves the binoxide of
lead, with evolution of carbonic acid. The cinnabar is then
washed, dried at 1000, and weighed.
E 2




52                 TIN AND COPPER.
The lead is precipitated from the solution by sulphuric
acid, with addition of some alcohol.
In order to analyze the cinnabar, it is dissolved (in this
case, together with the filter) in concentrated hydrochloric
acid, with careful addition of chlorate of potassa; the sulphuric acid is then precipitated from the diluted solution
by chloride of barium, the filtrate concentrated, and the
mercury precipitated by protoclloride of tin.
42. TIN AND COPPER.
(Bronze, Gun-metal, Bell-metal.)
I. The alloy, as finely divided as possible, is oxidized
with concentrated nitric acid, the greater excess of the
latter evaporated, the solution diluted with hot water, and
the undissolved binoxide of tin filtered off. The copper
is precipitated from the filtrate by caustic potassa, at a
boiling-heat.
If the bronze contain also zinc, lead and iron, the lead
is precipitated by sulphuric acid, and the copper by sulphuretted hydrogen. The solution filtered from the sulphide
of copper is heated with some chlorate of potassa in order
to peroxidize the iron, and the sesquioxide of the latter
metal precipitated by an excess of ammonia.  The oxide of
zinc remains dissolved in the alkali, and is precipitated by
sulphide of ammonium. Or the method described in No. 27
may be followed.
II. A surer method of obtaining the binoxide of tin free
from other metals consists in dissolving the alloy in weak
aqua-regia, precipitating with carbonate of soda, heating to
ebullition, and subsequently acidifying the liquid with nitric
acid, and allowing it to digest for some time. The binoxide




TIN AND LEAD.                   53
of tin is thus separated, while copper and other metals
remain dissolved.
III. A very accurate analysis may also be effected by
heating the alloy in a current of dry chlorine, when the
tin and a part of the iron are volatilized as chlorides, which
are conducted into water, and chloride of copper, chloride
of zinc, and chloride of lead are left. (See Fahl-ore.)
43. TIN AND LEAD.
(Pewter, Soft Solder.)
The alloy is oxidized with moderately strong nitric acid,
which leaves the tin undissolved in the form of binoxide;
after heating and diluting with water, the binoxide of tin
is filtered off, washed, dried and ignited.
From the filtrate the lead is precipitated by dilute sulphuric acid. The whole solution, containing the suspended
precipitate, is evaporated to expel the nitric acid, until the
sulphuric acid begins to volatilize; it is then diluted with
water, and the sulphate of lead collected upon a weighed
filter, which has been dried at 120~, and washed with spirit
of wine. A filter which has not been weighed may be
employed, if care be taken to remove as much as possible of
the precipitate from the filter, and to incinerate the latter
carefully apart, so that no reduction of lead may take place.
(Moreover, see No. 44.)
44. BISMUTH, LEAD, AND TIN.
The alloy is oxidized with moderately strong nitric acid,
the mass mixed with an excess of ammonia and sulphide of




54             BISMUTH, LEAD, AND TIN.
ammonium, and digested for some time in a closed flask.
In this way the tin is entirely dissolved as a sulphur-salt.
The solution is filtered off from the other sulphides, which
are then washed with very weak sulphide of ainmonium,
and dried.
From the solution'the bisulphide of tin is precipitated
by dilute hydrochloric acid, filtered off, washed and dried.
It is then gradually heated, together with the filter, in
a porcelain crucible, with free access of air; at first gently,
and ultimately to redness, so that it may be entirely converted into binoxide of tin. A fragment of carbonate of
ammonia is held in the crucible at the end of the operation,
to remove any sulphuric acid which may have been formed.
The mixture of sulphide of bismuth and sulphide of lead
is detached, as far as possible, from the filter, the latter
incinerated, and the ash added to the precipitate which is
then oxidized in a capacious capsule, with concentrated
nitric acid, a little sulphuric acid added lest there should
not be sufficient, and the excess of nitric acid expelled by
heat. The mass is then treated with a little water, the
solution of sulphate of bismuth filtered off from the sulphate of lead, the latter washed with water containing
sulphuric acid, dried and ignited.
From the filtrate the teroxide of bismuth is precipitated
by carbonate of ammonia in excess; the liquid is digested
for some time to ensure the complete separation of the
precipitate, which is then filtered off, washed, detached as
far as possible from the filter, and ignited in a porcelain
crucible, when it is converted into yellow teroxide of bismuth. The filter is incinerated separately.
Bismuth and lead may be converted into sulphates, and
separated in the same manner, when they are the sole constituents of the alloy.




SCHWEINFURT GREEN.                 55
45. SCHWEINFURT GREEN.
CuO, A + 3 (CuO, AsO3).
WThen this substance is heated with caustic potassa, the
acids are extracted, and red suboxide of copper left, ~ of
the arsenious acid being converted into arsenic acid.
If the filtered liquid be neutralized with nitric acid, and
nitrate of silver gradually added, a red-brown precipitate of
arseniate of silver is first produced, and afterwards a yellow
precipitate of arsenite of silver.
In order to separate the two acids, the solution, previously acidified with nitric acid, is mixed with excess of
ammonia, and sulphate of magnesia added, which has been
mixed with so much chloride of ammonium that it is no
longer precipitated by ammonia.  The arsenic acid is thus
precipitated as arseniate of magnesia-ammonia.  After the
lapse of twelve hours, the precipitate is collected upon a
dried and weighed filter, washed with dilute ammonia,
and thoroughly dried at 1000. It then has the composition 2 MgO, NH40, AsO5 + HO, and contains 62'9 per
cent of arsenic acid.-It is not safe to ignite this precipitate, since arsenic is then liable to be reduced and
volatilized.
The solution filtered from the magnesia-precipitate is
acidified with hydrochloric acid, and the arsenious acid
precipitated as tersulphide of arsenic.
If the original pigment be digested with a mixture of
concentrated hydrochloric acid and alcohol, a solution of
chloride of copper is obtained, and the arsenious acid
remains behind as a white powder.
By long digestion with an excess of sulphide of ammonium, the copper is separated as sulphide, while all the




56                ARSENIC AND LEAD.
arsenic is dissolved and may be precipitated as tersulphide
of arsenic by adding hydrochloric acid to the filtrate.
When Schweinfurt green is distilled with dilute sulphuric acid, the acetic acid passes over, and may be converted into acetate of baryta by adding that base. The
accurate quantitative estimation of the acetic acid can only
be effected by ultimate organic analysis.
46. ARSENIC AND LEAD.
The alloy, in a fine state of division, is oxidized with
nitric acid, the excess of acid evaporated, the solution
neutralized with ammonia, and the precipitated white mass
digested for some time with an excess of sulphide of ammonium in a closed vessel. The solution of sulphide of
arsenic is filtered from the sulphide of lead, which is
collected upon a weighed filter, washed, first with weak
sulphide of ammonium, then with water, dried and weighed.
The sulphide of arsenic is precipitated from the solution
by dilute hydrochloric acid, the sulphuretted hydrogen expelled by a gentle heat, the precipitate filtered off, washed,
and gently heated, together with the filter, in a beaker,
with concentrated hydrochloric acid, with gradual addition
of chlorate of potassa, until all the arsenic and part of the
sulphur are oxidized and dissolved. The solution is diluted
with water, passed through a filter, which must be well
washed, and the arsenic acid precipitated, as in No. 45,
with sulphate of magnesia and ammonia.
47. ARSENIC AND TIN.
The following is the best method for the separation of
these two metals from each other:




ARSENIC AND TIN.                 5 7
The finely-divided compound is gradually and carefully
oxidized with nitric acid, which is dropped upon it in
a weighed vessel. When it is converted into a dry white
mass, more nitric acid is added, and the whole evaporated
to perfect dryness in a water-bath. The mass dried at
1000 is weighed. A portion of it is then weighed in a
bulb-tube, one limb of which is bent downwards, and dips
into caustic ammonia contained in a small flask. A stream
of sulphuretted hydrogen is passed through the bulb-tube,
and when it is filled with gas, the mass is heated, gently at
first, afterwards more strongly, until a sublimation takes
place of sulphide of arsenic and sulphur, which dissolve in
the ammonia.  When no fresh sublimate is formed, the
apparatus is allowed to cool, and the piece of tube cut off
in which any sublimate still remains. This tube is placed in
warm solution of potassa, which easily dissolves the sublimate, the solution added to the sulphide of ammonium, and
the whole liquid carefully acidified with hydrochloric acid
which precipitates the sulphide of arsenic. Some powdered
chlorate of potassa is added to the liquid, without filtering,
and heat applied till there remains only pure sulphur, which
is filtered off. From the filtrate, the arsenic acid is then
precipitated by ammonia and sulphate of magnesia as in
No. 45.
All the tin is left in the bulb in the form of dark brown
bisulphide of tin, mixed, however, with a variable quantity
of sulphur, so that the amount of tin cannot be immediately inferred from the weight of the residue. In order
to determine the tin, the contents of the bulb are thrown
into a porcelain crucible, moistened with nitric acid, and
ignited, with access of air, until the tin is entirely
converted into white binoxide, which is then weighed.
The quantities of tin and arsenic are afterwards calcu



58                  TARTAR-EMETIC.
lated for the whole quantity of the original oxidized
mass.
Another method of analyzing the arseniferous tin consists in fusing it, in a finely-divided state, with 5 times
its weight of carbonate of soda, and the same quantity of
sulphur, in a porcelain crucible over a spirit-lamp; the
fused mass is then dissolved in water, and the two sulphides precipitated from the very diluted solution by dilute
hydrochloric acid.  When all the sulphuretted hydrogen
has been expelled by a gentle heat, the reddish-brown
precipitate is thrown upon a weighed filter, washed, and
dried at 1000; a weighed quantity of it is then heated, as
directed above, in a stream of sulphuretted hydrogen.
48. TARTAR-EMETIC.
KO, SbO3 T +2 HO.
The powdered salt loses all its water at 100~.
The substance is dissolved in about 300 times its
weight of warm water, and the solution saturated with
sulphuretted hydrogen. Some hydrochloric acid is afterwards added to promote the separation of the tersnlphide
of antimony; when the liquid has become clear, the precipitate is collected upon a weighed filter, well washed,
dried at 150~, and weighed.  In this case, the weight of
the antimony may be at once inferred from that of the
precipitate.
The filtrate is evaporated to dryness, the saline residue
heated till the tartaric acid is completely carbonized, the
carbonaceous mass digested with dilute hydrochloric acid,
filtered off and thoroughly washed. The solution is evapo



ANTIMONY AND LEAD.                59
rated, and the residual chloride of potassium gently ignited
in a covered crucible, and weighed.
The amount of the tartaric acid is inferred from the
difference. It can be directly determined only by ultimate
organic analysis.
49. ANTIMONY AND LEAD.
The finely-divided compound is oxidized with nitric acid,
the solution mixed with ammonia in slight excess, and
afterwards with an excess of yellow sulphide of ammonium,
with which it is digested for some time until the precipitate is perfectly black. The solution is then diluted with
water, the sulphide of lead collected upon a dried and
weighed filter, thoroughly washed with dilute sulphide of
ammonium, and afterwards with water, dried at 1500, and
weighed.
The sulphide of antimony is precipitated from the solution by dilute sulphuric acid, and the liquid exposed to
the air until most of the sulphuretted hydrogen has been
dissipated. The precipitate is then thrown upon a dried
and weighed filter, well washed, and dried at 1000 till its
weight is constant.
Since the quantitative composition of this precipitate is
not accurately known, and since, moreover, it contains
some free sulphur, it must now be analyzed, and either
the sulphur or the antimony in it determined.
To determine the amount of sulphur which it contains, a
weighed quantity is detached from the filter and oxidized,
very gradually and cautiously, in a flask, with concentrated
nitric acid. Concentrated hydrochloric acid is afterwards
added, and the mixture digested until all the antimony is




60                  BOURNONITE.
dissolved. As soon as this is the case, so much tartaric
acid is added, that the solution may be diluted with water
without any precipitation taking place. If any sulphur
should have been separated in an unoxidized state, it must
be collected upon a weighed filter. The sulphuric acid is
then precipitated from the diluted solution by chloride of
barium, and the precipitate washed with hot water. The
quantity of sulphur, and, in consequence, that of the
antimony, are calculated for the total weight of the precipitated sulphide of antimony.
For the direct estimation of the antimony, a weighed portion of the original precipitate is introduced into a weighed
bulb-tube, and heated in a stream of hydrogen-gas, at first
very gently, and ultimately to the fusing-point of the
antimony, from which the sulphur is thus completely separated.
Or, instead of the hydrogen, a stream of carbonic acid
gas may be passed through the tube, and the precipitate
heated in it until it does not lose any more sulphur, and is
converted into black tersulphide of antimony.
50. BOURNONITE.
3 Cu2S, SbS3 + 2 (3 PbS, SbS3).
The powdered mineral is gradually and carefully oxidized
with concentrated nitric acid, the mass mixed with ammonia, and digested for some time, in a closed vessel,
with yellow sulphide of ammonium. The solution is then
treated as directed in No. 49.
The residue containing sulphide of copper and sulphide
of lead is dried in the funnel, detached, as far as possible,
from the filter, the latter incinerated, and the sulphides




ZINKENITE.                    61
afterwards oxidized, in a dish, by the gradual addition of
fuming nitric acid. Some sulphuric acid is then added,
the whole of the nitric acid expelled by heat, and the
sulphate of copper extracted from the mass by water. The
sulphate of lead is washed, dried and ignited. The oxide
of copper is precipitated from the solution by caustic
potassa, at a boiling heat.
This method is not quite accurate, since a little sulphide
of copper dissolves in the sulphide of ammonium together
with the tersulphide of antimony; sulphate of lead, moreover,
is not quite insoluble. The determination of the lead is more
accurate if all free sulphuric acid be expelled by heat before
the sulphate of copper is extracted with water.
A more exact method for the analysis of this mineral
is that with chlorine, described in the article upon Fahlore.
51. ZINKENITE.*
PbS, SbS3.
The amount of sulphur present may be inferred from the
loss which the compound suffers when heated in a bulbtube, through which a stream  of hydrogen is passed, when
all the sulphur is evolved as sulphuretted hydrogen, and
PbSb remains behind.
The relative proportions of lead and antimony are determined as in No. 49.
For the direct estimation of the sulphur, the finely* Plagionite, jamesonite, and feather-ore, are similar combinations.
Zinkenite may be easily prepared artificially by fusing together 7~
parts of sulphide of lead, with 11 parts of black tersulphide of
antimony in a glass tube.




6'2                  BERTHIERITE.
divided compound is mixed with 3 parts of chlorate of
potassa, and 3 parts of carbonate of soda, and heated,
in a platinum crucible, at first gently, and ultimately to
redness, until the chlorate of potassa is completely decomposed. The salts are then extracted from the mass with
water, the residue well washed, the solution acidified slightly
with hydrochloric acid, and the sulphuric acid precipitated
by chloride of barium.
52. BERTHIERITE.
FeS, SbS3.
The mineral, in the state of fine powder, is oxidized
with hydrochloric acid and chlorate of potassa, until the
separated sulphur has a pure yellow colour. The solution
is mixed with tartaric acid, and may then be diluted with
water without any precipitation taking place. The separated sulphur is collected upon a dried filter, washed, and
dried at 100~. The sulphuric acid produced by the oxidation is precipitated from the solution by chloride of
barium, and the sulphate of baryta washed with hot
water.
When the excess of baryta has been removed from the
filtrate by sulphuric acid, a stream of sulphuretted hydrogen-gas is passed through the solution, and the antimony
precipitated.  (See also No. 49.)
From the filtered liquid the iron is precipitated by sulphide of ammonium. The mixture is -digested for some
time, and when the solution, which is at first tinged green
by the fine particles of suspended precipitate, has at length
become clear yellow, the precipitate is filtered off, washed




RED SILVER-ORE.                    63
several times with solution of sulphuretted hydrogen from
a wash-bottle, and dried in the funnel. The precipitate
is then heated, together with the filter, in a porcelain
crucible, until the paper is carbonized, then the iron dissolved out with aqua-regia, precipitated as sesquioxide by
ammonia, ignited and weighed.
53. RED SILVER-ORE.*
Light-coloured, 3 AgS, AsS3; dark, 3 AgS, SbS3.
1. DARK.-To  determine the amount of sulphur, a
weighed quantity of the mineral is fused in a bulb-tube,
over a large spirit-lamp or gas-burner, in a stream of dry
hydrogen, as long as any sulphuretted hydrogen is formed;
all the sulphur is thus expelled, in combination with hydrogen. The conclusion of the operation is also indicated by
a sort of coruscation which takes place, and the antimonide
of silver is left in the form of a perfectly bright, smooth,
moveable globule.
The tube is allowed to cool slowly, weighed, and placed
in communication with an apparatus for the evolution of
chlorine, in a current of which the antimonide of silver
* These compounds may be readily obtained artificially by fusing
their constituents together. That which contains antimony is prepared by fusing 46'5 parts of sulphide of silver with 22 parts of
black tersulphide of antimony in a crucible, beneath a layer of common salt; to prepare the arseniferous compound, 23 parts of sulphide
of silver and 7'5 parts of yellow tersulphide of arsenic, or 40'5 parts
of powdered silver, 12 parts of sulphur, and 9'4 parts of arsenic are
fused together in a glass tube closed at one end. Combination takes
place with incandescence.




64                 RED SILVER-ORE.
is fused, until no more pentachloride of antimony is volatilized, and pure fused chloride of silver remains. The
latter is then treated as in the case of grey copper-ore.
The antimonide of silver may also be oxidized by nitric
acid, and the silver and antimony separated by sulphide of
ammonium, as in antimonide of lead (No. 49).
2. LIGHT. —The light-coloured variety, when fused in a
current of hydrogen, loses all its sulphur and arsenic; but
the complete expulsion of the latter can scarcely be effected
in a glass tube. The experiment must be conducted in
a small porcelain boat, placed in a porcelain tube. After
a certain time, the fused substance suddenly swells up
to a voluminous bladder-like mass, from which the last
portions of arsenic can be but slowly expelled.
The analysis may also be effected by dissolving the red
silver-ore in concentrated nitric acid.  The digestion is
continued until the separated sulphur has a pure yellow
colour; the solution is then diluted with hot water, and
filtered from the sulphur, the total quantity of which may
here be determined from the loss, unless it be directly
determined, as in the case of copper-pyrites (No. 26); the
silver is precipitated by diluted hydrochloric acid (see
No. 1), the solution filtered off, concentrated by evaporation, with addition of some nitric acid or chlorate of
potassa, and the arsenic acid precipitated by sulphate of
magnesia and ammonia. (See No. 45.)
Or the very finely-powdered mineral may be fused with
5 times its weight of a mixture of equal parts of nitre
and carbonate of soda in a platinum crucible, at the
bottom of which a layer of carbonate of soda has been
placed. The mass is afterwards dissolved out with hot
water, the silver filtered off, washed, ignited and weighed.
The solution is acidified with hydrochloric acid, mixed with




TIN AND ANTIMONY.                 65
ammonia, and the arsenic acid precipitated by sulphate of
magnesia. The amount of sulphur is determined by loss,
unless it be precipitated from the original solution in the
form of sulphate of baryta, when it must be very carefully
washed with hot water to free it from the nitrate of baryta
which it carries down.
Both compounds may also be analyzed with great accuracy by means of chlorine gas, as described in the article
upon Grey Copper-ore.
In analyzing a mixture of light and dark red silver-ore,
the arsenic and antimony are separated according to the
method described in No. 55.
54. TIN AND ANTIMONY.
The weighed compound is dissolved in hydrochloric acid,
with gradual addition of nitric acid, and a piece of pure
tin placed in the solution, with which it is heated for
some time, until the whole of the antimony is precipitated;
the latter is collected upon a weighed filter, washed, dried
at 1000, and weighed; the amount of tin is inferred from
the difference.
In order to determine both metals directly, the compound, as finely divided as possible, is oxidized in a beaker
with strong pure nitric acid, the mass evaporated to dryness,
gently ignited, and fused, in a silver crucible, with a large
excess of hydrate of soda. WVhen cool, the mass is treated
with water, rinsed out into a beaker, and the solution mixed
with ~ its volume of strong alcohol. The insoluble antimoniate of soda is thus separated from the stannate, carbonate, and excess of hydrate of soda, which are dissolved
F




66             ARSENIC AND ANTIMONY.
by the weak spirit. When the liquid has become perfectly
clear, the precipitate is filtered off, and washed, first with a
mixture of equal volumes of alcohol and water, and finally
with strong alcohol.
The alkaline solution is heated to expel the alcohol,
diluted with water, acidified with dilute sulphuric acid,
and the tin precipitated by sulphuretted hydrogen.  The
bisulphide of tin is then converted into binoxide of tin, as
directed in No. 44.
The antimonate of soda is detached as far as possible
from the filter, and a mixture of hydrochloric and tartaric
acids poured over the latter, and allowed to flow into the
beaker containing the remainder of the precipitate. When
the salt is perfectly dissolved, and the filter has been
washed, the antimony is precipitated by sulphuretted
hydrogen.  The antimony contained in the precipitate is
determined as in No. 49.
The antimonate of soda may also be collected upon
a weighed filter, dried at 100~, and a weighed portion
mixed with sal-ammoniac in a porcelain crucible, and
ignited, when all the antimony is volatilized, and the salt
converted into chloride of sodium. The operation must be
repeated, several times till the weight is constant, and the
amount of the antimony may be calculated from that of
the chloride of sodium obtained.
55. ARSENIC AND ANTIMONY.
If only these two metals be present, as in native arsenic,
a complete separation may be effected by heating the compound in a bulb-tube through which a stream of dry car



ARSENIC AND ANTIMONY.              67
bonic acid gas is transmitted, when the whole of the arsenic
is volatilized, and the antimony remains behind. If too
strong a heat be applied, a portion of the latter metal may
also be volatilized.
When the compound under examination contains, as is
often the case, the two metals in the form of sulphides,
they may be at least approximately separated by digestion
with concentrated hydrochloric acid, which dissolves the
sulphide of antimony, and leaves that of arsenic. When
the latter has a pure yellow colour, the solution is mixed
with tartaric acid, diluted with water, and the sulphide of
arsenic filtered off and washed. It is afterwards oxidized
with hydrochloric acid and chlorate of potassa, and the
arsenic acid precipitated by sulphate of magnesia and
ammonia. (See No. 45.)
Or the two sulphides may be mixed with 6 times their
weight of a mixture of 4 parts of nitrate and 2 parts of
carbonate of soda, and the mass graduallyheated in a silver
crucible until perfectly white; it is then digested with
water, which leaves the antimony undissolved as antimonate of soda; this is filtered off, washed with weak
spirit, and weighed; its composition is NaO, SbO5. By
repeated ignition with sal-ammoniac, all the antimony may
be volatilized, and the salt converted into chloride of
sodium.
The solution, which contains the arsenate of soda together with the other salts, is acidified with nitric acid,
mixed with ammonia, and the arsenic acid precipitated by
sulphate of magnesia.
The most accurate method of separation is as follows:
The compound is carefully oxidized with aqua-regia, or
with hydrochloric acid and chlorate of potassa, some tartaric acid and a considerable quantity of chloride of amF 2




68             ARSENIC AND ANTIMONY.
monium added, and the mixture then treated with ammonia
in excess, which must dissolve the whole.  From this
solution the arsenic acid is precipitated by sulphate of magnesia. (See No. 45.)
The filtrate is acidulated with hydrochloric acid, and the
antimony precipitated by sulphuretted hydrogen.
Or the compound containing arsenic and antimony is
oxidized with aqua-regia, or with hydrochloric acid and
chlorate of potassa; and if any other metals precipitable
by sulphuretted hydrogen be present, the mass is neutralized with ammonia, and digested with an excess of yellow
sulphide of ammonium to extract the arsenic and antimony.
These are precipitated from the filtered solution by dilute
sulphuric acid, collected upon a weighed filter, and dried
at 1000~.
If, however, no other metals precipitable by sulphuretted
hydrogen be present, the solution in aqua-regia is mixed
with tartaric acid, diluted with water, heated to 600, and the
arsenic and antimony precipitated by sulphuretted hydrogen.
The solution, through which the gas is passed until it has
cooled, is allowed to stand in a covered vessel for at least
twenty-four hours; the excess of gas is then allowed to
pass off, the precipitate collected upon a weighed filter,
washed, dried at 1000, and weighed.
A weighed portion of the precipitate is then thrown
into a beaker, and treated with concentrated hydrochloric acid, in which some chlorate of potassa has been
previously dissolved by the aid of a gentle heat; more
chlorate of potassa is added, until all the unoxidized sulphur has separated with a pure yellow colour. The mass
is then mixed with tartaric acid, diluted with water, and
the sulphur collected upon a dried filter and weighed.
From the filtrate the sulphuric acid is precipitated by




ARSENIC, ANTIMONY, AND TIN.           69
chloride of barium, and the amount of sulphur, calculated
from the weight of the sulphate of baryta, is added to that
previously obtained.
Another portion of the sulphuretted hydrogen precipitate
is weighed in a bulb-tube, and heated in a stream of
hydrogen, when all the sulphur and arsenic are carried off,
and there remains only the antimony, which is weighed
after the sublimate of arsenic and sulphide of arsenic has
been expelled from the tube by gently heating in the
stream of hydrogen; the amount of arsenic is inferred
from the difference. The results are calculated for the
whole weight of the precipitate produced by sulphuretted
hydrogen.
Lastly, antimony and arsenic may also be separated by
mixing the dry sulphides intimately with 12 times their
weight of a mass consisting of 3 parts of dry carbonate of
soda, and 1 part of cyanide of potassium.  This mixture is
heated in a bulb-tube in a slow current of dry carbonic
acid, when the whole of the arsenic is reduced and sublimes
as a metallic mirror, whilst the antimony remains in the
mass.
56. ARSENIC, ANTIMONY, AND TIN.
The compound is divided as finely as possible, and carefully oxidized with strong and pure nitric acid, the mass
evaporated to dryness and fused in a silver crucible with
8 times its weight of hydrate of soda, the evaporating
vessel being previously rinsed with solution of soda, which
is added to the contents of the crucible and evaporated to
dryness. The fused mass is treated with hot water, then
diluted with water, and  ~ its volume of strong alcohol




70           ARSENIC, ANTIMONY, AND TIN.
added.  The mass is allowed to stand  for twenty-four
hours and  frequently stirred; the antimonate  of soda
is then filtered off, and washed first with a mixture of
2 vols. of water and 1 vol. of alcohol, next with a mixture
of equal vols., and lastly with a mixture of 3 vols. of alcohol
and 1 vol. of water, adding to each a few drops of solution of carbonate of soda. The washed salt is treated as
in No. 54.
The alkaline filtrate is supersaturated with hydrochloric
acid, which produces a bulky precipitate of arsenate of
binoxide of tin. Without filtering this off, the liquor is
saturated with sulphuretted hydrogen, the precipitate thus
converted into a dark brown mixture of bisulphide of tin
and tersulphide of arsenic, and the liquor then allowed to
stand for twenty-four hours in the closed vessel. The
precipitate is now collected on a weighed filter and dried at
100~. The separation of the tin and arsenic is effected by
heating in sulphuretted hydrogen, as in No. 47.
A weighed portion of the entire precipitate might also
be mixed with about 12 times its weight of a mixture of
3 parts of carbonate of soda and 1 part of cyanide of
potassium, and heated in a covered porcelain crucible until
all the arsenic is driven off. On treating the residue with
water, the tin would be left behind in the metallic state.Or the mixture could be heated in a long glass tube, in a
slow current of carbonic acid gas, and thus the arsenic
obtained as a sublimate in the tube. In order to secure a
more complete condensation, a weighed coil of fine sheet
copper could be introduced into the tube, and heated to
ignition at one place for the purpose of forming arsenide of
copper.




FAHL-ORE.                    71
57. FAHL-ORE.
4 (CuS, AgS, FeS, ZnS, HgS), (SbS3, AsS3).
Every specimen of fahl-ore does not contain all these
constituents; some of them may be entirely absent, and
generally they may replace each other in the different kinds
in varying quantities.
The analysis is best effected by gently heating the
mineral in dried chlorine gas, when sulphur, arsenic, antimony, mercury, and a portion of the iron are volatilized in
the form of chlorides, and copper, silver, zinc and part
of the iron remain behind, likewise converted into chlorides.
The above figure shows the construction of the apparatus
to be used in such analyses. The chlorine gas, for the
purpose of drying it, is first passed through a small cylinder
containing concentrated sulphuric acid, and thence through
the chloride-of-calcium-tube, which is fixed upon a wooden
stand.




7 2                   FAHL-ORE.
The mineral, finely divided, is weighed in the bulb-tube.
The latter is best provided with two bulbs, in order to
collect the greater portion of the sublimate in the second
bulb, and thus to prevent the tube from being stopped
up.
The end of the tube bent downwards is connected by
means of a good cork or a caoutchouc tube, with the threebulb-tube or receiver, in which the volatile products are to
be condensed. The other end-of the latter is provided with
a small conducting-tube, through which the excess of chlorine passes into a small flask containing alcohol, or milk of
lime.
In order to prevent the precipitation of antimony, the
three-bulb receiver is not filled with pure water, but with a
mixture of dilute hydrochloric and tartaric acids, whenever
that substance is present; the liquid should fill about 1 of
the two upper bulbs, which will require about 50 grms.
In this arrangement the liquid cannot rise above a certain
point in either limb, but must flow back again whenever it
has been raised to a certain height.
If such a bulb-receiver be not at hand, a flask with two
necks may be used, as shown
in the annexed figure.  The
perpendicular limb  of the
bulb-tube almost touches the
mixture of acids in the receiver, but does not dip into
it, because the liquor might
in that case recede into the
bulb-tube, the chlorine being rapidly absorbed. The conducting-tube, inserted through the second neck, expands at
its upper portion into a bulb, and is cut off below in an
oblique direction; it enters the liquid so far, that this can




AIIL-ORE.                     73
be pressed up into the bulb only, and must then flow back
again. To this tube a second one is attached, which is
bent at a right angle, and conducts the excess of chlorine
into alcohol, or milk of lime.
It is advisable not to connect the bulb-tube, containing
the mineral, with the chlorine apparatus, until most of the
atmospheric air has been expelled from it.
The complete decomposition of the fahl-ore takes place
even at the ordinary temperature, with strong evolution of
heat.  When the bulb has nearly cooled again, it is heated
by a very small spirit-lamp-flame, in order to separate the
volatile products from  the non-volatile, and to drive the
former into the second bulb. It is scarcely possible to
drive off all the sesquichloride of iron; the heating is
therefore discontinued as soon as vapours of this compound
only appear to be evolved.
The chlorine gas is to be passed through in a gentle
current only, especially towards the last, when the sublimation is effected, because otherwise the vapours of the
volatile products may pass unabsorbed through the receiver.
When the tube has become clear between the bulbs, and
the apparatus has cooled, it is cut through between the
bulbs by means of a file and a red-hot coal, and the end
with the bulb containing the sublimate is covered with
a short, glass tube, sealed at one end and moistened
with water on the inside.  The tubes are allowed to
remain connected in this manner for at least twenty-four
hours, in order to cause the sublimate gradually to attract
moisture and to prevent its becoming hot and thus occasioning loss on being afterwards dissolved in water, as
would otherwise be the case. It is then dissolved in a
little water, to which some hydrochloric and tartaric acids
have been added, the tube is carefully rinsed, and the




74                    FAHL-ORE.
rinsings added to the solution in the receiver. Should the
liquid be cloudy, in consequence of a separation of antimonious acid, a gentle heat must be applied, in order to
redissolve the latter. In case of sulphur having separated
in an unoxidized state, it must be filtered off.
I. ANALYSIS OF THE FIXED RESIDUE.-The bulb containing it is placed in a beaker with dilute hydrochloric
acid, and digested until the contents are dissolved, with the
exception of the chloride of silver. This is filtered off and
treated as in No. 1.  Should chloride of lead be present,
as is the case in the analysis of bournonite, it must be
dissolved by using a larger quantity of water. In this
case the contents of the bulb have to be heated very
cautiously, that the chloride of lead may not volatilize.
A slow current of sulphuretted hydrogen is then passed
through the solution until it is completely saturated. The
precipitated sulphide of copper is treated as in No. 25, or
if lead be present, as in No. 50.
The solution filtered off from the precipitate contains
part of the iron, and if too great a heat was avoided, all
the zinc; it is then heated to ebullition, and mixed with
some chlorate or hypochlorite of an alkali, in order to
convert the former metal into a higher oxide; the iron and
zinc are then separated and determined as in No. 27.
II. ANALYSIS OF THE VOLATILE PRODUCTS.-This solution contains the mercury, antimony, arsenic, a portion of
the iron, and the sulphur, partly in the form of sulphuric
acid, partly unoxidized.
The sulphuric acid can be precipitated with chloride of
barium, and the excess of baryta again removed by sulphuric acid.
It is, however, much more convenient to determine the
amount of sulphur in a separate portion of the mineral.




FAHL-ORE.                   7 
For this purpose it is finely divided, mixed with 3 times
its weight of finely-powdered chlorate of potassa and then
with as much of dry carbonate of soda, and the mixture very
gradually heated in a platinum crucible (the bottom of
which is previously covered with carbonate of soda, as a
precaution) until all the chlorate of potassa is decomposed.
When cold, the mass is treated with water, the solution
filtered, slightly acidulated with hydrochloric acid, and the
sulphuric acid precipitated by chloride of barium as in
No. 3.
For the determination of the other constituents, the
solution of the volatile chlorides is heated to about 60~ and
then a gentle current of sulphuretted hydrogen passed
through it until it is cold.  When completely saturated
with sulphuretted hydrogen, the solution is allowed to
stand for twelve hours, and then the precipitate, which
consists of the sulphides of mercury, antimony and arsenic,
collected on a filter which has been dried and weighed.
After being washed with sulphuretted-hydrogen-water, the
precipitate is removed from the filter, taking care not to
damage the latter; it is washed off as well as possible, and
a concentrated solution of sulphide of ammonium poured
upon it, with which it is digested in a closed vessel until the
whole of the sulphides of arsenic and antimony are dissolved, and the sulphide of mercury has assumed a pure
black colour.  When completely cold, it is again collected
on the filter previously used, washed first with dilute sulphide of ammonium, and towards the end with pure
water, dried and weighed.
From the solution in sulphide of ammonium, the sulphides of arsenic and antimony are precipitated by an
excess of dilute sulphuric acid, and separated and determined as in No. 55.




76                  GERM AN SLVTER.
From the liquid which has been filtered off from the
precipitate by sulphuretted hydrogen, the iron can only be
separated by sulphide of ammonium after neutralizing with
ammonia, on account of the presence of tartaric acid.
When the sulphide of iron is completely separated by
digestion at a gentle heat, it is filtered off, and washed with
sulphuretted-hydrogen-water; the filter is then put into a
beaker, and digested with hydrochloric acid until all the
sulphide of iron is dissolved. The solution is then filtered
off from  the paper, the latter washed, the liquid heated
with chlorate of potassa, and the sesquioxide of iron precipitated by ammonia.
If the amount of sulphide of iron be but small, the
filter is ignited with the precipitate, the air having free
access, until all the iron is converted into sesquioxide, and
its weight remains constant.
58. GERMAN SILVER (ARGENTAN).
(Cu, Ni, Zn).
The alloy is dissolved in nitric acid, the greater excess of
acid evaporated, the solution diluted with water, and the
copper precipitated by means of sulphuretted hydrogen (see
No. 25).
The filtered liquor is concentrated by evaporation, precipitated by an excess of solution of potassa, and heated
with it, when the protoxide of nickel is separated and the
oxide of zinc dissolved.  From this solution the latter is
precipitated by sulphide of potassium, or, after being
saturated with hydrochloric acid, by carbonate of soda at a
boiling heat.
In this manner, however, the oxides of nickel and zinc




GERMAN SILVER.                  77
cannot be separated with precision; some oxide of zinc
remains with the protoxide of nickel.
The separation is also effected incompletely by fusing
the mixture of the oxides with hydrated potassa, or by
precipitating both oxides with carbonate of soda at a boiling heat, converting the protoxide of nickel into black
sesquioxide by digestion with hypochlorite of soda, and then
extracting the oxide of zinc by means of caustic potassa.
I. More accurate results are obtained by igniting the
dried mixture of both oxides, reducing it to a fine powder
and heating it in a current of dry oxygen as long as water
is formed. From the mixture of nickel and oxide of zinc
the latter is then extracted by digestion for a somewhat
long period with a concentrated solution of carbonate of
ammonia, air being excluded.
II. Or the oxides precipitated from the hot solution
by carbonate of soda are dissolved in acetic acid, the solution mixed with a considerable quantity of free acetic acid,
and sulphuretted hydrogen passed through it, very gradually and with continued agitation of the liquid, as long
as the precipitate remains white, when only zinc is precipitated. The hydrochloric or nitric solution can also be
mixed with an excess of acetate of soda, and the zinc
precipitated by sulphuretted hydrogen.
III. The precipitated oxides are mixed with 3 parts of
carbonate of potassa and as much sulphur, the mass carefully heated in a porcelain crucible to tranquil fusion, and
on cooling, the alkaline sulphide extracted with water.
The metallic sulphides remaining behind are then treated
with dilute hydrochloric acid, which dissolves only the
sulphide of zinc.




78                   COPPER-NICKEL.
59. COPPER-NICKEL.*
Nix As.
I. PREPARATION OF PURE NICKEL.-A mixture of 1 part
of very finely-powdered arsenide of nickel, 2 parts of
nitrate of potassa, and 2 parts of carbonate of potassa, is
ignited for a considerable period, and all the arsenate of
potassa extracted from the mass by means of water.
Or the arsenide of nickel is fused with 3 times its weight
of sulphur and carbonate of potassa, and the sulph-arsenate
of sulphide of potassium thus formed, extracted with water.
The mixture of oxides remaining behind in the first case,
is dissolved in hydrochloric acid, that of the sulphides, in
the second case, in hydrochloric acid with gradual addition
of nitric acid and with application of heat.
The solution is heated to about 70~, and during that
time, and until it has cooled, saturated with sulphuretted
hydrogen; it is then allowed to stand in a closed vessel for
twenty-four hours, when copper, bismuth, and a residue of
arsenic are precipitated.
The sulphuretted hydrogen having been expelled by
heat, the solution is filtered, heated to boiling, and precipitated by carbonate of soda; the precipitate, containing all
the nickel, cobalt, and iron, is thoroughly washed.
It is then, whilst still moist, treated and digested with
an excess of a hot saturated solution of oxalic acid, when
all the iron is dissolved, and the nickel and cobalt are left
in the form of oxalates.  They are filtered off, washed, and
* Arsenide of nickel, with a varying amount of cobalt and iron
The smelting-products, known by the name of cobalt- and nickelspeiss, have a similar composition, and contain besides frequently
accidental admixtures of copper and bismuth.




COPPER-NICKEL.                 79
digested with concentrated caustic ammonia until they are
dissolved.
The blue solution is then set aside in an open vessel
until all the free ammonia has evaporated, during which
time the nickel separates in the form of green oxalate of
protoxide of nickel and ammonia, whilst the cobalt remains
in the solution to which it imparts a red colour.
The nickel-salt is filtered off, washed, and ignited in a
closed crucible or in a glass tube, when pure metallic nickel
remains behind.
The cobalt may be obtained from the solution by evaporation and ignition of the residue, or by boiling it with
caustic potassa until no farther disengagement of hmmonia
takes place; or when smaller quantities are operated upon,
by an alkaline sulphide, and subsequent addition of
dilute sulphuric acid in order to separate the sulphide of
cobalt.
The pure metal may be easily prepared from commercial
nickel by dissolving it in hydrochloric acid with the addition of some nitric acid, purifying the solution by sulphuretted hydrogen, and then precipitating nickel and cobalt
by the addition of a boiling saturated solution of binoxalate of potassa. The washed precipitate is then dissolved
in ammonia.
For the purpose of separating the iron, the solution, after
being again oxidized, may also be mixed with chliloride of
ammonium, and then with ammonia in excess, when sesquioxide of iron (with a little nickel and cobalt) is precipitated, whilst nickel and cobalt remain in solution.  Or the
solution is neutralized with carbonate of soda, mixed with
acetate of soda, and boiled, when sesquioxide of iron is
precipitated.
II. QUANTITATIVE ANALYsIs.-The very finely-powdered




80                  COPPER-NICKEL.
arsenide of nickel is fused with 21 parts of nitrate of
potassa and 3 parts of carbonate of soda, in a platinum
crucible, the bottom of which has previously been covered
with carbonate of soda; the mass is then ignited for some
time, and when cold is digested with water; the oxides
formed are filtered off and washed.
I. The solution contains all the arsenic in the form of
arsenates of the alkalies; it is supersaturated with hydrochloric acid, then evaporated almost to dryness, in order to
expel the nitric acid, the mass dissolved in water, and heated
to about 70~, while sulphuretted hydrogen is passed through
it.  When the precipitation of sulphide of arsenic appears
to be completed, the whole is allowed to cool, whilst the
current of sulphuretted hydrogen is still passing.
The liquid is then left to stand in a closed vessel for
twenty-four hours, the precipitate collected on a filter
(which has previously been dried at 1000 and weighed),
washed, dried at 1000 and weighed.
The precipitate is usually a mixture of AsS3 and sulphur.
A small portion of it is taken, weighed, and completely
oxidized by heating it with aqua-regia or with hydrochloric
acid and chlorate of potassa. From the solution diluted
with water, the sulphuric acid formed is precipitated by
chloride of barium, and from the quantity of sulphate of
baryta the amount of sulphur calculated, and consequently
also that of the arsenic, the amount found being afterwards
calculated for the whole quantity of the precipitate.
It is more convenient, and quite as exact, to precipitate
the arsenic acid from the alkaline solution in the form of
arsenate of ammonia and magnesia.  The solution is saturated with hydrochloric acid, mixed first with solution of
chloride of ammonium, then with concentrated caustic
ammonia, and lastly with sulphate of magnesia. After




COPPER-NICKET.                  81
twenty-four hours the precipitate is collected on a weighed
filter, washed with dilute caustic ammonia, dried at 1000
and weighed (see No. 45).
The arsenic may also be determined from the loss.
II. The oxides are dissolved in concentrated hydrochloric
acid, and the copper and bismuth precipitated from the
solution by sulphuretted hydrogen.  The precipitate is
treated as in No. 64.
III. The liquid filtered off from the precipitate is heated
nearly to boiling, and mixed with some chlorate of potassa
in order to peroxidize the iron, which may then be separated from the nickel and cobalt in the same manner as
from manganese, either by succinate of ammonia or by carbonate of baryta (see No. 23).
From the liquid filtered off from the succinate of iron,
nickel and cobalt are precipitated at a boiling-heat by
caustic potassa, filtered off, and washed with hot water.
From the liquid separated from the carbonate of baryta,
the dissolved baryta is precipitated by sulphuric acid, and
the nickel and cobalt are then precipitated from the hot
solution by caustic potassa.
IV. The precipitate containing the hydrated oxides of
nickel and cobalt is gradually mixed, whilst still moist, with
dilute hydrocyanic acid and solution of potassa (cyanide of
potassium), and a gentle heat applied until it is dissolved.
The yellowish-red solution is heated to boiling, in order to
expel the excess of the hydrocyanic acid and to convert the
cyanide of cobalt and potassium into the cobalticyanide, and
is then mixed, whilst still warm, with levigated protoxide of
mercury. By this treatment the cyanide of nickel and potassium is decomposed and 11 the nickel precipitated, partly
in the form of oxide, partly as cyanide, whilst mercury takes
its place.
G




8 2                 SPEISS COBALT.
The precipitate, when washed and ignited with access of
air, leaves pure oxide of nickel behind.
If the mixture of both oxides, previously to the treatment
with hydrocyanic acid and potassa, have been dried and
reduced to metal by igniting it in a current of hydrogen
(and the metal weighed), the amount of cobalt need not now
be determined directly.
If this be not the case, the solution which still contains
the cobalt is carefully neutralized with nitric acid, and solution of nitrate of suboxide of mercury, as neutral as possible,
added, as long as it produces a precipitate of cobalticyanide
of mercury. lifter being washed and dried, the precipitate
is ignited with access of air, when it is converted into black
oxide of cobalt, which, after being weighed, must be reduced
by strong ignition in a current of hydrogen, on account of
its amount of oxygen varying according to the temperature.
When the nickel-speiss contains lead and sulphur, the
same method is used which has been given for the analysis
of the fahl-ores, where the compound is decomposed by
heating it in a current of dry chlorine-gas.
60. ZEISS COBALT.*
CoAs.
The analysis and the preparation of pure cobalt can be
effected by the same process as the analysis of copper-nickel
and the preparation of pure nickel. The following modifications facilitate the preparation:
I. Since the arsenide of cobalt contains upwards of 70
* Arsenide of cobalt, with small quantities of nickel, iron and
copper.




SPEISS COBALT.                 83
per cent of arsenic, it is advisable to remove a great portion
of it by roasting. This is done by exposing it, finely
powdered and in a thin layer, to a gentle red heat, in a
crucible which is placed obliquely in the fire under a
chimney with a good draught, and continuing the operation
as long as vapours of arsenic escape. The roasted mass is
then dissolved, with the aid of heat, in concentrated hydrochloric acid, to which some nitric acid or chlorate of potassa
has been added.
II. From the dilute solution all the sesquioxide of iron
(with a portion of the arsenic acid) can be removed by the
careful addition of carbonate of soda.
III. On mixing the solution, which should contain all
the arsenic in the form of arsenic acid, with a sufficient
quantity of sesquichloride of iron, neutralizing with carbonate of soda, and then adding acetate of soda in excess,
and boiling, all the arsenic acid is precipitated along withl
the entire quantity of iron.  The solution is then filtered,
again acidulated with hydrochloric acid, and treated with
sulphuretted hydrogen in order to remove those metals which
are precipitated by that reagent (for instance, copper);
cobalt and nickel are then precipitated at a boiling heat by
means of caustic potassa.
IV. Or the solution mixed with hydrochloric acid is
considerably concentrated by evaporation, mixed with salammoniac and ammonia in excess, and the brown solution
allowed to stand exposed to the air until it has acquired a
fine purple tint. If it be now saturated with hydrochloric
acid and heated to boiling, the greater portion of the
cobalt separates in the form of a carmine crystalline
powder, which appears to be 2 CoNH+3 + 3I4C1, and
when ignited leaves protochloride of cobalt.
G 2




84                  COBALT-GLANCE.
61. COBALT-GLANCE.
CoS2 + CoAs.
I. The finely-powdered mineral is decomposed by heating
it in a current of dry chlorine-gas, as in the analysis of the
fahl-ores, when the cobalt remains behind in the form of
protocl-doride, whilst arsenic and sulphur are obtained as
acids, dissolved in the water of the receiver.  The protochloride of cobalt can then immediately be reduced to
metal, in the same tube, by heating it in hydrogen, and
weighed, if the determination of the small amount of iron
contained in it be neglected; or it is dissolved in water
acidulated with hydrochloric acid, and the solution precipitated at a boiling heat by caustic potassa.  The small
amounts of nickel and iron contained in the oxide of cobalt
are then determined as in No. 60.
The sulphuric acid is determined by means of chloride
of barium, and the excess of baryta removed by sulphuric
acid. The filtered solution is concentrated by evaporation,
and the arsenic acid precipitated by sulphate of magnesia
and ammonia as in No. 45.
II. The mineral is dissolved in concentrated hvdrochloric acid, with gradual addition of nitric acid, until it is
completely dissolved, or the undissolved sulphur is left
behind with a fine yellow tint.  The latter is then collected
on a weighed filter, dried at 1000 and weighed.
From the solution, the sulphuric acid is precipitated by
chloride of barium, and the amount of sulphur calculated
from the precipitate, is added to that directly determined.
The excess of baryta is removed from the solution by
sulphuric acid.
The filtrate is mixed with sulphurous acid, allowed to




COBALT-GLANCE.                  85
stand for twenty-four hours, then heated to boiling until
the excess of sulphurous acid is completely driven off,
and when cooled down to about 500, saturated with sulphuretted hydrogen. Thus saturated, it is left to stand
for twenty-four hours, the sulphuretted hydrogen removed
by gentle evaporation, and the sulphide of arsenic collected
on a weighed filter and dried at 1000.  It is then treated
as in No. 46.
The solution of cobalt filtered from this precipitate is
heated to boiling, mixed with a little chlorate of potassa,
in order to bring the iron to a higher state of oxidation,
carefully neutralized with carbonate of soda, and the iron
precipitated with succinate of soda as in No. 23.
The protoxide of cobalt is precipitated from the filtered
solution at a boiling heat by means of caustic soda, washed
with hot water, ignited, and reduced in a current of
hydrogen at as high a temperature as possible.  When
moistened with water after being weighed, the metal must
not exhibit an alkaline reaction.
III. One part of the very finely-powdered mineral is
mixed with 3 parts of finely-powdered chlorate of potassa
and 3 parts of dry carbonate of soda, and the mixture
heated very gradually in a platinum crucible over a spiritlamp until it is in a state of tranquil fusion. The mass is
then treated with warm water and the black oxide of cobalt
filtered off. The solution is slightly acidified with hydrochloric acid and the sulphuric acid precipitated by chloride
of barium. After the excess of baryta has been removed by
sulphuric acid, the solution is concentrated by evaporation,
mixed with sal-ammoniac and sulphate of magnesia, and
the arsenate of magnesia-ammonia precipitated by adding
ammonia.
The oxide of cobalt is dried, the filter incinerated, the ash




8 6                 COBALT-GLANCE.
added to the oxide, and the whole dissolved in concentrated
hydrochloric acid.  The sesquioxide of iron is then precipitated, by means of succinate of soda, from the dilute
solution, after carefully neutralizing with carbonate of
soda.
The sesquioxide of iron cannot be precipitated, in this
case, by carbonate of baryta, because some oxide of cobalt
is precipitated at the same time; neither does the precipitation by an excess of ammonia lead to exact results, on
account of some oxide of cobalt remaining combined with
the sesquioxide of iron.
An approximate separation of both oxides may also be
effected by neutralizing the solution with ammonia, precipitating both metals by sulphide of ammonium, and then
adding a slight excess of dilute hydrochloric acid, when
sulphide of iron is dissolved and sulphide of cobalt is left
undissolved.
Or both oxides are precipitated by caustic potassa, the
precipitate washed, removed from the filter, and the latter
carefully cleansed with water from the washing-bottle; the
mass is then mixed with a slight excess of powdered oxalic
acid, when the oxide of cobalt is converted into rosecoloured, insoluble oxalate, whilst the sesquioxide of iron
is dissolved. After twenty-four hours the former is collected on a weighed filter, washed with cold water, dried
at 100~, and a weighed portion of it ignited in a glass
tube, one end of which is sealed, whilst the other is drawn
out into a point; by this process the oxalate of cobalt is
reduced to metal. Whilst the tube is still red-hot the
point is sealed with the blow-pipe, and the tube weighed
when cold.




MANGANESE AND COBALT, OR NICKEL.           87
62. MANGANESE AND COBALT, OR NICKEL.'
For the merely approximate separation, the oxides are
precipitated by carbonate of soda, the precipitate dissolved
in an excess of acetic acid and the cobalt or nickel precipitated from the solution by sulphuretted hydrogen, when
manganese remains dissolved. The solution of the chlorides
or of the sulphates may also be mixed with acetate of soda,
and the nickel or cobalt precipitated by sulphuretted hydrogen.
A more accurate, but still not absolute separation, may
be effected by neutralizing the solution of the chlorides
with ammonia, precipitating the metals by sulphide of
ammonium, and mixing the solution with an excess of very
dilute hydrochloric acid, when the sulphide of manganese is
dissolved with great facility, whilst the sulphides of nickel
or cobalt remain undissolved.
This method of separation is perfectly exact if the sulphides be used which were formed at a high temperature.
The oxides are precipitated at a boiling heat by carbonate
or hydrate of soda, the precipitate ignited and weighed, and
then heated to dull redness in a current of sulphuretted
hydrogen, in a porcelain boat, placed in a porcelain tube.
When cold, the porcelain boat is put into very dilute
hydrochloric acid, which dissolves the manganese only, and
leaves the sulphide of cobalt or nickel behind.-The conversion of the oxides into sulphides may likewise be effected
* Black cobalt-ore (earthy ore of cobalt) is a compound of protoxide of cobalt with binoxide of manganese.  Moreover, almost
every variety of manganese-ore contains small quantities of cobalt
for the detection of which the residues of the preparation of chlorine may be used.




88                 METEORIC IRON.
by fusing them in a porcelain crucible with 3 times
their weight of carbonate of soda and as much sulphkur,
after which the mass is treated with dilute hydrochloric
acid.
The following method is likewise accurate: The acid
solution is mixed with cyanide of potassium, when the
cyanides of manganese and cobalt are precipitated. Cyanide
of potasssium is then added in excess, which dissolves all
the cyanide of cobalt and a portion of the cyanide of man —
ganese. The undissolved cyanide of manganese is filtered
off, washed, and ignited with access of air. The filtered
liquor is heated to boiling, and a drop of hydrochloric acid
added from time to time; the protocyanide of cobalt is
thus converted into sesquicyanide. Hydrochloric acid is
then added and the boiling continued until, on farther
addition of acid, the odour of hydrocyanic acid is no longer
perceptible. By this time the double cyanide of manganese is converted into chloride of manganese, and the
manganese can now be precipitated from the hot solution
by means of carbonate or hydrate of soda, whilst all the
cobalt remains in solution in the form of cobalticyanide of
potassium. The separation of the cobalt from this solution
is effected as in No. 59.
63. METEORIC IRON.
Iron of meteoric origin can be recognized by the following peculiarities:
I. Some meteoric iron contains olivine which may be
detected by the eye.
II. In certain kinds, especially on the oxidized surface,
yellowish, pliable laminae of a metallic lustre may be ob



3IETEORIC IRON.                   8 9
served; they are phosphide of nickel and iron (Schreibersite).
III. Some kinds are passive, i. e., they do not reduce
copper from a solution of neutral sulphate of copper.
IV. If a freshly filed, ground and polished surface be
immersed for five or ten minutes in dilute nitric acid,
peculiar, mostly crystalline delineations (Widmannstatt en's figures), or microscopic parallel lines or bright
points, make their appearance in most kinds, thus imparting to the surface a peculiar lustre when viewed in a
certain direction.
V. All meteoric iron, when dissolved in hydrochloric acid,
leaves a black, pulverulent residue, whilst in most cases
a trace of suldphuretted  hydrogen is developed, derived
from an admixture of sulphide of iron. On examining
this residue (previously washed and dried) under a magnifying power of from  50 to 100, in most cases crystalline
particles of metallic lustre, and frequently also wTell-defined
magnetic prisms of metallic lustre, are observed, consisting
of phosphide of iron, phosphide of iron and nickel, and
sometimes also chrome-iron and graphite; in addition to
these also transparent, partly colourless, partly coloured
grains of quartz, olivine and other minerals.
VI. Every specimen of iron of undoubted meteoric origin
contains as characteristic constituents, nickel, cobalt and
phosphide of iron and nickel.  The amount of nickel varies
between 2 and 20 per cent; the cobalt rarely amounts to
1 per cent, and the insoluble residue usually amounts to
3 per cent.
In order to detect the nickel, the hydrochloric solution
is first saturated with sulphuretted hydrogen in order to
precipitate traces of copper and tin, which occasionally
occur; the protochloride of iron is then converted into




90              BISMUTH AND COPPER.
sesquichloride by heating the solution nearly to boiling,
and adding small quantities of chlorate of potassa. The
solution is then mixed with an excess of ammonia, when all
the sesquioxide of iron is precipitated, whilst most of the
nickel remains dissolved.  When the amount of nickel is
rather large, the filtered liquor is more or less blue. Sulphide
of ammonium precipitates from it black sulphide of nickel.
In order to detect the phosphoric acid contained in the
sesquioxide of iron, it is dried and ignited with an equal
weight of carbonate of potassa and soda, and the alkaline
phosphates extracted with water. The solution is then
supersaturated with acid and the phosphoric acid precipitated by ammonia and sulphate of magnesia.
In order to obtain the amount of phosphorus contained
in the black residue left on dissolving meteoric iron in
hydrochloric acid, it is finely powdered, mixed with about
half its weight of nitrate of potassa and then with an equal
weight of carbonate of soda, and ignited; the mass is then
extracted with water and treated as above. The oxidized
residue is dissolved in hydrochloric acid and the nickel
detected as above.
In quantitative analyses the iron is separated from the
nickel and cobalt, either by succinate of ammonia, or by
carbonate of baryta, see No. 23. Cobalt and nickel are
separated by cyanide of potassium as in No. 59.
64. BISMUTH AND COPPER.
The solution of these two metals in an acid is mixed
with carbonate of ammonia in excess, when the protoxide of
copper remains in solution, whilst the teroxide of bismuth
is precipitated; it is filtered off, but only after some time,




PLATINUM-ORE.                  91
washed with carbonate of ammonia, dried and ignited. See
No. 44.
Or the solution of both metals is mixed first with caustic
potassa in excess, and then with hydrocyanic acid (cyanide
of potassium), when the copper is dissolved as double
cyanide, whilst the oxide of bismuth is left undissolved.
See No. 27.
When the two metals have been precipitated by means
of sulphuretted hydrogen, the precipitate is washed with
water containing sulphuretted hydrogen, dried on the
funnel, removed from the filter as much as possible, the
latter carefully incinerated, and the ash added to the precipitate; this is then oxidized and dissolved by strong
nitric acid, with gradual addition of some sulphuric acid,
and the solution treated as above.
65. PLATINUM-ORE.
(Platinum with small quantities of Iridium, Palladium,
Rhodium, Osmium, Ruthenium, Iron and Copper.)
An accurate quantitative analysis of native platinum is
very difficult and tedious.  In order to determine, at least,
the amount of platinum, the following method is used:
The real grains of platinum are first picked out and
separated chiefly from the darker steel-coloured grains of
osm-iridium. The magnetic grains are next picked out by
means of a magnet; these, which contain a larger amount
of iron, are to be analyzed by themselves.
Two to three grins. of the mineral are then dissolved, at
a boiling heat, in a mixture of 5 parts of fuming hydrochloric acid and 1 part of fuming nitric acid, in a retort
connected with a receiver which is to be kept perfectly




9'2                 PLATINUM-ORE.
cold. The acid is distilled off until the contents of the
retort have acquired the consistence of a syrup. The mass
becomes solid on cooling; it is then dissolved in a small
quantity of water and the clear solution carefully poured
off from the residue. The acid which was distilled over,
contains osmic acid and is coloured yellow by a portion of
the solution which was mechanically carried over; it is
poured back on the residue and again distilled, in order to
complete the solution.
The distillate containing osmic acid may be saturated with
ammonia and the osmium separated as in No. 66. Or it
is nearly saturated with hydrate of lime, mixed with an
alkaline formate and boiled, when the osmium is reduced
as a bluish-black powder. Or the distillate is saturated
with caustic potassa, some alcohol added, and gently heated,
when osmite of potassa (KO, OS03) is precipitated in the
form of a beautiful red crystalline powder. It is washed
with alcohol, on account of its being soluble in water, and
ignited in a current of hydrogen when the osmium is
obtained in the metallic state.
The platinum-solution is filtered off from the insoluble
residue, which is collected on a weighed filter and washed.
It consists of osm-iridium, and is farther treated as in No. 66.
The solution is much concentrated by evaporation, mixed
with a warm saturated solution of sal-ammoniac and then
with about twice its bulk of alcohol. Platinum and iridium
are thus precipitated in the form of ammonio-chlorides.
When the platinum preponderates, the precipitate is yellow;
when the amount of iridium is large, it is reddish or red.
Not being perfectly insoluble in water, the precipitate is
washed with alcohol containing chloride of ammonium.
When dried it is ignited without being taken out of the
filter; to incinerate the filter completely, air should have




PLATINUM-ORE.                   93
access towards the end. By placing a few crystals of oxalic
acid in the crucible, the complete reduction is very materially facilitated. Platinum and iridium may then be
separated approximatively by very dilute aqua-regia.
This separation is more accurately effected by proceeding
in the following manner.
The concentrated (crude) solution of platinum is mixed
with twice its bulk of alcohol, and then with a warm saturated solution of chloride of potassium until no farther
precipitate is formed. This consists of the potassio-chlorides
of platinum and iridium with traces of rhodium and palladium, and is yellow or reddish, according to the amount
of iridium which it contains. It is filtered off and washed
with alcohol containing chloride of potassium.
a. When dried, this precipitate is put into a porcelain
crucible, and very intimately mixed with an equal weight
of carbonate of soda. The filter is incinerated, and its ash
added to the contents of the crucible. The mass is then
gently heated until it has become black throughout. By
this process the platinum  becomes reduced whilst the
iridium  and osmium are oxidized.  The mass is then exhausted with water, the alkali extracted by means of hydrochloric acid, the entire mass washed, dried and ignited, the
filter being incinerated separately and weighed.
In order to extract the rhodium, the ignited mass is
mixed with 6 times its weight of bisulphate of potassa, and
fused at a moderate, but long-continued heat. The rhodiumsalt formed is extracted with water; the amount of the
oxide of rhodium may then be estimated from the loss, or
it is precipitated as stated above in the case of the platinumresidue.  When reduced with hydrogen it is treated with
nitric acid, in order to extract any of the palladium which it
may contain.




94                  PLATINIJUM-ORE.
The mixture of platinum and oxide of iridium is digested
with very dilute aqua-regia, and thus part of the platinum
extracted. The cleared solution is poured off, saturated
with ammonia, evaporated to dryness, and carefully ignited,
when pure platinum is left behind.
The residue of platinum and oxide of iridium is mixed
with chloride of sodium and concentrated nitro-hydrochloric
acid, and evaporated to dryness. The platinum-salt is
then extracted from the mass by means of water, whilst
oxide of iridium remains undissolved.  The latter must
be washed with solution of chloride of sodium, and
towards the end with solution of chloride of ammonium,
in order to prevent its passing through the filter. The
oxide is ignited with the filter and reduced to the metallic
slate in a current of hydrogen.
The solution of platinum filtered off from the oxide of
iridium still contains some iridium. It is evaporated, and
the saline mass once more ignited with carbonate of soda as
above.
b. The alcoholic solution filtered from the precipitate
of platinum and iridium, which contains the rhodium,
palladium, iron, copper and some iridium,* is evaporated
to dryness, the mass digested with strong nitro-hydrochloric
acid, chloride of potassium added, and the whole again
evaporated to dryness in the water-bath. The chlorides of
iron and copper are then washed out with alcohol and
separated by means of sulphuretted hydrogen. The double
chlorides of rhodium, palladium and iridium, which remain
undissolved, are fused with bichromate of potassa, and the
mass treated with water, when oxide of iridium remains
behind.
* It contains no ruthenium, which appears to be present only
in the undissolved osm-iridium.




PLATINUM-RESIDiES.                9 5
The solution is neutralized with carbonate of soda, and
the palladium precipitated by a solution of cyanide of mercury. The yellowish-white cyanide of palladium having
settled, it is filtered off, washed and ignited, when metallic
palladium is left behind.
The filtered solution is boiled with hydrochloric acid
until it has assumed a red tint, and the hydrated oxide
of rhodium is then precipitated by caustic potassa. By
ignition in hydrogen it is reduced to the metallic state.
From the solution which contains the rhodium and palladium both metals may also be precipitated by pure zinc,
with the addition of hydrochloric acid, the precipitate
washed, and the palladium extracted by nitric acid, in
which the rhodium is insoluble.
If the rhodium be not reduced by formic acid, the
solution obtained with bisulphate of potassa might also be
mixed with formate of soda and boiled, when palladium is
separated in the metallic state. If both be reduced, the
palladium could be extracted from the mixture by means
of nitric acid.
66. PLATINUM-R1ESIDUES.*
(From the solution of the crude platinum-ore in nitrohydrochloric acid, consisting chiefly of scales and grains
of osm-iridium, of the powder of iridium, of magnetic-,
titanic-, and chromic-iron-ores, and sometimes also of some
platinum and gold.)
The coarse granular residue is first pounded and triturated as finely as possible, to reduce the grains of the iron* To be obtained from St. Petersburg or Paris.




96                PLATINUM-RESIDTTES.
ores to powder. It is then levigated with water, when most
of the osm-iridium is separated in larger grains and scales.
The levigated black powder is intimately mixed with
about its own bulk of decrepitated and finely-powdered
clforide of sodium, the mixture introduced into a porcelain
or glass tube, and gently ignited in a slow current of
undried chlorine-gas until the latter commences to pass
through the tube unabsorbed.
The other end of the tube dips into a well-cooled, tubulated receiver from the tubulure of which a gas-tube
conducts the excess of chlorine into alcohol.
By this process sodio-chlorides of iridium and of osmium
are formed. The greater portion of the latter is decomposed by the moisture of the chlorine-gas, and the osmic
acid formed from it partly sublimes in the receiver, and is
partly conducted into the alcohol.
The residue in the tube, when cold, is treated with water,
and is at last washed with hot water.
The dark yellowish-red solution of iridium filtered off
from the iron-ore is mixed with concentrated nitric acid
and distilled, when osmic acid passes over, dissolved in
water.  The liquid thus very much concentrated, is, whilst
still hot, mixed with a saturated solution of sal-ammoniac,
when, on cooling, a great portion of the iridium separates
in the form of crystalline dark red ammonio-chloride of
iridium, which is filtered off and several times washed with
solution of chloride of ammonium. On ignition it leaves
grey spongy iridium.
A small amount of platinum in this salt can be detected
by dividing it very finely, pouring 8 times its weight of
water on it and passing sulphurous acid through the latter,
when the iridium-salt is dissolved, whilst the platinum-salt
is left behind of a yellow colour.




PLATINUM  RESEDUES.               97
The remaining solution is mixed with crystallized carbonate of soda in excess, evaporated to dryness, the mass
gently ignited in a crucible, and when cold, washed with
hot water, which usually acquires a yellow colour, owing to
the presence of an alkaline chromate.
The black powder which is left undissolved, consists of a
compound of sesquioxide of iridium with soda, contaminated with sesquioxide of iron. It is reduced by being
gently heated in a current of hydrogen.  Water then
extracts caustic soda, and the iron is removed by digestion
with hydrochloric acid. On digesting it, after this treatment, with some very dilute nitro-hydrochloric acid, a small
amount of platinum is usually extracted, which may then
be precipitated with chloride of ammonium.
The iridium thus purified is washed, submitted to a very
powerful pressure, and exposed in a crucible to as strong a
white heat as possible, when it is obtained in a somewhat
coherent, dense state.
In order to extract the ruthenium, the iridium, previously
to ignition, is to be fused for at least an hour, in a silver
crucible, with a mixture of nitrate and hydrate of potassa.
The mass is treated with water, the yellow solution of
ruthenate of potassa poured off (not filtered), the undissolved oxide of iridium repeatedly washed by decantation,
and the solution of ruthenate of potassa neutralized with
nitric acid, when black sesquioxide of ruthenium is precipitated. By ignition in hydrogen it is reduced to metal, like
the oxide of iridium.
In order to detect any rhodium in the iridium, it is
fused at a moderate, out long-continued heat, with bisulphate of potassa, and t&e rhodium-salt formed is then
extracted by water. The solution, which is yellow, is boiled
with hydrochloric acid, when it becomes red, chloride of
H




98               PLATINUM RESIDUES.
rhodium being formed. Potassa precipitates from it a
brownish-yellow hydrated oxide. By ignition in hydrogen
it is reduced. During this treatment with bisulphate of
potassa, the iridium is likewise converted into black sesquioxide, but is not dissolved.
For the purpose of reducing the osmium from the osmic
acid, the latter, in the state of vapour, is mixed with hydrogen
and passed through a glass tube heated to redness at one
part; or the solution of osmic acid is mixed with formic acid
and heated; or it may be mixed with ammonia and chloride
of ammonium, evaporated to dryness, and the mass heated
in a retort until all the chloride of ammonium is volatilized,
when bluish-black osmium remains behind.
The platinum-residue, when once treated in the above
manner, is not yet exhausted; by repeating the same opera.
tion, more osmium and iridium may be obtained from it.
When the solution of iridium contains gold, it may be
precipitated by heating with oxalic acid.
The pure grains of osm-iridium, which contain also ruthenium, can be treated in the same manner, after they have
been powdered as finely as possible in a steel mortar, and
again freed from iron by hydrochloric acid. The mass,
after being ignited in chlorine-gas, is dissolved in water, a
few drops of ammonia added to the solution, and heat
applied, when a mixture of the oxides of ruthenium,
osmium and iridium is separated. By distilling the precipitate with nitro-hydrochloric acid, the osmium is separated in the form of osmic acid.  The residue in the retort
is evaporated to dryness, the mass fused at a red heat with
a mixture of nitrate and hydrate of potassa, dissolved in
water, the yellow solution of ruthenate of potassa poured
off from the oxide of iridium, and carefully neutralized with
nitric acid, when black oxide of ruthenium is precipitated.




PALLADITM.                    99
Or the entire grains are fused in a capacious platinum
crucible, over a spirit-lamp, with a mixture of equal parts
of hydrate and chlorate of potassa; from the cold mass
water extracts osmate and ruthenate of potassa, and black
oxide of iridium  is left behind, mixed with unoxidized
grains.  The solution minst not be filtered.
67. PALLADIUM.
The palladium of commerce, usually contains iron and
copper, and sometimes also silver.  In  order to prepare
the pure metal from it, it is dissolved by the aid of heat
in dilute nitro-hydrocllloric acid; the solution is then
diluted and the chloride of silver filtered off. The filtrate
is then concentrated to a great extent by evaporation,
and mixed with ammonia in excess, when, in addition
to the sesquioxide of iron, dark flesh-coloured ammoniochloride of palladium is precipitated.  When digested with
ammonia for a longer period, the latter is dissolved, leaving
the sesquioxide of iron, which is separated by filtration.
The solution is then mixed with strong hydrochloric acid
in slight excess, when most of the palladium is precipitated
in the form of lemon-coloured, crystalline chloride of
palladamine (NPdH3 Cl).  The precipitate is filtered off
after the lapse of twenty-four hours, and washed with as cold
water as possible, but only until the washings are free from
copper. When dried it is very gradually heated to ignition.
It then leaves 50 per cent of bluish spongy palladium.
The solution containing the copper still retains some
palladium; it is mixed with an alkaline formate and heated
to boiling, when the remainder of the palladium is precipitated in the metallic state.  In this manner, at least when
H 2




100                 TELLURIUM-ORE.
operating with small quantities, all the palladium may be
precipitated from the original solution; it is then, however,
not quite free from copper.
Another method of purifying palladium consists in mixing the nitro-hydrochloric solution of the crude palladium
with a quantity of chloride of potassium, amounting to
1! times that of the metal employed; the solution is then
evaporated to dryness, taking care to add towards the end
a little nitro-hydrochloric acid.  By this process, dark red,
crystalline potassio-chloride of palladium is formed; this
is to be finely divided, mixed with alcohol, filtered, and
washed with alcohol, which dissolves all the chlorides of
iron and copper. The salt is then exposed in a porcelain
crucible to a strong white heat, either by itself, or mixed
with some sal-ammoniac or oxalic acid, and the chloride of
potassium  extracted with water.-Palladium  can readily be
fused on charcoal by means of the oxygen blow-pipe.
68. TELLURIUJ M-ORE.*
The powdered ore contains graphic and foliated tellurium-ore; i. e., the tellurides of gold, silver, lead, and
sulphide of tellurium, mixed with various other minerals.
In order to remove a great portion of the gangue, the
finely-powdered ore is mixed with dilute hydrochloric acid,
with which it is left in contact until no farther disengagement of carbonic acid takes place, the whole being frequently agitated by stirring.   It is then washed and
* The telluriferous gold-ores of Transylvania may be obtained in
the powdered state, through the kindness of Professor Schr6tter,
at Vienna, for the value of the gold they contain.




TELLURIUM-ORE.                 101
dried.  Various methods can be  used to extract the
tellurium  and to recover at the same time the noble
metals.
I. The ore is dissolved in nitro-hydrochloric acid, with
the precaution, however, that the nitric acid is only gradually added, and in such quantities that it may all be
decomposed.  When the  mass has become completely
white and all the nitric acid has been expelled by heat,
some sulphuric and tartaric acids are added, the former
to ensure the complete precipitation of the lead and the
decomposition of the tellurite of lead, the latter to prevent
the precipitation of tellurous acid; after this, about twice
its bulk of water is added to the mass.  When completely
cold, the solution is filtered off and the residue washed.
The latter consists of quartz, heavy spar, sulphate of lead,
and a small quantity of chloride of silver, which may be
extracted by ammonia.
From the solution the gold is precipitated by a concentrated solution of sulphate of protoxide of iron. When
the metal has subsided, it is washed and ignited.
The liquor filtered off from it is considerably concentrated by evaporation in a flask, allowed to cool, and
mixed with a solution of an alkaline sulphite, when the
tellurium is precipitated as a grey powder. After standing
for twelve or twenty-four hours it is filtered off, and
washed, first with dilute sulphurous acid, and then with
water.
Gold and tellurium may also be precipitated together by
an alkaline sulphite, and the latter metal then extracted by
means of nitric acid. The filtered liquid is again evaporated to a small bulk, and mixed with an alkaline sulphite,
when, in most cases, a farther quantity of tellurium is
obtained.




10 2                TELLURITUM-ORE.
II. The ore, freed from most of the gangue by means of
hydrochloric acid, is intimately mixed with twice its weight
of bisulphate of potassa; 4 to 6 times its quantity of
bisulphate of potassa is then fused in a capacious Hessian
crucible at a gentle heat, and into the fusing salt the abovementioned mixture is introduced by small portions at a
time, waiting between each addition, until the frothing of
the mass has subsided.  When this has ceased, and a
sample of the mass being taken out appears quite white,
the fused mass is poured off from  the gold, which has
settled at the bottom  of the crucible.  The remainder of
the salt is then washed out of the crucible with hot water
containing sulphuric acid, and the gold collected.
The mass which was poured off is then dissolved in this
water, with a farther addition of sulphuric acid, the solution filtered off from the sulphate of lead, &c., and then the
silver precipitated by means of hydrochloric acid.
The filtered solution is concentrated by evaporation, and
the tellurium precipitated by sulphurous acid.
The tellurium thus obtained is not quite pure. In order
to purify it, it is distilled in a tube of hard glass, at a
strong red heat, in a current of hydrogen. The traces of
lead and copper remain behind as tellurides, and a slight
admixture of selenium is carried off by the gas.
Accurate quantitative analyses of pure graphic tellurium
and foliated tellurium are best made by means of chlorine
gas, as in the case of fahl-ores. Tellurium is volatilized in
this process as chloride of tellurium;it requires, however,
a very wide tube, on account of its being very bulky.
From the telluride of bismuth (tetradymite) of Schemnitz,
in Hungary, the tellurium is best obtained by the following
process: The finely-divided ore is intimately mixed with
3 times its weight of ignited cream of tartar, and exposed




MIESOTYPE.                   103
to a moderate red heat in a covered crucible during one
hour, when all the tellurium  is converted into telluride of
potassium, and the bismuth separated. The cold mass is
reduced to powder, thrown on a filter, and completely
washed with cold water which has been freed from air by
boiling.  The dark-red solution of telluride of potassium
passing through the filter, when exposed to the air, soon
deposits all the tellurium in the form of a grey powder.
This method is not applicable to graphic and foliated
tellurium-ore.
69. MIESOTYPE."
(NaO, SiO3 + A1203, SiO3) + 2 HO.
The amount of water is determined by igniting a weighed
quantity of the material, which has previously been dried at
100~.
The finely-divided, unignited mineral, dried at 100~, is
mixed in a porcelain dish with moderately strong hydrdchloric acid, and digested with it, with constant stirring,
until the mass is completely converted into a jelly, and all
the mineral is dissolved.
This mass is then evaporated to complete dryness, being
carefully stirred, in order to render the silica insoluble; the
evaporation is best effected, at least towards the end, in the
water-bath.
The remaining salt mass is moistened with hydrochloric
acid, after some time a little hot water is poured upon it,
+ The yellow variety, the so-called Natrolite, from the phonolite
of Hohentwiel, in the H6gau, Wiirtemburg, is most easily procured.




104                     MESOTYPE.
and the silica filtered off, washed with hot water, dried,
carefully ignited and weighed.
From the filtered solution the alumina is precipitatedlby
sulphide of ammonium, and treated as in No. 15.
When  the  zeolite contains sesquioxide of iron, the
alumina is coloured more or less black or greenish-black
by sulphide of iron.  The iron is separated from  it as in
No. 19.
The solution filtered from the alumina is evaporated to a
small bulk, in a dish, transferred to a weighed platinum
crucible, and carefully evaporated to dryness. The saline
mass is gradually heated till the sal-ammoniac is volatilized,
and finally heated to redness, the cover being loosely placed
upon the mouth of the crucible.  The residue is chloride
of sodium.
The silicic acid obtained in the decomposition of a silicate, especially if it separate rather in a pulverulent than
a gelatinous state, must always be examined  ag to its
purity, since it may sometimes contain other constituents
of the mineral, especially alumina, or even portions of the
unclecomposed mineral itself.
Pure silicic acid must entirely dissolve in a boiling
solution of carbonate of soda.  An insoluble residue indicates an impurity, which  should be filtered  off and
examined. It is preferable, however, to fuse such silicic
acid with 3 parts of carbonate of potassa and soda, and to
treat it as in No. 74.
Silicic acid, if perfectly pure, when dissolved in hydrofluoric acid, in a platinum capsule, entirely disappears on
evaporation.  Should there be any residue, it is again
treated with hydrofluoric acid, afterwards with  concentrated sulphuric acid, evaporated to dryness, and examined.
It sometimes consists of, or contains titanic acid.




LIEVRITE.                    10 5
70. LIEVRITE.*
3 CaO, SiO3 + 2 (3 FeO, SiO3) + 2 Fe2O3, SiO3.
The finely-powdered mineral is moistened with a suitable
quantity of water, in a porcelain capsule, some concentrated
hydrochloric acid and a little nitric acid added, and the
whole heated to complete gelatinization. The mass is then
evaporated to perfect dryness on a water-bath, during which
operation it is frequently stirred.
The dry mass is moistened with concentrated hydrochloric acid, then dissolved in chlorine-water, the silicic
acid filtered off, and treated in the usual manner (No. 69).
From the solution, diluted with the washing-water, the
sesquioxide of iron is precipitated by ammonia, the precipitate allowed to subside in a covered vessel, and rapidly
filtered off; the solution should first be passed through the
filter, which is kept covered, as far as possible, to prevent
absorption of carbonic acid. The precipitate is washed by
means of the wash-bottle arranged for the purpose, dried,
ignited, and weighed as sesquioxide of iron.
The filtrate from the sesquioxide of iron is acidulated with
hydrochloric acid, concentrated by evaporation, in a flask,
mixed with ammonia, the lime precipitated by oxalate of
ammonia, and treated as in No. 12.
The mineral contains about 1'5 per cent of protoxide of
manganese, and 0 5 per cent of alumina, both which are
* The compact variety from Elba is not rare. It may also be
obtained artificially by fusing together 6 parts of smithy-scales,
3 parts of fine white quartz-sand, and 1I parts of calcined marble, at
a strong white heat.




106                    OLIVINE.
contained in the precipitated sesquioxide of iron, and must
be separated from it as in Nos. 23 and 19.
About 1 5 per cent of water is also present as an unessential constituent; its quantity may be ascertained by
ignition in a covered crucible.
In order to ascertain directly the relative amounts of
protoxide and sesquioxide of iron, the process described in
No. 22 must be followed.
71. OLIVINE.
3 (FeO, MgO), SiO3.
The very finely-powdered mineral is decomposed by
digestion with concentrated hydrochloric acid, the mass
dried upon the water-bath, moistened with concentrated
hydrochloric acid, and, after some time, mixed with water
and filtered from the separated silica.
Small amounts of copper and tin, which are contained
in many specimens of olivine, are detected and separated by mixing the solution with saturated sulphuretted
hydrogen-water, until it smells strongly, and allowing it to
stand for some time in a closed vessel.
The solution filtered from the precipitate is concentrated
by evaporation, some chlorate of potassa being added to
peroxidize the iron.
By mixing the cooled solution with chloride of ammonium
and ammonia, the sesquioxide of iron may be precipitated
and separated from the magnesia. A small quantity of the
latter, however, is always precipitated with the sesquioxide.
A better method consists in treating the solution with a




OLIVINE.                  107
slight excess of carbonate of baryta, and allowing it to
digest for twelve hours, with frequent agitation; the precipitate is then filtered off, and treated as in _No. 23, III;
the small amount of alumina which it contains may also
be separated (No. 74).
The baryta must be precipitated from the solution by dilute
sulphuric acid, and the filtrate neutralized with ammonia.
This filtrate contains, besides magnesia, a small quantity
of protoxide of manganese and protoxide of nickel, which
latter is wanting only in the olivine of meteoric iron.
These are precipitated by sulphide of ammonium, an excess of which is, as far as possible, to be avoided. The
precipitate is not to be filtered off until it has separated
so as to leave the solution perfectly clear; it may then be
washed with very dilute sulphide of ammonium.  If
both metals are present only in small quantities, the sulphide of manganese may then be separated from the sulphide of nickel by treating it, upon the filter, with very
dilute hydrochloric acid, in which the sulphide of nickel is,
practically, insoluble. The small quantity of sulphide of
nickel is then ignited in air, and weighed as protoxide.
The manganese is precipitated from the solution by carbonate of soda, at a boiling heat.
The liquid filtered from the precipitate produced by sulphide of ammonium, is mixed with ammonia, and the
magnesia precipitated by phosphate of soda (No. 6).
In the analysis of olivine, the iron, when converted into
sesquioxide, may also be separated from the other bases by
succinate of ammonia (No. 23).




108                   FELDSPAR.
72. DATOLITE.
3 (CaO, BO3) + 3 CaO, 3 HO, 4 SiO3.
For the determination of water, a weighed quantity of
the mineral is heated to bright redness.
If the unignited mineral, in a finely-powdered state, be
digested with moderately strong hydrochloric acid, it becomes a gelatinous mass.  If the mixture be heated to
boiling, and filtered while hot, boracic acid separates from
the solution in crystals.
No accurate method is at present known for the direct
estimation of boracic acid; its amount must, therefore, be
inferred from the loss.
The finely-powdered mineral is decomposed by digestion
with hydrochloric acid, and the mass evaporated to dryness,
when a great part of the boracic acid is volatilized; after
exposure for a considerable time to a temperature of 100~,
the residue is heated with water containing hydrochlloric
acid, the silicic acid filtered off, washed, dried and
ignited.
The filtrate is neutralized with ammonia, and the lime
precipitated by oxalate of ammonia (No. 12).
73. FELDSPAR.
KO, SiO3 ~- A1203, 3 SiO3.
I. The very finely-powdered and levigated mineral, dried
at about 200~, is very intimately mixed, in a capacious
platinum crucible, with 4 or 5 parts of carbonate of baryta;
the crucible is then enclosed in an earthen crucible, which
is placed in a wind-furnace with a good draught, and
exposed for at least half-an-hour to an intense white heat,




FELDSPAR.                    109
so that the contents may be firmly aggregated into a
cinder-like mass.  The decomposition takes place more
rapidly, and with greater certainty, when the crucible is
exposed to a blow-pipe flame, so that the mass fuses
completely.
Or the mineral is mixed, in a silver crucible, with 4 parts
of hydrate of baryta, previously freed by heat from its
water of crystallization, and the mixture heated to fusion.
The mass is then turned out of the crucible into a
capacious dish, a quantity of water poured over it, and
hydrochloric acid gradually added in slight excess, until,
with the aid of a gentle digestion, it is completely decomposed and dissolved, with exception of some gelatinous
silicic acid which is separated. The whole solution is then
evaporated to perfect dryness, in order to render the silicic
acid insoluble, the evaporation being conducted towards
the last upon a water-bath, with constant stirring.
The saline mass is afterwards moistened with hydrochloric acid, a proper proportion of water added, and, after
digestion, the silica filtered off, washed, thoroughly dried,
ignited, and weighed in a covered crucible.
From the solution the baryta is precipitated by gradual
and cautious addition of dilute sulphuric acid, a great excess
of which is to be carefully avoided; the sulphate of baryta
is then filtered off and washed.  (See No. 3.)
The filtrate is concentrated, if need be, by evaporation,
the alumina precipitated by sulphide of ammonium, and
treated as in No. 15.
The liquid filtered from the alumina is evaporated to
dryness, and the dry mass ignited to expel the ammoniacal
salts. This process requires so much the more care, to
avoid spirting, the more sulphate of ammonia it contains,
in consequence of the careless addition of sulphuric acid.




110                   FELDSPAR.
At the end of the operation, in order to convert any
alkaline bisulphate into neutral sulphate, a fragment of
carbonate of ammonia is held in the covered crucible.
The residue is sulphate of potassa, and is weighed as
such. Should soda also be present in the mineral, the
residue must be treated as in No. 4.
Another method consists in precipitating most of the
baryta from the original solution by gradually and cautiously adding dilute sulphuric acid; the rest of the baryta,
together with the alumina, is then precipitated by a mixture
of carbonate of ammonia and free ammonia, added in slight
excess.
After twenty-four hours, the precipitate is filtered off,
washed, the alumina (together with the baryta) extracted
by dilute hydrochloric acid, precipitated by freshly-prepared
sulphide of ammonium, and rapidly washed, with as little
exposure to air as possible.
The liquid containing the alkali, filtered off from  the
precipitate produced by carbonate of ammonia, is concentrated by evaporation, acidified with hydrochloric acid,
evaporated to dryness, and the saline mass heated in a
covered crucible ultimately to redness; the residue is
chloride of potassium (or chloride of sodium). It must
be tested for baryta with sulphuric acid, since carbonate
of baryta is not absolutely insoluble, and would have been
converted into chloride of barium  by ignition with salammoniac.
II. A second method of decomposing feldspar is that
with hydrofluoric acid.  The levigated mineral is placed
in a platinum dish, or in a capacious platinum crucible,
mixed with a suitable quantity of fuming hydrofluoric acid,
and digested with it to complete decomposition.
Or the mineral may be spread out in a shallow platinum




FELDSPAR.                    1  1
capsule, moistened with water, and exposed for a long time
to the vapour of hydrofluoric acid, in an appropriate leaden
vessel closed with a lid. The hydrofluoric acid is evolved
from powdered fluor-spar, which is placed at the bottom
of the vessel, moistened with concentrated sulphuric acid,
and gently heated.
When the decomposition of the feldspar is completed,
the mass is gradually and cautiously mixed with pure concentrated sulphuric acid, and evaporated, slowly and carefully, to dryness. All the fluorine and silicon are thus
expelled, and after the volatilization of the excess of sulphuric acid, the bases remain as sulphates.
The dry mass is moistened with concentrated sulphuric
acid, and after a little time mixed with water, in which,
if the decomposition be complete, it should entirely dissolve.
From this solution the alumina and alkalies are separated
as directed above.
A small quantity of iron, which is frequently present,
is to be sought in the alumina.
In the analysis of a feldspar containing lime (labradorite,
anorthite), the latter is precipitated, after the separation of
the alumina, by oxalate of ammonia.
When petalite and spodumene are analyzed by the above
methods, a mixture of salts of soda and lithia is obtained
at last,  and must be analyzed as in the case of triphylline.




112                   GARNET.
74. AUGITE, HORNBLENDE, GARNET, IDOCRASE,
EPIDOTE.
Silicates of CaO, MgO, FeO, MnO and A1,03.
The very finely-powdered mineral must be decomposed
by fusion with 4 parts of carbonate of potassa and soda.
The mass is softened with water, dissolved in hvdrochloric acid, the silica rendered insoluble by evaporation,
as in the analysis of feldspar; the dry mass moistened with
hydrocllloric acid, dissolved in chlorine-water, in order to
oxidize the iron and manganese, and the silicic acid
filtered off.
From  the solution, the alumina, sesquioxide of iron
and sesquioxide of manganese, are precipitated by ammonia.
The lime and magnesia are precipitated from the filtrate,
and separated, as in No. 1i.
The precipitate, which, besides alumina, sesquioxide of
iron and sesquioxide of manganese, may also contain magnesia, is dissolved in hydrochloric acid, the solution heated
to boiling, in order to convert the sesquichloride of manganese into protochloride, diluted with much water, and
gradually neutralized, with constant stirring, by carbonate
of soda'; so that the solution may be saturated with carbonic acid, and the addition of the last portions of carbonate
of soda may give rise to the formation of bicarbonate.
In this manner the sesquioxide of iron and alumina are
entirely precipitated, while magnesia and protoxide of
manganese remain in solution.
The two former are then filtered off,. and separated as in
No. 19.
The solution filtered from the iron- and alumina-preci



BERYL.                     113
pitate is mixed with more or less hypochlorite of soda,
according to the quantity of manganese present, and allowed
to stand for twenty-four hours, when the manganese is
entirely precipitated as hydrated sesquioxide, which is converted by ignition into proto-sesquioxide.
The filtrate is concentrated by evaporation in a flask
placed obliquely, acidified with hydrochloric acid, taking
care to avoid loss by spirting, mixed with ammonia in
excess, and the magnesia precipitated by phosphate of soda,
as in No. 6.
When a mineral of this description contains very little
lime or protoxide of manganese, the solution filtered from
the silica may be precipitated at once with bicarbonate of
soda, which throws down the alumina and sesquioxide of
iron, leaving protoxide of manganese, lime and magnesia
in solution.
The alumina and sesquioxide of iron may also be precipitated from the solution by carbonate of baryta, and
farther treated as in No. 23.
These and all similar minerals, not attacked by hydrochloric acid, may likewise be conveniently decomposed
by hydrofluoric acid; in which case, however, the silica
must be determined by loss.  (See Feldspar.)
75. BERYL.*
Be2O3, 2 SiO3 + A1203, 2 SiO3.
The very finely-powdered mineral, previously well dried,
is fused in a platinum crucible with 4 times its weight of
* The beryl from Haddam in North America, from Limoges in
France, from the Rabenstein near Zwiesel, Bavaria, may be easily
procured.
I




114                      BERYL.
carbonate of potassa and soda (see No. 10); the mass is
softened with water, digested with excess of hydrochloric
acid until the decomposition is complete, and evaporated
to perfect dryness to render the silica insoluble.  The
residue is moistened with hydrochloric acid, and treated
with warm water; the silica is then filtered off, the solution
concentrated by evaporation, and dropped very gradually,
with constant stirring, into an excess of a warm concentrated solution of carbonate of ammonia, which precipitates
the alumina, and dissolves the berylla (glucina). When the
precipitate has been digested for some time with the solution
in a closed vessel, the solution is filtered off, boiled for
a long time, until the greater part of the carbonate of
ammonia is expelled, slightly acidified with hydrochloric
acid, digested for some time to expel the carbonic acid, and
the berylla finally precipitated by caustic ammonia.
If it be intended to obtain merely the berylla, it is only
necessary to boil the ammoniacal solution, when, in proportion as the carbonate of ammonia is volatilized, the berylla
separates as carbonate.
The following is another method: The two earths are
precipitated by ammonia, the precipitate filtered off, the
greater part detached from the filter, and the remainder
dissolved off it in a cold solution of potassa, the filter being
afterwards well washed.  The alkaline solution is allowed
to flow upon that portion of the precipitate which was
separated, and potassa is afterwards added until the precipitate is completely dissolved.  Any sesquioxide of iron
which remains must be filtered off.
The solution is then diluted with much water, and boiled
for fifteen minutes, when all the berylla is precipitated.
It must be filtered while hot, and the precipitate washed
with hot water.




TOPAZ.                    115
The alkaline solution of alumina is feebly acidified with
hydrochloric acid, and the alumina precipitated by sulphide
of ammonium.
A third method consists in boiling the hydrated earths,
freshly precipitated by ammonia, with a concentrated solution of chloride of ammonium, as long as ammonia is
evolved, when the berylla passes into solution, and the
alumina is left.
76. TOPAZ.*
6 (3 A1203, 2 SiO3) + (3 A12F3 + 2 SiF3).
At a very intense white heat, the topaz loses all its
fluorine in the form of terfluoride of silicon.
When fused, in the state of very fine powder, with
4 times its weight of anhydrous carbonate of soda, it is
decomposed, with formation of fluoride of sodium, which is
extracted by water. Before filtering off the residual silicate
of alumina, however, the solution should be digested with
some carbonate of ammonia, in order to precipitate anlly
small quantities of alumina and silica which may have been
dissolved.
The residue is then filtered off, washed with dilute carbonate of ammonia, and farther treated as in No. 69.
The alkaline filtrate is concentrated and freed from
ammonia by evaporation, and the greater part of the carbonate of soda neutralized by nitric acid, so that some
carbonate may still remain undecomposed. The solution
is then mixed with chloride of calcium, which precipitates a
* Defective crystals of Brazilian topaz may frequently be obtained
at a cheap rate.
I 2




116                     ZIRCON.
mixture of carbonate of lime and fluoride of calcium. When
the precipitate has separated, by the aid of a gentle heat,
it is filtered off, washed and ignited. The carbonate of
lime is then dissolved in dilute acetic acid, the solution
evaporated to dryness on a water-bath to expel the excess
of acid, and the acetate of lime extracted from the dry mass
with hot water.  The residual fluoride of calcium is filtered
off, washed, dried, ignited and weighed. If the precipitate
of carbonate of lime and fluoride of calcium had not been
ignited previously to the treatment with acetic acid, the
fluoride would have entered the pores of the filter, and the
filtrate would have been turbid.
77. ZIRCON.
Zr2O3, SiO3.
A carefully-selected specimen of zircon which has been
ignited, and thus deprived of colour, is levigated to a very
fine powder, and fused, at a good heat, in a platinum
crucible, with 4 parts of anhydrous carbonate of soda.
The mass is digested with water, which dissolves the
silicate of soda, and leaves a silicate of soda and zirconia
as a crystalline powder; this is washed and decomposed by
digestion with concentrated hydrochloric acid. The mass
is dried up in a water-bath, treated with water containing
hydrochloric acid, the silica filtered off, and the zirconia
precipitated by ammonia.
Another process for decomposing zircon consists in
igniting the very finely-levigated mineral with several Iparts
of pure sugar, introducing the mass, while hot, into a
tube of very hard glass, in which it is heated to full redness,
while a stream of dry chlorine-gas is passed over it. The




ZIRCON.                    117
terclhioride of silicon which is formed passes off as gas,
while the chloride of zirconium sublimes into the cooler
portion of the tube.
If the zirconia obtained by the first process contain any
iron, the precipitate is digested with oxalic acid, which
dissolves the sesquioxide of iron, leaving oxalate of zirconia,
at least in part, undissolved.
Or the precipitate may be treated with sulphide of ammonium, to convert the iron into sulphide, the solution
once more decanted, and the black precipitate treated with
solution of sulphurous acid, which immediately dissolves
the sulphide of iron, leaving the zirconia colourless. A
shorter method is to heat the solution containing zirconia
and iron, after neutralization, with bisulphite of soda, when
all the zirconia is precipitated free from iron.
}For accurate quantitative separation, the solution of
zirconia containing iron is mixed with tartaric acid and
excess of ammonia, which should not cause any precipitate;
the iron is then removed by sulphide of ammonium, the
precipitate allowed to separate completely, filtered off without intermission, and washed with dilute sulphide of
ammonium. The solution is evaporated to dryness, and
the residue ignited, till all the carbon has burnt off, and
the zirconia has become white.
From a neutral solution, zirconia is completely precipitated by a boiling saturated solution of sulphate of potassa,
as a white pulverulent double salt.  After boiling, this
precipitate is sparingly soluble in water, and even in acids.
The substance usually termed zirconia is said to consist
of several very similar oxides, which have not been accurately separated from each other.




118                     CERITE.
78. CERITE.*
3 (CeO, LaO, DiO, FeO, CaO), SiO3 + 3 HO.
Cerite, in fine powder, is treated with concentrated
sulphuric acid, with which it is digested, until the high
temperature produced by the combination has caused it to
form a dry mass.
Cold water is then poured over it, and the mixture
allowed to digest, in the cold, until the sulphates are dissolved. The solution filtered from the silica, which must
be concentrated by evaporation if too largely diluted by
the washings, is mixed with a boiling saturated solution
of sulphate of potassa, and allowed to cool.   Cerium,
lanthanilm  and didymium are thus precipitated as double
sulphates, while iron, &c.,'remain dissolved.  The precipitate is filtered off, and washed with a saturated solution
of sulphate of potassa. Crystalline crusts of sulphate of
potassa are placed in the filtrate, and in this way the remainder of the double salt is precipitated.
The precipitated salt is dissolved in the necessary quantity of boiling water, with addition of some hydrochloric acid,
and the bases precipitated from the hot solution by an excess
of caustic potassa.  (Ammonia precipitates basic salts.)
After ignition, they appear as a cinnamon-brown powder.
When converted into sulphates by digestion with concentrated sulphuric acid, they give, with water, a yellow
solution, from which sulphate of potassa precipitates a
lemon-yellow mixture of double salts.
Another method of obtaining the oxide of cerium consists in precipitating the original sulphuric solution, while
* Only to be found in one locality —the mine of Bastnas, near
Riddarhytta in Westmanland. May be obtained from dealers in
minerals, or from Stockholm.




CERITE.                   119
hot, with an excess of hydrate of potassa, washing the
precipitate, and digesting it with an excess of solution of
oxalic acid, when the iron and lime are dissolved, and the
oxide of cerium, &c., left as white oxalates, which are
filtered off aind washed.  By ignition in air, they are converted into the brown oxides.
There is at present no method of accurately separating
these three oxides from each other.
The HYDRATED PROTOXIDE OF CERIUM is colourless, but
oxidizes rapidly on exposure to air, and becomes yellow.
The SESQUIOXIDE OF CERIUM, in the pure state, is yellow,
with a tinge of red; when impure, it is brick-red.  It is
produced when the hydrate is ignited in air. The sesquioxide is soluble only in hot concentrated sulphuric acid;
the solution has a fine yellow colour.  The hydrated sesquioxide is dissolved, in quantity, with a yellow colour, by
the alkaline bicarbonates, especially by bicarbonate of
ammonia.  The sesquioxide is insoluble in concentrated
hydrochloric acid, but on addition of alcohol, it is dissolved in the form of protochloride.
OXIDE OF LANTHANIUM is colourless; when heated with
water, it is converted into the hydrate, which has an alkaline
reaction.  It is dissolved by a hot solution of chloride of ammonium, with evolution of ammonia. Its salts are colourless.
The carbonate is insoluble in carbonate of ammonia.
OXIDE OF DIDYMIUM, when ignited, is brown.  When
exposed to a white heat it assumes a dingy white colour,
with a tinge of green.  It is soluble in acids; its salts
have the colour of amethyst, with a tinge of blue; with
hydrate of potassa they yield a violet hydrate. The carbonate is insoluble in carbonate of ammonia.
The ignited brown mixture of the three oxides is dissolved by hydrochloric acid, with evolution of chlorine.




120                     ORTHITE.
If the mixed hydrates, precipitated by potassa, be dissolved in nitric acid, the solution evaporated to dryness,
and ignited, a dark brown oxide is obtained, from which a
part, at least, of the oxide of lanthanium may be obtained
in a pure state. For this purpose, the finely-powdered
oxide is mixed with water, to which nitric acid, free from
nitrous acid, is added in single drops with continual agitation,
in proportion as it is saturated. From the filtered solution,
at a boiling-heat, carbonate of ammonia precipitates carbonate of oxide of lanthanium in shining, crystalline scales.
When the oxides precipitated by potassa are mixed with
a concentrated solution of potassa, and the latter saturated
with chlorine-gas, and frequently agitated, the cerium is
converted into an insoluble yellow compound of the sesquioxide, while didymium and lanthanium, together with some
cerium, are dissolved as protochlorides. The yellow sesquioxide of cerium is digested still longer with chlorine-water,
filtered off, washed, and digested with dilute potassa to
remove hypochlorous acid; any potassa which it has taken
up is then extracted by dilute nitric acid. The solution
of the protochlorides (of didymium and lanthanium) is
again precipitated by potassa, and the precipitate treated a
second time with potassa and chlorine-gas.
79. ORTHITE.YO, CeO, LaO, CaO, MgO, MnO, FeO, Fe2O3, A]203, SiO3.
The finely-powdered mineral, dried at 100~, is decomposed by digestion, in a porcelain dish, with concentrated
* This is the least rare of the minerals containing yttria. The
preparation of yttria from gadolinite, which is much rarer, but
contains more of that base, may be effected in a similar manner.




ORTHITE.                    121
hydrochloric acid, to which some nitric acid has been added,
to peroxidize the iron; the mass is completely dried up,
with frequent stirring, in a water-bath, and maintained for
some time at that temperature.
It is then digested with a little water acidulated with
hydrochloric acid, the silica filtered off, washed with hot
water, thoroughly dried, ignited and weighed.
The washing-water is evaporated to a small bulk, mixed
with the filtrate, and saturated with chlorine-gas to convert
manganese into sesquichloride; the solution is precipitated by ammonia, which separates all the bases except
lime.
The precipitate is allowed to subside in a closely-covered
vessel, the clear liquid rapidly poured through the filter,
upon which the precipitate is afterwards thrown (always
keeping it covered), and washed thoroughly with hot water
by means of the wash-bottle properly arranged for that
purpose.
The washings, slightly acidified with hydrochloric acid,
are evaporated to a small bulk, mixed with the first filtrate, neutralized with ammonia, and the lime precipitated
by oxalate of ammonia. (See No. 12.)
The filtrate, after concentration, is tested for magnesia,
since perhaps this base may not have been entirely precipitated with the alumina.
The precipitate produced by ammonia is carefully detached from the filter, while yet moist, without perforating
the paper; that portion which cannot be mechanically
removed is then dissolved off with a few drops of hydrochloric acid, the filter well washed, the solution added to
the other portion of the precipitate, and the latter dissolved
in the smallest possible quantity of hydrochloric acid; the
solution is afterwards heated for some time nearly to boil



122                     ORTEHITE.
ing, to convert all the manganese and cerium into protochlorides.  When the liquid has become perfectly cool,
an excess of finely-powdered carbonate of baryta is added,
and the whole allowed to stand for twenty-four hours, with
frequent agitation. In this way, all the sesquioxide of iron
and alumina are precipitated.
The mixture is filtered, the precipitate well washed,
dissolved in hydrochloric acid, the baryta precipitated by
dilute sulphuric acid, and the sesquioxide of iron and alumina separated from the filtrate as in No. 19.
In the solution filtered from the precipitate of alumina
and sesquioxide of iron, the dissolved baryta is precipitated
by dilute sulphuric acid, the precipitate filtered off, and the
solution evaporated to a small bulk. It is then mixed
with several times its volume of a boiling saturated solution
of sulphate of potassa, which precipitates the oxides of
cerium, &c. (CeO, LaO, DiO) in the form of a white, pulverulent double salt. After the lapse of twenty-four hours,
this is filtered off, and thoroughly washed with a saturated
solution of sulphate of potassa, in which it is perfectly
insoluble.
It is then dissolved in a sufficient quantity of boiling
water, with addition of some hydrochloric acid, the solution
precipitated, while hot, by an excess of caustic potassa,
the precipitate filtered off, washed, ignited and weighed as
brown sesquioxide of cerium. (See No. 78.)
(If a similar mineral contained also zirconia or thoria,
these would be present in the precipitate produced by
sulphate of potassa, although a part of the zirconia might
be found in the precipitate produced by carbonate of baryta.
It is insoluble in caustic potassa.)
The solution filtered from the precipitate produced by
sulphate of potassa, which still contains the yttria, is neu



ORTHITE.                    123
tralized with ammmonia, and the yttria precipitated by oxalic
acid. After twenty-four hours, the precipitate is filtered off,
washed, ignited and weighed as yttria (YO, TbO, EO).
A little manganese may still be contained in the filtrate.
After neutralization, it may be precipitated by pentasulphide of potassium.
If the ignited yttria had a brownish colour, it would contain manganese, from which it might be separated by dilute
nitric acid, free from nitrous acid; perhaps also the separation might be effected by heating with excess of solution
of oxalic acid, since oxalate of yttria is perfectly insoluble
in that acid.
(If such a mineral should contain also berylla, it would
be found in the solution filtered from the oxalate of yttria,
and might be precipitated thence by ammonia.
In order to detect the presence of berylla in yttria, it is
necessary, since the latter cannot be extracted by caustic
potassa, to mix the precipitate with pure sugar, and to
carbonize the mass in a platinum crucible; it is then ignited
in a stream of dry chlorine-gas, when the chloride of
beryllium sublimes, and chloride of yttrium remains in the
carbonized mass.)
The precipitate produced by ammonia, which contains,
in addition to lime, all the other bases of the orthite, may
also be analyzed by digesting it with an excess of solution
of oxalic acid, when the sesquioxide of cerium and the
yttria remain undissolved. Before these are separated
farther, they must be ignited, to destroy the oxalic acid.




124                     APATITE.
80. TIIOR1TE.*
3 ThO, SiO3~3 HO.
The finely-powdered mineral gelatinizes entirely with
concentrated hydrochloric acid. The solution is evaporated
to dryness, the silica filtered off, the filtrate highly concentrated by evaporation, and mixed with a boiling saturated
solution of sulphate of potassa.  In this way all the thoria,
like the oxides of the cerium-class, is precipitated as a
white pulverulent double salt. After cooling, this is filtered off, and washed with a saturated solution of sulphate
of potassa. It is then dissolved in boiling water and the
alumina precipitated by caustic potassa.
After ignition, thoria is white, and has a spec. grav. of
9'4. It can only be dissolved in hot concentrated sulphuric acid. The hydrate of thoria is insoluble in potassa.
Chloride of thorium is fusible, and may be sublimed.
Sulphate of thoria dissolves but slowly in water.  When
the solution is heated, a tissue of fine crystalline needles
separates, consisting of a salt containing less water, which
is very sparingly soluble.
81. APATITE.
3 (3 CaO, PO) + CaCl (or +CaF).
For the determination of chlorine, a weighed portion of
the mineral (which need not be powdered) is dissolved in
* This black, amorphous mineral, from Ldv6n, near Brevig in
Norway, is taken here, without regard to its rarity, as an example of
a compound of thoria, in order to direct attention to the detection of
this earth, which must certainly occur more frequently. The orangecoloured orangite of Brevig has a similar composition.




APATITE.                     125
dilute nitric acid,* and the chlorine precipitated by nitrate
of silver.
In order to detect the small quantity of fluorine which is
contained in some specimens of apatite, the finely-powdered
mineral is mixed, in a platinum crucible, with concentrated
sulphuric acid, and the crucible covered with a glass
plate coated with a thin film of wax, through which some
characters have been written with a needle; the crucible is
then heated with a flame so small as not to melt the wax.
If fluorine be present, the characters are found etched upon
the glass after the removal of the wax. The quantity of
the fluorine is inferred from the loss of weight in the whole
analysis.
The phosphoric acid and lime may be determined by the
methods described in the analysis of bone-earth. The following process may also be employed.
The mineral is dissolved in nitric acid, in a dish, and so
much pure mercury added that, after saturating the acid, a
portion still remains undissolved. The mixture is then evaporated to perfect dryness on the water-bath. Should it still
emit an odour of nitric acid, this acid must be completely
expelled by adding more water, and again evaporating to
dryness. The mass is treated with water, filtered through
the smallest possible filter, and the residue, which contains
all the phosphoric acid, well washed.
The solution contains, besides the excess of the mercervsalt, the whole of the lime. The suboxide of mercury is precipitated by hydrochloric acid. Any protoxide of mercury
which may have been formed, is precipitated from the
filtrate by ammonia. If the mineral contain iron, or other
* Many compact apatites, when treated with nitric acid, leave a
small quantity of a crystalline powder, which is kryptolite (phosphate
of protoxide of cerium).




126                  TRIPiHYLLINE.
bases precipitable by ammonia, these will remain behind on
igniting this precipitate.  From the solution, which should
be filtered rapidly, and with as little exposure to air as
possible, the lime is precipitated by oxalate of ammonia.
The filter with the mercury-residue, which contains the
phosphoric acid, is well dried, and the contents thrown into
a platinum crucible in which they are mixed with carbonate
of potassa and soda; the filter is rolled up and buried in
the mixture. The crucible is now heated (but not to redness) under a chimney with a good draught, until the
mercury is volatilized, after which the mass may be heated
to redness and fused.  It is then dissolved in water, an
excess of hydrochloric acid added, and the phosphoric acid
precipitated by ammonia and sulphate of magnesia.
82. TRIPHYLLINE.*
3 (FeO, MnO, LiO), PO5.
In order to obtain the lithia, the coarsely-powdered
mineral is dissolved in concentrated hydrochloric acid, with
gradual addition of nitric acid; the solution is heated, to
ensure the conversion of all protoxide of iron into sesquioxide, and poured off from any extraneous minerals which
generally remain undissolved. It is then evaporated completely to dryness, being constantly stirred towards the
last, and the mass heated until all free acid is evaporated.
It is then finely powdered, boiled out with water, and the
solution filtered. This now contains not a trace of iron, which
* Occurs in largest quantity in a vein of granite at the Rabenstein,
near Zwiesel, in the Bavarian forest. It may also be obtained from
Dr. H. Muiller, at Weiden in Bavaria.




FLVOR-SPAR.                  127
remains undissolved as white phosphate, but only chloride
of lithium, mixed with the chlorides of manganese, magnesium and sodium. In order to precipitate the two
former, together with a small quantity of phosphoric acid
which may be present, the solution is mixed with pure
hydrate of lime, and boiled, with access of air, until all the
hydrate of protoxide of manganese is converted into the
brown sesquioxide. All the lithia remains in the solution;
it is filtered off, and the dissolved lime precipitated by a
mixture of carbonate of ammonia and free ammonia. After
filtration, the solution is evaporated, and the chloride of
lithium heated to fusion in a porcelain crucible.
The chloride of lithium still contains chloride of sodium,
which is separated by digesting the mass with a mixture
of alcohol and ether, which dissolves the chloride of lithium,
and leaves the chloride of sodium undissolved. Or the
impure chloride of lithium may be converted into carbonate
by dissolving it in the smallest possible quantity of concentrated ammonia, and placing in the solution, which should
be kept as cold as possible, fragments of carbonate of
ammonia. The precipitated carbonate of lithia is filtered
off and washed with alcohol.
Pure chloride of lithium is easily fusible, it imparts to
the flame of alcohol a dark carmine-red colour; when soda
is present, the colour is rather orange-red.
83. FLUOR-SPAR.
CaF.
A weighed quantity of the finely-powdered mineral is
mixed, in a platinum crucible, with concentrated sulphuric
acid, and heated until all the hydrofluoric acid is expelled,




128                  FLUOR-SPAR.
and the greater excess of sulphuric acid volatilized. The
residual sulphate of lime is then mixed with alcohol, filtered
off, washed with alcohol, ignited and weighed.  Or it may
be dissolved in water containing hydrochloric acid, the
solution mixed with ammonia, and the lime precipitated by
oxalate of ammonia.
The fluorine is determined from the loss. In order to
estimate it directly, the decomposition must be effected in
a platinum retort, the vapours of hydrofluoric acid conducted into solution of carbonate of soda, and the fluorine
precipitated from the solution by chloride of calcium, as in
the analysis of topaz.
Or the very finely-powdered mineral may be mixed with
an excess-that is, with at least an equal weight-of finelypowdered silicic acid (that prepared from terfluoride of
silicon is the best), the mixture introduced into an apparatus
similar to that employed in alkalimetry, and the sulphuric
acid, which must for this purpose be most concentrated,
allowed to flow upon it.  With the aid of a gentle heat,
terfluoride of silicon is formed, which is allowed to escape
in the gaseous state through a tube filled with chloride of
calcium; the last portions are withdrawn from the apparatus by sucking air through it, for which purpose, there is
attached to the chloride-of-calcium-tube a small tube filled
with fragments of moist hydrate of potassa, through which
the air is drawn.  The loss of weight expresses the amount
of terfluoride of silicon which has been evolved, and of
which 100 parts correspond to 72'79 of fluorine.




SPHENE.                     129
84. SPHENE (TITANITE).
2 (CaO, SiO3) + CaO, 3 TiO2.
This mineral, even in the state of very fine powder, is
only attacked with difficulty, and at best incompletely, by
hydrochloric or sulphuric acid.
It is better to heat it in a platinum capsule with bisulphate of ammonia, gradually raising the temperature,
with constant stirring, till the salt fuses; the heat is
finally increased to ignition. A little dilute sulphuric acid
is then added, and heat again applied until the acid begins
to volatilize.  When the mass is perfectly cold, it is mixed
with water, the silicic acid filtered off, and the sulphate of
lime thoroughly washed.
From the solution, the titanic acid is precipitated in the
cold, together with the small quantity of sesquioxide of
iron, by ammonia, the solution filtered rapidly, with as
little exposure to air as possible, and the lime precipitated
by oxalate of ammonia.
The titanic acid containing iron is dissolved in hydrochloric acid, the solution mixed with pure tartaric acid and
excess of ammonia, which ought not to cause any precipitate. Sulphide of ammonium is afterwards added, to
precipitate the whole of the iron.  (See Zircon.)
The solution filtered from the sulphide of iron is evaporated to dryness, the mass carbonized, and heated with
access of air, or in a stream of oxygen, until all the carbon
is burnt off, and the titanic acid is perfectly white.
Another method (in which, however, the silicic acid is
determined by loss) consists in decomposing the mineral
by concentrated hydrofluoric acid. The mass is afterwards
mixed with concentrated sulphuric acid, heated until all
K




130                  TITANIC IRON.
the terfluoride of silicon and most of the sulphuric acid
are expelled, mixed once more with concentrated sulphuric
acid, and heated until it begins to evaporate. The whole
may then be dissolved by adding a sufficient quantity of
water.
85. TITANIC IRON.*
Fe203, Ti2O3, and FeO, Tia03.
For the analysis of this mineral, and for the preparation
of pure titanic acid, various methods are employed. The
titanic iron dissolves in concentrated hydrochloric acid,
but very slowly.  When the levigated powder is ignited
in hydrogen-gas, the iron is reduced, and may be extracted by hydrochloric acid; the reduction, however, requires a very long time and an intense red heat, and, after
all, the titanic acid is not free from iron. The following
nethods are more efficient:
1. The very finely-powdered mineral is fused in a platinum crucible, placed within an earthen crucible, with
3 parts of carbonate of potassa; the fused mass is powdered,
and dissolved in a platinum  capsule, in the requisite quantity of dilute hydrofluoric acid. Titano-fluoride of potassium
is thus produced, which is sparingly soluble, and crystallizes readily, while most of the sesquioxide of iron is separated free from titanium.  The mixture is heated to boiling,
so much water being added as is requisite to dissolve all
the salt, and filtered while boiling hot; glass vessels may
now be employed, provided an unnecessary excess of hydro* Titanic iron occurs in considerable quantity at Egersund in
Norway, and may be obtained of the dealers in minerals.




TITANIC IRON.                  131
fluoric acid has been avoided. On cooling, the greater part
of the salt separates in lustrous crystalline scales.  It is
filtered off, pressed, washed once or twice with cold water,
and purified completely by recrystallization from boiling
water.
The sesquioxide of iron is washed, the washing-water
mixed with the mother-liquor from the salt, and with the
washing-water from the latter, and the dissolved sesquioxide of iron, together with a very little titanic acid, precipitated from the mixed solution, in the cold, by dilute
ammonia.   The precipitate must be filtered off immediately, for otherwise the titanic acid also begins to separate.  The filtrate is then heated to ebullition, when all
the titanic acid is precipitated as white titanate of ammonia.
In the same manner the titanic acid may be obtained from
the crystallized titano-fluoride of potassium previously separated.
The titanate of ammonia is easily soluble in hydrochloric
acid, and, at a red heat, is converted, with incandescence,
into pure titanic acid.
II. The finely-powdered mineral is fused with at least
6 parts of bisulphate of potassa, in a platinum crucible,
until it is completely dissolved; the fused mass, when cool,
is powdered and dissolved in cold water.
This solution has the peculiarity, when long boiled, of
depositing the whole of the titanic acid, which is not,
however, quite free from iron.
In order to obtain it perfectly free from the latter metal,
the sesquioxide of iron and titanic acid are precipitated by
ammonia, the clear solution decanted from the precipitate,
and the latter treated with excess of sulphide of ammonium,
which converts all the iron into black sulphide. After
standing for several hours, the mixture is diluted witll
K 2




132                     RUTInE.
water, the clear liquor decanted, and the precipitate washed
once or twice by decantation.
It is afterwards mixed with sulphurous acid, when it
immediately becomes white, since the sulphide of iron dissolves in the form of dithionate of protoxide of iron.  The
titanic acid is filtered off, washed and ignited, a fragment
of carbonate of ammonia being held in the crucible to
expel any sulphuric acid.
A little more titanic acid separates from the filtrate on
standing for some time, and on gently heating. The iron,
when converted into sesquichloride by chlorine, or by
heating with hydrochloric acid and clforate of potassa,
may be precipitated from the solution by ammonia.
III. Or the whole of the titanic acid, together with the
sesquioxide of iron, may be precipitated by ammonia from
the solution of the mass obtained by fusion with bisulphate of potassa; the precipitate is washed with cold water,
dissolved in hydrochloric acid, the solution treated with
sulphurous acid or metallic zinc to reduce the sesquioxide
of iron to the state of protoxide, and the titanic acid
precipitated by an excess of carbonate of baryta. The
precipitate is rapidly filtered off, washed, dissolved in cold
hydrochloric acid, the baryta precipitated by sulphuric
acid, and afterwards, the titanic acid separated by ammonia.
86. RUTILE.*
TiO2.
In order to obtain pure titanic acid from rutile, the same
* Occurs most abundantly at St. Yrieux, in France, and may be
purchased very reasonably.




RUTLEX.                    133
method may be employed as for titanic iron; the first
process is especially applicable to this purpose.
Another process consists in converting the titanic acid
into bichloride. The very finely-powdered rutile is mixed
with ignited lamp-black (1  part of carbon for 5 parts of
rutile) and so much starch-paste as will suffice to form a
plastic mass. This is moulded into cylinders about 1 or 2
inches long, and I of an inch thick, which are slowly dried.
They are then thoroughly ignited in a covered crucible,
and, while still hot, before they have absorbed any moisture,
introduced into a tube of porcelain or of hard glass. A
stream of dry chlorine is passed in at one end of the tube,
while the other opens into a cooled receiver furnished with
an egress-tube.  As soon as the apparatus is filled with
chlorine, the tube is heated to bright redness, and the separation carried on till no more drops of bichloride of titanium
distil over. The carbonic oxide and excess of chlorine are
passed into a small quantity of alcohol, which absorbs the
latter.
The bichloride of titanium, which has a brown colour
due to sesquichloride of iron, is poured into a small tubulated retort containing some mercury or bright copperturnings; the neck of the retort is drawn out to a point,
which is bent downwards. When the bichloride of titanium
has been left for some time in contact with the metal, it is
distilled off by gentle ebullition, and immediately received
in tubes, which are afterwards hermetically sealed.
In order to prepare pure titanic acid from the bichloride,
it is gradually mixed with water, avoiding all rise of temperature, which would render the solution turbid, and the
titanic acid precipitated by ammonia.
Pure ignited titanic acid is white, frequently with a
tinge of yellow. During ignition it has a lemon-yellow




134                  COL-TUBITE.
colour. When exposed to a very high degree of heat
it becomes brownish.  It is then perfectly insoluble in
hydrochloric acid. By long digestion with concentrated
sulphuric acid, it is dissolved.
87. COLUMBITE.
The columbite from Bodenmais in Bavaria, and from
Haddaim in Connecticut, contains niobic and pelopic acids
combined with the protoxides of iron and manganese. The
American variety contains the least pelopic acid. Niobic
acid is also present, together with titanic acid, in the
pyrochlore from Norway and Siberia, in combination with
lime, protoxide of cerium and alumina.
The tantalite and yttrotantalite from Finland and Sweden,
however, contain tantalic acid, combined, in the former,
with the protoxides of iron and manganese, in the latter,
with yttria, lime, protoxide of uranium and protoxide of
iron.
These minerals, with exception of pyroclore, which is
decomposed by concentrated sulphuric acid, are not attacked by acids.
They are best decomposed by fusing them, in the form
of a levigated powder, with 6 parts of bisulphate of potassa,
in a platinum crucible. The salt is first fused by itself,
allowed to solidify, the powdered mineral thrown upon it,
and the two gradually fused together. The fusion is continued until the mineral has entirely dissolved.
The mass is afterwards repeatedly boiled with water, and
the undissolved acids filtered off and washed. They still
contain sesquioxide of iron, and commonly also small quantities of binoxide of tin and tungstic acid.
The acids are now digested with sulphide of ammonium,




COLULMBITE.                  135
which dissolves the two latter and converts the sesquioxide
of iron into sulphide, which imparts a black colour to the
acids. This may be effected upon the filter itself, if the
stem of the funnel be passed air-tight into a flask; the
funnel should be kept as closely covered as possible after
the mass upon the filter has been carefully mixed with
sulphide of ammonium.
After washing, very dilute hydrochloric acid is allowed
to flow over the mass upon the filter, when the sulphide of
iron is dissolved, and the acids again become white. They
are then washed, dried and ignited, when the sulphuric
acid with which they are combined is volatilized, which may
be effected with greater rapidity and certainty if a fragment
of carbonate of ammonia be held in the closed crucible
during the ignition.
Tantalic, pelopic and niobic acids are white powders.
They are characterized by the following properties:
TANTALIC ACID remains white when ignited. Its hydrate,
prepared by decomposing the chloride with water, exhibits, when ignited, a vivid incandescence; it is afterwards
insoluble even in sulphuric acid.
The chloride corresponding to tantalic acid is yellowish,
volatile, and fusible to a yellow liquid. It fumes in the air
without deliquescence; it is partly dissolved by solution of
potassa; it is decomposed by water into hydrochloric acid
and white hydrated tantalic acid; it is dissolved, but not
completely, by hot hydrochloric acid; sulphuric acid produces a white precipitate in the solution.
When strongly ignited in hydrogen-gas, tantalic acid
remains white.
Tantalic acid is dissolved in large quantity by phosphorus-salt before the blow-pipe. The bead remains colourless, even in the inner flame.




136                   COLUMBITE.
PELOPIC ACID becomes yellow on ignition, and white
again on cooling. Its hydrate, prepared from the chloride,
exhibits incandescence when ignited; it is afterwards
perfectly insoluble in acids.
The chloride of pelopium is yellower than the perchloride of tantalum, which in other respects it entirely
resembles.  It is partially dissolved by solution of potassa.
Its solution in cold hydrochloric acid becomes thick after
some time; when diluted with water and boiled, nearly all
the pelopic acid is precipitated.  If the solution be prepared with the aid of heat, it does not exhibit these
properties.  This solution is precipitated by sulphuric acid
only on boiling.
When intensely ignited in hydrogen, pelopic acid becomes black.
Pelopic acid is dissolved in large quantity by phosphorussalt, before the blow-pipe, to a clear and colourless bead.
In the inner flame, the bead becomes brown, with a tinge
of violet.
NIOBIC ACID, precipitated by ammonia, forms, after
ignition, compact, very lustrous fragments. During ignition, it has an intense yellow colour, and becomes white
again on cooling. The hydrate, prepared from the chloride, exhibits intense incandescence when ignited, and
becomes perfectly insoluble in acids; if, however, it have
not been too strongly ignited, it is dissolved by warm concentrated sulphuric acid.  When diluted with water, the
solution, after a long time, allows all the niobic acid to
precipitate; this takes place immediately on boiling the
solution.
The chloride of niobium is white, very bulky, infusible,
and more difficult of volatilization than the chlorides of
tantalum  and pelopium.   It fumes in the air, and is




COLUMBITE.                   137
decomposed by water into hydrochloric acid and a white
hydrate. It is not dissolved by hydrochloric acid, nor
precipitated by it.  When boiled with hydrochloric acid,
however, it dissolves, if water be subsequently added; and
the solution is not precipitated by boiling, even on addition
of sulphuric acid. Chloride of niobium is easily dissolved
by solution of potassa.
When strongly ignited in hydrogen, niobic acid becomes
darker than pelopic acid.
NTiobic acid is dissolved in large quantity by phosphorussalt, before the blow-pipe, to a clear, colourless bead. In
the inner flame, the saturated bead assumes a pure blue
colour, without a tinge of violet.
If the chlorides corresponding to these acids are moistened with sulphuric acid, diluted with a little water, and
a piece of zinc placed in the mixture, all three acids give
a fine blue colour.  All the acids, when fused with hydrate
of potassa, yield salts which are soluble in water. The
soda-salts are insoluble in a solution of soda or carbonate
of soda, but dissolve in pure water.
Tantalic acid has not been found at present in company
with the other two acids.  Niobic and pelopic acids, however, nearly always occur together.
In order to detect one of these acids in the presence of
the other, they are converted into the chlorides which are
very different in their properties.  The acids are mixed
with pure sugar and lamp-black, and ignited; the carbonized mass is introduced into a wide tube of very infusible glass, and heated to redness in a current of perfectly
dry chlorine.
If the mixed acids contained also titanic acid, the
strongly-fuming liquid chloride of titanium would also be
formed.




138                     WOLFRAM.
No method is at present known of accurately separating
pelopic, niobic and titanic acids. After fusion with bisulphate of potassa, most but not all the titanic acid may
be extracted by water. If the sublimate which contains
the three chlorides be dissolved in hydrochloric acid, pelopic
acid at least (perhaps also niobic acid) may be precipitated
by sulphuric acid, while titanic acid remains in solution.
The mixture of acids containing sulphuric acid, which
remains after fusion with bisulphate of potassa and treatment with water, is soluble in solution of potassa, as well
as in concentrated hydrochloric acid.  From  the latter
solution, pelopic acid (and niobic acid?) may be precipitated by sulphuric acid.
88. WOLFRAM.*
(MAnO, FeO), WO3.
1. In order to effect merely a qualitative separation, for
obtaining tungstic acid, the very finely-powdered mineral
is digested with a mixture of concentrated hydrochloric
acid and about I of nitric acid, until it is converted into
yellow, pulverulent tungstic acid.   This is filtered  off,
washed, dissolved in ammonia,t the solution filtered, and
* May be obtained very reasonably from Zilnuwald or Schlackenwald, in Bohemia, or through the kindness of Dr. Knopp, at
Chemnitz.
t By this treatment, there is left undissolved, besides the undecomposed particles of mineral which have not been finely powdered,
a white substance, consisting of silica and niobic acid, of which
latter the wolfram contains about 2 per cent. In order to remove
the silica, it is repeatedly evaporated with hydrofluoric and sulphuric
acids, then fused with bisulphate of potassa and farther treated
as directed for columbite.




WOLFRAMB.                     139
evaporated to crystallization. On igniting the salt in the
air, pure yellow tungstic acid is left.
Or the finely-powdered wolfram  is mixed with 4 parts
of carbonate of soda, and an equal weight of sulphur, the
mass heated till it enters into tranquil fusion (which is best
effected in a cast-iron crucible), powdered, boiled with
water, and filtered.  From  the dark red-brown solution,
the sulphide of tungsten is precipitated by dilute sulphuric
acid, the precipitate washed, dried and ignited, with access
of air, in a large crucible placed obliquely, until it is converted into tungstic acid, which is purified by solution in
ammonia.
Again, 3 parts of the mineral, very finely powdered, may
be mixed with 3 parts of carbonate of potassa, and the mixture heated to redness for half-an-hour the tungstate of
potassa which has been formed may be extracted from the
cooled mass with water.*
From this solution, the tungstic acid may be separated
by two different methods:
a. The solution is neutralized with nitric acid and mixed
with nitrate of suboxide of mercury, as long as any precipitate is produced. The precipitated salt is washed, dried,
and heated in a glass retort, when mercury distils over, and
pure tungstic acid is left.
b. The neutralized solution is precipitated by chloride of
calcium, the precipitated tungstate of lime washed, and
boiled with hydrochloric acid, when pure yellow tungstic
acid remains behind.
II. For quantitative analysis, the levigated mineral is
* On dissolving the residual proto-sesquioxides of iron and manganese or the metallic sulphides obtained as above mentioned in
concentrated hydrochloric acid, niobic acid remains behind.




140                    WOLFRAM.
digested with a mixture of 4 parts of concentrated hydrochloric acid and 1 part of nitric acid, until it is completely
decomposed; the solution is then evaporated to dryness,
which operation should be finished on the water-bath, the
chloride of manganese and sesquichloride of iron dissolved
out, the tungstic acid filtered off, washed with alcohol, dissolved in ammonia, separated by filtration from the niobic
acid, the solution evaporated, the residual ammonia-salt
ignited with access of air, and the tungstic acid weighed.
The filtrate, containing alcohol, is evaporated to expel
the latter, diluted with water, and the oxides of manganese and iron separated as in No. 23. They usually contain
a little lime.
Or the levigated mineral is ignited, in a platinum crucible, with 3 parts of carbonate of potassa, the mass dissolved in water, the residual oxides thoroughly washed, the
solution neutralized with nitric acid, and the tungstic acid
precipitated by nitrate of suboxide of mercury, the free
nitric acid being afterwards neutralized with a few drops of
ammonia, so that a black precipitate begins to appear. The
precipitate is thoroughly washed, a very dilute solution of
nitrate of suboxide of mercury being used at last, since
otherwise, the precipitate is liable to pass through the
filter; it is then dried and ignited, when pure tungstic
acid is left.
The mixture of the oxides of iron and manganese is
dissolved in concentrated hydrochloric acid, which usually
leaves undissolved a small quantity of tungstic, niobic and
silicic acids. The two oxides are then separated as in
No. 23.




MOLYBDATE OF LEAD.                141
89. SCHEELITE.
CaO, WO3.
The mineral, very finely powdered, is digested with concentrated nitric acid, the mass evaporated nearly to dryness,
mixed with alcohol, and filtered.  The residual yellow
tungstic acid is washed with alcohol, ignited and weighed.
The alcohol is expelled from the solution by evaporation,
the latter neutralized with ammonia, and the lime precipitated by oxalate of ammonia.
90. MOLYBDATE OF LEAD.*
PbO, MoO3.
Several methods are employed for obtaining the molybdic
acid from this mineral.
I. In order to remove the carbonates of zinc and of
protoxide of iron, the finely-powdered ore is treated for
some time, and frequently agitated, with dilute hydrochloric acid; it is afterwards washed  by decantation,
and decomposed by boiling concentrated hydrochloric
acid. The mixture is then evaporated to dryness, the
residue powdered, and digested with ammonia. Insoluble
basic chloride of lead and molybdate of ammonia are thus
formed; the solution containing the latter is filtered off,
and evaporated to crystallization. The mother-liquor from
the crystals, or even the entire solution, may be mixed with
* May be purchased very reasonably, in compact masses, of
Jo P. Biebcl, at Garmisch, Partenkirchen, Bavaria.




142              MOLYBDATE OF LEAD.
nitric acid, evaporated to dryness, and the residue extracted
with water, when the molybdic acid is left.
II. The powdered ore is fused with an equal weight of
dry carbonate of soda, the fused mass poured out, taking
care to separate it as far as possible from the oxide of lead
which has settled at the bottom, and dissolved in hot
water; the small quantity of lead which has been carried
into solution is precipitated from the latter, while hot, by
a mixture of ammonia and carbonate of ammonia, the solution filtered, acidified with nitric acid, evaporated to dryness,
the nitrate of soda extracted from the mass with water,
and the molybdic acid thoroughly washed.
III. In order to avoid the perforation of the crucible,
which  occurs frequently in this process, the  ore  may
be fused with an equal weight of carbonized bitartrate of
potassa, when the lead separates in the metallic state,
without any reduction of molybdic acid taking place.
IV. The powdered ore is fused with an equal weight of
calcined bitartrate of potassa and as much sulphur; the
sulphomolybdate of potassa thus produced is dissolved in
water, and the sulphide of molybdenum precipitated from
the solution by dilute sulphuric acid. When this precipitate is washed, dried and ignited in a covered crucible, it
leaves a crystalline grey sulphide, from which molybdic
acid may be prepared by the method employed in treating
molybdenite.
V. The finely-powdered mineral is digested, with constant stirring, with 14 parts of concentrated sulphuric acid,
until it is perfectly white. The heat is then raised to
incipient volatilization  of sulphuric  acid, the mixture
allowed to cool, and the blue pasty mass stirred up with
much water, in order to separate the sulphate of lead; the
solution containing the molybdic acid is decanted, filtered




MOLYBDATE OF LEAD.              143
and evaporated in a porcelain dish, with addition of some
nitric acid, until the sulphuric acid begins to evaporate; the mixture should be constantly stirred. The
molybdic acid is thus separated as a white precipitate;
when the greater part of the sulphuric acid has been expelled, the mixture is diluted with water, the molybdic acid
filtered off and well washed, water containing nitric acid
being used towards the end. Some more molybdic acid
may be obtained by evaporating the filtrate and washings.
It is free from phosphoric acid.
If it contain any phosphoric acid, its ammoniacal solution, when acidified with nitric acid, and heated, becomes
yellow and deposits a yellow powder.
The molybdic acid may be obtained from molybdate of
ammonia by gradually heating the salt, with full access of
air.
It is always obtained in a perfectly pure state by sublimation, for which purpose it is heated in a platinum
crucible, which is covered with a platinum capsule kept
full of water.
For quantitative analysis, the pure crystallized mineral
is finely powdered, completely decomposed by digestion
with nitric acid, the mixture neutralized with ammonia,
and digested with an excess of sulphide of ammonium.
The sulphide of lead which is thus formed, is filtered off
from the dissolved miolybdate, washed with dilute sulphide
of ammonium, dried at 1000, and weighed.  From the
solution, the sulphide of molybdenum is precipitated by
dilute nitric acid, collected upon a filter, dried at 1000,
washed, dried and weighed. A weighed portion of it is
then introduced into a bulb-tube, and heated in a stream
of hydrogen until it loses no more sulphur. From the
weight of the residual MoS2, calculated for the total




144                  MOLYBDENITE.
amount of the precipitate, that of the molybdic acid is
ascertained.
91. MOLYBDENITE.*
MoS2.
The finely-powdered mineral is roasted, with frequent
stirring, in a crucible placed obliquely, as long as any
odour of sulphurous acid is perceptible.
The molybdic acid which has been formed is extracted
from the yellow mass thus produced, by digestion with
dilute ammonia. The residue, should it still contain sulphide of molybdenum, is then again roasted.
The filtered solution is mixed with one or two drops of
sulphide of ammonium, to separate the copper, the precipitate filtered off, the solution evaporated to dryness, the
salt again dissolved in dilute ammonia, the solution filtered
from any impurities, and evaporated to crystallization.
(See Molybdate of Lead.)
The molybdic acid may also be precipitated from the
solution of an alkaline molybdate neutralized with nitric
acid, by basic nitrate of suboxide of mercury. The yellow
precipitate is allowed to subside, filtered off, washed with
a dilute solution of the mercury-salt, dried and ignited.
Molybdic acid may also be quantitatively determined, by
this method. The precipitate is collected upon a filter
(previously dried at 1000 and weighed), dried at 100~,
and a weighed portion of it gently ignited in a bulb-tube,
through which a stream of hydrogen is passed, when dark
brown binoxide of molybdenum, MoO2, is left.
* May be obtained of Franz Holenias, at Bleiberg, where also
crude molybdic acid may be purchased at a moderate price.




BROWN IRON-ORE, CONTAINING VANADIUM.   145
92. BROWN IRON-ORE, CONTAINING VANADIUM.
In order to extract the vanadium, the quantity of which
does not amount even to 1 per cent, the finely-powdered
ore is intimately mixed with I its weight of nitre, and
exposed, for an hour, in a crucible, to a gentle ignition.
When cool, the mass is powdered and boiled with water.
The filtered solution has a yellow colour, and contains
the vanadates, chromates (molybdates?), arsenates, phosphates, nitrites and silicates of potassa and alumina.
It is gradually mixed, and well stirred, with nitric acid,
taking care that it may still remain slightly alkaline and
that no nitrous acid is liberated, which would reduce the
vanadic and chromic acids. The precipitate of alumina
and silica thus separated is filtered off.
The solution is then mixed with an excess of solution of
chloride of barium, as long as any precipitate is produced.
The precipitate, consisting of the baryta-salts of the abovementioned acids, is filtered off, washed and boiled while
yet moist, with dilute sulphuric acid, which must not be
added in too great excess. The reddish-yellow acid filtrate
is neutralized with ammonia, concentrated by evaporation,
and a fragment of chloride of ammonium is placed in it.
In proportion as the solution becomes saturated with chloride of ammonium, vanadate of ammonia is deposited as a
white or yellow crystalline powder, which is allowed to
separate completely, filtered off, and washed with a saturated solution of chloride of ammonium.  When gradually
heated with full access of air, it leaves dark red vanadic
acid, which fuses when heated more strongly,. and solidifies,
on cooling, to a very crystalline mass.
The solution  obtained by lixiviating the mass after
L




146              VANADATE OF LEAD.
fusion with nitre, may also be mixed with sal-ammoniac,
and boiled, in order to neutralize the free alkali, and to
precipitate silica and phosphate of alumina. This precipitate usually contains also vanadic acid, which may be
converted into sulphide by fusion with an equal weight of
carbonate of potassa and sulphur; the fused mass is extracted with water, and the brown sulphide of vanadium
precipitated from the filtered solution by dilute sulphuric
acid.
If the iron-ore be reduced by fusion with borax (see Iron
Assay), in a crucible lined with charcoal, a well-fused, crystalline regulus of iron is obtained, which contains vanadium,
chromium, arsenic, phosphorus, silicon and carbon.
Moreover, see Ash of the Refining-hearth.
93. VANADATE OF LEAD.
PbC1, PbO + 2 (2 PbO, 03).
There exist some varieties of this mineral, at present
very rare, which contain no chloride of lead.
This mineral, when treated with nitric acid, first becomes
red, then dissolves. If the solution be mixed with ammonia, and afterwards with an excess of sulphide of ammonium, sulphide of lead is precipitated, and a dark red
solution obtained, from  which acids precipitate the dark
brown sulphide of vanadium. The precipitate is roasted
in air, and afterwards converted into vanadate of potassa
by fusion with a small quantity of nitre. This salt is
dissolved in a little water, and vanadate of ammonia precipitated from the solution by sal-ammomniac. (See No. 92.)
The mineral is only imperfectly decomposed by sulphuric




CHIROME-IRON-ORE.               14 7
acid. The decomposition, however, is complete if it be
fused with bisulphate of potassa. On treating the mass
with water, the lead remains behind as sulphate, while
vanadic acid is dissolved.
94. CHROME-IRON-ORE.
FeO, Cr203.
I. For the mere qualitative separation, the very finelypowdered ore is fused for at least half an hour, at a bright
red heat, with an equal weight of nitre and as much
carbonate of potassa; from the fused mass, when cool, the
chromate of potassa which has been produced is extracted
with water.
The residue, consisting of sesquioxide of iron and variable quantities of alumina and magnesia, is dissolved in
concentrated hydrochloric acid, which generally leaves some
undecomposed mineral, and the three oxides are then separated as in No. 74.
The solution of chromate of potassa usually contains a
little alumina, silica and manganic acid, to precipitate
which it is mixed with a little carbonate of ammonia and
boiled.
In order to obtain bichromate of potassa from this solution, it is acidified with nitric acid, concentrated by
evaporation, and the salt allowed to crystallize out.
The chromic acid may be precipitated as chromate of
lead, by neutralizing the solution with acetic acid and
adding acetate of lead.
To separate the chromium as sesquioxide, the solution is
acidified with sulphuric acid, sulphurous acid added till the
L 2




148               CHROME-IRON-ORE.
solution has an emerald-green colour, the sesquioxide of
chromium  precipitated by ammonia, washed and ignited.
Or the yellow solution may be exactly neutralized with
nitric acid, and the chromic acid precipitated by nitrate of
suboxide of mercury.  When washed, dried and ignited,
the yellowish-red chromate of suboxide of mercury leaves a
pure green sesquioxide of chromium.
II. Chrome-iron-ore may also be quantitatively analyzed
by the above process, the fusion being conducted in a
platinum crucible, though it will be found that a quantity
of ore will be left undecomposed, varying according to the
state of division to which it was reduced. From the solution, after neutralization with nitric acid, the chromic
acid is best precipitated by nitrate of suboxide of mercury;
the precipitate is washed with a dilute solution of that salt
and ignited. The following method is more certain.
The mineral, which should be powdered as finely as
possible and weighed, is fused, in a platinum crucible, with
4 times its weight of bisulphate of potassa, care being
taken that the mass, which froths up at first, may not run
over the side of the crucible. Ultimately, it is heated to
redness, and retained in fusion, at a red heat, for a considerable time. The salts formed are sparingly soluble in
water and acids; the sesquioxide of chromium must therefore be converted into alkaline chromates, for which purpose there is added to the cooled mass, in the crucible,
about twice its volume of a mixture of equal parts of nitre
and carbonate of soda.  The mass is then heated to complete fusion.
On cooling, the chromate of potassa is extracted with
hot water, the residue of sesquioxide of iron, alumina and
magnesia, thoroughly washed, dissolved in concentrated
hydrocllloric acid, and analyzed as in No. 74.




CHROMATE OF LEAD.               149
The solution of chromate of potassa is acidified with
hydrochloric acid, heated to ebullition, and alcohol added
to the boiling solution until it has acquired an emeraldgreen-colour, when the sesquioxide of chromium is precipitated by ammonia, ignited and weighed.
95. CHROMATE OF LEAD.
PbO, CrO3.
(Chrome-yellow, often adulterated with white clay,
with BaO, SO3,-CaO, C02,-CaO, SO3, or with PbO, SO3.)
I. Pure chromate of lead should give the quantities of
oxide of lead and chromic acid calculated from the formula.
For analysis, it is digested with a mixture of fuming
hydrochloric acid and alcohol, when a green solution of
sesquichloride of chromium is produced, the lead remaining
undissolved as a white chloride. The latter is collected
upon a filter dried at 100~, washed with alcohol, and dried
at 1000. The acid solution is diluted with water, evaporated to expel the alcohol, and the sesquioxide of chromium
precipitated by ammonia; the liquid is heated to ebullition,
the precipitate filtered off, ignited and weighed.
II. For the mere qualitative analysis of a specimen of
chrome-yellow mixed with the substances mentioned above,
it is treated as before, with alcohol and hydrochloric acid,
as little as possible of the latter being employed, in order
that the clay may remain untouched.
From the solution, the sesquioxide of chromium is precipitated by ammonia; it always, however, carries down
some lime.
In order to separate them accurately, they must be
precipitated together, from the hot solution, by a mixture




150              CHROMATE OF LEAD.
of ammonia and carbonate of ammonia.  After drying, the
precipitate is fused with 3 times its weight of a mixture
of carbonate and nitrate of potassa, and the fused mass
treated with water, which dissolves the chromate of potassa,
and leaves the carbonate of lime.
Or the precipitate, while yet moist, may be digested with
hypochlorite of soda, which dissolves the sesquioxide of
chromium, as chromate of soda, leaving the carbonate of
lime undissolved.  The solution is then heated to ebullition, in order to decompose any bicarbonate.
From the residue, which may consist of the sulphates of
lime, baryta and lead, the first may be entirely extracted by
washing with water, or with a solution of common salt or
of sal-ammoniac, in which it is far more soluble.  In the
solution, either the sulphuric acid is precipitated, by a
baryta-salt, or the lime by an oxalate.
The sulphate of lead is extracted from the residue by
digestion with tartrate of ammonia containing free ammonia, and the lead precipitated from the solution by
sulphuretted hydrogen or chromate of potassa.
The mixture of clay and sulphate of baryta which remains at last, is heated with concentrated sulphuric acid
until the greater excess of the latter has been expelled,
when the sulphate of alumina is extracted with water, and
the alumina precipitated by ammonia.
In order to extract the silica from the residue, which
contains also sulphate of baryta, it is boiled in a concentrated solution of carbonate of soda, in which the silica is
dissolved and may be reprecipitated by sal-ammoniac. The
residue consists of carbonate of baryta mixed with more or
less undecomposed sulphate of baryta. (See No. 14.)
A good method of determining the amount of chromic
acid (and therefore of chromate of lead) contained in a




PITCH-BLEENDE.                151
specimen of commercial chrome-yellow, consists in reducing
the chromic acid to the state of sesquioxide of chromium
by means of oxalic acid, and in determining the quantity
of carbonic acid produced.
Tlhis may be effected in the same way as the testing of
manganese-ores in an apparatus arranged for the quantitative determination of carbonic acid, the weighed chromate
of lead being mixed with oxalate of potassa, and sulphuric
acid allowed to flow upon it. 10 parts by weight of carbonic acid indicate 7'6 parts of chromic acid, or 24'5 of
pure chromate of lead.  Hence, 100 parts of pure chromeyellow should give 40'4 of carbonic acid.
96. PITCH-BLENDE.
UO, U203,
(together with various extraneous substances, in variable
quantities, including silica. iron, nickel, cobalt, zinc, copper,
bismuth, lead, manganese, arsenic, antimony, sulphur, lime
and manganese; sometimes also selenium and vanadium.)
PREPARATION orF PURE SESQUIOXIDE OF URANIUM.The finely-powdered ore is digested with moderately dilute
sulphuric acid, with gradiul addition of nitric acid, until it
is converted into a white powder, and partly dissolved.
The greater excess of sulhduric acid is then evaporated, the
mass digested with much water, and the cold solution, after
subsidence of the residue, filtered off.
This residue consists of silica, sulphate of lead and basic
sulphate and arsenate of )ismuth.
The solution is then leated to about 60~, and sulphuretted hydrogen-gas passed through it, at this temperature,




15 2                 PITCH-BLENDE.
for some time; the solution is afterwards allowed to cool
while the gas is still passing, and, when fully saturated, set
aside in a covered vessel for twenty-four hours. The sulphuretted hydrogen is then expelled by a gentle heat, and
the precipitate filtered off.
The precipitate contains arsenic, antimony, copper, and
the rest of the lead and bismuth.
The solution is then heated to ebullition, and fuming
nitric acid gradually added to the boiling liquid, until all
the protoxide of iron is reconverted into sesquioxide, and
the solution has acquired a pure yellow colour. It is then
precipitated by an excess of ammonia, and the yellowishbrown precipitate filtered off.
Part of the nickel, cobalt, zinc, lime and magnesia remain
in solution, but the remainder is precipitated together with
the sesquioxides of uranium and iron.
The washed precipitate is treated with a hot, pretty
strong solution of carbonate of ammonia containing free
ammonia, with which the precipitate is digested, at a
moderate heat, until it has the appearance of hydrated
sesquioxide of iron. The solution of uranium is rapidly
filtered off, while hot, and the residue of hydrated sesquioxide of iron (still containing uranium) is washed, the
washings being received apart from the filtrate.
The solution (which is yellow, or coloured reddish by
the  cobalt) deposits on cooling, if sufficiently concentrated, crystals of the pure doulie carbonate of ammonia
and sesquioxide  of uranium, which may  be collected,
and washed several times with cold water.  When ignited, this salt leaves pure dark geen proto-sesquioxide of
uranium.
The mother-liquor is mixed witl the washing-water, and
sulphide of ammonium  carefully aided, drop by drop, as




PITCHI-BLENDE.                1 53
long as it produces a dark brown precipitate, which is
immediately filtered off.
The precipitate consists of the sulphides of cobalt, nickel
and zinc.
The yellow filtrate is then boiled till the greater part of
the ammoniacal salt is volatilized, and all the sesquioxide
of uranium precipitated.
The pure yellow precipitate, uranate of ammonia is filtered off, and, when the filtrate begins to pass through
turbid, washed with solution of sal-ammoniac.
When ignited, it leaves dark green proto-sesquioxide of
uranium. By digesting this with dilute hydrochloric acid,
any lime and magnesia may be extracted.
In order to prepare protoxide of uranium from the
uranate of ammonia, it is dissolved in hydrochloric acid,
the solution mixed with an excess of pure sal-ammoniac,
and about an equal quantity of pure common salt; it is
then evaporated to dryness, and the mass heated in a
covered crucible until the sal-ammoniac is volatilized, and,
lastly, until the common salt filses. On dissolving it in
water the protoxide of uranium is left as a hard crystalline
powder. The common salt only serves to shield the oxide
from the action of air.
In order to extract from the hydrated sesquioxide of
iron the small quantity of sesquioxide of uranium which
is chemically combined with it, it is dissolved in the
smallest possible quantity of hydrochloric acid, the solution neutralized with carbonate of ammonia, and added,
drop by drop, with constant stirring, to a mixture of
carbonate of ammonia and sulphide of ammonium, when
all the iron is separated as sulphide, and the sesquioxide
of uranium remains in solution; the latter may be precipitated by boiling the filtrate.




154            SELEMNIFEROUS DEPOSIT.
Or the sesquioxide of iron may be reduced in a stream of
hydrogen, and the reduced pyrophoric mass allowed to fall,
immediately, into dilute hydrochloric acid, which dissolves
the iron, leaving the uranium as protoxide.
In order to detect selenium, arsenic and vanadium in
pitch-blende, it is ignited with 4 its weight of a mixture of
carbonate of soda and nitre. The selenates, vanadates and
arsenates of the alkalies may then be extracted with water.
97. SELENIFEROUS DEPOSIT FROM THE SULPHURICACID CHAMBERS.*
(Sulphate of lead, selenium, selenide of mercury, selenates and selenites, &c.)
The dry mass is rubbed to a thin paste with a mixture
of about equal parts of sulphuric acid and water, and
boiled for a long time, concentrated nitric acid or chlorate
of potassa being added at intervals, to oxidize the free
selenium, until all the reddish colour has disappeared.
The mixture is then diluted with water and filtered.
The solution contains, besides iron, copper, mercury and
a little lead, all the selenium as selenous and selenic acids.
it is mixed either with about as much common salt as
amounts to half the weight of the deposit originally employed, or with ~ of its volume of crude fuming hydrochloric acid, and boiled down to about ~ of its original bulk.
The hydrochloric acid reduces the selenic acid to selenious
acid.
On cooling, the solution is poured off from any sulphate
of potassa and common salt which may have been depo* To be obtained from the "Communion Schwefelsaure-Niederlage," at Goslar in the Hartz.




SELENIYEROUS DEPOSIT.             155
sited; these are washed several times with water, and the
solution saturated with sulphurous acid gas, evolved from
a mixture of powdered charcoal and concentrated sulphuric
acid.
The selenium is thus precipitated of a fine red colour.
Its separation is promoted by digestion, and ultimately by
boiling for a quarter of an hour, when it becomes black,
and collects into a dense hard mass.  It is well washed
and dried.
The filtered liquid is boiled once more with hydrochloric
acid, and again treated with sulphurous acid, in case it
should still contain selenium.
The selenium thus obtained contains still small quantities
of lead, copper and iron, and especially mercury. On distilling it in a small retort or bent tube closed at one end,
the first-mentioned impurities are left behind as selenides.
In order to free it from mercury, the distilled selenium is
dissolved in aqua-regia, the greater excess of acid evaporated, so that no nitric acid may remain, the solution
mixed with excess of carbonate of soda, evaporated to
dryness, and the saline mass ignited to expel the mercury.
The mass is redissolved in water, the solution boiled
with hydrochloric acid, and the selenium again precipitated by sulphurous acid.
Or the ignited mass may be mixed with about an equal
weight of chloride of ammonium, and heated in a retort
till the greater part of that salt has sublimed, when the
selenium is reduced, and remains behind on dissolving the
saline mass in water.
The selenium may also be at once extracted, and obtained
free from mercury, by fusing the deposit with an equal weight
of carbonate of soda and about I of nitre, in a crucible.
When the mass is in a state of tranquil fusion, it is poured




156                SELENIDE  OF LEAD.
out, so as to leave the oxide of lead, as far as possible, at
the bottom of the crucible. It is then dissolved in water,
the solution acidulated with sulphuric acid, the precipitated sulphate of lead filtered off, and the filtrate treated,
as above, with hydrochloric acid and sulphurous acid. It
is necessary in this process that all the nitric acid from the
nitre should either be expelled or decomposed, for otherwise part of the selenium will escape precipitation.
98. SELENIDE OF LEAD.
PbSe.
The analysis is best effected, like that of fahl-ore
(No. 57), by means of chlorine-gas. After the decomposition, the bulb is again weighed, in order to ascertain
the amount of lead present.  The greater part of the
selenium is volatilized in the form of the solid chloride;
only a small quantity of the liquid chloride passes over at
first. These are conducted into water, which is afterwards
saturated with chlorine, in order to convert all the selenious
acid into selenic acid; the latter is then precipitated by
chloride of barium, and the selenium determined as selenate
of baryta; 100 parts of the latter correspond to 28'2 of
selenium.
If the metallic selenides are mixed or combined with the
metallic sulphides, as, for example, in the native selenide of
mercury which contains sulphide of mercury, the sulphuric
acid and selenic acid formed in the analysis are precipitated
together by chloride of barium, the precipitate ignited and
weighed. A weighed quantity is then heated in a bulbtube, through which a stream of dry hydrogen is passed,




SELENIDE OF LEAD.                157
when the selenate of baryta is reduced, with great facility,
to the state of selenide of barium, while the sulphate of
baryta remains unaltered. The selenide of barium is then
extracted with dilute hydrochloric acid.
In the same way the other metallic selenides which occur
as minerals may be analyzed, viz., the selenide of silver and
lead, the selenide of cobalt and lead, and the selenide of
mercury and lead.
In order to obtain the selenium from the selenide of lead
occurring in many places in the Hartz, the mineral is
powdered, treated with dilute hydrochloric acid to remove
the calcareous spar and spathic iron-ore, well washed and
dried.  It is then very intimately mixed with an equal
weight of carbonate of potassa containing charcoal (calcined bitartrate of potassa), covered with coarse charcoalpowder in a crucible, the cover of which is then luted on,
and exposed for an hour to a moderate red heat.  When
cool, the mass, which contains all the selenium as selenide
of potassium, is quickly powdered in a warm mortar, thrown
on a filter, and washed with well-boiled hot water, as long
as the washings are coloured; during this operation, the
funnel should always be kept full of water, so that the
mass may not come in contact with the air.
The yellowish-red solution of selenide of potassium begins
immediately to deposit upon its surface a film of selenium,
the whole of which separates, after some days, in the form
of a thin reddish-black crust; only a small quantity remains
in solution in an oxidized state. It may afterwards be precipitated by heating the solution with sulphurous and hydrochloric acids.
Since selenide of lead frequently contains selenide of
silver, the carbonaceous mass remaining after the extraction
of the selenide of potassium may be fused with carbonate of




158          SILVER ASSAY.-IRON ASSAY,
potassa and some nitre.  A metallic button of argentiferous
lead is thus obtained, from which the silver may best be
separated by cupellation.
99. SILVER ASSAY.
From argentiferous galena, fahl.-ore, copper- and ironpyrites, &c., even when intimately mixed with gangue, the
whole of the silver, concentrated in a small quantity of lead,
may be extracted in the following manner:
One hundred grms. of galena, finely powdered, are fused
with 30 grms. of nitre and 100 grms. of litharge.
Or 1 part of the ore is fused together with 30 to 50
parts of litharge.
Or 1 part of ore may be fused with 3 parts of anhydrous
acetate of lead and 2 parts of potashes, under a layer of
common salt.
In the button of lead obtained, the silver is determined
by cupellation, or in the moist way.
100. IRON ASSAY.
The weighed iron-ore, in the state of fine powder, roasted
or not, as the case may be, is mixed with dried borax, and
the mixture exposed for an hour, in a crucible lined with
charcoal, to the most intense heat of a wind-furnace with a
good draught; the quantity of borax varies according to
the nature of the iron-ore. The greater the quantity of
extraneous matter which is present, the more borax it requires.  For 10 grms. of iron-ore, 3 grms. of borax may
be taken as the minimum, 10 grms. as the maximum.  In




AET ASSAY OF TRON.                    159
a well-conducted assay, all the iron is found reduced to
a single well-fused button.
101. WET ASSAY OF IRON.
The process for determining in the moist way with great
accuracy, and without a complete analysis, the amount of
iron contained in an ore, consists in ascertaining the number
of measures of a solution of permanganate of potassa of
known strength which may be decolorized by the solution
of protoxide of iron obtained from a given quantity of the
ore.*
One equiv. = 1980 grms. of crystallized permanganate of
potassa convQrts the protoxide of iron from  10 equivs.=
3'500 grins. of pure iron into sesquioxide.
So that if 19'80 grms. of the salt be dissolved in 1 litre
(=1000 grms. or 1000 cub. cent.) of water; 100 cub. cent.
of this solution will correspond to 3'50 grins. of iron. It
must be kept in a well-stopped bottle.
An equivalent quantity (say  3'5  grms., or half that
amount) of the ore to be tested is dissolved in concentrated
hydrochloric acid, in a capacious flask, by the aid of heat.
* To prepare the permanganate of potassa, 8 parts of very finelypowdered manganese-ore are mixed with 7 parts of chlorate of
potassa, the mixture saturated with a very concentrated solution of
10 parts of hydrate of potassa and the wet mass gradually heated in
an earthen crucible to dull redness, so that it cinders together, but
does not fuse. When cool, it is powdered, treated, in a flask, with
a considerable quantity of hot water, and boiled until the colour of
the solution has changed to a pure purple-red. It is then allowed
to stand for twelve hours, the clear solution poured off from the
binoxide of manganese which is deposited, and evaporated to the point
of crystallization.




160              WET ASSAY OF IRON.
If the insoluble residue of foreign matters, such as clay,
silica, &c., be not very considerable, it is unnecessary to
filter the solution. The iron must now be entirely reduced
to the state of protoxide, either by mixing the solution
with several times its volume of a saturated solution of
sulphurous acid, and boiling so long as any trace of that
gas is perceptible; or better, by allowing a piece of zinc,
free from iron, to remain in the liquid until its colour is
changed to a pale green. It is then decanted from the
zinc, the latter thoroughly rinsed, the solution diluted
with the washing-water, and mixed with some more hydrochloric acid; the solution of permanganate of potassa is
then dropped in from a burette (see Alkalimetry), until
the yellow colour which the solution then acquires is
changed to a clear red by adding another.drop of the
permanganate.  The number of cubic centimeters of the
manganese-solution which have been employed, at once
indicates the percentage of iron in the ore.
Instead of the crystallized permanganate of potassa, the
crude solution originally obtained in the preparation of that
salt may be employed, provided it be first graduated-that
is, quantitatively tested as to its oxidizing power.  For this
purpose, 3'5 grms. (or half that quantity, 1'75 grms.) of
pure iron-wire are dissolved in a capacious flask by concentrated hydrochloric acid, with the aid of heat.  The solution is diluted with several times its volume of cold water,
and the solution of permanganate dropped into it, as
directed above. When the quantity of solution employed
has been read off, the whole is diluted with so much water,
that 100 cub. cents. may correspond to 3'5 grms.  It
must be kept in a well-stopped bottle.




CAST-IRON.                  1 61
102. CAST-IRON.
For the detection and estimation of the foreign substances,
the total weight of which does not usually exceed 5 per
cent, it is best to employ separate portions of iron.
I. CaRBON.-The total amount of carbon may be determined by burning the iron, in the state of very fine filings,
with the aid of a slow stream of pure oxygen, as in organic
analysis; the carbonic acid which is produced being collected in a weighed potassa-apparatus.
Another quantity of the iron-filings is dissolved in dilute
sulphuric acid, when the combined carbon is evolved in
combination with hydrogen, while the graphite is left
undissolved. In this operation, the gas may be conducted
through a solution of acetate of lead, when the presence of
sulphur is indicated by the precipitation of sulphide of
lead.
The residue insoluble in the acid is well washed, dried
at 200~, and burnt, as above, in oxygen-gas. From the
amount of carbonic acid, that of the graphite is calculated.
II. SILICON.-The residue from the first carbon-determination, which contains all the silicon in the form of
silicic acid, is dissolved in concentrated hydrochloric acid,
the solution evaporated to dryness on the water-bath, the
mass digested with dilute hydrochloric acid, and the silicic
acid filtered off.
III. PHOSPHORUS. -From the solution filtered from the
silica, the phosphoric acid is separated as in No. 20. If
the iron contain arsenic, it is obtained as arsenic acid,
together with the phosphoric acid.
The amount of phosphorus may be less accurately determined by heating the fine iron-filings to redness with
M




162                   CAST-IRON.
2 parts of nitre and 1 part of carbonate of soda, extracting
the mass with water, acidifying the solution with hydrochloric acid, and adding excess of ammonia and sulphate of
magnesia.
IV. ARSENIC. —The presence of arsenic may be detected by dissolving the iron in dilute sulphuric acid, filtering off the black residue, and digesting it with sulphide
of ammonium. From the filtered solution, dilute sulphuric
acid precipitates the pentasulphide of arsenic. The precipitate is dissolved in aqua-regia, the nitric acid expelled by
evaporation, and the arsenic reduced in Marsh's apparatus.
The solution of iron filtered from the black residue is
neutralized with carbonate of soda, mixed with a few drops
of sesquichloride of iron, and then with acetate of soda,
when arseniate of sesquioxide of iron is precipitated, which
may be easily decomposed by sulphide of ammonium.
For the quantitative determination of the arsenic, the
cast-iron is dissolved in hydrochloric acid, with gradual
addition of nitric acid, the solution filtered from the carbon,
and heated withl sulphurous acid till all the sesquichloride
of iron is converted into protochloride; the excess of sulphurous acid is then expelled by heat, and the solution
saturated with sulphuretted hydrogen, and allowed to stand
for twenty-four hours in a closed vessel; the excess of gas
is afterwards evaporated, and the precipitate filtered off.
V. COPPER. —This metal is contained in the precipitate
produced  as above, by sulphuretted hydrogen.  After
drying, it is distilled in a tube, when sulphide of copper
remains behind. Or the sulphide of arsenic may be dissolved out by solution of potassa, or more completely, by
solution of monosulphide of potassium.
VI. MANGANESE.-The solution filtered from the precipitate produced by sulphuretted hydrogen, in V, is heated




CAST-IRON.                 163
to the boiling-point, and the protoxide of iron entirely converted into sesquioxide by adding chlorate of potassa or
hypocliorite of soda. The oxide of manganese and sesquioxide of iron are then separated from each other by means
of bicarbonate of soda, as in No. 23.
VII. ALUMINUM.-The alumina is contained in the sesquioxide of iron which is then precipitated, and may be
separated from it as in No. 19.
VIII. MAGNESIUM AND CALCIUM remain, together with
the protoxide of manganese, in the solution filtered from the
precipitate produced by bicarbonate of soda. (See No. 23.)
IX. CHROMIUM AND VANADIUM.-A large quantity of
the iron-filings is ignited with 2 parts of nitre and 1 part
of carbonate of soda, the mass extracted with water, and the
solution treated as in No. 92, when phosphoric and arsenic
acids may likewise be sought.  It is safer to employ for this
purpose the carbonaceous residue obtained by dissolving a
large quantity of the iron in dilute sulphuric acid.
X. MoLYBDENUM.-Sometimes this metal is extracted,
together with the arsenic, by sulphide of ammonium, from
the black carbonaceous residue; in such a case, it is reprecipitated, together with the pentasulphide of arsenic, on
adding an acid to the solution.  If this precipitate be
distilled in a tube, the sulphide of molybdenum is left
behind.
XI. SULPHUR. —The sulphur may be determined approximately by evolving it as sulphuretted hydrogen, as in
No. 1, when the iron is dissolved in dilute sulphuric acid.
Or it exists as sulphuric acid in the solutions obtained at
III, and VI, and may be precipitated by chloride of barium.
Or a large quantity of iron may be dissolved in aqua-regia,
and the sulphuric acid formed may by precipitated from
the diluted solution by chloride of barium.
M 2




164                  CAST-IRON.
XII. NICKEL AND COBALT may be detected in the solution from which the copper has been removed by sulphuretted hydrogen. This solution is re-oxidized, and the
sesquioxide of iron precipitated by carbonate of baryta,
after which the nickel and cobalt are precipitated by
sulphide of ammonium.
For the detection of most of the admixtures, it is best to
employ the black residue which is left on dissolving the
iron in dilute sulphuric acid, and which can easily be
prepared in considerable quantity. It contains silicic acid,
carbon, carbide of iron, phosphide of iron, arsenide of iron,
compounds of chromium and vanadium with iron, molybdenum, &c.
The total amount of the carbon (phosphorus, arsenic,
chromium, &c.?) in iron may be separated by digesting
the fine iron-filings with a solution of chloride of copper,
when all the uncombined iron is dissolved, and copper
precipitated in its stead.  When the solution has been
poured off, the precipitated metal is digested, out of
contact of air, with a neutral solution of sesquichloride of
iron which redissolves the metallic copper.
When this residue is digested with potassa, the latter
dissolves a newly formed brown humus-like substance,
together with phosphoric acid, arsenic acid, and silicic acid.
Almost the whole of the silicic acid may be determined in
this residue.
It is yet to be ascertained whether this residue can be
analyzed by heating in chlorine-gas.




ASH OF TIE REFINING-H-EARTH.           165
103. ASH OF TIIE REFINING-HEARTH.
Crystallized= 3 FeO, SiO3.
The analysis of pure crystals picked out of the mass is
simple and easy, since they consist essentially only of protoxide of iron and silicic acid. They are finely powdered,
and treated with hydrochloric acid and some concentrated
nitric acid until they are completely gelatinized, the analysis
being conducted as in the case of Lievrite. The sesquioxide
of iron obtained is calculated as protoxide.
The quantitative analysis of the ordinary compact slag is
far more difficult and complex, since it may contain, in
addition to the above principal constituents, small variable
quantities of the protoxides of copper, nickel, cobalt and
manganese, beside the oxides of chromium, molybdenum
and vanadium, together with alumina, potassa, lime, magnesia, arsenic and phosphoric acids.
Several of these constituents can only be discovered by
a qualitative analysis, for which a large amount of slag is
employed. The process is conducted as follows:
A pound of the slag, powdered as finely as possible,
is intimately mixed with an equal weight of nitre, and as
much carbonate of potassa,* and exposed for an hour, in a
crucible, to a moderate red heat.  The mass is finely
powdered, boiled out with water, the solution filtered ofi,
and the residue washed several times with hot water.
The solution may contain, besides alkaline carbonates
and nitrites, vanadic acid, chromic acid, molybdic acid,
phosphoric acid, silicic acid and alumina.  A yellow colour
indicates the presence of chromic acid.
* Perhaps smaller quantities of both might be employed.




166         ASH OF THE REFINING-HEARTH.
It is now carefully mixed with nitric acid, so that it may
still remain alkaline, and any silica which may be precipitated is filtered off. A yellow colour at this stage of the
process bespeaks the presence of vanadic acid. The liquid
is then evaporated to crystallization, and the greater part
of the alkaline nitrate allowed to crystallize out in as cool
a place as possible. The mother-liquor is poured off from
the crystals, which are washed several times with a little
perfectly cold water; the washings are mixed with the
mother-liquor, and acetate of lead added as long as any
precipitate is produced. This precipitate contains all the
substances above enumerated, in combination with oxide of
lead. It is filtered off and washed once or twice.
Chromic and vanadic acids cannot be completely separated from oxide of lead by means of sulphuric acid. The
precipitate is therefore treated, while still moist, with a
mixture of fuming hydrochloric acid and strong alcohol, with
which it is heated nearly to ebullition, when all the lead and
silica are separated in an insoluble state, and the metallic
acids are converted into green chlorides, and dissolved together with the phosphoric and arsenic acids. The chloride
of lead is filtered off and washed with alcohol; the green
solution is evaporated to the consistency of a syrup, mixed
with a slight excess of a concentrated solution of potassa,
and chlorine passed into it until the metallic oxides have
redissolved in the form of acids, imparting a yellow colour
to the solution.*   The liquid is then neutralized with
ammonia, concentrated as far as possible by evaporation,
allowed to cool, and a fragment of chloride of ammonium
placed in it, so large as not to be entirely dissolved. The
vanadic acid is thus almost completely precipitated as an
* Phosphate of alumina may precipitate here, and must be
analyzed separately. (See No. 18.)




ASH OF THE REFINING-IEARTH.              167
ammonia-salt, in the form  of a white or yellow crystalline
powder. After twenty-hours it is filtered off and washed,
first with a saturated solution of sal-ammoniac, afterwards
with alcohol. It may be purified by dissolving in boiling
water with the addition of some ammonia.?
When dry, it is very gradually heated in a shallow platinum dish to expel the ammonia, and the residual vanadic
acid is fused at a low red heat. If pure, it solidifies, on
cooling, to a dark brown-red, very crystalline mass.
The solution filtered from  the vanadate of ammonia is
mixed with ammonia, and afterwards with a solution of
chloride of magnesium, which precipitates all the phosphoric, and most of the arsenic acid. After twenty-four
hours, the precipitated double salts are filtered off, washed
with dilute ammonia, dissolved in hydrochloric acid, the
solution heated to 500, and the arsenic precipitated by a
stream of sulphuretted hydrogen-gas. In the filtrate from
the sulphide of arsenic, the phosphoric acid may again be
precipitated as a double salt by adding ammonia.
The solution filtered from the magnesia-precipitate, which
still contains the chromic and molybdic acids, is saturated
with sulphuretted hydrogen and heated, when all the chromium is precipitated as green sesquioxide.
From  the solution  filtered from  this precipitate, the
molybdenum is precipitated by dilute sulphuric acid as a
* It is possible that, if molybdenum be present, a yellow compound of phosphoric acid, molybdic acid and ammonia might be
precipitated here. It is insoluble in hot dilute nitric acid. This
circumstance might be made use of for separating the molybdic acid
at once from the solution after treatment with chlorine. The solution would be mixed with ammonia, and afterwards boiled, with
addition of nitric acid in slight excess, when the compound would
separate as a yellow powder. It contains 3 per cent of phosphoric
acid.




168                    GLASS.
brown sulphide of molybdenum, from which, when heated
in a tube, a mixture of sulphur and sulphide of arsenic
sublimes, while black lustrous MoS, remains behind.
The residue of sesquioxide of iron which is left after
ignition with nitre and alkali, and extraction with water,
is partly dissolved by digestion with concentrated hydrochloric acid, and if sulphuretted hydrogen be passed through
the solution, the copper will be precipitated.
The solution filtered from the precipitate is heated to the
boiling-point, and a sufficient quantity of chlorate of potassa
gradually added, to convert the protochloride of iron into
sesquichloride. The small quantities of nickel, cobalt and
manganese which are present may be detected by precipitating the solution either with excess of ammonia or with
carbonate of lime, when those metals remain in solution,
and may be precipitated by sulphide of ammonium.
104. GLASS.
Silicates of CaO, and KO or NaO, frequently also, of PbO.
Two analyses are made, one by fusion with an alkaline
carbonate, for the determination of silicic acid; the other
by decomposing the glass with hydrofluoric acid, in order
to estimate the alkali.
1. The very finely-powdered glass is fused with 3 times
its weight of carbonate of potassa and soda (No. 10), the
mass softened in water, dissolved in dilute hydrochloric
acid, evaporated to dryness, redissolved in water, acidulated with hydrochloric acid, the silica filtered off and
washed.
From the solution, the small accidental impurities of




CLAY.                     169
sesquioxide of iron, oxide of manganese, and alumina, which
are usually contained even in white glass, are precipitated
by ammonia, after the solution has been mixed with some
chlorine-water to peroxidize the protoxide of manganese.
The lime is afterwards precipitated by oxalic acid, and
the solution filtered from the oxalate of lime is tested for
magnesia, which may, moreover, have been precipitated
with the alumina.
If the glass contain oxide of lead, that metal is precipitated by sulphuretted hydrogen from the solution filtered
from the silicic acid.
II. For the determination of alkalies, a second quantity
of the very finely-powdered glass is decomposed by hydrofluoric acid, or by ignition with carbonate of baryta, as in
the analysis of feldspar, the subsequent process being also
conducted as in that analysis, so that the other bases may,
if necessary, be again determined here.
105. CLAY.
3 A1203, 4 SiO3+ 6 HO, with variable quantities of
KO, MgO, FeO, MnO, Feldspar, Sand, &c.
The water is determined by igniting the clay previously
dried at 100~.
I. The clay is heated with concentrated sulphuric acid,
the greater excess of acid evaporated, the residue dissolved
in concentrated hydrochloric acid, by the aid of heat,
and the silicic acid filtered off. If the clay contain an
admixture of sand or feldspar, the silica is dissolved in a
boiling concentrated solution of carbonate of soda, when
the sand and feldspar remain undissolved.
The hydrochloric solution is considerably diluted, and




170                     cLAY.
gradually neutralized with carbonate of soda, so that
sesquioxide of iron and alumina are precipitated, while
protoxide of manganese, lime and magnesia remain in solution as bicarbonates.  The separation of alumina and
sesquioxide of iron is then effected as in No. 19, that of
the other bases as in No. 23.
II. The clay is fused with 3 times its weight of carbonate of potassa and soda (see No. 10), the fused mass
dissolved in dilute hydrochloric acid, the solution evaporated to dryness, the residue dissolved in water containing
hydrochloric acid, and the solution filtered off.
The separation of the other bases contained in the solution is then effected as in I.
III. For the determination of the alkali, a separate
portion of the clay is decomposed by fusion with hydrate
or carbonate of baryta, and the process conducted as in
No. 73, the baryta and the other bases being precipitated
from the solution by a mixture of ammonia and carbonate
of ammonia; after gently heating, the precipitate is filtered
off, the solution evaporated, and the residue ignited, when
chloride of potassium and chloride of sodium are left. Or
the analysis may be made with hydrofluoric acid, as in
No. 73.
106. COMMON LIMESTONE, HYDRAULIC LIMESTONE,
MARL.
Carbonates of CaO, MgO, FeO, MnO, with Clay containing
alkali, and sometimes 3 CaO, P05.
I. For the detection of the alkali, large fragments of the
mineral, when it contains carbonate of lime in predominating quantity, are placed in a charcoal fire, and heated




LIMESTONE.                  171
for half an hour to whiteness, when the clay, which contains the alkali, is decomposed.
The ignited mass is carefully freed from adhering ash,
powdered, exhausted with water, the solution mixed with
some carbonate of ammonia, evaporated, the precipitated
carbonate of lime filtered off, the solution acidified with
hydrochloric acid, evaporated to dryness, and the residual
chloride of potassium or sodium heated to dull redness.
If both salts be present, they are separated by bichloride of
platinum.
II. From a portion of the mineral which has been dried
at 1000 and weighed, the water is expelled by ignition in a
glass tube, and its quantity determined by collecting it in a
weighed chloride-of-calcium-tube.
III. The carbonic acid may be expelled from another
portion of the mineral by nitric acid in the apparatus
employed for testing potashes, and its amount determined
directly by the loss of weight.
Or a weighed quantity of the substance is fused with
about 4 parts, accurately weighed, of vitrified borax, in a
platinum crucible, when all the carbonic acid is expelled,
and its amount may be determined from the loss of weight,
if the water expelled at the same time be taken into
account in the calculation. (See No. 7.)
IV. Another very finely-powdered portion is digested
with very dilute nitric acid, which dissolves the carbonates,
together with the phosphate of lime, leaving the clay, which
is filtered off, ignited and weighed. It is then analyzed as
in No. 105.
The separation of the other constituents present in the
solution is effected as in No. 13.




172  IODIDE, BROMIDE, AND CHLORIDE OF SODIUMI.
107. IODIDE, BROMIDE, AND CHLORIDE OF SODIUM.
The solution is mixed with nitrate of protoxide of palladium, when all the iodine is precipitated as dark brown
iodide of palladium, the bromide of palladium remaining
in solution because chloride of sodium is present. After
the lapse of twelve hours, the precipitate is collected upon
a weighed filter, dried over oil of vitriol, or at a temperature
not exceeding 80~, and weighed.
The excess of palladium in the filtrate is separated by
means of sulphuretted hydrogen, in order to prevent the
formation of a precipitate containing palladium upon the
subsequent addition of nitrate of silver. The excess of
sulphuretted hydrogen is then removed from the solution
by sulphate of sesquioxide of iron, and the filtrate mixed
with nitrate of silver, when a precipitate of chloride and
bromide of silver is formed, which is collected, washed,
dried and fused. A quantity of this precipitate, weighed
in a bulb-tube, is fused in a current of dry chlorine until
bromine vapour ceases to be evolved, and the tube changes
no longer in weight. Before weighing, every trace of chlorine must be removed from the bulb.
A simpler method consists in pouring water over the
weighed mixture of bromide and chloride of silver, adding
a few drops of hydrochloric acid, and a fragment of zinc.
In twenty-four hours the silver is completely reduced; it is
rubbed to powder, boiled with water containing hydrochloric acid, afterwards washed with pure water, ignited
and weighed.
The difference between the equivalents of chlorine and
bromine is to the equivalent of bromine, as the differ



CRUDE COMMON SALT.             173
ence between the amounts of chloride and bromide of
silver employed, and the amount of chloride which the
reduced silver ought to yield, is to the amount of bromine
present.
For example: 200 parts of a mixture of equal weights
of chloride and bromide of silver gave, when reduced,
132'73 of silver, which would yield 176'31 of chloride of
silver.
Difference between the equivalents of chlorine and
bromine= 44'5.   Difference  obtained= 23'69.   Then
44-'5: 80 = 2369: x (=42'5 bromine).
By the same indirect method, the amount of iodine contained in a mixture of iodide with chloride or bromide of
sodium may be determined.
The iodine may also be determined in a mixture of
chloride and iodide of potassium or sodium, by adding a
solution of sulphate of copper mixed with sulphurous acid,
when the iodine is precipitated as white subiodide of copper,
which is then washed.
This method is also applicable for the approximative
separation of iodine and bromine.
108. CRUDE COMMON SALT.
I. A weighed quantity of the moist salt is dried for
some time at about 100~, then heated to about 300~ in
a covered crucible, and the water determined from the
loss.
II. For the estimation of the sulphuric acid, the salt is
dissolved in water (when any insoluble impurities are left),




174             CRUDE COMMON SALT.
the solution slightly acidified with hydrochloric acid, and
precipitated by chloride of barium.
III. The lime is determined in a larger quantity of the salt,
by precipitating it from its solution by oxalate of ammonia,
and filtering off the oxalate of lime when it has subsided.
IV. The filtrate is concentrated by evaporation and
mixed with ammonia and phosphate of soda to precipitate
the magnesia; after the lapse of twenty-four hours, the
precipitate is filtered off and washed with ammonia.
V. The very small quantity of potassa which is usually
present, may be detected by concentrating the solution of a
large quantity of the salt so that a great part of the
chloride of sodium may crystallize out; the potassium is
then precipitated from the mother-liquor with bichloride of
platinum.
VI. The bromine may be detected by passing chlorine
into the mother-liquor obtained from a large quantity of
the saline solution, and agitating the liquid with ether,
which takes up the bromine, and thence acquires a yellow
colour. The bromine may then be converted into bromide
of ammonium by adding ammonia.
VII. In order to detect the iodine, the mother-liquor is
mixed with some starch-paste, and weak chlorine-water
added drop by drop; or the vapour of bromine or of nitrous
acid may be allowed to flow on to the surface of the
mixture.
For the quantitative determination of iodine and bromine, see No. 107.




INCRUSTATIONS FROM SALT-PANS.         175
109. INCRUSTATIONS FROM SALT-PANS.*
NaCl,-rNaO, S03,-CaO, SO3, —MgO, SO,-CaO,CO2,
MgO,CO2.
I. A weighed portion is heated nearly to redness in order
to determine the water.
II. Another portion is finely powdered and boiled with
water, the residual carbonates of lime and magnesia filtered
off, washed with hot water, and the two bases separated as
in No. 12. This residue sometimes contains iron and
manganese.
III. The filtrate is mixed with chloride of ammonium,
and the lime precipitated by oxalate of ammonia. (See
No. 12.)
IV. The solution filtered from the precipitate is mixed
with ammonia, and the magnesia precipitated by phosphate
of soda. (See No. 6.)
V. Another portion of the incrustation is dissolved in
hot dilute hydrochloric acid, and the sulphuric acid precipitated by chloride of barium (No. 3).
VI. A smaller quantity is dissolved in dilute nitric
acid, and the chlorine precipitated by nitrate of silver
(No. 1).
VII. The sodium and soda are calculated from the
loss.
VIII. In order to detect a small quantity of sulphate
of potassa, a large quantity of the incrustation is finely
powdered, boiled with an excess of hydrate of baryta, the
* Easily obtained at the salt-works.




176  MIINERAL WATERS, WELL-TATERS, SALINE SPRINGS.
solution filtered off, the lime and baryta precipitated by a
mixture of ammonia and carbonate of ammonia, the filtrate
acidified with hydrochloric acid and evaporated to dryness;
the residue is ignited, dissolved in water, and the solution
treated with bichloride of platinum.
In this process also, the soda which previously existed
as sulphate, may be obtained in the form of carbonate.
110. MINERAL WATERS, WELL-WATERS, SALINE
SPRINGS.
It is supposed that the analyst has an unlimited quantity
of water at his disposal, so that separate portions may be
employed for the determination of most of the individual
constituents. For the estimation of those substances which
are present in large quantity, small portions of water must
be employed, larger quantities being taken for such constituents as exist in small proportion.
I. The specific gravity is first determined, in order to
ascertain, by calculation, the weight of 10, 50, or 100 cub.
cents. or grain measures of water, so that the quantities of
water employed may be determined by measure.
II. Carbonic acid and sulphuretted hydrogen-gases can
only be determined at the well itself by means of the appropriate apparatus.
111I. The total weight of the fixed constituents is ascertained by evaporating a measured quantity of the water to
dryness, and carefully heating the residue to about 200~.
Should the water contain much chloride of magnesium, an
error will result from the partial decomposition of that salt,
hydrochloric acid and magnesia being produced; this may,
however, be avoided by dissolving a weighed quantity of




MINERAL WATERS, AELL-WATERS, SALINE SPRINGS.  177
pure ignited carbonate of soda in the water before evaporating.
IV. The carbonzates of protoxide of iron, p1roloxide of
vaiiganese, lime and magnesia, held in solution by free
carbonic acid, are precipitated when a large quantity of
water is boiled for an hour in a flask. The precipitate is
filtered off, dissolved in hydrochloric acid, the sesquioxide
of iron precipitated by ammonia, and the protoxide of
manganese, lime and magnesia separated as in No. 23.
V. The silicic acid is left undissolved on treating the
residue obtained by evaporation, with dilute hydrochloric
acid.  Should the water contain carbonate of soda, it must
be acidulated with hydrochloric acid previously to evaporation. If gypsum be present, a large quantity of water
must be employed to redissolve it.
VI. Boracic acid may be detected by mixing the water
with carbonate of soda, concentrating by evaporation to a
small bulk, and acidifying with hydrochloric acid; if turmeric-paper be dipped in this solution, and dried, it will
become brown if boracic acid be present.
VII. The chlorine is precipitated by nitrate of silver
after acidifying the water with nitric acid; the precipitate
is treated as in No. 1.
VIII. Bromine and iodine, present only in very small
quantity, can only be detected and estimated in large quantities of water, or in the mother-liquor. They are recognized
as in No. 107.  In order to concentrate the bromine, the
water may be evaporated to dryness, and all the bromide of
sodium, with but little chloride, extracted from the residue
by absolute alcohol. When the alcohol has been evaporated
or distilled off, the residue is dissolved in water, and a
small quantity of nitrate of silver added, with constant
N




178   MINERAL WATERS, WELL-WATERS, SALINE SPRINGS.
stirring, so that only about - of the chlorine may be precipitated as chloride of silver; the precipitate, which contains
all the bromine, is weighed, and a certain portion of it
analyzed as in No. 107.
IX. The sulphuric acid is precipitated by chloride of
barium from the water slightly acidified with hydrochloric
acid.
X. Potassa and soda. The water is evaporated to about
one-half, and mixed, without filtering, with excess of barytawater; the mixture is allowed to cool, and carbonate of
ammonia added; in this way, the sulphuric acid, lime, and
excess of baryta are precipitated. The filtrate is acidified
with hydrochloric acid, evaporated to dryness, and the
residue, which is a mixture of chloride of sodium, chloride
of potassium and chloride of magnesium, is then cautiously
heated nearly to redness. The three metals are separated
as in No. 11.
XI. Carbonate of soda.  The water is boiled for a long
time, the precipitated earthy carbonates filtered off, and the
filtrate divided into two equal parts. In one of these, previously acidified slightly with nitric acid, the chlorine is
determined by precipitation with nitrate of silver.  The
other portion is mixed with a slight excess of hydrochloric
acid, evaporated to dryness, and the residue heated nearly
to redness; it is then dissolved in water and precipitated
by nitrate of silver. The difference between this amount of
chloride of silver and the former, corresponds to the quantity of carbonate of soda which was contained in the water.
XII.'Lime. In the solution filtered from the precipitate obtained in IV, the lime is precipitated by oxalate of
ammonia, after addition of chloride of ammonium.  See
No. 12.




MINERAL WATERS, WELL-WATERS, SALINE SPRINGS.  179
XIII. lMagnesia. The solution filtered from the limeprecipitate is concentrated by evaporation, allowed to cool,
mixed with concentrated ammonia, and the magnesia precipitated by phosphate of soda. See No. 6.
XIV. Lithia. The lithia is best obtained from the
mother-liquor according to the method given in X. The
solution filtered from the precipitate is mixed with phosphate of soda, evaporated to dryness, and the residue treated
with a very small quantity of water, when phosphate of
soda and lithia is left, which should, however, be tested for
magnesia.
Or the mother-liquor may be evaporated to dryness
with excess of carbonate of soda, the residue extracted with
hot water, the filtered solution mixed with phosphate of
soda and evaporated to dryness.
XV. Strontia may be sought in the ferruginous and
calcareous stalactites and ochreous deposits from waters
containing carbonic acid.
XVI. Phosphloric acid. The foregoing remark applies
also to the phosphates. Or a large quantity of water may
be evaporated to a small bulk, mixed with ammonia, the
precipitate filtered off, dissolved in nitric acid, and tested
for phosphoric acid with molybdate of ammonia.
XVII. Arsenic acid, in combination with lime or sesquioxide of iron, must likewise be sought, in the stalactites or
ochres from such waters, with the aid of Marsh's apparatus.
(See Poisoning by Arsenic.)
XVIII. Antimony and copper, to be tested for in the
deposit, by sulphuretted hydrogen.
XIX. Fluorine, also contained in. the deposit as fluoride
of calcium. Or it may be sought in the precipitate obtained
by ammonia in XVI, a part of which should be dried and
moistened with concentrated sulphuric acid in a platinum
N 2




180                      SOILS.
crucible covered with a glass-plate coated with wax and
marked in order to test for fluorine.  (See No. Sl.)
111. SOILS.
The ordinary constituents of soils, which differ much in
different soils, and are very variable in quantity, are salts
of chlorine, sulphuric acid, phosphoric acid, silicic acid,
carbonic acid, nitric acid, with potassa, soda, ammonia,
lime, magnesia, alumina, protoxide of manganese and protoxide of iron, together with sand and organic matters
consisting of the debris of plants, and of the humous substances produced by their decay.
Some of these constituents are soluble in water.
Others are insoluble in water, but soluble in dilute acids,
as, for example, the carbonates and phosphates of lime and
magnesia.
The remainder are insoluble even in dilute acids; these
consist of quartz and of particles of feldspar, mica and
hornblende arising from the disintegration of different
kinds of rock.
The soil to be examined is collected from different parts
of the field, well powdered, allowed to dry in the air, and
uniformly mixed.
It is most convenient to determine the greater number
of the constituents in separate portions of the soil.
I. Water. A weighed portion of air-dried soil is heated
to 100~, and retained at that temperature till its weight is
constant. In this way the amount of hygroscopic water is
ascertained.
In order to determine the combined water in the salts,




soIs.                    181
clay, &c., the soil may be heated to 200~ or 300~, when
-the ammonia also may be expelled.
II. Organic matters. The dry soil is ignited with access
of air, moistened with carbonate of ammonia, and again
heated nearly to redness. The loss of weight (ammonia and
nitric acid being taken into account) indicates the total
amount of organic matter.
The amount of nitrogenized organic matter can only be
determined by ultimate analysis, when the ammonia and
nitric acid must not be neglected in the calculation.
Certain organic substances, such as fatty and resinous
matters may be extracted from the dried soil by hot alcohol
and ether.
The humous substances may be extracted by boiling the
soil with solution of potassa; they are separated, though
not completely, from the brown filtered solution, in the
form of a brown precipitate, on adding hydrochloric acid.
III. Ammonia. The soil is distilled with solution of
soda, and the ammonia collected and determined as in
No. 5.
IV. Nitric acid. The analyst must be satisfied with the
qualitative detection of nitric acid. The soil is extracted
with water, the filtered solution evaporated to a small bulk,
mixed with about 4 its volume of pure concentrated sulphuric acid, and solution of protosulphate of iron added
drop by drop; if nitric acid be present, a dark brown, or,
if its quantity be very small, a purple-red colour will be
produced.  Or the very concentrated solution may be
heated, in a tube, with copper-filings and concentrated
sulphuric acid, when yellowish-red vapours of nitrous acid
make their appearance. Or the dry residue may be mixed
with anhydrous sulphate of copper and heated in a tube,
when yellowish-red vapours are likewise evolved.




182                      sores.
V. The constituents soluble in water.  A large quantity
of the air-dried soil, from 1000 to 2000 grms, is heated
nearly to ebullition, with water, for a considerable time;
the residue is filtered off and thoroughly washed with hot
water. The whole liquid is evaporated to about its original
volume, carefully weighed or measured, and separate portions of it, weighed or measured off, are employed for the
determination of the following constituents.
a. The total weight of the portion soluble in water is
ascertained by evaporation to dryness.
6. Sulphuric acid is precipitated by chloride of barium
from the solution acidified with hydrochloric acid.
c. Chlorine is precipitated by nitrate of silver, after
acidification with nitric acid.
d. Silicic acid. The solution is mixed with hydrochloric
acid, evaporated to dryness, the residue extracted with
dilute hydrochloric acid, and the silica filtered off.
e. Lime, magnesia, alumina, protoxide of iron and protoxide of manganese may be contained in the filtrate from d;
they may be separated as in No. 74.
f. Potassa and soda.  The solution is mixed with hydrochloric acid, evaporated to dryness, the residue dissolved in
a little water, baryta-water added in excess, the mixture
digested for some time, filtered off, and the baryta and lime
precipitated from the filtrate by carbonate of ammonia.
The solution filtered from these can contain only potassa
and soda, which are estimated as chlorides, and separated
as usual.
g. Phosphoric acid, which can only be present if the
solution contain no lime, &c., is precipitated as phosphate
of magnesia-ammonia.
VI. Constituents insoluble in water, but soluble in dilute
hydrochloric acid.  From 50 to 100 grms. of the residue




SOILS.                    183
obtained in V (previously washed, dried and uniformly
mixed), are weighed off, mixed with water, in a flask, to a
thin paste, heated, and hydrochloric acid gradually added
until the effervescence ceases; the mixture is then heated
for some time, with frequent agitation, the insoluble residue
filtered off and well washed. The solution is concentrated
by evaporation, weighed or measured, and divided into
separate portions for the different determinations. If the
soil contain much organic matter, it must be feebly ignited
with access of air previously to the extraction with hydrochloric acid.
a. Silicic acid. The solution is evaporated to dryness
with addition of some nitric acid.
b. Sulophuric acid. From a weighed portion of the acid
solution, filtered from the silica, the sulphuric acid is
precipitated by chloride of barium.
c. Alkalies. Another portion of this solution is treated
as in V,f, with baryta-water.
d. Phosphoric acid, lime, magnesia, alumina, protoxide
of manganese, and protoxide of iron are separated and
determined in the greater portion of the solution filtered
from the silica, according to the method given in No. 24.
e. The carbonic acid may be determined in a separate
portion of the washed soil, as in alkalimetrical examinations.
f. A small quantity of copper and arsenic sometimes
contained in the soil may be determined by a special
experiment. See No. 24.
VII. Constituents insoluble in dilute hydrochloric acid.
A small quantity (about 5 or 10 grms.) of the residue
obtained in VI, is heated with several times its weight of
concentrated sulphuric acid, until the greater part of the
acid has been expelled. By this treatment especially the




184                ASHES OF PLANTS.
clay is decomposed. The nearly dry residue is digested
with dilute hydrochloric acid, the solution filtered off, and
analyzed as above, omitting the determination of silicic
acid.
The residue left by hydrochloric acid is boiled for a long
time with a concentrated solution of carbonate of soda,
which dissolves the silica separated by the sulphuric acid.
The filtered solution is acidified with hydrochloric acid,
evaporated to dryness, and the silica filtered off.
The portion insoluble in carbonate of soda may be a
mixture of sand, feldspar, and other minerals not decomposed by sulphuric acid, which may be separated to some
extent with the aid of a magnifier. In order to decompose them, they must be treated as in the analysis of
feldspar, No. 73.
The greater part of the residue obtained in VI,
previously to  treatment with  sulphuric  acid, may be
mechanically separated, with tolerable accuracy, into its
constituents, by levigation.  The residue is stirred up
with much water by means of a feather, and the finer
suspended portions, consisting chiefly of clay, are repeatedly
poured off until only the grains of sand, feldspar, &c.,
remain behind.
112. ASHES OF PLANTS.*
Salts of KO, NaO, CaO, MgO, A1,203, Fe2O3 and MnO,
with C1, F, SO3, CO2, and SiO3
Manganese does not occur in all ashes, and is seldom
present in sufficient quantity to determine. Fluorine has
* By Professor Stadeler.




ASHES OF PLANTS.                185
been hitherto found only in the stalks of some of the
Graminacece. Alumina is an essential constituent of the
ashes of the Lycopodiaceee, but is seldom present in appreciable quantity in other ashes. Even iodine, bromine,
oxide of copper, and titanic acid have been found, though
generally in very minute quantities, in some ashes.
The process of analysis differs according as the ashes
do or do not contain more phosphoric acid than is requisite
to combine with the sesquioxide of iron, protoxide of
manganese, lime, magnesia, and alumina. To the former
(containing more phosphoric acid) belong those of seeds, to
the latter, those of woods, succulent plants, &c.
I. Asees of seedls. About 50 grms. of the seeds which
have been dried in the air, or at 100~, are thoroughly
carbonized by gentle ignition in a platinum crucible; the
carbonaceous mass is powdered, moistened with water, and
exposed for some time to the air, when the sulphides are
converted into sulphates; it is then digested with concentrated acetic acid, water added, the mixture filtered, and
the residue washed with hot water till the washings are
only slightly acid to test-papers. The carbonized mass
is thus entirely, or almo t entirely, freed from metallic
chlorides; it is introduced, while yet moist, into a platinum
crucible, and incinerated as far as possible by a protracted
gentle ignition. (At a bright red heat, phosphide of platinum
is formed and the crucible corroded.) Finally, a few drops
of concentrated nitric acid are added to the ash, which is
then ignited in the crucible, the cover of which is placed
against its mouth, until the last traces of carbon are burnt
off, and a perfectly white ash remains. This ash is added
to the saline mass obtained by evaporating the acetic
solution; the mixture is gently ignited to decompose the
acetates, and weighed.




186                ASHES OF PLANTS.
The ash is dissolved by nitric acid in a carbonic acid
apparatus, and the carbonic acid determined  from  the
loss.
The solution is mixed with 10 or 12 volumes of water,
and the residue, consisting of undissolved silica (sometimes
also of sand) and charcoal, is collected upon a filter (previously dried at 1000~, weighed, carefully removed from
the filter, and digested with very dilute solution of soda,
which readily dissolves all the silica, except that present in
the form of sand; the residue of sand and charcoal is collected upon the filter previously employed; its weight,
after being dried at 100~, is deducted from the total
weight of the ash. The weight of the silicic acid is determined from the loss.
From the filtered solution containing the saline constituents, the chlorine is precipitated by nitrate of silver,
an excess of the precipitate removed by hydrochloric acid,
the sulphuric acid precipitated by chloride of barium, and
the excess of baryta separated by careful addition of
sulphuric acid.
The filtrate is evaporated to dryness, the residue treated
with concentrated hydrochloric acid, and digested with it
for some time, in order completely to expel the nitric acid,
and to convert any pyrophosphoric acid into the tribasic
form. The hydrochloric acid is expelled as far as possible,
a sufficient quantity of water afterwards added, and the
solution filtered from the undissolved silica, which is
ignited, weighed, and calculated together with that previously obtained.
From the solution, the iron, manganese, alumina, lime,
and magnesia, are precipitated by ammonia as phosphates,
which are collected, after six or eight hours, upon a filter,
ignited and weighed.  The precipitate is dissolved by




ASHES OF PLANTS.               187
digestion with concentrated hydrochloric acid, the free acid
nearly neutralized with soda, and the solution mixed with
acetate of soda, when the phosphates of sesquioxide of iron
and alumina are precipitated.  These are ignited and
weighed, and if necessary (unless the ignited precipitate
has a pure brown colour), separated according to No. 19.From the filtrate, the lime is precipitated by oxalate of
ammonia, and the magnesia, as phosphate of magnesiaammonia, by merely adding an excess of ammonia; the
phosphoric acid previously in combination with lime is
calculated from the loss.-If manganese be present, it is
precipitated together with the phosphate of magnesiaammonia, to which it imparts a grey or black colour
after ignition. The separation is effected as in No. 24.
The solution from which the phosphates have been
precipitated by ammonia, now contains only the alkalies
and the remainder of the phosphoric acid. The latter is
precipitated (together with sulphuric acid) by chloride of
barium, and the excess of baryta removed by sulphuric
acid or by neutral carbonate of ammonia; the filtrate is
evaporated to dryness, the residue ignited, and the alkalies
weighed as chlorides or sulphates.  For their separation,,ee No. 4.-The precipitate produced by chloride of barium
is exhausted with nitric acid, sulphuric acid added to effect
the complete separation of the baryta, and the phosphoric
acid precipitated from the filtrate, previously mixed with an
excess of ammonia, as phosphate of magnesia-ammonia.
II. As8es of wood, vegetables, Sc. Of those vegetables
which yield a large amount of ash, 50 grms. may be taken
for examination; but of the different kinds of wood, which
are usually poorer in mineral constituents, and of the
Graminaceee, the ash of which contains much silica, about
100 grms. should be employed. The substances are car



188               ASIIES OF PLANTS.
bonized in a platinum crucible, and the mass thrown
immediately into a flat porcelain dish, where it generally
smoulders for a long time, and is, for the most part, converted into ash. The incineration is completed in the
platinum crucible.
The analysis of these ashes only differs from that of the
preceding ill that these contain a larger quantity of the
alkaline earths than is necessary to combine with the
phosphoric acid, so that the total amount of that acid is
separated upon adding ammonia. The precipitate is immnediately filtered off, and the filtrate mixed, first with
sulphide of ammonium, to precipitate the manganese, then
with oxalic acid for the lime, and lastly with phosphate
of ammonia to separate the magnesia.  Any excess of
phosphoric acid may be separated, as directed above, from
the alkalies, which are then weighed as chlorides or sulphates.
The stalks of the Graminacece usually leave an ash which
cannot be completely decomposed by nitric or hydrochloric
acid.  The weighed  silicate remaining undissolved, is
decomposed most conveniently with hydrofluoric acid, and
the bases, previously in combination with silicic acid, may
then be estimated in the solution. The silicic acid is
determined from the loss. In this case, the determination
of the charcoal and sand must, of course, be omitted.
113. GUANO.
Guano consists of the partially decomposed excrement
of sea-birds. It contains a great many substances, some
soluble, others insoluble in water. The constituents upon
which depend its important action and application as a




GUANO.                    189
manure, are: organic, chiefly nitrogenized matters; salts of
ammonia; phosphates, especially phosphate of lime; and
salts of the alkalies. The amount of these constituents
indicates the value of the guano. It is important to test
this manure, since different specimens consist not only
of various kinds of genuine guano of different degrees of
richness, but samples also come into the market which
are adulterated with common earth, loam, lime, sand,
pebbles, and crude common salt or Glauber's-salt.
Genuine guano presents the appearance of a moist yellowish-brown earth, mixed here and there with white
fragments or lumps.  Very few and rare specimens are
white. It has a peculiar excrementitious or urinous odour,
and a feeble penetrating saline taste.
It is chemically tested in the following manner:
I. The guano is mixed, in a dish, with hydrate of lime
(slaked lime stirred with water to a thin cream), when it
should emit, especially when heated, a powerful odour of
ammonia. In order to compare different specimens, the
same quantity, say 4 oz. of each, is taken.  Since the
value depends partly upon the amount of ammonia present,
the better sorts of guano will evolve the stronger odour
of that gas.
II. Two ounces (or from 50 to 60 grms.) of guano,
finely powdered and uniformly mixed, are weighed in a
counterpoised porcelain capsule, and heated on a water-bath
until it is perfectly dry and suffers no farther diminution
of weight.   The loss of weight expresses the amount
of moisture contained in the guano. Good guano loses
only between 8 and 15 per cent of water, but if fraudulently moistened, it may lose 20 per cent, or even
more.
III. Half an ounce (or from 1 5 to 20 grms.) of guano is




190                    GUANO.
weighed, and heated over a large spirit-lamp, or gas-burner,
in a porcelain or platinum crucible, with free access of air,
until all organic matter has burnt off, and the guano is converted into a white or greyish ash. Good guano, when treated
in this way, leaves from 30 to 35 per cent of ash, while bad
guano leaves from 60 to 80 per cent, and that which has
been fraudulently adulterated leaves still more. The ash of
genuine guano, whether of good or bad quality, is always
white or greyish; a yellow or reddish colour bespeaks
an admixture of clay or earth. Good guano, when first
heated, evolves white vapours, with a powerful odour of
ammonia.
IV. A similar quantity of guano is mixed, in a dish,
with several times its volume of water; heat is then
applied, and the mass thrown upon a small filter (previously dried in the water-bath and weighed); the residue
on the filter is washed with hot water till a small portion
of the washing-water is not rendered turbid by adding
chloride of calcium and ammonia. The filter, with the
washed guano, is then thoroughly dried in a water-bath,
and weighed. The better the quality of the specimen, the
less insoluble residue will be obtained. Good samples of
guano leave from 40 to 45 per cent, those of bad quality as
much as 70 or 80. If the guano be adulterated with
common salt or with Glauber's-salt, it will behave, to this
test, like a genuine specimen, but will furnish a greater
quantity of ash in Experiment III.
V. The guano under examination, may be treated with
moderately strong hydrochloric acid.  Good guano effervesces but slightly; a specimen of guano, adulterated with
chalk, would effervesce strongly, and would leave a proportionally larger quantity of ash in Experiment III.
VI. The ash obtained in III, is dissolved in dilute




GUANO.                     191
hydrochloric acid, which should give rise only to slight
effervescence, if the guano be unadulterated.  The solution
is filtered from the residue, the latter washed, dried,
thoroughly burnt, together with the filter, in a weighed
crucible, over the spirit-lamp, and weighed. This insoluble
residue, consisting partly of sand, amounts, in good
(undried) guano, to only 1 or 2 per cent.
VII. The filtered hydrochloric solution is mixed with a
slight excess of ammonia. The precipitate thus produced
consists almost entirely of phosphate of lime. It is filtered
off, washed, dried, and ignited; its quantity in good
guano amounts to 20 or 25 per cent.
VIII. The filtrate from this precipitate should furnish
only slight indications of lime on addition of oxalic acid; but
if the guano be adulterated with chalk, this reagent will
produce a very considerable precipitate.  This solution
ought therefore to contain only the alkaline salts, amounting to 5 or 10 per cent of the original undried guano.
In order to determine them directly, which is generally
unnecessary for practical purposes, the solution must be
mixed with some more chloride of ammonium, and evaporated to dryness; the residue is heated to volatilize the
excess of chloride of ammonium, and to  convert the
sulphates into chlorides, weighed, and farther treated as
in No. 4.
IX. The aqueous solution, which was obtained in the
lixiviation-test (IV), and of which a fresh quantity may
be prepared so as to be saturated, has a brown colour
and a saline taste. When evaporated it evolves ammonia,
emits an urinous odour, and leaves a brown crystalline
mass, consisting chiefly of sulphates of potassa and soda,
chloride of ammonium, oxalate and phosphate of ammonia.
This solution exhibits the following reactions:




19 2                   GUANO.
When mixed with hydrate of potassa, it smells strongly
of ammonia.
With chloride of ammonium, ammonia, and sulphate of
magnesia, it gives an abundant pulverulent precipitate
of phosphate of magnesia-ammonia.
When acidified with acetic acid and tested with chloride
of calcium, it gives a copious precipitate of oxalate of
lime.
After addition of excess of hydrochloric acid, it gives,
with  chloride of barium, a considerable precipitate of
sulphate of baryta.
X. When guano is exhausted with cold water, and the
residue digested with a weak solution of caustic soda,
uric acid is extracted. The solution is filtered, and feebly
acidulated with hydrochloric acid, when the uric acid
is precipitated.  After being filtered off and washed, it
is easily soluble in caustic potassa, and may be reprecipitated by hydrochloric acid. If it be dissolved in warm
dilute nitric acid, the solution evaporated to dryness, and
the residue moistened with carbonate of ammonia, a fine
purple-red colour is produced.
XI. The quantity of organic matter can be estimated
directly only by an ultimate organic analysis.  In good
undried guano it amounts, taking the ammonia into
account, to about 50 per cent.
XII. The exact determination of the nitrogen requires
also an ultimate analysis. This element should amount to
12 or 14 per cent; bad samples contain only from 1 to' 6 per
cent. The quantity of nitrogen may, however, be approximatively determined by the following method, which therefore allows us to ascertain rapidly the value of different
specimens of guano. It depends upon the circumstance
that when guano is treated with a solution of chloride of




GUANO.                       193
lime (hypochlorite of lime), the nitrogen of the organic
matter and of the ammoniacal salts is evolved as gas.*
Instead of collecting and measuring the gas evolved, which
would be scarcely practicable, on account of the violent
effervescence, the volume of water which is expelled by the
gas is ascertained by means of the
simple apparatus represented in the
figure; it consists of a flask capable
of containing  about I pint, provided with a narrow  gas-deliverytube bent twice  at right angles.
One limb, rather the  shorter of
the two, is passed, air-tight, through
~   the cork of the flask, and bent
upwards to prevent, as far as possible, the escape of bubbles of gas. This tube descends
nearly to the bottom of the flask. A second very narrow
short tube is also passed through the cork, and serves for
the escape of air when the cork is introduced. The longer
limb of the delivery-tube dips into a tall cylinder or tube,
which is graduated to cubic centimeters, or cubic inches.
The flask is half-filled with solution of chloride of lime;t
1 grm. of guano is then weighed in the small glass vessel
(the end of a test-tube) in which a few small shot have
been placed, in order that it may float upright.  With the
aid of the handle of iron-wire shown in the figure, the
tube is let down so as to float upon the surface of the
* Farther experiments are required to show that all the nitrogen
is here evolved in the gaseous state, and to ascertain how the various
nitrogen-compounds behave with chloride of lime.
t This solution must be carefully prepared and kept in a dark
place, in a closed vessel. It must contain an excess of hydrate of
lime, and therefore need not be perfectly clear.
o




194      OXALATE AND PHOSPHATE OF LIME.
solution of chloride of lime; the cork with the tube is
then tightly adjusted, the orifice of the smaller tube closed
with wax, and the flask shaken so that the little vessel
may fill and sink. A volume of liquid equal to that of the
nitrogen evolved from the guano then flows into the
graduated cylinder; when no more liquid passes over, the
cylinder is depressed so as to bring the liquid to the same
level as that in the generating-flask; the wax plug is then
removed, the cork withdrawn, and the liquid still contained in the delivery-tube is allowed to run into the
cylinder, where the whole is carefully measured.  1 grin.
of good guano evolves between 70 and 80 cub. cents. of
gas.
114. OXALATE AND PHOSPHATE OF LIME.
A mixture of these two salts dissolves in nitric acid
without effervescence, and is reprecipitated from the solution by ammonia. If it be digested, when freshly precipitated, with acetic acid, the phosphate of lime may be
dissolved, while the oxalate is left.
If the mixture be previously ignited, it dissolves in nitric
acid with effervescence, and ammonia then precipitates
from the solution only the phosphate of lime, while the
lime which had been in combination with oxalic acid
remains in solution, and may be precipitated by oxalate of
ammonia, and quantitatively determined.  Phosphate of
lime, when freshly precipitated, may be recognized by the
yellow colour which it assumes when moistened, on the
filter, with nitrate of silver. It is analyzed as in No. 13.
If the two salts be dissolved in the smallest possible
quantity of hydrochloric acid, and the solution mixed with




OXALATE AND PPHOSPHATE OF LIME.        195
an excess of acetate of soda, the oxalate of lime is precipitated, while the phosphate remains in solution; from the
latter, the lime may be precipitated by oxalate of ammonia,
and afterwards the phosphoric acid by sulphat~ of magnesia and ammonia, as in No. 9.
When the mixture of the two salts is treated with concentrated sulphuric acid, oxalic acid is converted into carbonic acid and carbonic oxide, so that by employing the
apparatus described in the article upon alkalimetry, its
amount may be inferred from the loss of weight.
By gently heating the mixture with an excess of finelypowdered binoxide of manganese or neutral chromate of
potassa, or with binoxide of lead and dilute sulphuric acid,
all the oxalic acid is converted into carbonic acid, the
quantity of which may be determined by the use of the
apparatus above alluded to. 2 equivs. of carbonic acid
correspond to 1 equiv. of oxalic acid.
If binoxide of lead be employed in this operation, the
quantitative determination of the phosphoric acid may be
effected at the same time; for this purpose, the mixture is
digested for some time, to liberate the whole of the phosphoric acid; several volumes of alcohol are then added,
in order to separate the sulphate of lime, the solution
filtered, and the residue washed with alcohol. From the
filtrate, after the evaporation of the alcohol, the phosphoric
acid may be precipitated by sulphate of magnesia and
ammonia.
A very accurate method of estimating oxalic acid consists in converting it into carbonic acid by means of a
solution of terchloride of gold, weighing the reduced gold,
and calculating thence the amount of oxalic acid; 3 equivs.
of the latter reduce 1 equiv. of gold= 197.
For this purpose the mixture of the two salts is dissolved
o 2




196                 ALKALIMETRY.
in the smallest possible quantity of hydrochloric acid
(a large excess impedes the reduction of the gold), mixed
with an excess of a solution of terchloride of gold, or
better, of sodio-chloride of gold, diluted with much
water, and heated to ebullition.  The reduced coherent
gold is easily washed; it is to be dried, ignited, and
weighed.
The excess of gold is removed from the solution by
sulphuretted hydrogen, or by boiling with oxalic acid, and
the phosphoric acid and lime are then separated and
estimated as in No. 13.
115. ALKALIMETRY.
The specimens of potashes and soda-ashes met with in
commerce contain very variable quantities of foreign substances. The amount of carbonated alkali, upon which their
value alone depends, varies between 40 and 95 per cent.
The potashes contain chiefly chloride of potassium, sulphate, silicate, and phosphate of potassa, and carbonate,
phosphate, and silicate of lime.
The soda generally contains chloride and sulphide of
sodium, sulphate, silicate and hyposulphite of soda, and
often also hydrate of soda.
The amount of alkaline carbonate present in the sample,
may be determined by several methods.
1. By the standard solution te-st, i. e., by exactly neutralizinzg a weighed portion with dilute ssulphuric acid of
known strength.
In order to prepare the test-acid, a known quantity, say
70 grmins., of concentrated sulphuric acid, are diluted with
600 grins. of water.




ALYKLIMETRY.                   197
5 grms. of pure anhydrous carbonate of soda are weighed,
dissolved in hot water, and the solution coloured blue with
a little tincture of litmus.
The test-acid is then added to the solution, from a
burette, very carefully as the point of neutralization is
approached, until the colour is just changed to red, and
streaks which are made with the liquid upon litmus-paper,
remain red after drying.
The number of measures of acid employed is then observed, and the whole of the test-acid is diluted with so
much water, that exactly 100 measures are required to
neutralize 5 grms. of pure carbonate of soda. This stock
of test-acid is preserved  in a well-stopped bottle.  It
indicates immediately the percentage of caustic or carbonated alkali in a specimen of potashes or soda, provided
that a quantity of the sample be employed, which is
equivalent to 5 grms. of carbonate of soda.
100 measures of test-acid saturate 5'000 grms. of carb. of soda,
100,,,,,,   2935,, of soda,
100,,,,,,   6487,,  of carb. of potassa,
100,,,,,,   4421,,  of potassa.
So that if 6'487 grms. of a sample of potashes be taken,
the number of measures of acid employed will express,
directly, the percentage of carbonate of potassa, or if
4'421 grms. be used, of anhydrous potassa, contained in
the specimen.
Instead of sulphuric acid, pure crystallized oxalic acid
may be very conveniently employed for preparing the
test-solution.  An equivalent of the acid (63 grins.) is
introduced into a flask of 1 litre capacity, which is then
two-thirds filled with water; the acid is allowed to dissolve,
and so much water added that the whole solution may
measure 1 litre or 1000 cubic centimeters, at 17'5~ C.




198                   ALIALIMETRY.
One hundred cub. cents. of this test-acid then will exactly
neutralize ylO of an equivalent proportion of either alkali.
It is therefore necessary to weigh out I-o of an equivalent
proportion (in grammes) of the anhydrous alkali to be
tested, that is, 6'92 grms. of potashes, or 5'32 grms. of
soda-ash.  In order to obtain perfectly accurate results,
the process is conducted as follows: The solution of alkali
to be tested, is introduced into  a flask, coloured with
tincture of litmus, and the test-acid poured into it from  a
burette, until the colour changes from blue to violet,
and the effervescence is very feeble. The solution is now
heated to ebullition, and more acid added until the colour
has become decidedly red.  5 or 10 cub. cents. of the
test-acid are then added in excess; the alkali will be
now supersaturated. By boiling, agitating, and finally
sucking out with a glass tube, the last traces of carbonic
acid are removed. It is now required to determine exactly
how far the neutralization of the alkali has been exceeded;
for this purpose a standard solution of caustic soda is
employed, of such strength that it is exactly neutralized by
an equal volume of the test-acid;* this solution is added
from a burette graduated to'- cub. cent., when the red
colour rapidly changes to violet, and then suddenly to
pure blue. The number of cubic centimeters of sodasolution employed, is then deducted from the volume of
test-acid previously added; the remainder gives the percentage of pure alkaline carbonate.
The dropping-tubes or burettes employed for these
* This solution of soda must be perfectly free from carbonic acid.
In order to preserve it in that state, the bottle is closed with a cork,
through which passes an ordinary chloride-of-calcium-tube, open at
both ends, and filled with a mixture of Glauber's-salt and quick-lime
in powder.




ALKALIMETRY.                 199
analyses with standard solutions, are made
of different forms. The commonest is that
represented in Fig. 1, and consists of a
glass tube, closed at one end, about 0'25
meter (or 12 inches) long, and 0'01 meter
(or I inch) in diameter; into the lower
part of this tube is cemented another, very
much narrower, which is fixed parallel with
the larger tube; the extremity of the small
tube is bent outwards and sharply cut off,
2 so that the liquid may be conveniently
poured from it. The whole of the vessel is divided into
known volumes, and it is preferable to take from 25 to 50
cub. cents., and to divide these into fractional parts. The
zero should be placed at the top of the scale, below the
level of the orifice of the spout.
Another form is that shown in Fig. 2, which consists of
a single divided tube furnished at the top with a spout,
and with an orifice for pouring in the liquid.
A third form  of burette, which is the most
suitable and convenient, and can be very easily
made by the analyst himself, is that represented
by the adjoining figure. It consists of a glass
tube, about 0'01 meter in diameter, which is
divided into 25 or 50 cubic centimeters, and
drawn out to a point at the lower extremity. To
this open point is attached a narrow tube of vulcanized caoutchouc, about an inch long, and in
the lower end of this tube is inserted a short glass
tube drawn out to a narrow point and cut smoothly
off; this tube serves for dropping the liquid out, and is
tightly connected with the graduated tube in such a




200                  ALKALIMETRY.
manner that a considerable interval may be left between
the ends of the two tubes. Upon this part of the caoutchouc tube is fixed a clamp made of thick brass-wire,
shown with its actual dimensions, in the accompanying
figure, so constructed that the caoutchouc
tube may be opened by pressing upon the
two ends of the clamp, and closed when
the pressure is removed.  In order to use
this tube, it is fixed in a stand, in a vertical
position, above the vessel containing the
liquid to be tested.  By pressing upon the
ends of the little clamp, the caoutchouc
tube is opened, and the liquid allowed to
flow  out, even in  single drops, if required.*  At the
commencement of the operation, the tube is filled with
the test-liquid, a portion of which is then made to flow
out, by pressing upon the clamp until it stands exactly
at the zero of the scale.
II. By determining the carbonic acid evolved.
The carbonic acid is liberated from a weighed portion
of the alkali, in an apparatus which is previously weighed
(together with the acid used to effect the decomposition), and the carbonic acid determined from the loss of
weight.
The apparatus employed for this purpose may be
arranged in different ways. That represented in the adjoining figure, of about 1 its real dimensions, will render
* This apparatus may be obtained through the kindness of its
inventor, Dr. Mohr, of Coblenz.  It is not applicable, however, to
the testing with perinanganate of potassa (No. 101), since that salt
is decomposed by the caoutchouc.




ALKALIMETRY.                  201
apparent the  general principle, upon
which  they  are constructed, aIld will
itself fully answer the purpose.  It consists of a small light flask, closed by a
cork perforated with two holes, in one
of which is inserted a tube filled with
fragments of chloride of calcium, and in
the other, a narrow glass tube, running
nearly parallel with the inner wall of
the flask, and reaching almost to the
surface of the liquid; above the cork, this tube is bent
at right angles;
The specimen to be examined is weighed in the flask,
the latter about one-third filled with water, and the small
tube full of acid introduced with a pair of pincers; this
tube must be of such a length that it cannot fall down in
the flask, but may assume the position indicated in the
figure. Sulphuric acid is to be preferred for effecting the
decomposition of the carbonate, and should be employed
in quantity more than sufficient to expel the whole of the
carbonic acid. (For the carbonates of lime, baryta and
lead, nitric acid must be employed.) —The cork, with the
chloride-of-calcium-tube, and the bent tube is then introduced, air-tight, into the neck of the flask, the whole
apparatus accurately weighed, and the orifice of the bent
tube perfectly closed with a small cork or with wax.
The flask is then carefully inclined so that a small
quantity of the acid may run out of the tube and decompose the carbonate. The carbonic acid which is evolved
escapes through the chloride-of-calcium-tube, in which any
water which may have been carried off with it is retained.
No fresh acid is allowed to flow out of the tube until the




202                 ALKAIIMETRY.
effervescence caused by the first portion has ceased, and
does not recommence upon gentle agitation. When, at
length, the effervescence has entirely ceased, so that the
salt is completely decomposed, the plug is removed from
the small tube and suction applied, by the mouth, to the
tube containing chloride of calcium, until the air passing
through the flask no longer tastes of carbonic acid. In
very exact experiments, a second chloride-of-calcium-tube
must be attached to the small bent tube, to retain the
moisture of the air.
1. Potashes.-The amount of water is ascertained by
heating the specimen, for some time, to about 200~.
For this purpose from 2 to 5 grms. of potashes may be
taken.
In order to determine immediately, without calculation,
the percentage of potassa in carbonate of potassa, by means
of the above apparatus, 3'14 grms. of the specimen must
be taken.  Since 314 grms. of pure carbonate of potassa
evolve 100 grm. of carbonic acid, the number of centigrammes of carbonic acid evolved will represent the percentage of carbonate of potassa.
2. Soda. —241 grms. of soda are employed. This is the
quantity of pure carbonate of soda which evolves 1O00
grm. of carbonic acid.
Should caustic soda be contained in the specimen,
which may be known by the alkaline reaction of the solution after adding an excess of chloride of barium, the following modification of the process is necessary:
2'41 grms. of the anhydrous sample are mixed with
about 3 parts of pure quartz-sand, and about 1 part of
powdered carbonate of ammonia; the mixture is moistened with water, and, after some time, gently' heated till




VALUATION OF MANGANESE-ORES.         203
all water and ammonia are expelled. The dry residue is
then treated, as usual, in the above apparatus.
In order to prevent any inaccuracy arising from the
presence of sulphide of sodium or hyposulphite of soda in
the specimen, a solution of chromate of potassa is added
previously to the evolution of carbonic acid, in order to
oxidize these impurities.
116. VALUATION OF MANGANESE-ORES.
Good manganese-ore, which consists almost entirely of
binoxide of manganese, is crystalline, yields a black powder,
and, after being dried at a gentle heat, gives no water, or
only traces, when heated to redness.  Manganese-ore,
however, generally contains foreign minerals, especially
the hydrated sesquioxide of manganese. In order to determine the amount of binoxide, or, in other words, of
available oxygen, several methods may be employed.
I. A weighed quantity of the manganese-ore, powdered
as finely as possible, is introduced into the apparatus
employed for the quantitative estimation of carbonic acid,
where it is brought in contact with sulphuric acid and a
solution of oxalic acid, when sulphate of protoxide of manganese is produced, since all the available oxygen, which
may be regarded as in combination with the protoxide of
manganese, is evolved in the form of carbonic acid.
One equiv. of pure binoxide of manganese=43'6, yields
2 equivs.=44 of carbonic acid.  So that 0'99 grm. of
binoxide of manganese evolves 1O00 grm. of carbonic
acid. It is best to employ three times that quantity of
the manganese-ore, viz.: 2'97 grms., which are mixed
with a solution of 2'5 grms. of neutral oxalate of potassa;




204                 CILORIALETRY.
the sulphuric acid is allowed to flow into this mixture, and
the amount of carbonic. acid evolved is divided by 3. The
quotient expresses the percentage of binoxide of manganese
contained in the ore.
II. The finely-divided manganese-ore is weighed, and
mixed with water, in a flask capable of being tightly
closed; several bright strips of copper, previously weighed,
are then introduced, and a quantity of hydrochloric acid
added.  The flask is then closed with a cork and narrow
tube, and the contents digested until all the manganese
has dissolved, care being taken that no chlorine is evolved.
The liquid is then heated to ebullition for a quarter of an
hour, the flask closed air-tight, and allowed to cool; the
solution is poured off, the residual copper washed, first
with very dilute hydrochloric acid, then with pure water,
dried, and weighed.   2 equivs. of copper=-634 parts.
require for their conversion into subchloride, 1 equiv.=
71 parts of chlorine.
Then 634: 71 as the amount of copper dissolved is to
x (the amount of chlorine sought.)
122 grins. of pure binoxide of manganese evolve 1'00
grm. of chlorine, and therefore are capable of effecting the
solution of 1'78 grms. of copper.
117. CHLORIMETRY.
The "lime-bleach" of commerce is a variable mixture of
hypochlorite of lime and chloride of calcium, with hydrate
of lime.  When treated with an acid, it evolves the whole
of the chlorine in a free state.  In order to determine its
value, i. e., the amount of available chlorine which it contains, different methods are employed.




CIHLORIMETRY.                 205
I. Fourteen grms. of pure arsenious acid are dissolved
in solution of potassa, and so much water added that the
liquid may occupy 2000 divisions of the graduated burette.
100 measures, therefore, of this solution contain 0'7 grm.
of arsenious acid, and the solution of chlorine which is
required to convert this into arsenic acid, contains 0'5
grm. of chlorine, since 1 equiv.=99 of arsenious acid,
requires, for its conversion into arsenic acid, 2 equivs.=
71 of chlorine.
Five grms. of chloride of lime are weighed off, intimately
mixed with water, by trituration, rinsed into a cylindrical
glass, and so much water added that the whole may occupy
200 measures of the burette.
One hundred measures of the arsenic-solution are then
introduced into a beaker, diluted with water, an excess of
hydrochloric acid added, and the liquid coloured with olle
or two drops of sulphindigotic acid.
The solution of chloride of lime is well mixed by agitation, introduced into the burette, and added to the coloured
arsenic-solution until the colour just disappears.  The
solution of chloride of lime required to produce this effect
contains 0'5 grm. of chlorine.
For example, if 90 measures of the solution of chloride
of lime had been employed, the 5 grms. of chloride of
lime would have contained 1]111 grins. of chlorine, or
22'22 per cent.
Perfectly pure chloride of lime (Ca Cl+CaO, C1O),
which is never met with in commerce, contains 48'9 per
cent of available chlorine.
II. A weighed quantity of chloride of lime is mixed with
water, in a flask, an excess of protochloride of iron, free
from sesquichloride, added, and afterwards some hydrochloric acid. Several bright weighed strips of copper are




206               ANALYSIS OF NITRE.
then introduced, and the solution boiled until the protochloride at first formed is converted into subchloride; the
copper is then withdrawn, washed, dried, and weighed.
The calculation is effected as in No. 116.
118. ANALYSIS OF NITRE.
In order to determine the amount of moisture in crude
nitre, from  5 to 10 grms. of the specimen, previously
reduced to powder and dried by exposure to air, are heated
to about 150~.
The determination of the quantities of the foreign salts
present in the specimen, such as sulphates and chlorides,
lime and magnesia, by the ordinary methods, would occupy
too much time; it would be preferable to estimate them
by means of standard solutions of the reagents, i. e., by
measuring the quantities of the latter required to effect
complete precipitation.
The appearance of the fracture is regarded as an indication of the quality of the nitre; in pure nitre, the fracture
is lustrous, and exhibits a well-defined crystalline appearance; but if not more than 2 per cent of common salt
be present, it is granular and dull.  An admixture of
nitrate of soda (Chili saltpetre) has the same effect.
Another method, which is likewise, however, inaccurate,
but is most readily applied in practice, depends upon the
circumstance that a solution of pure nitre, at the temperature at which it is saturated, is still capable of
dissolving other salts, especially chloride of sodium.
400 grms. of the powdered specimen are shaken with
500 cub. cents. of a solution of pure nitre; the salt
is then filtered off, again washed with 250 cub. cents. of a
saturated solution of nitre, dried at 100~, and weighed.




ANALYSIS OF NITRE.              207
The loss of weight expresses the amount of the foreign
salts.  Since this process is liable to error from many
causes, and gives the amount of pure nitre, on an average,
2 per cent too high, these 2 per cent must not be
neglected in calculating the amount of impurity present.
The following process is more accurate, which consists
in converting the nitre contained in any specimen into
carbonate of potassa, the amount of which is then determined by means of the standard acid, as in testing
potashes.
90475 grms. of pure nitre furnish a quantity of carbonate
potassa, which is capable of saturating 100 measures of
the acid mentioned in the testing of potashes; so that if
this amount of impure nitre be employed, the number of
measures of acid indicate at once the percentage of pure
nitrate of potassa in the specimen.
One-fourth of the above quantity (2'369 grms.) of the
crude nitre is weighed out, intimately mixed with 1 grm.
of ignited lamp-black, and with 12 grms. of ignited and
finely-powdered common salt, which serves to moderate
the violence of the combustion. The mixture is introduced
into a platinum crucible, and heated to redness over a
large spirit-lamp or gas-burner.  When cool, it is dissolved in water, and the standard acid added in the manner
directed for testing samples of potashes. The number of
measures of acid employed is multiplied by 4, in order
to obtain the percentage of pure nitre in the specimen.
In following this method it is impossible to determine
the weight of the expelled carbonic acid by means of the
apparatus generally employed for this purpose, on account
of the large quantity of common salt which has been added.




208                  GUNPOWDER.
119. GUNPOWDER.
I. For the estimation of moisture, 5 or 6 grms. of
powder are dried over sulphuric acid, or in the air-bath
at 1000~.
II. A similar quantity of powder is moistened with
water, triturated in a mortar, rinsed into a filter, and
thoroughly washed. The solution of nitre thus obtained is
evaporated to dryness in a small weighed porcelain dish,
the dry residue heated for some time to 200~, or even till
the nitre fuses, and its weight determined.
III. In order to determine the sulphur, 5 grms. of
powder are intimately mixed with 5 grms. of anhydrous
carbonate of soda, 5 grms. of nitre, and 20 grms. of
decrepitated chloride of sodium, and the mixture heated to
redness in a platinum  crucible.  When cool, the mass is
dissolved in water, the solution slightly acidified with
nitric acid, and the sulphuric acid precipitated by chloride
of barium. (See No. 3.)
The amount of carbon may be inferred by difference.
In order to determine its quality, and to ascertain whether
it has been completely or incompletely carbonized, the
mixture of sulphur and carbon is boiled with a solution of
protosulphide of potassium, which dissolves the sulphur,
leaving the carbon which must be well washed and dried.
The sulphide of potassium should not contain any free
potassa, since this might dissolve an imperfectly carbonized
charcoal.-Bisulphide of carbon may also be employed for
the extraction of the sulphur.




HYDROCYANIC ACID.               209
120. HYDROCYANIC ACID.
In order to determine the strength of a solution of pure
hydrocyanic acid, a weighed quantity of it is treated with
solution of nitrate of silver, which is added gradually, and
with frequent agitation, until no farther precipitation takes
place, and the odour of hydrocyanic acid has entirely
disappeared.
The precipitated cyanide of silver is collected upon a
filter (previously dried at 120~ and weighed), washed, dried
at 120~, and its weight determined.
For the estimation of the amount of hydrocyanic acid in
the aqua amygdalarum  amararum  and aqua laurocerasi,
they must first be mixed with ammonia, then with nitrate
of silver, and lastly with nitric acid.
If hydrochloric acid be contained in the solution
together with hydrocyanic acid, they are both precipitated
from a weighed portion of the solution by nitrate of silver,
and the precipitate weighed upon a filter dried at 120~.
Another weighed portion of the solution is mixed with
solution of borax and evaporated to perfect dryness. In
this way, all the hydrocyanic acid is volatilized, and the
hydrochlioric acid converted into chloride of sodium. The
dry residue is dissolved in water, the solution acidulated
with nitric acid, and the chlorine precipitated by nitrate of
silver.
Another method, which may be executed with great
rapidity, and suffices for the determination of the hydrocyanic. acid in any solution, whether bitter almond-water or
laurel-water, &c., or for ascertaining the quantity of cyanogen
in crude cyanide of potassium, depends upon the circumstance
that 1 equiv. of cyanide of potassium forms, with 1 equiv.
P




210         FERROCYANIDE OF POTASSIUM.
of cyanide of silver, a soluble compound which is not decomposed by an excess of alkali, but from which nitrate
of silver precipitates the cyanide, or if a little solution of
chloride of sodium be previously added, the chloride of
silver.  The weighed solution, containing  hydrocyanic
acid is mixed with solution of potassa till it has a strongly
alkaline reaction, and a standard solution of silver is then
added till a permanent precipitate begins to appear.
1 equiv. of silver employed in the standard solution corresponds exactly to 2 equivs. of hydrocyanic acid.
Ten grms. of pure silver are dissolved in nitric acid, the
solution evaporated to perfect dryness, and diluted with so
much water, that the whole solution may occupy 1000 cub.
cents.  100 cub. cents. of this solution, which contain
therefore 1 grmin. of silver, represent 0'5 grm. of anhydrous
hydrocyanic acid, or 0'481 cyanogen, or 1'206 of cyanide
of potassium.
121. FERROCYANIDE OF POTASSIUM.
2 K Cy+ Fe Cy+ 3 HO=K  Cfy+ 3 HO.
The water is determined by heating the finely-powdered
salt for some time to about 200~.
The cyanogen can be directly determined only by an
organic analysis, i. e., by a combustion.
For the determination of the amount of iron, the salt is
intimately mixed with 1} parts of nitre, and as much
carbonate of soda, and the mixture gradually heated to
redness in a platinum crucible. On dissolving the fused
mass in water, the iron remains behind in the form of
sesquioxide, which is washed, ignited, and weighed.




EXAMINATION FOR ARSENIC.           211
Since it is liable to contain a small amount of alkali, it
should be dissolved in hydrochloric acid, reprecipitated by
ammonia, washed and ignited.
In order to determine the potassium and iron, the salt is
dissolved in water, and the solution precipitated by acetate
of lead. The precipitate of ferrocyanide of lead is filtered
off and washed.
From the solution, which contains all the potassium as
acetate of potassa, the excess of lead is precipitated by
sulphuretted hydrogen or sulphide of ammonium, the
filtered solution evaporated, the residue ignited, the carbonate of potassa converted, by hydrochloric  acid, into
chloride of potassium, and weighed in that form, after
gentle ignition. The ferrocyanide of lead is decomposed
by digestion with sulphide of ammonium, the solution of
ferrocyanide of ammonium filtered off, evaporated, and the
residual mass ignited, with access of air, until only pure
sesquioxide of iron is left.
Ferrocyanide of potassium may probably also be decomposed by heating with bisulphate of ammonia. The residue
after ignition would then consist of a mixture of sesquioxide
of iron and sulphate of potassa, from which the latter
might be extracted with water. Or, to ensure an accurate
result, the ignited residue might be dissolved in hydrochloric acid, the sesquioxide of iron precipitated by
ammonia, the solution evaporated, and the residual sulphate of potassa ignited and weighed.
122. EXAMINATION FOR ARSENIC IN CASES OF
POISONING.
When poisoning by arsenic is suspected, the poison
must be sought in the contents of the stomach and inP 2




212           EXAMINATION FOR ARSENIC
testines, in the substance of these organs even, and in
other entire organs, as the liver, spleen, and lungs; an
examination must also be made of the vomited matters,
and of the surrounding objects, upon which these may
have fallen; the urine and freces should also be tested for
arsenic. The nature of the case will decide in which
particular direction the arsenic is to be looked for. It may
also sometimes be necessary to examine the remaining
portions of suspected food, or the vessels in which the
food has been contained, or even the vessel or paper which
may have been used to contain the arsenic.  When the
body has been long interred, and is far advanced in putrefaction, and the wood of the coffin has rotted away, it
becomes necessary to test the surrounding earth for arsenic
which may have been derived from the body.
The chemical investigation must be preceded by a very
careful examination of the contents of the stomach and
intestines, or of the vomited matters. The substances to
be examined are spread out in new and clean porcelain
dishes, turned over with perfectly clean glass rods or
spatulas, and examined with the help of a lens.  The
analyst should seek especially for small white hard
particles or grains of undissolved arsenious acid, which
may be carefully picked out with a pair of pincers. These
must be looked for especially in the folds of the mucous
coat of the stomach and intestines. By stirring up the
contents with.distilled water, or better, with spirit, and
pouring off the lighter organic matters, it is often possible
to separate a considerable quantity of the heavy arsenicpowder.
In a judicial investigation of this description, the aim
of all chemical operations is to obtain the arsenic in its
elementary solid state, as the so-called metallic arsenic.




IN CASES OF POISONING.             213
In this form alone it is possessed of such highly characteristic properties as to render it impossible to confound it
with any other substance, and to allow it to be distinctly
recognized even when in almost imponderable quantities.
Moreover, all evidence of its presence is insufficient, unless
it can be laid before the tribunal in this form; and all
other forms and states of combination must be considered
as affording inconclusive testimony as to the existence
of arsenic in the substance under examination. This preparation or isolation of arsenic in its metallic state, even in
the smallest, almost imponderable quantities, is very simple
and easy. Great difficulties, however, present themselves,
when it is necessary to extract these traces of arsenic,
which are diffused through a whole body, from the great
mass of organic matter, and to convert them into some
form of combination, from which the arsenic can be
extracted in the metallic state.
It is most convenient, in considering the process employed for the chemical examination, to regard thrAee
different cases as possible:
I. The arsenious acid is found in the solid state in the
contents of the stomach and intestines, or in the vomited
matters.
II. The poison is intimately and invisibly mixed with,
or dissolved in, the contents, &c., and can therefore no
longer be found, or separated by mechanical means, in the
solid state.
III. The stomach and intestines are empty, or no arsenic
can be detected in them, since it has already been absorbed
into the mass of the blood, or into the substance of the
different organs.
I. The arsenic is still to be found in the solid state,
and may be picked out or separated by levigation from




214            EXAMINATION FOR ARSENIC
the contents of the stomach, &c.  This case is the easiest
of the three since it is only to be proved that the substance
found is really arsenic.  This may be known by the grains
or particles exhibiting the following characters, after
having been properly freed from organic matter:
1. The particles are generally milk-white, more rarely
clear and semi-transparent, hard, and brittle.
2. A particle of arsenious acid, however small, when
introduced into a small tube closed at one end, and heated
in the edge of the spirit-flame, volatilizes and recondenses
farther up the tube, in the form of a white sublimate
which may be seen, especially when examined with a lens,
by sun-light, to consist of very lustrous octohedral crystals.
3. A small fragment placed upon red-hot charcoal, is
volatilized, emitting a powerful odour of garlic (on red-hot
glass or porcelain it volatilizes without garlic odour, because
it is not reduced to the state of metal).
4. A particle of the substance is placed in the end of a
very narrow tube, and above it several splinters of freshlyignited charcoal so that they may occupy about 2 inch of
the tube. This part of the tube is now held horizontally,
in the flame of the spirit-lamp, in such a manner that
the spot where the arsenious acid is placed may remain
without the flame.  When the charcoal is heated to redness, that portion of the' tube is also brought into the
flame, when the volatilized arsenious acid, passing over
the red-hot charcoal, is reduced, and the metallic arsenic
deposited beyond the charcoal, in the form of a dark,
lustrous, metallic ring.  By a gentle heat, this metallic
incrustation may be carried still farther up the tube.
If the incrustation be chased hither and thither in the
tube, it is oxidized, or at least partly, and converted into
small shining, colourless, volatile crystals of arsenious




IN CASES OF POISONING.              21 5
acid. If the tube be cut off, just before the part which
contains the metallic ring, and the latter then gently
heated, the characteristic garlic odour of arsenic may
be perceived on approaching the nose to the orifice of the
tube.
5. This reduction of arsenic to the metallic state may
be effected with greater ease and certainty by dissolving a
small quantity of the substance in water containing hydrochloric acid, and testing the solution in Marsh's
apparatus, in the manner to be presently described more
particularly.
6. A particle of the arsenious acid is heated in a small
glass tube, closed at one end, with a piece of dry acetate
of potassa about as large as a pin's head, when the
indescribably offensive and characteristic odour of kakodyl
should be evolved.
7. One or more fragments are finely powdered, under
distilled water, the powder rinsed into a small beakerglass with 20 or 30 drops of water, and the mixture heated
nearly to ebullition until the powder is dissolved.   A
part of this solution is mixed, in a small test-tube, with
several drops of solution of nitrate of silver, and afterwards with very dilute ammonia, added drop by drop.
In this way, if the substance were arsenious acid, a considerable bright yellow precipitate of arsenite of silver
will be produced.-Another portion of the liquid, mixed
with several drops of a clear solution of ammonio-sulphate
of copper, gives a fine yellowish-green precipitate of
arsenite of copper. A third quantity of the solution,
mixed with a few drops of hydrochloric acid, and afterwards with several times its volume of sulphurettedhydrogen-water, gives a bright yellow precipitate of




216           EXAMINATION FOR ARSENIC
tersulphide of arsenic, which redissolves perfectly on
adding ammonia.
Of all these reactions, the reduction to the metallic
state in Nos. 4 and 5 is the most necessary, because
it is most characteristic and conclusive. The others are
to be viewed rather in the light of superfluous confirmations, and  are only employed when  a considerable
quantity of substance is at the analyst's disposal.
II. Arsenic can no longer be perceived by the eye, or
mechanically separated, in the solid state, but is contained
in a state of solution, or of intimate mixture, in the
contents of the stomach, &c. In this case, which is
more difficult and of more frequent occurrence than the
preceding, the problem consists in dissolving and destroying, by appropriate reagents, the whole mass of the
organic matter composing the contents, the vomited
matters, the food, and even the stomach and intestines
themselves. This is always necessary before the arsenic
can be detected with certainty.
It is indispensably necessary that this operation should
be preceded by a most careful examination of the reagents
to be employed, in order to ascertain whether they contain,
as is not unfrequently the case, a small quantity of arsenic.
This is equally requisite whether the reagents have been
purchased or have been prepared by the analyst himself.
The distilled sulphuric acid, the hydrochloric acid, and
the zinc must especially be examined.  This is most
conveniently effected in Marsh' s apparatus, which will be
presently described, and which is invaluable as allowing
the reagents, which are employed in it, to be so readily and
surely tested. Without such previous proof of the absence
of arsenic in the reagents, upon which the chemist must




IN CASES OF POISONIN G.            217
lay great stress in his depositions, the detection of arsenic
in investigations of this description cannot be brought
forward in evidence, since it might have been derived
from the reagents employed. It should farther be observed and stated in evidence, that the investigation was
conducted with new utensils and vessels which had not
been used before; and it is advisable, moreover, to ensure
perfect satisfaction, that it should not be carried out in an
ordinary chemical laboratory, or, at all events, that the
laboratory should be well cleared before the judicial inquiry
is entered upon.
If arsenic should be found in an examination conducted
with all these precautions, it is still necessary to reflect
that it might occur in the body quite accidentally; especially after the administration of certain medicinal
remedies, such as the antimonial compounds, preparations
of phosphorous, phosphoric, sulphuric, and hydrochloric
acids, which may contain arsenic from carelessness in
their preparation. Even the hydrated sesquioxide of iron,
administered as an antidote in a suspected case of poisoning, might have contained arsenic, unless prepared with
great care. Or the arsenic may have been administered
as a remedy (especially as a secret medicine). When bodies
have been exhumed, it becomes necessary to test the
earth with which the coffin has been in contact, since
it sometimes happens that soils, especially such as are
ferruginous, contain appreciable quantities of arsenic,
which might have entered into the body.
Various methods are employed for the modification or
destruction of the organic matters, with a view to the
extraction of the arsenic.
1. When the substance is in the form of a paste, as in
the contents of the stomach and in the fueces, chlorine



218           EXAMINATION FOR ARSENIC
gas is passed to saturation. The chlorine is prepared
by means of sulphuric acid and manganese, which have
been previously tested, and is washed by passing through
a small but high column of water. In order to assist
the action, the mass may, at the same time, be gently
heated. Lastly, when it is completely saturated with gas,
coagulated, and bleached, the mixture is heated nearly
to ebullition to expel the excess of chlorine, and the
solution, which must contain the arsenic, is filtered through
paper free from smalt.
2. The stomach and intestines, with their contents, are
cut into fine shreds, placed in a porcelain dish, and the
whole mass uniformly mixed. About i is then set aside
in a clean covered glass, in case any accident should
happen to the remainder. The mass is then treated with
a moderately concentrated solution of potassa, and heat
applied until it is entirely or almost entirely dissolved.
Only a small quantity of potassa is necessary for this
purpose, and the potassa should therefore be gradually
added to the mixture, so as to avoid an excess, which
would interfere with the subsequent operations.  The
solution is afterwards slightly acidified with dilute sulphuric acid, and chlorine-gas is passed, to saturation,
into the mass thus coagulated, as in 1.
3. The organic matter cut into shreds, is treated with
about as much pure concentrated hydrochloric acid as
is equal to the weight of the dry substances contained
in the mass; enough water is then added to form  a thin
paste. The dish is heated on a water-bath, the contents
stirred every five minutes, and about 30 grs. of chlorate of
potassa (free from lead) added to the hot liquid until
it has become clear yellow, homogeneous, and limpid.
After being heated for some time longer, the solution




IN CASES OF POISONING.               219
is strained through a moistened filter of white paper, free
from smalt, the residue washed upon the filter with hot
water till the washings are no longer acid, the whole liquid
poured together into a porcelain dish, and evaporated to
about 1 pound upon the water-bath.
The solution obtained by one of these methods is poured
into a cylindrical glass or into a flask, and a slow stream
of sulphuretted hydrogen gas passed into it to complete
saturation. All the arsenic is thus precipitated as sulphide. Its precipitation is much promoted if the liquid be
heated for about half an hour to 500 or 60~, while the gas
is passing, and allowed to cool before the stream of gas
is discontinued.  When saturated, the liquid is allowed to
remain for twenty-four hours in a closed vessel. The precipitate which is then deposited has generally, even if
much arsenic be present, a dirty, undecided, greyish-brown
colour.*  The greater portion of the solution is poured off,
and the precipitate thrown upon the smallest possible filter
of Swedish paper, free from smalt, upon which it is well
washed. The filtrate, before being thrown away, should,
for greater certainty, again be saturated with sulphuretted
hydrogen gas and set aside for some time in a closed vessel.
This precipitate always contains, in addition to sulphide
of arsenic, certain sulphuretted organic matters which are
precipitated with it, and must be completely destroyed;
this is best effected in the following manner:
The filter containing the precipitate is placed in a somewhat capacious crucible of genuine porcelain, and digested
with concentrated nitric acid until the whole is converted
into a homogeneous mass. The free nitric acid, of which
* If lead, copper, mercury, or antimony were present, the precipitate would also contain the sulphides of these metals, for which
it would have to be particularly examined.




220           EXAMINATION FOR ARSENIC
more may be added if necessary, is neutralized with pure
carbonate of soda, and the solution carefully evaporated to
dryness. It is important that the mass should contain a
sufficient quantity of nitrate of soda, which is easily ensured. It is gradually heated over a large spirit-lamp, or
gas-burner, until the salt fuses; it blackens at first, but
afterwards fuses, Iquietly and without deflagration, to a clear
colourless liquid. The whole of the organic matter is now
burnt, and the arsenic converted into arsenate of soda.
Pure concentrated sulphuric acid is then gradually
dropped upon the cooled saline mass in the crucible, and
a gentle heat applied, until, after addition of an excess of
acid, the nitric and nitrous acids are completely expelled,
and the mass is converted into bisulphate of soda.  If
nitric acid containing hydrochloric acid had been originally employed for the oxidation of the sulphuretted hydrogen precipitate, a loss of arsenic might now result, from
its volatilization as chloride of arsenic. The purity, in
this respect, of the nitric acid and carbonate of soda, must
therefore have been previously ascertained.
The acid saline mass is now dissolved, in the crucible
itself, with the smallest quantity of hot water, and the
solution introduced into Marsh's apparatus.
4. The organic matter is introduced, together with the
whole of the liquid, into a capacious tubulated retort, and
about an equal weight of rock-salt, or of fused common
salt, in small fragments, added. The retort is connected
with a tubulated receiver, furnished with a delivery-tube
which dips into water. A quantity of (tested) sulphuric
acid, sufficient to decompose the whole of the chloride of
sodium, is then poured upon the mass through a funnel
tube passed into the tubulure of the retort. When the intumescence and evolution of hydrochloric acid have ceased,




TN CASES OF POISONING.             221
the contents of the retort are heated to boiling, the receiver
being kept thoroughly cool. All the arsenic is thus distilled off as chloride, especially towards the last, in proportion as the contents of the retort become more concentrated, on which account the distillation should be carried
pretty far. The arsenic is converted into chloride, even
when it exists in the mass, in the form of sulphide. The
distillate may be at once introduced into Marsh's apparatus.
It is safer, since some organic matter might possibly have
passed over, to precipitate the arsenic from the solution by
sulphuretted hydrogen, and to treat the precipitate as
directed above. In the same way the small quantity of
arsenic contained in the water in which the hvdrochloric
acid was condensed, may be precipitated.
Marsh's apparatus has the following simple construction: a is a
two -necked
bottle capable of holding 2, or at most
1 pint.  Both necks are fitted with new
perforated corks, which must be perfectly
tight.  Through one of these, the funneltube b is passed air-tight, and through
the other, the bent tube c, which is expanded at c into a bulb about an inch in
diameter. This bulb serves to collect the
particles of liquid which are thrown up from the contents
of the bottle, and which drop down again into the latter,
from the obliquely cut end of the tube. The other end of
this tube is connected, by means of a cork, with the tube d,
about 6 inches long, which is filled with fused pure chloride of calcium, free from powder, destined to retain the
moisture. In the opposite end of the tube d, is fixed,
air-tight, another tube e, made of glass free from lead,




222           EXAMINATION FOR ARSENIC
12 inches long, and at most T-  inch in internal diameter.
It should be made of rather thick glass, and somewhat
drawn out at the end.  It must be observed that the
funnel-tube d is indispensably necessary. If a two-necked
bottle cannot be procured, one with a single neck must
be provided with a cork bored with two holes.
Several ounces of granulated zinc are introduced into
the bottle, which is then half-filled with distilled water;
when the apparatus is all arranged, distilled concentrated
sulphuric acid is added in small portions by the funnel
tube b, very gradually, so that the mixture may not become
too hot, lest sulphuretted hydrogen should be formed.
The evolution of hydrogen is allowed to proceed until it is
judged that all atmospheric air is expelled, and that the
apparatus is perfectly filled with hydrogen.
The narrow delivery-tube is then heated to redness at
e, for at least half an hour, by a spirit-lamp with a double
draught, or a powerful gas-burner, the evolution of hydrogen being constantly maintained by adding acid from
time to time. In this way, the acid and zinc are tested for
any trace of arsenic which might be present. If they are
pure, no incrustation will be deposited at the ignited spot, e.
If arsenic be present, a metallic mirror is obtained at this
portion of the tube, and the acid and zinc cannot be used;
even the apparatus must then be carefully cleaned, or,
better, replaced by a new one.  In the same manner any
arsenic might be detected in the hydrochloric acid, the
chlorate of potassa (after having been completely converted
by fusion into chloride of potassium), the nitre, and the
hydrate of potassa (for the third case), which must first be
converted into sulphate by adding sulphuric acid. The
quantities employed for testing should not be too small;
at least an ounce of each reagent should be taken.




IN CASES OF POISONING.           223
When the reagents have been tested in this manner, and
shown to be absolutely free from arsenic, the examination
of the substance may be proceeded with. The solution to
be tested, containing any arsenic which may have existed
in the body, is poured through the funnel tube b into the
apparatus filled with Itydroyen, and from which hydrogen
is being evolved, the tube e being already heated to redness
at the same spot. In order that none of the liquid may
remain in the tube b, the latter is rinsed with about the
same quantity of pure water, care being taken that no air
is poured in with it.
If arsenic be present, there will soon appear, in the
portion of the tube e, beyond the heated spot, a dark stain
which is at first brownish, and afterwards becomes lustrous
and gradually increases until, when large quantities of
arsenic are present, it forms an opaque metallic mirror.
At the same time, the gas issuing from the tube e may
be kindled, and a dish of white genuine porcelain held
in the flame, which should not be too feeble; lustrous
black or brownish spots of metallic arsenic will then be
deposited, and a great many may sometimes be obtained.
When the heated portion of the tube is not very long,
more or less arsenetted hydrogen escapes decomposition
and furnishes the above-mentioned spots. No imitation of
porcelain (stone-ware or delf) should be employed for this
purpose, since the glaze of these materials very often
contains lead, the reduction of which might produce dark
spots even though no arsenic were present. If a large
quantity of arsenic be contained in the mixture, so that
many thick arsenic-spots can be obtained, they may be
easily recognized by means of the characteristic reactions
given above, after they have been dissolved in a few drops
of nitric acid, and the greater excess of acid has been




224           EXAMINATION FOR ARSENIC
expelled by a very gentle heat. If only traces of arsenic
be present, the spots are so feeble that their nature may
remain uncertain. The only indication, which is perfectly
conclusive is the production, in the red-hot tube, of a
metallic mirror, which must volatilize when gently heatebd,
and re-condense upon a cool part of the tube, at the
same time imparting to the evolved gas the peculiar garlic
odour.
WVThen the arsenical mirror no longer increases, and the
flame ceases to deposit the spots, the operation is discontinued. It is then very convenient to draw the tube e
gently out, while it is still red-hot and soft, and to close it,
when the metallic mirror is obtained in a tube, which
may be sealed also at the other end, and laid before the
authorities.
If the analyst have reason to believe that a large quantity
of arsenic is present, it is well not to employ the whole
quantity of liquid at once, but to divide it into several
portions, and to make use of a much longer tube e, so
as to obtain the arsenic-mirror in several places. The tube
is then cut with a file into as many pieces as there are
mirrors of arsenic. That which contains the most characteristic mirror is sealed at both ends and produced in
court; the remaining mirrors are subjected to the tests
given at p. 214, among which the ready volatility and
alliaceous odour are the most characteristic and decisive.
If, after heating the tube for one hour, no stain or
mirror make its appearance, and no traces of spots have
been obtained from the flame, the absence of arsenic may
be inferred, provided that proper care have been taken
in the former part of the examination, so that the arsenic
cannot have been lost through negligence or awkwardness.
It is very important, in connection with this test




IN CASES OF POISONING.             2 2 5
(Marsh's) to remember that antimony also, whether as
teroxide, or as antimonic acid, and especially when in
solution in the form of a salt, yields, under the same
conditions as arsenic, a gaseous antimonetted hydrogen,
which deposits upon the heated tube, and upon porcelain,
a mirror and spots very similar to those obtained with
arsenic. This fact assumes so much greater importance,
when it is remembered that preparations of antimony,
especially tartar emetic, are administered as internal remedies, so that, in such cases, metallic mirrors are obtained,
similar to those of arsenic, but consisting, not of that
metal, but of antimony.  On the other hand, it must not
be forgotten that commercial arsenic, as it is employed for
poisoning, frequently contains antimony.
If the question be merely whether a metallic mirror
consist of arsenic or antimony, it may be readily decided.
The arsenic may be easily recognized by the reactions
mentioned above, while the antimony-mirror presents very
different characters.  The antimony-mirror has a lighter
colour, and is more lustrous than that of arsenic, the antimony spots are darker and have often a tinge of blue.
Antimony is not nearly so easily volatilized as arsenic, and
although both mirrors may be chased from one part of the
tube to another, there is a great difference in the heat necessary in the two cases. A very striking difference between
the two deposits is seen in their behaviour when heated;
the mirror of antimony, before volatilizing, fuses into small
lustrous globules, which may, in all cases, be seen with
the aid of a lens; the arsenic, however, exhibits no sign
of fusion.  The most characteristic distinction is the
production of the garlic odour when the arsenic is volatilized, while the antimony passes off in vapour without
any perceptible odour. If that portion of the tube which




226           EXAMINATION FOR ARSENIC
contains the mirror be heated while the hydrogen is
still passing, the gas issuing from the orifice of the tube
will have a distinct garlic odour if the deposit consist
of arsenic, but will be inodorous if antimony only be
present.  The following reactions may also be applied
to distinguish arsenic and antimony.
The arsenical spots deposited upon porcelain disappear
when moistened with a concentrated alkaline solution of
hypochlorite of soda; those of antimony, however, are
not affected by this reagent.  If the spots consist of
arsenic and antimony, the latter not exceeding 5 per
cent, the spots will also be entirely dissolved.  Spots
or mirrors of arsenic disappear when moistened with a
drop of nitric acid, and gently warmed, forming a clear
solution. If a drop of nitrate of silver be added to the
solution, and a glass rod moistened with caustic ammonia
be held over the liquid, but not allowed to touch it, the
mixture assumes a yellow colour, from the formation of
a precipitate of arsenite of silver.  Sometimes, if too
strong an acid or too great a heat have been applied, the
precipitate consists of reddish-brown arsenate of silver.
This characteristic colour is always produced by nitrate
of silver, when the arsenic spots are dissolved by placing
the capsule over a vessel containing solution of chloride
of lime and sulphuric acid.
It is true that spots and mirrors of antimony also
disappear when treated with nitric acid, the antimony,
however, is not dissolved, but merely converted into white
oxide, which gives no reaction with solution of nitrate
of silver. The antimony dissolves in a mixture of one
drop of nitric acid and one drop of hydrochloric acid; if
the greater excess of acid be carefully evaporated, and
sulphuretted-hydrogen-water be dropt upon the residue,




IN CASES OF POISONING.           227
a fiery-red precipitate of sulphide of antimony is produced.
If the spot had consisted of arsenic, a lemon-yellow precipitate would have been obtained.
If the spots be moistened with sulphide of ammonium,
and dried at a very gentle heat, the arsenic becomes yellow
the antimony orange. The yellow spots of sulphide of
arsenic are not affected by hydrochloric acid, while those of
sulphide of antimony disappear on gently heating.
If sulphuretted hydrogen gas be passed through the
tube containing the metallic mirror, and heat applied, the
metal is converted into a sulphide. If the mirror consist
of antimony, black, or partly orange-red, sulphide of
antimony is produced, while arsenic gives a yellow sulphide. The colour, however, is not the only distinction
between these compounds, another is afforded by their
unequal volatility, sulphide of arsenic being far more
volatile than that of antimony.
Moreover, antimony and arsenic, in the form of sulphides, may be separated by cyanide of potassium, according to the method given in No. 55.
The presence of antimony in the precipitated sulphides
may also be ascertained by oxidizing them as directed at
p. 220. In that case, the fused mass, before treatment
with sulphuric acid, should be dissolved in water, when the
antimony would remain undissolved in the form of antimonate of soda.
III. If no arsenic have been found in the stomach and
intestines, it must be supposed to have been partly carried
away in the vomited matters and faeces, and partly absorbed into the mass of the blood, and into those organs
which are rich in blood. In this case, the same process is
employed as in the preceding, the arsenic being sought,
according to the same method, in the liver, spleen, lungs,
a 2




2 28          EXAMINIATIOmN FOR ARSENIC
heart, and kidneys. If urine were found in the bladder,
or frecal matter in the large intestines, they should be
examined first. The urine must not be introduced at once
into Marsh's apparatus, since the frothing to which it
gives rise would interfere with the progress of the experiment; the urine should therefore be slightly acidified,
with hydrochloric acid, sulphuretted hydrogen passed
through it, and the subsequent process conducted as in
the second case.
Investigations of this description are in the highest degree
laborious, troublesome, and disgusting, when the body to
be examined has been interred for months or years, aind
has passed into a state of putrefaction.  In such a case, it
is frequently no longer possible to distinguish or separate
individual organs, and the analyst is then necessitated to
examine the whole mass of putrified organs, or the whole
of the soft parts which dry up under some particular local
circumstances, and even the bones.  When this is the case,
the body should not be laid in a bath of chlorine-water or
solution of chloride of lime, in order to destroy the offensive
odour, since arsenic may thereby be extracted and lost.
If chlorine-gas be employed to disinfect the body, it must
be evolved by means of distilled sulphuric acid free from
arsenic.  All the soft parts, especially those which may
have formed parts of the abdominal viscera, are carefully
separated from the bones, and treated as in the second
case.
The following is another convenient process to be
especially preferred for the treatment of bodies which have
been exhumed entire after some months interment.
The entire soft parts are treated in a large dish of
genuine porcelain, with moderately strong nitric acid,
which has been previously tested for arsenic; the dish is




IN CASES OF POISONING.             229
then heated upon a sand-bath, and its contents well stirred,
until the organic matters are so far destroyed and dissolved
as to form a homogeneous pasty mixture. This is now
neutralized with a solution of pure hydrate or carbonate of
potassa, and about as much finely-powdered nitre (previously tested) added, as is equal in weight to the soft
parts. The whole is now evaporated to dryness, with constant stirring, and the dry mass introduced by degrees, in
small portions, into a new clean Hessian crucible heated
to dull redness. In this manner, the whole of the organic
matter is burnt, and the arsenic, if present, converted into
arsenate of potassa. In this process, it is important, and
not very easy, to add the proper quantity of nitre. If
too little nitre be employed, part of the organic matter
may remain unburnt, and arsenic may be volatilized from
the carbonaceous mass; on the other hand, too much
nitre would interfere with the subsequent treatment of
the mass. It is better to make a preliminary test with
a small portion of the mixture, by introducing it into
a small red-hot crucible, and observing whether the mass
is perfectly white after defiagration. If it be black and
carbonaceous, more nitre must be added.
The mass, which now consists essentially of carbonate,
nitrate, and nitrite of potassa, and may also contain arsenate of potassa, is dissolved in the smallest possible quantity of boiling water, and the solution, without filtering off
from the suspended phosphate of lime and silica, gradually
mixed, in a porcelain dish, with a slight excess of sulphuric acid.  The pasty saline mass thus produced is
carefully heated till all the nitrous and nitric acids are
expelled, a point to which great attention must be paid.
On cooling, the mass is stirred up with a little cold water,
and the solution poured off from the large deposit of sul



230  EXAMINATION FOR ARSENIC IN CASES OF POISONING.
phate of potassa. The latter is washed several times with
cold water, the washings mixed with the first solution, and
the liquid, treated as above, with sulphuretted hydrogen.
The precipitate then only requires to be oxidized with nitric
acid, with the precaution that the acid must be entirely
removed by evaporation before the solution is introduced
into Marsh's apparatus.
It is rarely of importance to the evidence that the
weight of arsenic existing in a body should be determined.
Such an estimation can only be relative, since it is impossible to extract and weigh the whole of the arsenic contained in all the parts of a body. In such a case, a somewhat longer reduction-tube should be employed, into which
is introduced a closely twisted spiral of pure bright copper,
about two inches in length; this spiral is accurately
weighed with the tube. The latter is then heated in two
places, one nearer the evolution-bottle, for the deposition
of a mirror; the other, at some distance, where the strip of
copper is placed, which combines with all the remaining
arsenic, forming steel-grey arsenide of copper.  The increase of weight of the tube indicates the amount of
arsenic, which is calculated as arsenious acid.




EQUIVALENT WEIGHTS OF THE ELEMENTS.
0=100.   H=1.
Aluminum..Al  342'5  27'4
Antimony...    Sb      1612'5    129
Arsenic...As                      937'5      75
Barium...Ba                     856'25    68'5
Beryllium...      Be       176'25    14'1
Bismuth...   Bi    2600        208
Boron..           B        136'25    10'9
Bromine..    Br    1000          80
Cadmium.Cd                          700       56
Calcium.. Ca   250   20
Carbon.C   75   ~ 6
Cerium.                     Ce  587-5  47
Chlorine..   C1                    443 75    35'5
Chromium....              Cr   33375  26'7
Cobalt...o    368'75  29'5
Copper..  u   396'25  31 7
Didymium.                   D        625       50
Erbium...E
%Fluorine.F.                        237'5     19
Gold..     Au    2462'5    197
Hydrogen                    H         12'5      1
Iodine..    I.                  1588'75   ]2,71
Iridium......        Ir     123750    99
Iron.                      Fe  350  28
Lanthanium..    La       587'5      47
Lead..  Pb        1296"25   103'7




232   EQUIVALENT WEIGHTS OF THE ELEMENTS.
O=100.   H=1.
Lithium...            Li        81.25      6'5
Magnesium...      Mg        150        12
Manganese...      Mn        345        27'6
Mercury...   Hg                    1250        100
Molybdenum...        Mo        575        46
Nickel.                      Ni       370        29'6
Niobium..    Nb
Nitrogen.                   N        175        14
Norium... No
Osmium..     Os     1245         99'6
Oxygen.0..                        100         8
Palladium....        Pd       666'25    53-3
Pelopium.... Pe
Phosphorus..     P        387'5      31
Platinum..    Pt                  1233'75    98'7
Potassium..   K        490        39'2
Rhodium.R.  R                        652'5      52'5
Ruthenium.. Ru   652'5  52'5
Selenium..     Se       493'75    39'5
Silicium....                Si   266'25  21'3
Silver..           Ag     1351'25   108'1
Sodium.. Na  287 5  23
Strontium.. Sr   547'5   43 8
Sulphur.                             200        16
Tantalum..     Ta     2300        184
Tellurium....Te                 802'5      64'2
Terbium...   Tb
Thorium...           Th       745        59'6
Tin.Sn  725  58
Titanium..          Ti.      312'5      25
Tungsten....         W      1150         92
Uranium...   U        750        60
Vanadium...                 V    857'5   68'6
Yttrium...                  Y
Zinc..   Zn  407'5  32'6
Zirconium.. Zr   840   67'2




EQUIVALENT WEIGHTS OF COMPOUND BODIES.
O =100.
0= 100. H = 1.
Alum...          { KO, SO3, Al03,1  59325 502
3S.3 + 24Ho 
Alumina..         A1203           642-5   78-8
Ammonia...             NH             212'5  17
----  carbonate of...  2NH40, 3CO2    1475    118
Ammonium...    NH4            225      18
- chloride of.              NH4Cl            668'75  53-5
oxide of...  NH40             325      26
- platinochloride of.       NH4C1, PtCl2      2790    223'2
Antimonious acid..SbO3                  1912-5  153
Arsenate of magnesia-ammonia. 2MgO,NH40,As05 + HO 2375    190
Arsenic acid.         AsO5           1437-5  115
Arsenious acid.                 AsO3           1237-5   99
Barium, chloride of.              BaCl           1300    104
silicofluoride of.         3BaF, 2SiF3       5238'75 419-1
Baryta...             BaO            956-25 76-5
carbonate of.             BaO, CO2         1231-25  98'5
-    chromate of.            BaO, CrO3        1590    127'2
Berylla (glucina)...  Be2O3           476'25  52'2
Biborate of soda.   NaO, 2BO3 -t 10HO   2385    190'8
Binoxalate of potassa... KO, 2C203 + 3HO110    1827'5  146'2
Bismuth, teroxide of...      BiO3          2900    232
Bitartrate of potassa...   KO, HO T         2352'5   188'2
Cadmium, oxide of...    CdO             800      64
Calcium, chloride of..       CaCl            693'75   55'5
Carbonic acid.                  CO2            275      22
Chromate of lead.            PbO, CrO3        2030    162'4
Chromic acid.                 CrO3            633-75  5017
Chromium, sesquioxide of.            Cr203           967-50   77'4
Cobalt, protoxide of.                   CoO            468-75   37-5
Copper, protoxide of...    CuO            496.25   39'7
-— ~  suboxide of.              Cu20O           892-5   71'4
Cyanide of silver...  AgCy           1676-25 134'1
Cyanogen...           C2N = Cy          325   26
Ferrocyanide of potassium.  2KCy, FeCy = K2Cfy  2305    184-4...,,,,   contain-   2KCy, FeCy + 3 HO   26425  211-4
ing water of crystallization.    = K2Cfy + 3HO 10




234      EQUIVALENT WEIGHTS OF COMPOUND  BODIES.
0=100. H=1.
Fluoride of calcium...   CaF            4875    39
Hydrochloric acid...    HC1            55625   36-5
Iodide of palladium...   PdI           2255    180'4
--  of potassium.                KI           2078'75 166-3
Iron, protoxide of...   FeO            450      36
-- sesquioxide of.         Fe2O3           1000     80
Lead, acetate of.             PbO, A + 3HO110  2371'25  189'7
chloride of..       PbC            1740    139-2
-- protoxide of..        PbO           1396'25 11117
-- red oxide of.            PbO, Pb20,,      4288-75 343'1
Lime...             CaO   350  28
-     carbonate of.             CaO, CO2         625      50
Magnesia...             MgO             250  20
Manganese, peroxide of.            MnO2            545      43'6
- protosesquioxide of.         MnO, Mn2O3        1435    114-8
-  protoxide of...       MnO             445      35-6
Mercury, protochloride of..         HgC1          169375  135 5
- protoxide of...   HgO            1350    108
subchloride of..        Hg2C           2943-75 235'5
---   suboxide of.                     Hg2O           2600    208
Molybdenum, binoxide of.             MoO2            775     62
Molybdic acid.                 MoO3            875      70
Nickel, protoxide of.               NiO  470                37'6
Nitrate of baryta.            BaO, NO5         1631'25 130-5
-   lead...            PbO, NO5        2071'25 165'7
potassa....        KO, NO5          1265    101'2
silver...            AgO, NO5        2126-25 170'1
-. soda...            NaO, NO5         1062-5   85
------ strontia..             SrO, NO5        1322'5  105'8
Nitric acid..          NO5             675     54.hydrated.          HO, NO5           787-5   63
Oxalic acid.  C203                    450     36
hydrated.       3110, C203         787'5   63
aPhosphate of magnesia.          2MgO, P05         13875  111
b ____-  soda.            2NaO, P05         16625  133
b            soda with water of
crystallization.. 2NaO, HO, P05 + 24HO110 4475    358
Phosphoric acid..          P05             8875   71
Potassa..                               KO              590  47'2
bichromate of.          KO, 2CrO3        1857'5  148'6
--  carbonate of.             KO, CO2           865'    69-2
------- chlorate of.        KO, C105         1534'75 122'7
chromate of...  KO, CrO3        1223'75  97'9
hydrate of.             KO, HO           702-5   56'2
Potassium, chloride of.            KC1             933.75  74'7
platino-chloride of.     KC1, PtCl2        3055    244'4
Silicic acid.                  SiO3          566-25  45'3
Silicon, terfluoride of.               SiF3           987'75  78-3
Silver, chloride of...         AgCl          1795    143-6




EQUIVALENT WEIGHTS OF COMPOUND BODIES    235
0-100.1H=1.
Silver, oxide of..                  AgO          1451-25 1 6-1
Soda..                                 NaO            387-5  31
Soda, carbonate of                   NaO, CO2          6625   53
--.. containing water
of crystallization...   NaO, CO2+ 10HO    1787-5  143
-   hydrate of..       NaO, HO           500    40
Sodium, chloride of..            NaCl            731-25  58-5
Stannic acid.                      SnO2            925     74
Strontia.                             SrO            647-5  518
Sulphate of ammonia.             NH40, S03 + HO       937'5   75
baryta.. ~           BaO, S03        1456-25 116-5
copper...    CuO, SO: + 5HO110     1558-75 124-7.  lead.                  PbO, SO3         1896-25 151'7
- lime.                    CaO, SO3          850    68
potassa..             KO, S03         1090    87-2
protoxide of iron        FeO, S03 + 7HO     1737'5  139
soda.                      NaO, SO3         887-5  71
-strontia                      SrO, S03        1147-5  91'8
Sulphide of antimony..            SbS3           2212'5  177
arsenic...          AsS3          1537-5  123
-  copper...        CuS            992-5  47'7
lead.                       PbS           1496-25 119'7
mercury..          HgS           1450   116-0
- molybdenum..         MoS2            975'5   78'0
silver.                       AgS           1551-25 124-1
-  — zinc...                  ZnS            607'5   48'6
Sulphuretted hydrogen.             1 HS           212-5  17
Sulphuric acid..  S03                       500    40..-  hydrated..         HO, SO 3         612'5   49
Sulphurous acid....               SO2            400    32
Tin, protoxide of...         SnO            825    66
Titanic acid.                       TiO2           512-5  41
Tungstic acid...                   W03           1450   116
Water..                  HO             112'5  9
2HO            225     18
3HO            337-5  27
4HO            450    36
5HO            562-5  45
61HO           675    54
7HO            787-5  63
8HO            900    72
9HO           1012-5  81
10HO           1125    90
Zinc, oxide of...           ZnO            507'5   40'6




INDE X.
A.                           Bournonite, 60
Brass, 37
Alkalies, 3                                   Bromine, 177
Alkalimetry, 196                              Bronze, 52
Alkaline earths, 17                           Brown iron-ore, 25, 145
Alum, 18
Alumina, 18
and sesquioxide of chromium,                          C.
20
and sesquioxide of iron, 23          Cadmium, 39
--         and phosphoric acid, 21            Calamine, 36
-  and magnesia, 112                 Carbonate of lead, 41
-chrome-alum, 20                     Carbonic acid, 176
Amalgams, 49                                  Cast-iron, 161
Ammonia, 181                                  Celestine, 17
Antimony, 59                                  Cements, 170
Apatite, 124                                  Cerite, 118
Argentan, 76                                  Cerium, oxides of, 119.
Arsenic and antimony, 66                      Chloride of lime, valuation of, 204
Arsenic, poisoning by, 211                             of silver, 2
Arsenious and arsenic acid, 179                  -     of sodium, 1
Ashes, analysis of, 184                       Chlorides of potassium, sodium, and
Augite, 112                                     magnesium, 13
Ash of the refining-hearth, 165               Chlorine, 177
and bromine, 177
Chromate of lead, 149
Chrome-alum, 20
Baryta, 17                                    -      -iron-ore, 147
Berthierite, 62                               Chromic acid, 149
Beryl and berylla, 113                        Chromium, sesquioxide of, 20, 149
Bismuth, 53                                   Clay, 169
and copper, 90                       Cobalt, 82, 84
Bitter-spar, 14                                    - and arsenic, 84
Bog-iron-ore, 30                              -      -glance, 84
Bone-earth, 15                                       -speiss 82
Boracic acid, 177                             Columbite, 134




INDEX.                                237
Common salt,                               Iodine, bromine, and chlorine, 177
Copper, 91, 162                            Iridium, 91
amalgam of, 49                      Iron-ammonia-alum, 19
and antimony, 179                   Iron and antimony, 62
and arsenic,                        Iron assay, 158
and gold, 47                        -          in the wet way, 159.
and iron, 91                        Iron, sesquioxide and protoxide of, 26
and lead, 60                        -     sesquioxide of, and sesquioxide of
-nickel, 78                           chromium, 47
-pyrites, 32
Copperas, blue and green, 37                                L.
Lanthanium, 119.
Lead, 53.
Datolite, 108                              -     and antimony, 59
Didymium, 19                               -- and arsenic, 56
Dolomite, 14.                              -    molybdate of, 141
- phosphate of, 42
--  vanadate of, 146
Epidote, 112                               Lievrite, 105
Epsom-salt, 9                              Lime, 178
- and sesquioxide of iron, 105
F.                         Limestone, 170
Fahl-ore, 71                               Lithia, 179
Feldspar, 108
Ferrocyanide of potassium, 210                             M.
Fluorine, 179
Fluor-spar, 127                            Magnesia, 179
Fluor-spar, 127  and alkalies, 13
carbonate of potassa, and, 8
G..                and lime 14
Galena, 40.        and manganese, 28
Garnet, 112                                         phosphate of ammonia, and,
Glass, 168                                   11
Glauber's-salt and Epsom-salt, 9                    and sesquioxide of iron, 28
Gold, 47                                            sulphate of, 9
Green vitriol, 37                                   sulphate of potassa, and, 7
Guano, 188                                 Magnetic iron-ore, 26
Gun-metal, 52                              Manganese, 162
Gunpowder, 208                             ----   and cobalt, 87
Gypsum, 17                                 ----    and iron, 28
and lime, 28
H.                         --     -   -ore, valuation of, 203
Marl, 170
Heavy-spar, 17                             Marl, 170
Hornblende, 112                                     and copper, 49
Hydrocyalnic acid, 209                     ------- oxide of, with oxide of lead, 51
Mesotype, 103
I.                        Meteoric iron, 88
Idocrase, 112                              Mineral waters, 176
Incrustations from salt-pans, 175          Minium, 51




238                                INDEX.
Molybdenite, 144                            Scheelite, 141
Molybdic acid, 144.                         Schweinfurt green, 55
Selenide of lead, 156
Seleniferous deposit, 154
Selenium, 154
andNickel, 87 arSilicates, 103, 108
and arsenic, 87                      Silicic acid, 177
and cobalt, 164                      Silver, 1, 2, 44, 45, 47
-   and copper, 761-    and antimony, 63
--   and arsenic, 63
and manganese, 87                         and copper 45
Niobic acid, 136                                 and gold, 47
Nitre, analysis of, 206                          and lead, 44
Nitric acid, 181                                 and mercury, 50
- assay, 158
O.                         Slags, 165
Olivine, 106                                Soda and potassa, 178
Orthite, 120                                 -  valuation of, 196
Osmium, 91                                  Soils, 180
Oxalic acid, 194                            Spathic iron-ore, 28
Specular iron-ore, 25
Speiss-cobalt, 82
Sphene, 129
Palladium, 99                               Strontia, 179
Pelopic acid, 136                                    and baryta, 17
Phosphate and oxalate of lime, 194                   and lime, 17
of soda and ammonia, 10                  - sulphate of, 17
Phosphoric acid, 179                        Sulphate of baryta, 17
and arsenic acid, 42                  of copper, 32
and lime, 15, 124                    of lime, 17
- - -— ~- -  and oxide of lead, 42          -     of soda and ammonia, 5
and sesquioxide of iron,              of strontia, 17
24.                                       Sulphide of antimony, 58, 59
Pitch-blende, 151                                    of arsenic, 66, 78
Plant-ashes, 184                                     of copper, 32
Platinum, 91                                         of lead, 40
and iridium, 92                             of zinc, 34
-.-ore, 91                           Sulphur, 163.residues, 95                      Sulphuric acid, 178
Potassa, 178
Pyromorphite, 42                                             T.
Tantalic acid, 135
Tartar-emetic, 58
Red silver-ore, 63                          Tartrate of potassa and soda, 3
Rhodium, 91                                 Tellurium and tellurium-ore (1), 100
Ruthenium, 91                               Thorite and thoria, 124
Rutile, 132.                                Tin, 53.
-   amalgam of, 49
S.                         -    and antimony, 65
Salt-brines, 176                            -    and arsenic, 56




INDEX.                                 239
Tin, antimony and arsenic, 69                                W.
-   bismuth and lead, 53                    White-lead, 41
-   and copper, 52                          Wolfram 138
- and lead, 53
Titanic acid, 129, 130
Titanic iron, 130                                            Y.
Titanite, see Sphene                        Yttria, 123
Topaz, 115
Triphylline, 126                                             Z.
Tungstic acid, 138                          Zinc, 39
and cadmium, 39
U.                           -  and copper, 38
Uranium, sesquioxide of, 151                  -  and iron, 32
and nickel (2), 76
V   -blende, 34
- oxides of iron, manganese, and, 39
Vanadate of lead, 146                       -    sulphates of iron, copper, and, 37
Vanadic acid, 145, 146                      Zinkenite, 61
iron ore, 145                        Zircon and zirconia, 116
ADDEND A.
(1) PURIFICATION OF TELLURIUM.-Tellurium may be readily distilled from a little
porcelain retort, which is placed in an ordinary small wind.furnace, without a current of
hydrogen being necessary.
Crude tellurium, containing lead, may now be had for ~1 at Vienna. See foot-note to
p. 100.
(2) SEPARATION OF NICKEL FROM  Z1NC.-A better method of separating zinc and
nickel consists in mixing the solution, previously much concentrated by evaporation, with
excess of hydrate of potassa, and afterwards with hydrocyanic acid, so that the two oxides
may be entirely dissolved as double cyanides.  From this solution the zilc is entirely
precipitated, as sulphide of zinc, by protosulphide of potassium (not sulphide of ammonium), while the nickel remains in solution.  The filtered liquid is then boiled with
aqua-regia, and the oxide of nickel precipitated by hydrate of potassa.
THE END.




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Inclined Plane.-9, 10, 11. Pulleys.-12. Hunter's Screw. —13 and 14. Toothed
Wheels.-15. Combination of the Mechanical Powers.




WALTON AND MABERLY.                                    7
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De Morgan's Syllabus of a Proposed System of Logic. 8vo. Is.
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ENGLISH COMPOSITION.
Nell's Elements of Rhetoric; a Manual of the Laws of
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DRAWING.
Lineal Drawing Copies for the earliest Instruction.    Com.
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**~ The Vocal Exercises, Moral Songs, and Hymns, with the Music, may also be had,
printed on Cards, price Twopence each Card, or Twenty-five for Three Shillings.




8  WORKS PUBLISHED BY WALTON AND MABERLY.
CHEMISTRY.
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Chemistry  for Schools.   By  Dr. Lardner.    190  Illustrations. Large 12mo. 3s. 6d. cloth.
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Guesses at Truth.   By Two Brothers.   New  Edition.
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