THE ELEMENTS OF BLOWPIPE ANALYSIS

THE

ELEMENTS OF BLOWPIPE

ANALYSIS

BY

FREDERICK HUTTON GETMAN, F.C.S.

INSTRUCTOR IN CHEMISTRY IN THE STAMFORD HIGH SCHOOL

New York
THE MACMILLAN COMPANY
LONDON: MACMILLAN & CO., LTD.
1899

All rights reserved

Copyright, 1899,

By THE MACMILLAN COMPANY.

Norwood Press
J. S. Cushing & Co.—Berwick & Smith
Norwood Mass. U.S.A.

[Pg v]

PREFACE

These few pages are intended to serve a twofold purpose,—to give the
student a general outline of Blowpipe Analysis, and to introduce him to
the methods of Determinative Mineralogy.

Every effort has been made to simplify details so that the book may be
used in both High Schools and Colleges.

Tables for “systematic” examination have been intentionally omitted, for
in the author’s estimation these tend to dull the student’s power of
observation, and to make him place little value upon minute details.

The alphabetic arrangement has been followed for the sake of convenience
when referring to the book.[Pg vi]

The last chapter is not intended to serve as a key to determining the
minerals therein described, but rather it is added to give the student
exercise in Blowpipe Analysis, and at the same time to point out the
methods of Determinative Mineralogy.

Finally, the author would acknowledge his indebtedness to the following
works: “Manual of Qualitative Analysis,” Fresenius; “Qualitative
Chemical Analysis,” Venable; Roscoe and Schorlemmer’s “Treatise on
Chemistry”; Foye’s “Hand-Book of Mineralogy”; Dana’s “Mineralogy”;
Kobell’s “Tafeln zur Bestimmung der Mineralien”; etc.

Frederick Hutton Getman.

Stamford, Conn.,

Feb. 22, 1899.

[Pg vii]

TABLE OF CONTENTS

CHAPTER I
PAGE
Apparatus and Reagents 1-7

CHAPTER II

General Outline of Blowpipe Analysis 8

Definitions 9

Examination on Charcoal Alone 10

Examination on Charcoal with Sodium Carbonate 13

Examination in Tube with Sodium Carbonate and Charcoal 15

Examination on Platinum Wire 16

Examination in Borax Bead 17

Examination with Cobalt Nitrate 20

CHAPTER III

General Reactions for the Detection of the Metallic
Elements in Simple Compounds 22

Aluminum 23

Antimony 24

Arsenic 25

Bismuth 25

Cadmium 26

Chromium 26

[Pg viii]Cobalt 27

Copper 28

Iron 28

Lead 29

Manganese 30

Mercury 30

Nickel 31

Silver 32

Tin 32

Zinc 33

The Alkali Metals 34

Ammonium 34

Potassium 35

Sodium 35

Lithium 36

The Alkaline Earths 36

Barium 36

Calcium 37

Strontium 37

The Acid Elements 37

Borates 37

Bromides 38

Chlorides 38

Fluorides 38

Iodides 39

Nitrates 39

Phosphates 40

Silicates 40

[Pg ix]Sulphides 41

CHAPTER IV

Behavior of Some of the Principal Ores before the Blowpipe 43

Ores of Antimony 46

Ores of Arsenic 47

Ores of Bismuth 48

Ores of Chromium 49

Ores of Cobalt 50

Ores of Copper 52

Ores of Iron 57

Ores of Lead 60

Ores of Manganese 63

Ores of Mercury 64

Ores of Nickel 65

Ores of Silver 66

Ores of Tin 69

Ores of Zinc 70

COMPARATIVE TABLES

I. Colors of Coatings on Charcoal 73

II. Flame Colorations 73

III. Colors of Borax Beads in oxidizing Flame 74

IV. Colors of Borax Beads in reducing Flame 75

V. Colors of Microcosmic Salt Beads in oxidizing Flame 76

VI. Colors of Microcosmic Salt Beads in reducing Flame 77

[Pg x]

[Pg 1]

BLOWPIPE ANALYSIS

CHAPTER I

The blowpipe was first applied to mineral analysis in 1733 by Anton
Swab, and its applications have since been improved and extended by
various chemists, among whom may be mentioned Bergmann, Cronstedt, Gahn,
Berzelius, and Plattner.

Blowpipe.—The common blowpipe of the jeweller is not particularly well
suited to the operations of blowpipe analysis, since the flame has often
to be kept playing upon the assay for some time, and the condensed
moisture of the breath would seriously interfere with the passage of
the[Pg 2] air through the jet. One of the best and least expensive forms of
blowpipe is shown in Fig. 1. This consists, as is seen from the
illustration, of a conical-shaped tube of tin closed at the wide end and
formed into a mouthpiece at the small end; soldered into the tube at the
large end, and at right angles to its axis, is a small brass tube which
terminates in a conical tip pierced with a very fine hole. With this
pipe it is possible to perform all of the operations of mineral
analysis.

Some little practice is necessary to keep the flame steady and to take
the breath at the same time.

No rule can well be given to the beginner, but his experience becomes
his best guide.

Bunsen Flame.—Any kind of flame can be used for the blowpipe, provided
it be[Pg 3] not too small; but since almost every laboratory to-day is
furnished with gas and the Bunsen burner (Fig. 2), it will only be
necessary to describe the use of the flame from this source. Upon
examining the Bunsen flame with care, it will be seen that the flame
consists of three distinct parts.

A dark inner cone which consists of gas not yet raised to the ignition
point. Beyond this there is a luminous cone, where combustion is
incomplete owing to lack of oxygen, and outside of this we find the
non-luminous cone where the gas is completely burned.

This outer envelope is the hottest portion of the flame, and is known as
the “oxidizing” flame because there is an excess of oxygen which is
imparted to substances placed therein.

The luminous cone is known as the “reducing” flame, for in it metallic
oxides[Pg 4] are reduced, the oxygen being taken up by the small incandescent
particles of carbon.

If the air-holes at the base of the Bunsen burner be opened, the two
inner cones become elongated, and the flame appears almost colorless.

The blowpipe enables us to get an oxidizing and a reducing flame of
better form and greater power. To do this we cut off the air supply at
the base of the burner and turn off the gas until the flame is about 1
cm. high; then upon introducing the blowpipe, and blowing a strong
continuous jet of air across the Bunsen flame, we produce an oxidizing
flame about 4-5 cm. in length. If the tip of the blowpipe be held
outside of the Bunsen flame, and the pressure of the stream of air be
diminished, we obtain a reducing flame.[Pg 5]

Supports.—For supports, charcoal, platinum, and glass are chiefly used.
The charcoal should be made from some light wood, such as alder. It
should be well burnt, and should not scintillate or smoke.

The platinum supports are generally in the form of wire and foil.
Platinum-tipped forceps are frequently employed in blowpipe analysis.

Glass is used in the form of tubing.

Hard glass tubing, 3 mm. bore, is drawn off into ignition tubes 7-8 cm.
in length. Several dozen of these tubes should be made before commencing
the tests of the next chapter.

Apparatus.—A small agate mortar, 4-5 cm. in diameter, should be
provided in which to grind the samples to be examined.

The pestle, which should also be of agate,[Pg 6] must be adapted to the
mortar in shape and size.

Two pairs of forceps will also be needed.

One pair should be of steel, and the other pair of brass, with fine
points.

Of other apparatus, the most necessary is:—

Chemicals.—A list of the principal chemicals is here given:—

Any other special reagents which may be needed will be mentioned as
required.

[Pg 8]

CHAPTER II

GENERAL OUTLINE OF BLOWPIPE ANALYSIS

In order to examine a substance before the blowpipe to determine the
presence or absence of certain elements, it becomes necessary to arrange
a systematic method. As with all branches of chemical work, one’s
success is largely dependent upon neatness of manipulation and
carefulness of observation.

The following order of observation is essentially that given by
Berzelius:—

After having examined a body in these six different ways, we shall be
able to say what are its principal constituents.

Before describing the method of carrying out these six different
operations, it will be necessary to give a few definitions of terms
which we shall have frequent occasion to employ.

Definitions.—Ignition is the heating of a substance to a high
temperature.

Fusion is the heating of a substance to the melting-point.

Intumescence is the swelling of the substance upon heating.[Pg 10]

Decrepitation is the crackling of a substance due to the sudden
expansion of combined water upon heating.

Deflagration is the burning of a substance with explosive violence,
generally due to excess of oxygen.

Incandescence is the white light emitted by a substance that is
infusible when subjected to a high temperature.

Examination on Charcoal alone.—The size of the assay should be about
that of a mustard seed. This is sufficiently large to show all of the
reactions clearly, and though a larger piece would exhibit the
characteristic phenomena, yet much more effort is required. A very
small, shallow hole should be cut in the Ch. to receive the assay. The
Bp. flame should be directed at an angle of about 30° with the surface
of the Ch. Considerable care must be taken lest the hole in[Pg 11] the Ch. is
burned too deep and the assay lost in the coal.

The force of the air from the jet must also be borne in mind for a
strong blast, or sudden puffs may blow the substance away.

The following changes are to be looked for:—

a. Whether the substance is volatile or non-volatile.

Illustrations. Examine before the Bp. on Ch. some arsenious oxide,
As₂O₃, also some alumina, Al₂O₃.

b. Whether the substance is fusible or infusible.

Illustrations. Examine before the Bp. on Ch. some silver oxide, AgO,
also some zinc oxide, ZnO.

c. Whether the substance is alkaline or non-alkaline when placed upon
moistened red litmus.[Pg 12]

Illustrations. Ignite some calcium carbonate, CaCO₃, before the Bp.
on Ch., and place residue on moistened red litmus. In like manner,
examine some magnesium carbonate, MgCO₃.

d. Color of coating on Ch. caused by combination of metal and oxygen
due to heat of Bp. flame.

Illustrations. Examine some oxide of lead, PbO, before the Bp. on Ch.,
also some oxide of cadmium, CdO.

e. Decrepitation.

Illustration. Examine some sodium chloride, NaCl, before the Bp. on
Ch.

f. Deflagration.

Illustrations. Examine some potassium nitrate, KNO₃, before the Bp.
[Pg 13]on Ch., also some ammonium nitrate, NH₄NO₃.

g. Intumescence.

Illustration. Examine some alum,

before the Bp. on Ch.

h. Incandescence.

Illustration. Examine some oxide of barium, BaO, before the Bp. on Ch.

i. Formation of a metallic bead—color and malleability.

Illustration. Examine some silver oxide, AgO, before the Bp. on Ch.

Examination on Charcoal with Na₂CO₃.—Metallic compounds are often
difficult to reduce with the blowpipe flame alone, and hence no bead is
obtained. In order to facilitate reduction and the obtaining of a
metallic bead, the substance in a finely powdered condition is mixed
[Pg 14]with four parts of sodium carbonate, Na₂CO₃, and ignited before
the Bp. on Ch. The metallic compound is decomposed, the metal being
transformed into the carbonate, which in turn, through the agency of the
Ch. and the heat of the flame, is reduced to the free metal. Sometimes
the reduction is made easier by adding to the substance about its own
bulk of potassium cyanide, KCN, which takes up oxygen from the compound
and is converted into potassium cyanate, KCNO.

The reactions in reducing copper sulphate, CuSO₄, with Na₂CO₃
and with KCN before the blowpipe, are here given:—

[Pg 15]

After obtaining beads, it is well to obtain their coatings, for
oftentimes it is only in this way that we can distinguish between the
metals.

Examination in Tube with Na₂CO₃ and Charcoal.—If the substance in
a finely pulverized condition be mixed with twelve parts, Na₂CO₃,
and six parts of charcoal powder and the mixture be placed in an
ignition tube and subjected to heat, the acid of the substance combines
with the soda and the metal is set free.

If this metal is volatile, a sublimate is formed in the upper end of the
tube.

Mercury deposits in minute globules, which may be seen with the
magnifying glass. Arsenic forms a ring, which, when examined with the
magnifying glass, is seen to be made up of minute crystals. Ammonia is
recognized by its characteristic[Pg 16] odor, and also by its turning a slip
of moistened red litmus (held over the mouth of the tube) blue.

Examination on Platinum Wire.—Many substances possess the property of
imparting to the colorless flame of the Bunsen burner characteristic
colors.

The chlorides of these substances exhibit these flame reactions best,
and hence before applying the flame tests we dip the wire which serves
as a support into hydrochloric acid and then into the substance. When
the substance has been taken up on the wire, it is placed in the edge of
the long colorless flame of the Bunsen burner near the apex, when
instantly the flame becomes tinged with the characteristic color of the
substance.

Illustrations. Sodium compounds color the flame yellow, and a crystal
of potassium[Pg 17] dichromate appears colorless in the sodium light.

This sodium reaction is extremely delicate, it being possible to detect
with ease a quantity of a sodium salt less than 1/3000000 of a milligram
in weight.

Potassium colors the flame purplish-violet.

Barium colors the flame apple-green.

Strontium colors the flame crimson.

Calcium colors the flame orange-red, distinguished from strontium, by
appearing gray when seen through blue glass.

Boracic acid colors the flame green when the substance has been
moistened with glycerine.

Examination in Borax Bead.—Borax, Na₂B₄O₇, and microcosmic
salt,

possess the property of dissolving many of[Pg 18] the metallic oxides at the
temperature of the Bunsen flame.

For example, with oxide of cobalt, the following reactions take place
with the two fluxes:—

On heating, NaNH₄H. PO₄, it is decomposed into the metaphosphate
of sodium, NaPO₃,

Now in such cases of solution the metallic oxides impart a
characteristic color to the flux.

The platinum wire is the best support,—it is heated to incandescence in
the Bunsen flame, and then is quickly dipped into the borax, when a
small globule will adhere,—this is removed to the flame again when the
borax melts to a clear glassy bead. While the bead is still melted,
touch it to[Pg 19] the finely pulverized substance and replace in the flame.
In a few seconds the small particles of the substance will have
dissolved, and the bead will be seen to have assumed the color
characteristic of the substance. Note the color when hot and then when
cold; often there is a wide difference. Then, too, the test should be
made in both O. F. and R. F.

Some analysts prefer to make a small loop in the end of the wire before
taking up the borax to make the bead. Care should be taken to see that
the bead is colorless before bringing it in contact with the substance.

As the depth of color produced is largely dependent upon the amount of
substance taken, some little caution should be exercised to insure
taking up about the same quantity each time.

Illustrations. Make several beads, and[Pg 20] note the colors characteristic
of the following oxides: cobalt, nickel, iron, manganese, chromium, and
copper.

The microcosmic salt bead dissolves almost every oxide except silica,
SiO₂, and this is seen to float about in the melted mass. This is
used as a test for silica.

Examination with Co(NO₃)₂.—If after examination on the Ch. per
se, a white infusible residue remains, it is moistened with a drop of
cobalt nitrate Co(NO₃)₂ and re-ignited before the Bp., when a
change of color will be observed. This change in color is owing to the
fact that the heat of the Bp. flame decomposes the cobalt nitrate,
nitric acid being driven off, and the remaining CoO forming with the
oxide of the residue a colored mass.

Illustrations. Ignite before the Bp. on Ch. the following
[Pg 21]oxides,—allow to cool, add a drop of Co(NO₃)₂, re-ignite, and
note color,—aluminum, magnesium, zinc, and calcium.

Care should be taken to thoroughly ignite before adding the cobalt
nitrate solution.

With the six methods of examination just given almost every simple
substance can be detected, but should any doubt remain, a few simple
tests in the “liquid way” will be sufficient to substantiate the
blowpipe examination.

[Pg 22]

CHAPTER III

GENERAL REACTIONS FOR THE DETECTION OF THE METALLIC ELEMENTS IN SIMPLE
COMPOUNDS

For the sake of convenience, rather than for scientific reasons, the
following compounds have been arranged in alphabetic order. Also the
oxides of the elements have been taken, since they exhibit the reactions
to best advantage.

The student should work through carefully each one of the tests and
satisfy himself as to the characteristic reactions of the various
elements, for only in this way can he expect to recognize the substances
when presented to him as “unknowns.” It is advisable to provide a
note-book and rule it as follows:[Pg 23]—

1. Aluminum, Al₂O₃.—Before the Bp. on Ch. Infusible. No change.

Before the Bp. on Ch. with Na₂CO₃. Forms an infusible compound
with slight intumescence.

In ignition tube with Na₂CO₃ and Ch. No change. Moisture driven
off.

In flame on platinum wire. No change. Becomes incandescent.

In flame with borax bead. In O. F.[Pg 24] dissolves slowly, forming a
colorless glass which remains so on cooling.

With Co(NO₃)₂. Mass becomes blue upon re-ignition.

2. Antimony, Sb₂O₃.—Before the Bp. on Ch. In O. F. volatilizes
without change. In R. F. is reduced and volatilized. White coating of
antimonious oxide deposited on Ch. Blue tinge imparted to flame.

Before the Bp. on Ch. with Na₂CO₃. Readily reduced. White brittle
bead. Very volatile, giving characteristic white coating.

In ignition tube with Na₂CO₃ and Ch. Volatilized.

In flame on platinum wire. Volatilized. Colors flame greenish blue.

With borax bead on platinum wire. In O. F. dissolves to a colorless
glass.

[Pg 25]

With Co(NO₃)₂.____

3. Arsenic, As₂O₃.—Before the Bp. on Ch. Very volatile. Strong
garlic odor to fumes.

Before the Bp. on Ch. with Na₂CO₃. Reduced with emission of
arsenical fumes.

In ignition tube with Na₂CO₃ and Ch. Volatilizes, forming a
mirror-like deposit of metallic As in the cooler part of tube.

In flame on platinum wire____

With borax bead on platinum wire____

With Co(NO₃)₂.____

4. Bismuth, Bi₂O₃.—Before the Bp. on Ch. Yields a
coating—orange-yellow when hot, lemon-yellow when cold. The yellow
coating usually has a white outline.

Before the Bp. on Ch. with Na₂CO₃. Easily reduced to metallic
bismuth. Yellow bead brittle, but less so than antimony.

[Pg 26]

In ignition tube with Na₂CO₃ and Ch.____

In flame on platinum wire____

With borax bead on platinum wire. In O. F. small quantity dissolves to a
clear yellow glass, which becomes colorless when cold.

With Co(NO₃)₂____

5. Cadmium, CdO.—Before the Bp. on Ch. Gives a coating on the coal.
Reddish-brown when cold. Very volatile.

Before the Bp. on Ch. with Na₂CO₃. Readily reduced. The metal
volatilizes easily, giving the characteristic coating.

In ignition tube with Na₂CO₃ and Ch.____

In flame on platinum wire____

With borax bead. In O. F. dissolves to a clear yellowish bead, colorless
when cold.

With Co(NO₃)₂____

[Pg 27]

6. Chromium, Cr₂O₃.—Before the Bp. on Ch. No change.

Before the Bp. on Ch. with Na₂CO₃. Cannot be reduced. Soda sinks
in Ch. and a green colored mass remains.

In ignition tube with Na₂CO₃ and Ch.____

In flame on platinum wire____

With borax bead. Dissolves slowly but colors intensely. Yellow while
hot, green when cold.

With microcosmic salt bead. Colors red when hot, green when cold.

With Co(NO₃)₂____

7. Cobalt, CoO.—Before the Bp. on Ch. In O. F. unchanged. In R. F. is
reduced to the metal and is magnetic.

Before the Bp. on Ch. with Na₂CO₃. Reduced to a gray magnetic
mass.

In ignition tube with Na₂CO₃ and Ch.____

In flame on platinum wire____[Pg 28]

With borax bead on platinum wire. In O. F. colors very intensely blue,
both hot and cold.

With Co(NO₃)₂____

8. Copper, CuO.—Before the Bp. on Ch. Fuses to a black globule, which
can be reduced with some difficulty.

Before the Bp. on Ch. with Na₂CO₃. Readily reduced to metallic
bead, which is red in color, hard, malleable.

In ignition tube with Na₂CO₃ and Ch.____

In flame on platinum wire. Colors flame emerald-green.

With borax bead on platinum wire. In O. F. green when hot, blue when
cold.

With Co(NO₃)₂____

9. Iron, Fe₂O₃.—Before the Bp. on Ch. In O. F. unchanged. In R.
F. becomes black and magnetic.[Pg 29]

Before the Bp. on Ch. with Na₂CO₃ Reduced to a metallic powder,
magnetic.

In ignition tube with Na₂CO₃ and Ch.____

In flame on platinum wire____

With borax bead on platinum wire. In O. F. red while hot, yellow when
cold.

With Co(NO₃)₂____

10. Lead, PbO.—Before the Bp. on Ch. Easily reduced to the metal, bead
very malleable. Coating yellow, surrounded by white ring.

Before the Bp. on Ch. with Na₂CO₃. Instantly reduced. Coats the
Ch. upon further blowing.

In ignition tube with Na₂CO₃ and Ch. Reduced to the metal.

In flame on platinum wire. Tinges flame blue.

With borax bead on platinum wire.[Pg 30] In O. F. dissolves easily, forming a
limpid glass.

With Co(NO₃)₂____

11. Manganese, Mn₂O₃.—Before the Bp. on Ch. At high temperature
turns red.

Before the Bp. on Ch. with Na₂CO₃. Is not reduced.

Before the Bp. in O. F. on platinum foil with Na₂CO₃. Transparent
green mass when hot. Opaque, bluish-green when cold.

In ignition tube with Na₂CO₃ and Ch. Not reduced.

In flame on platinum wire____

With borax bead on platinum wire. In O. F. violet-red while hot,
amethyst-red when cold.

With Co(NO₃)₂____

12. Mercury, HgO.—Before the Bp. on Ch. Instantly reduced. Very
volatile.

[Pg 31]

Before the Bp. on Ch. with Na₂CO₃. Reduced and volatilized.

In ignition tube with Na₂CO₃ and Ch. Sublimes condensing in the
upper part of the tube as a metallic ring which is seen with the lens to
consist of minute globules of mercury.

In flame on platinum wire____

With borax bead on platinum wire____

With Co(NO₃)₂____

13. Nickel, NiO.—Before the Bp. on Ch. In O. F. unchanged. In R. F.
reduced to metal, slightly magnetic.

Before the Bp. on Ch. with Na₂CO₃. Easily reduced to the metal.

In ignition tube with Na₂CO₃ and Ch.____

In flame on platinum wire____

With borax bead on platinum wire. In O. F. violet while hot,
reddish-brown when cold.

[Pg 32]

With Co(NO₃)₂____

14. Silver, AgO.—Before the Bp. on Ch. Easily reduced to the metal.
White, malleable, hard bead. Coats the coal dark red near assay.

Before the Bp. on Ch. with Na₂CO₃. Instantly reduced to metallic
globule.

In ignition tube with Na₂CO₃ and Ch. Reduced to the metal.

In flame on platinum wire____

With borax bead on platinum wire. In O. F. partially dissolved. Bead
becomes milk-white.

With Co(NO₃)₂____

15. Tin, SnO₂.—Before the Bp. on Ch. Coats the coal yellow while
hot, dirty white when cool. Not reduced.

Before the Bp. on Ch. with Na₂CO₃. Reduced to metallic tin. White,
hard, malleable bead. Coating white and close to assay.[Pg 33]

In ignition tube with Na₂CO₃ and Ch.____

In flame on platinum wire____

With borax bead on platinum wire. In O. F. small quantity dissolves to
limpid glass.

With Co(NO₃)₂. Greenish-blue color.

16. Zinc, ZnO.—Before the Bp. on Ch. Upon ignition becomes yellow. Is
not reduced.

Before the Bp. on Ch. with Na₂CO₃. Reduced to metal. Rapidly
volatilized, coating the coal white.

In ignition tube with Na₂CO₃ and Ch.____

In flame on platinum wire____

With borax bead on platinum wire. In O. F. yellow while hot, limpid
glass when cold.

[Pg 34]

With Co(NO₃)₂. Green mass.

Having now given the principal reactions for the most important metals,
we will proceed to the examination of the alkali metals, the alkaline
earths, and some of the acid elements.

The Alkali Metals

17. Ammonium, NH₄.—This hypothetical compound is commonly classed
among the alkali metals from its close resemblance to the members of
this group.

To detect the presence of this hypothetical metal, mix the assay with
about four parts of Na₂CO₃, place in an ignition tube, and apply
heat. The odor of the evolved gas will be recognized, and if a piece of
red litmus paper be moistened and held at the mouth of the tube, it will
be turned blue by the escaping ammonia gas.

We are not authorized to infer the pre-existence of ammonium, however,
from the[Pg 35] appearance of this reaction, for the presence of nitrogenous
organic matter in the substance, which would be decomposed by this
treatment, would give rise to such a reaction.

18. Potassium.—Potassium is recognized by the color which its salts
impart to the Bunsen flame. If a portion of a salt of potassium be held
on a platinum wire in the flame, it imparts a blue-violet tint which
rapidly disappears.

19. Sodium.—Like potassium, this alkali metal is detected by the color
which its salts give to the flame.

If a sodium salt be held on the platinum wire in the flame, it imparts
an intense yellow color.

The extreme delicacy of this reaction has been mentioned elsewhere. The
value[Pg 36] of this test is really lessened by its great delicacy, for it is
possible to detect minute quantities of sodium in almost all substances,
although it may not be in chemical combination. As an example, draw the
platinum wire between the fingers, and then place in flame, and note
presence of sodium.

20. Lithium, Li₂O.—In the Bunsen flame on the platinum wire it
imparts a carmine-red tinge.

Hydrochloric acid on the sample augments the coloration.

The Alkaline Earths

21. Barium, BaO.—In the Bunsen flame on the platinum wire it imparts an
apple-green coloration. This reaction is intensified by moistening the
sample with hydrochloric acid.[Pg 37]

22. Calcium, CaO.—In the Bunsen flame on the platinum wire it imparts
an orange-red color, which appears gray when seen through blue glass.

Hydrochloric acid on the sample makes the color more intense.

23. Strontium, SrO.—In the Bunsen flame on the platinum wire it imparts
an intensely red color, which is increased by converting the substance
into the chloride.

The Acid Elements

24. Borates.—If the substance be finely powdered, moistened with
glycerine, and then placed on a platinum wire in the Bunsen flame, it
imparts a brilliant green color.

If turmeric paper be dipped into a solution of a borate, and then be
dried at 100° C., it is turned to a peculiar red[Pg 38] color. These two
reactions are extremely delicate.

25. Bromides.—Bromides treated with microcosmic salt and oxide of
copper on platinum wire impart to the flame a greenish-blue color, the
edges being decidedly green.

26. Chlorides.—Chlorides are treated in the same way as bromides. The
color imparted to the flame is azure-blue.

To discriminate between bromides and chlorides more clearly, the
substance is mixed with anhydrous potassium bisulphate and fused in an
ignition tube.

Bromine and sulphur dioxide are evolved (if the substance be a bromide),
the tube being filled with a yellow gas possessing the characteristic
odor of bromine.

27. Fluorides.—A small portion of the substance in a finely powdered
condition is[Pg 39] placed in one of the ignition tubes, a strip of moist
Brazil-wood paper is introduced into the open end, and heat is applied.
Hydrofluoric acid is evolved, and the red color of the paper is changed
into a straw-yellow.

Mica, containing only 0.75% of fluorine, shows the reaction clearly.

28. Iodides.—Iodides are treated, as the bromides and chlorides, in a
bead of microcosmic salt with oxide of copper. The flame is colored
green.

Fused with potassium bisulphate in an ignition tube the violet vapors of
iodine are evolved, and thus iodides may be distinguished from chlorides
and bromides.

29. Nitrates.—If a nitrate be heated upon charcoal before the Bp.,
violent deflagration occurs. If the substance containing[Pg 40] the nitric
acid be mixed with a very small quantity of finely powdered potassium
cyanide, the deflagration is accompanied with ignition and detonation.

If the substance be mixed in a dry condition with dry potassium
bisulphate, and is then heated in an ignition tube, red-brown nitrous
fumes are evolved. This reaction takes place if there is but a small
quantity of nitrate present.

30. Phosphates.—Phosphates impart to the flame a bluish green color.
The color is made more intense by moistening the substance with
sulphuric acid, and then taking the paste so formed on the platinum wire
and placing it in the Bunsen flame.

31. Silicates.—Silicates, when treated with microcosmic salt on a
platinum wire,[Pg 41] suffer decomposition; the bases unite with the
phosphoric acid to form a transparent glass in which the silica may be
seen floating as a cloudy mass.

The bead must only be examined for silica while hot, since on cooling it
becomes opaque.

32. Sulphides.—Many sulphides, when heated in an ignition tube,
volatilize and give a sublimate of sulphur in combination with the
metallic portion of the substance.

A very delicate test for sulphur in whatever combination it may be found
in a substance, and which may be performed with great ease, is to mix
the finely powdered assay with four parts, Na₂CO₃, and fuse in an
ignition tube. When thoroughly fused the tube is broken, and the fused
mass is placed on a bright silver coin, and a drop[Pg 42] of water is added.
If the substance contains sulphur, a black spot will be observed on the
coin where the fused mass was placed.

Before going on to the next chapter, the student should assure himself
of his familiarity with the reactions just given, and he should practise
with various substances, the nature of which is unknown to him.

[Pg 43]

CHAPTER IV

BEHAVIOR OF SOME OF THE PRINCIPAL ORES BEFORE THE BLOWPIPE

For the sake of practice, and as a fitting introduction to
“Determinative Mineralogy,” this chapter is appended. It is not intended
to give a detailed account of the minerals, but rather to set before the
student the most marked characters, such as hardness, specific gravity,
color, lustre, etc.

To determine the hardness of a mineral, we try to scratch it with the
minerals forming an arbitrary “scale of hardness,” proceeding
successively from the softest to the hardest. When we say that a certain
mineral has hardness = 4, we mean that the mineral is scratched by 4 on
the scale, and[Pg 44] that 4 on the scale is scratched by the mineral. The
scale of hardness chiefly in use is the Mohs-Breithaupt scale, which is
as follows:—

It seldom happens in determining the hardness of a mineral that its
hardness exactly conforms to that of some one member of the scale. In
such cases we generally estimate the hardness. For example, suppose[Pg 45] a
mineral was harder than 4, but softer than 5, and that it was nearer 5
than 4, then we would call its hardness 4-3/4.

In order to preserve the scale some operators use a three-cornered file,
first cutting the mineral and then the scale until a number is found,
which is abraded to about the same depth as the mineral under
examination.

Since a set of minerals forming a scale of hardness is not always at
hand, the following scale given by Chapman is appended:—

Specific gravity cannot well be determined without the aid of a balance,
and hence its value here is not great.

As in the preceding chapter, alphabetic arrangement will be employed.

Ores of Antimony

Stibnite, Sb₂S₃, Sb . 71, S . 29.—[A]H = 2, G = 4.52-4.62. Of
lead-gray color and metallic lustre. Consists of a large number[Pg 47] of
needle-shaped crystals. Brittle. Fuses in candle flame. In an ignition
tube yields a sublimate of sulphur. On Ch. before the Bp. it is
volatilized, giving antimony coating and tinges the flame pale blue.

Ores of Arsenic

Native Arsenic, As.—This contains traces of Sb, Ag, Fe, Co, and Ni.

H = 3.5, G = 5.7-5.8. Dark gray in color. Fracture tin-white, tarnishing
rapidly. Volatilizes before the Bp. on Ch. without melting, giving white
coating of arsenious acid and characteristic garlic odor. In ignition
tube it sublimes, giving arsenical ring.

Realgar, AsS, As . 70, S . 30.—H = 1.5-2, G = 3.56. Bright red to
orange-red color and resinous lustre. In an ignition tube it fuses and
finally sublimes. The sublimate[Pg 48] when cool is red and transparent. Fuses
readily before the Bp. on Ch. and burns with pale yellowish flame,
emitting gray-white fumes having garlic odor.

Orpiment, As₂S₃, As . 61, S . 39.—

Lemon-yellow in color and resinous or pearly lustre. Sectile. Before the
Bp. on Ch. behaves like realgar, but in an ignition tube it gives a dark
yellow sublimate which is transparent.

Ores OF Bismuth

Native Bismuth, Bi.—This contains traces of As, Te, and S.

H = 2.0-2.5, G = 9.7-9.83. Color, silver-white, slightly tinged with
red. Metallic lustre. Brittle when cold, but may be laminated when hot.
Before the Bp. on Ch. behaves like pure Bi.[Pg 49]

Bismuthite, Bi₂O₃ . 90, CO₂ . 7, H₂O . 3,—

Usually of a white or light greenish color and vitreous lustre, in
acicular crystallizations. In an ignition tube decrepitates, yielding
water and turning gray. Before the Bp. on Ch. it fuses easily and is
reduced to metallic globule, coating the Ch. with Bi₂O₃. With
Na₂CO₃ it occasionally gives the sulphur reaction.

Ores OF Chromium

Chromic Iron Ore, FeO . 32, Cr₂O₃ . 68.—Al₂O₃, Fe₂O₃,
MnO, and MgO are commonly present. H = 5.5, G = 4.32-4.57. Occurs
usually massive. Color, iron-black to brownish black. In many varieties
strongly magnetic. Lustre, shining and somewhat metallic. Heated in an
ignition tube, remains unchanged. Infusible before the Bp. on Ch.[Pg 50]
Before the Bp. on Ch. with Na₂CO₃ and KCN yields metallic iron. In
borax bead it slowly dissolves to a clear transparent glass, which is a
beautiful green when cool.

Ores of Cobalt

Smaltite, Co(Fe, Ni) As₂, Co . 28, As . 72.—H = 5.5, G = 6.37-7.30.
Color, tin-white or steel-gray. Lustre, metallic. When heated to redness
in an ignition tube it yields a sublimate of metallic arsenic. Before
the Bp. on Ch. it fuses readily, with emission of arsenical fumes, to a
grayish black magnetic globule. This globule may be examined for iron,
cobalt, and nickel with the borax bead.

Cobaltite, CoS₂ + CoAs₂, Co . 36, As . 45, S . 19.—H = 5.5, G =
6.0-6.3. Color, silver-white tinged with red. Metallic lustre. Before
the Bp. on Ch. fuses easily, with[Pg 51] emission of copious arsenical fumes,
to a gray magnetic globule. Remains unchanged in the ignition tube.

Linnaeite, (Co, Ni)₃S₄, (Co, Ni)58, S . 42.—H = 5.5, G = 4.8-5.0.
Color, bright steel-gray, sometimes reddish. Lustre, metallic.
Crystallizes in the regular octahedron. Before the Bp. on Ch. fuses to a
metallic globule which is attracted by the magnet. With borax bead gives
reaction for cobalt.

Erythrite, Co₃O₈As₂ + 8 H₂O, As₂S₅ . 38.4, CoO . 37.6,
H₂O . 24.0.—

Color, crimson to peach-red. When crystallized, of pearly lustre, but
frequently dull and earthy. Heated in ignition tube gives off water, and
color changes to blue or green. Before the Bp. on Ch. in R. F. it[Pg 52] emits
arsenical fumes and melts to a dark gray globule which with the borax
bead reacts for cobalt.

Ores of Copper

Native Copper, Cu.—

Color, copper-red. Lustre, metallic. Occurs usually massive and very
arborescent. Before the Bp. on Ch. it fuses, and if the heat is
sufficiently high it assumes a bright bluish-green surface; on cooling
it is covered with a coat of black oxide. In the borax bead it reacts
for copper.

Chalcopyrite, CuFeS₂, Cu . 35, Fe . 30, S . 35.—H = 3.5-4, G =
4.1-4.3. Color, brass-yellow, often golden-yellow. Lustre, metallic.
Occurs crystallized, but is generally found massive. Is easily
scratched[Pg 53] with a knife. Heated in an ignition tube decrepitates, and
occasionally yields a faint sublimate of sulphur. Before the Bp. on Ch.
it blackens, but becomes red again on cooling. Before the Bp. on Ch.
with Na₂CO₃ and KCN it is reduced, and the metals are obtained in
separate masses. It reacts with the borax bead for copper and iron.

Copper Glance, Cu₂S, Cu . 80, S . 20.—H = 2.5-3.0, G = 5.5-5.8.
Color, dark blue to steel-gray. Occurs in compact masses, often very
shining. Before the Bp. on Ch. fuses to a globule which boils and emits
glowing drops. Sulphur dioxide escapes abundantly, and the outer flame
is colored blue. Before the Bp. on Ch. with Na₂CO₃ yielding a
metallic globule.

Tetrahedrite, 4 CuS + Sb₂S₃.—Frequently contains silver, iron,
mercury, and zinc.[Pg 54] H = 3.0-4.0, G = 4.5-5. Color, steel-gray to
iron-black. Heated in an ignition tube fuses and gives a sublimate of
antimonious oxide. When mercury is present this condenses in the upper
part of the tube, forming the characteristic mirror. Before the Bp. on
Ch. it fuses readily to a metallic globule, emitting dense white fumes;
zinc and antimony coatings are deposited on the Ch. After long ignition
before the Bp., if the mineral is finely powdered and mixed with
Na₂CO₃ and KCN, the ore is reduced to the metal.

Cuprite, Cu₂O, Cu . 89, O . 11.—

Color, intense crimson-red. Before the Bp. on Ch. blackens and fuses
quietly, and finally yields a metallic globule of copper. Before the Bp.
[Pg 55]on Ch. with Na₂CO₃ and KCN it is easily reduced.

Malachite, 2 CuO + CO₂ + H₂O, CuO . 72, CO₂ . 20, H₂O . 8.—

Color, bright green. Occurs generally in mammillated concretions.
Lustre, shining and fracture, silky. Heated in an ignition tube yields
water and blackens. Before the Bp. on Ch. it fuses to a metallic
globule. Before the Bp. on Ch. with Na₂CO₃ and KCN it is easily
reduced. With borax bead gives characteristic coloration.

Azurite, 3 CuO + 2 CO₂ + H₂O, CuO . 69, CO₂ . 26, H₂O . 5.—

Color, azure-blue. Occurs usually in crystallized or globular masses.
Lustre, earthy or vitreous. Before the Bp. and with other reagents
behaves like malachite.[Pg 56]

Chrysocolla, CuO + SiO₂ + 2 H₂O, SiO₂ . 34.2, CuO . 45.3,
H₂O . 20.5.—H = 2.0-3.0, G = 2. Color, bluish-green, closely
resembling malachite. Occurs usually as an incrustation, its surface
being very smooth, like enamel. In an ignition tube it blackens and
yields water. Before the Bp. on Ch. in O. F. it blackens, coloring the
flame bright green; in the R. F. it turns red. Before the Bp. on Ch.
with Na₂CO₃ yields metallic copper. In borax bead it reacts for
copper.

Atacamite, CuCl₂ + 3 CuO₂H₂—Cl . 16.6, O . 20.3, Cu . 50.1,
H₂O . 13.0.—

Color, green to blackish green. Lustre, adamantine to vitreous. In an
ignition tube yields water. Before the Bp. on Ch. colors flame blue.
Before the Bp. on Ch. with Na₂CO₃ and KCN is reduced to the metal.
In borax bead it reacts for copper.[Pg 57]

Ores of Iron

Limonite, 2 Fe₂O₃ + 3 H₂O, Fe₂O₃ . 86, H₂O . 14.—H =
5.0-5.5, G = 3.6-4.0. Color, brown to ochre-yellow. Earthy or
semi-metallic in appearance. In an ignition tube yields water. Before
the Bp. on Ch. infusible. In borax bead reacts for iron.

Hematite, Fe₂O₃, Fe . 70, O . 30.—

Color, dark steel-gray to iron-black. Lustre, metallic. When pulverized
yields a red powder. Before the Bp. on Ch. infusible. After long
roasting becomes magnetic. In borax bead gives usual indications of
iron.

Magnetite, Fe₃O₄, FeO . 31, Fe₂O₃ . 69.—

Color, iron-black. Lustre, shining and metallic. Pulverized, its powder
is black. It is strongly magnetic. Fuses with difficulty before the Bp.
on Ch. In borax bead reacts for iron.

Pyrites, FeS₂, Fe . 47, S . 53.—

Color, brass-yellow. Lustre, metallic. Occurs commonly in cubes. It
often contains small quantities of Au, Ag, Cu, As, Co, and Mn. Heated in
an ignition tube gives a sublimate of sulphur, the residue becoming
magnetic. Before the Bp. on Ch. in O. F. sulphur is burned off and the
red oxide remains. This residue may then be examined for iron, etc.

Marcasite (White Iron Pyrites).—Having the same general composition as
pyrite, but much lighter in color. Crystals, prismatic. Before the Bp.
on Ch. behaves like pyrite.[Pg 59]

Pyrrhotite, Fe₇S₈, Fe . 60.5, S . 39.5.—

Color, bronze-yellow. Closely resembles pyrite, but may be distinguished
from it by being feebly magnetic. Heated in an ignition tube yields no
sublimate. Before the Bp. on Ch. fuses to a magnetic globule, which
exhibits a yellowish crystalline structure when fractured.

Mispickel, FeAsS, Fe . 34, As . 46, S . 20.—H = 5.5-6.0, G = 6.0-6.2.
Color, silver-white. Lustre, metallic; very brittle. Often associated
with it we find small quantities of Co, Ag, and Au. Heated in an
ignition tube it first yields a red sublimate of sulphide of arsenic,
and then afterward a crystalline sublimate of metallic arsenic. Before
the Bp. on Ch. emits dense fumes of arsenic and deposits a coating on
the[Pg 60] coal; it then fuses to a globule which behaves like pyrrhotite.

Siderite, FeCO₃, FeO . 62, CO₂ . 38.—H = 3.5-4.5, G = 3.7-3.9.
Color, grayish yellow to reddish brown. Lustre, pearly. Crystallizes in
rhombohedrons with curved faces; these crystals are distinctly cleavable
and massive. Heated in an ignition tube it decrepitates with evolution
of carbon dioxide. Before the Bp. on Ch. infusible. Before the Bp. on
Ch. with Na₂CO₃ it fuses to a magnetic mass. With borax bead it
reacts for iron and sometimes for manganese.

Ores of Lead

Galena, PbS, Pb . 87, S . 13.—

Color, bluish gray, slowly tarnishing. Lustre, metallic. Crystals in the
form of cubes.[Pg 61] Heated in an ignition tube it sometimes decrepitates and
yields a sublimate of sulphur. Before the Bp. on Ch. easily reduced to
the metallic state, the Ch. becoming coated with sulphate and oxide of
lead. The metallic globule usually contains a little silver. To separate
this, the process known as “cupellation” is employed. A hole is bored
into the Ch. about 1 cm. in diameter and about 6 mm. deep. Into this
hole is placed a stiff paste made by mixing finely pulverized bone-ash
with a little soda and water. This paste is pressed in hard, and then
the surface is smoothed off, and the centre is slightly depressed with
the rounded end of a glass rod. The charcoal so prepared is set in a
warm place to allow the paste to dry. When the paste is quite dry the
small globule of lead is placed in the depression in the centre of the
bone-ash “cupel,” and is there exposed to the[Pg 62] O. F. from the Bp. The
lead is oxidized and is absorbed by the bone-ash, while any silver
present will remain in the central depression as a bright shining bead.

Cerusite, PbCO₃, PbO . 84, CO₂ . 16.—H = 3.0-3.5, G = 6.46-6.57.
Color, white, gray, or yellow. Lustre, adamantine. Crystallizes in
prismatic needles. When heated in an ignition tube carbon dioxide is
evolved and the residue turns yellow. Before the Bp. on Ch. readily
reduced to metallic lead.

Anglesite, PbSO₄, PbO . 74, SO₃ . 26.—H = 2.0-3.0, G = 6.12-6.39.
Color, yellow, gray, and brown. Lustre, adamantine, resinous. Heated in
an ignition tube decrepitates, and sometimes yields a little water.
Before the Bp. on Ch. fuses to a clear bead, which on cooling becomes[Pg 63]
opaque. Before the Bp. on Ch. with Na₂CO₃ is reduced to the metal
giving a yellow coating. The Na₂CO₃ absorbed by the coal reacts
for S.

Ores of Manganese

Pyrolusite, MnO₂, Mn . 63.2, O . 36.8.—H = 2.0-2.5, G = 4.82. Color,
iron-black to steel-gray. Lustre, non-metallic. Heated in an ignition
tube yields generally a little water, and if the temperature be high
enough, oxygen is evolved. Before the Bp. on Ch. infusible. In borax
bead gives characteristic color.

Psilomelane, Mn₂O₃ + H₂O.—

Color, iron-black to steel-gray. Generally resembles pyrolusite, but is
distinguished from it by its superior hardness. It frequently[Pg 64] contains
BaO and Li₂O. It behaves before the Bp. like pyrolusite.

Wad (Bog Manganese).—This mineral is essentially MnO₂, MnO, and
H₂O, with small quantities of Fe₂O₃, Al₂O₃, BaO, SiO₂,
etc., associated with it.

H = 0.5-6.0, G = 3.0-4.2. Color, dull black. Heated in an ignition tube
yields water in abundance, otherwise it behaves like pyrolusite.

Ores of Mercury

Native Mercury, Hg.—G = 13.5-13.6. Color, silver-white. Is liquid at
all ordinary temperatures. Heated in an ignition tube is volatilized,
the vapors condensing in the upper end of tube to small metallic
globules of Hg. Before the Bp. on Ch. it is volatilized. Frequently
contains Ag.[Pg 65]

Cinnabar, HgS₂, Hg . 86, S . 14.—

Color, scarlet-red to brick-red. Lustre, non-metallic. When pulverized
yields a powder of vermilion-red color. Heated in an ignition tube it
volatilizes, yielding a black sublimate, which by friction becomes red.
Before the Bp. on Ch. it is wholly volatilized. Heated in an ignition
tube with Na₂CO₃ metallic mercury sublimes, condensing in the
upper portion of the tube in minute globules.

Ores of Nickel

Millerite, NiS, Ni . 64.4, S . 35.6.—

Color, brass-yellow. Brittle. Before the Bp. on Ch. it fuses to a
magnetic, metallic globule. The roasted mineral gives in the borax bead
the color reaction characteristic[Pg 66] of nickel, and sometimes that of
cobalt, which is often associated with it.

Niccolite, NiAs, Ni . 44, As . 56.—

Color, pale copper-red. Lustre, metallic. Very brittle. Heated in an
ignition tube yields a copious sublimate of arsenious oxide, the residue
falling to a greenish powder. Before the Bp. on Ch. fuses to a white
brittle globule emitting arsenical fumes. In borax bead gives color
characteristic of nickel. Frequently in this mineral a portion of the
arsenic is replaced by antimony.

Ores of Silver

Native Silver, Ag.—

Color, silver-white. Lustre, metallic. Ductile and malleable. Usually
occurs associated[Pg 67] with Au, As, Sb, Cu, Fe, etc. Before the Bp. on Ch.
easily fuses to a globule which is surrounded with a dark red coating on
the coal.

Argentite, Ag₂S, Ag . 87.1, S . 12.9.—

Color, blackish lead-gray. Lustre, metallic. Very sectile. Before the
Bp. on Ch. in O. F. intumesces with evolution of sulphur dioxide,
finally yielding a metallic globule of Ag.

Pyrargyrite, Ag₃SbS₃, Ag . 59.8, Sb . 22.5, S . 17.7.—H = 2.5, G
= 5.77-5.86. Color, black to dark cochineal-red. Lustre, metallic,
adamantine. In an ignition tube it yields on continued heating a
sublimate of antimony sulphide. Before the Bp. on Ch. it gives a coating
[Pg 68]of antimony trioxide. Before the Bp. on Ch. with Na₂CO₃ is
reduced to metallic silver.

Proustite, Ag₃S₃As, Ag . 65.5, As . 15.1, S . 19.4.—H = 2.0-2.5,
G = 5.57-5.64. Color, light red. Lustre, splendent, adamantine. Before
the Bp. on Ch. it behaves like pyrargyrite, save that it gives off
arsenical fumes instead of antimonious oxide.

Stephanite, Ag₅S₄Sb, Ag . 68.5, Sb . 15.3, S . 16.2.—H = 2.0-2.5,
G = 6.2-6.3. Color, iron-black to blackish gray. Lustre, metallic. Very
brittle and fragile. In an ignition tube it decrepitates, fuses, and
finally yields a slight sublimate of antimony trisulphide. Before the
Bp. on Ch. gives a coating of antimonious oxide. Before the Bp. on Ch.
with Na₂CO₃ a globule of metallic silver is obtained. The mineral
frequently contains copper and iron.[Pg 69]

Kerargyrite, AgCl, Ag . 75.3, Cl . 24.7.—H = 1.0-1.5, G = 5.52. Color,
white, gray, yellowish, greenish to blue. Lustre, resinous, adamantine.
Soft like wax. Fuses easily in a candle-flame. Before the Bp. on Ch. it
is readily reduced to metallic silver.

Ores of Tin

Cassiterite, SnO₂, Sn . 79, O . 21.—

Color, brown, black. Lustre, adamantine, brilliant. Occurs crystallized
in square prisms. Reëntrant angles characteristic. Before the Bp. on Ch.
with Na₂CO₃ and KCN reduced to a metallic globule of tin. In the
borax bead gives characteristic reaction.

Stannite, 2 Cu₂S . SnS₂ + 2 (FeS . ZnS) Sn . S₂.—H = 4.0, G =
4.3-4.5. Color,[Pg 70] steel-gray to iron-black. Lustre, metallic. Occurs
usually massive and disseminated. Heated in an ignition tube it yields
sulphur dioxide. Before the Bp. on Ch. it emits sulphur dioxide and
becomes covered with oxide of tin. Before the Bp. on Ch. with
Na₂CO₃ and KCN it gives an impure globule of copper. A very
difficult mineral to determine.

Ores of Zinc

Calamine, H₂Zn₂O₅Si, SiO₂ . 25.0, ZnO . 67.5, H₂O .
7.5.—H = 4.5-5.0, G = 3.4-3.5. Color, white, gray, bluish, or brown.
Lustre, vitreous. Brittle. In an ignition tube yields water when heated
and becomes milky white. Before the Bp. on Ch. practically infusible.
With Co(NO₃)₂ it assumes a green color which passes into a fine
blue when the heat is increased.[Pg 71]

Smithsonite,

H = 5, G = 4.30-4.45. Color, gray, yellow, brown, and green. Lustre,
vitreous, pearly. Heated in an ignition tube CO₂ is evolved, residue
appearing white. It often contains impurities of Cd, Pb, Fe, Mn, Ca, and
Mg. When these are present the residue in the ignition tube becomes dark
on cooling. Before the Bp. on Ch. with Na₂CO₃ and exposed to the
R. F. it is decomposed. It gives the characteristic reaction for zinc
with Co(NO₃)₂.

Zincite, ZnO, Zn . 80.3, O . 19.7—

Color, blood-red. Lustre, brilliant, subadamantine. Before the Bp. on
Ch. infusible. Before the Bp. on Ch. with Na₂CO₃ gives coating of
[Pg 72]zinc oxide. Gives characteristic reaction with Co(NO₃)₂. It
frequently contains a small quantity of Mn₂O₃, which may be
detected in the borax bead.

Sphalerite, ZnS, Zn . 67, S . 33.—

Color, yellow to black. Lustre, resinous, brilliant, and sometimes
submetallic. Heated in an ignition tube sometimes decrepitates. Before
the Bp. on Ch. infusible. Before the Bp. on Ch. with Na₂CO₃ easily
reduced. With Co(NO₃)₂ gives the characteristic reaction. It
frequently contains small quantities of Cd, Hg, Sn, Pb, Au, Ag, etc.[Pg 73]

I

Table of Colors of Coatings on Charcoal

II

Table of Flame Colorations

[Pg 74]

III

Table of Colors of Borax Beads in Oxidizing Flame

[Pg 75]

IV

Table of Colors of Borax Beads in Reducing Flame

[Pg 76]

V

Table of Colors of Microcosmic Salt Beads in Oxidizing Flame

[Pg 77]

VI

Table of Colors of Microcosmic Salt Beads in Reducing Flame

THE PRACTICAL METHODS

OF

ORGANIC CHEMISTRY

AUTHORIZED TRANSLATION

12mo. Cloth. Price, $1.60, net

THE GUARDIAN.

PHARMACEUTICAL REVIEW.

NATURE.

PUBLISHED BY
THE MACMILLAN COMPANY
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OUTLINES

OF

INDUSTRIAL CHEMISTRY

A TEXT-BOOK FOR STUDENTS

By FRANK HALL THORP, Ph.D.,

Instructor in Industrial Chemistry in the Massachusetts Institute of
Technology.

Cloth. 8vo. Price, $3.50 net

JAMES LEWIS HOWE,

Department of Chemistry, Washington and Lee University.

CHARLES E. COATES, Jr., Ph.D.,

Professor of Chemistry, Louisiana State University.

W. A. NOYES, in Science.

PUBLISHED BY
THE MACMILLAN COMPANY
66 FIFTH AVENUE, NEW YORK