* * * * *
3. Oxide of Didymium, DO.
Behavior with Borax on Platinum wire
in the oxidizing flame:
Dissolves to a clear dark amethystine glass.
in the reducing flame.
No reaction.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
As with borax.
in the reducing flame.
No reaction.
* * * * *
4. Oxide of Manganese, Mn^{2}O^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Affords an intense amethyst color, which on cooling becomes
violet. A large quantity of the oxide produces an apparently
black bead, which however, if pressed flat, is seen to be
transparent.
in the reducing flame.
The colored bead becomes colorless. With a large amount of the
oxide, this reaction is best obtained upon charcoal, and is
facilitated by the addition of tin foil.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
With a considerable quantity of oxide an amethyst color is
obtained, but never so dark as in borax. With but little oxide a
colorless bead is obtained, in which, however, the
amethyst-color may be brought out by adding a little nitre.
While the bead is kept fused, it froths and gives off bubbles of
gas.
in the reducing flame.
The colored bead immediately loses its color, either on platinum
wire or on charcoal. After the reduction the fluid bead remains
still.
* * * * *
5. Oxide of Iron, Fe^{2}O^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
With a small proportion of oxide, the glass is of a yellow
color, while warm, and colorless when cold; with a larger
proportion, red, while warm, and yellow, when cold; and with a
still larger amount, dark-red, while warm, and dark-yellow, when
cold.
in the reducing flame.
Treated alone on platinum wire, the glass becomes of a
bottle-green color (F^{3}O^{4}), and if touched with tin, it
becomes of a pale sea-green. On charcoal with tin, it assumes at
first a bottle-green color, which by continued blowing changes
to a sea-green (FeO).
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
With a certain amount of oxide, the glass is of a yellowish-red
color, which on cooling changes to yellow, then green, and
finally becomes colorless. With a large addition of oxide, the
color is, when warm, dark red, and passes, while cooling, into
brownish-red, dark green, and finally brownish-red. During the
cooling process, the colors change more rapidly than with borax.
in the reducing flame.
With a small proportion of oxide there is no reaction. With a
larger amount the bead is red, while warm, and becomes on
cooling successively yellow, green, and russet. With the
addition of tin the glass becomes, during cooling, first green
and then colorless.
* * * * *
6. Oxide of Cobalt, CoO.
Behavior with Borax on Platinum wire
in the oxidizing flame:
Colors the glass of an intense smalt blue both whilst hot and
when cold. When much oxide is present, the color is so deep as
to appear black.
in the reducing flame:
As in the oxidizing flame.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
As with borax, but less intensively colored. During cooling the
color becomes somewhat paler.
in the reducing flame.
As in the oxidizing flames.
* * * * *
7. Oxide of Nickel, NiO.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Colors intensely. A small amount of oxide affords a glass which,
while warm, is violet, and becomes of a pale reddish-brown on
cooling. A larger addition produces a dark violet color in the
warm and reddish-brown in the cold bead.
in the reducing flame.
The oxide is reduced and the metallic particles give the bead a
turbid grey appearance. If the blast be continued the metallic
particles fall together without fusing, and the glass becomes
colorless. This reaction is readily obtained with tin upon
charcoal, and the reduced nickel fuses to a bead with the tin.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Dissolves into a reddish glass which becomes yellow on cooling.
With a large addition of the oxide, the glass is brownish while
hot, and orange when cold.
in the reducing flame.
On platinum wire the nickeliferous bead undergoes no change.
Treated with tin upon charcoal, it becomes at first opaque and
grey, and after long continued blowing the reduced nickel forms
a bead, and the glass remains colorless.
* * * * *
8. Oxide of Zinc, ZnO.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Dissolves easily into a clear colorless glass, which, when much
oxide is present, may be rendered opaque and flocculent by an
intermittent flame, and becomes so spontaneously with a still
larger addition. When a considerable quantity is dissolved, a
glass is obtained which is pale yellow, while hot, and colorless
when cold.
in the reducing flame.
On platinum wire the saturated glass becomes at first opaque and
grey, but by a sustained blast is again rendered clear. On
charcoal the oxide is gradually reduced; the metal is
volatilized and in crusts the charcoal with oxide.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
As with borax.
in the reducing flame.
As with borax.
* * * * *
9. Oxide of Cadmium, CdO.
Behavior with Borax on Platinum wire
in the oxidizing flame.
When in very large proportion, dissolves to a clear yellow
glass, which becomes nearly colorless on cooling. When the oxide
is present in any considerable quantity, the glass can be
rendered opaque with an intermittent flame, and, with a larger
addition, it becomes so spontaneously on cooling.
in the reducing flame.
Upon charcoal ebullition takes place and the oxide is reduced.
The metallic cadmium is volatilized and incrusts the charcoal
with its characteristic deep yellow oxide.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
When in very large proportion dissolves to a clear glass, having
a yellow tinge, while hot, which disappears on cooling, and when
perfectly saturated, becomes milk-white.
in the reducing flame.
On charcoal the oxide is slowly and imperfectly reduced. The
reduced metal forms the characteristic incrustation on the
charcoal, but the is thin and does not exhibit its color clearly
until quite cold. The addition of tin hastens the reaction.
* * * * *
10. Oxide of Lead, PbO.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Dissolves readily to a clear yellow glass, which loses its color
upon cooling, and when containing much oxide can be rendered
dull under an intermittent flame. With a still larger addition
of oxide it becomes opaline yellow on cooling.
in the reducing flame.
The plumbiferous glass spreads out on charcoal, becomes turbid,
bubbles up, until the whole of the oxide is reduced, when it
again becomes clear. It is, however, difficult to bring the lead
together into a bead.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
As with borax, but a larger addition of oxide, required to
produce a yellow color in the warm bead.
in the reducing flame.
On charcoal the plumbiferous glass becomes grey and dull. With
an over dose of oxide a part is volatilized and forms an
incrustation on the charcoal beyond the bead. The addition of
tin does not render the glass opaque, but somewhat more dull and
grey than in its absence.
* * * * *
11. Oxide of Tin, SnO^{2}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
In small quantity dissolves slowly into a clear colorless glass,
which, when cold, remains clear, and cannot be rendered opaque
with an intermittent flame. If a saturated bead, which has been
allowed to cool, be reheated to incipient redness, it loses its
rounded form and exhibits imperfect crystallization.
in the reducing flame.
A glass containing but little oxide undergoes no change. If much
of the latter be present, a part may be reduced upon charcoal.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
In small quantity dissolves very slowly to a colorless glass,
which remains clear on cooling.
in the reducing flame.
The glass undergoes no change, either on charcoal or platinum wire.
* * * * *
12. Oxide of Bismuth, BiO^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Dissolves readily to a clear glass which with a small amount of
the oxide is yellow, while warm, and becomes colorless on
cooling. With a larger addition, the glass is, in the hot state,
of a deep orange color, which changes to yellow and finally
becomes opaline in process of cooling.
in the reducing flame.
A glass becomes at first grey and turbid, then begins to
effervesce, which action continues during the reduction of the
oxide, and it finally becomes perfectly clear. If tin be added,
the glass becomes at first grey from the reduced bismuth, but,
when the metal is collected into a bead, the glass is again
clear and colorless.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Dissolves in small quantity to a clear colorless glass. A larger
addition affords a glass which, while warm, is yellow, and
becomes colorless on cooling. When in sufficient proportion the
glass may be rendered opaque under an intermittent flame, and a
still larger addition of oxide renders the bead spontaneously
opaque on cooling.
in the reducing flame.
On charcoal, and especially with the addition of tin, the glass
remains colorless and clear, while warm, but becomes on cooling
of a dark grey color and opaque.
* * * * *
13. Oxide of Uranium, U^{2}O^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Behaves similarly to oxide of iron, with the exception that the
color of the former is somewhat paler. When sufficiently
saturated, the glass may be rendered of an opaque yellow by an
intermittent flame.
in the reducing flame.
Affords the same color as the oxide of iron. The green glass
obtained in this flame, if sufficiently saturated, can be
rendered black by an intermittent flame, but it has under these
circumstances no enameline appearance. On charcoal, with the
addition of tin, the glass takes a dark green color.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Dissolves to a clear yellow glass, which assumes a
yellowish-green color on cooling.
in the reducing flame.
The glass assumes a beautiful green color, which becomes more
brilliant as the bead cools. The addition of tin upon charcoal
produces no further change.
* * * * *
14. Oxide of Copper, CuO.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Produces an intense coloration. If in small quantity, the glass
is green, while warm, and becomes blue on cooling. If in large
proportion, the green color is so intense as to appear black.
When cool, this becomes paler, and changes to a greenish blue.
in the reducing flame.
If not too saturated, the cupriferous glass soon becomes nearly
colorless, but immediately on solidifying assumes a red color
and becomes opaque. By long continued blowing on charcoal, the
copper in the bead is reduced and separates out as a small
metallic bead, leaving the glass colorless. With the addition of
tin, the glass becomes of an opaque dull-red on cooling.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
With an equal proportion of oxide, this salt is not so strongly
colored as borax. A small amount imparts a green color in the
warm and a blue in the cold. With a very large addition of
oxide, the glass is opaque in the hot state, and after cooling
of a greenish-blue.
in the reducing flame.
A tolerably saturated glass assumes a dark green color under a
good flame, and on cooling becomes of an opaque brick-red, the
moment it solidifies. A glass containing but a small proportion
of the oxide becomes equally red and opaque on cooling, if
treated with tin upon charcoal.
* * * * *
15. Oxide of Mercury, HgO.
Behavior with Borax on Platinum wire
in the oxidizing flame.
No reaction.
in the reducing flame.
No reaction.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
No reaction.
in the reducing flame.
No reaction.
* * * * *
16. Oxide of Silver, AgO.
Behavior with Borax on Platinum wire
in the oxidizing flame.
The oxide is partly dissolved and partly reduced. In small
quantity, it colors the glass yellow while warm, the color
disappearing on cooling. In larger quantity, the glass is yellow
while warm, but during cooling becomes paler to a certain point,
and then again deeper. If reheated slightly, the glass becomes
opalescent.
in the reducing flame.
On charcoal the argentiferous glass becomes at first grey from
the reduced metal, but afterwards, when the silver is collected
into a bead, it becomes clear and colorless.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Both the oxide and the metal afford a yellowish glass, which,
when containing much oxide becomes opaline, exhibiting a yellow
color by daylight and a red one by artificial light.
in the reducing flame.
As in borax.
* * * * *
17. Oxide of Platinum, PtO^{2}.
18. Oxide of Palladium, PdO^{2}.
19. Oxide of Rhodium, R^{2}O^{3}.
20. Oxide of Iridium, Ir^{2}O^{3}.
21. Oxide of Ruthenium, Ru^{2}O^{9}.
22. Oxide of Osmium OsO^{2}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Are reduced without being dissolved. The reduced metal, being
infusible, cannot however be collected into a bead.
in the reducing flame.
As in the oxidizing flame.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
As in borax.
in the reducing flame.
As in borax.
* * * * *
23. Oxide of Gold, Au^{2}O^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Is reduced without being dissolved and can be collected into a
bead on charcoal.
in the reducing flame.
As in the oxidizing flame.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
As in borax.
in the reducing flame.
As in borax.
* * * * *
24. Titanic Acid, TiO^{2}
Behavior with Borax on Platinum wire
in the oxidizing flame.
Dissolves readily to a clear glass which, when but little acid
is present, is colorless, but when in larger proportion, yellow,
and, on cooling, colorless. When sufficiently saturated, it may
be rendered opaque with an intermittent flame, and with a still
larger addition of the acid becomes so spontaneously on cooling.
in the reducing flame.
In small proportion, it renders the glass yellow in larger
quantity dark-yellow or brown. A saturated bead assumes a
blue enamel-like appearance under an intermittent flame.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Dissolves readily to a clear glass, which, when sufficiently
saturated, is yellow white hot, and becomes colorless on
cooling.
in the reducing flame.
The glass obtained in the oxidizing glame becomes yellow in the
hot state, but on cooling assumes a beautiful violet color. If
too saturated, this color is so deep as to appear opaque, but is
not enameline. If the titanic acid contains iron, the glass
becomes on cooling of a brownish-yellow or red color. The
addition of tin neutralizes the iron, and the glass then becomes
violet.
* * * * *
25. Tantalic Acid, TaO^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Dissolves readily to a clear colorless glass, which, when
sufficiently saturated, may be rendered opaque with an
intermittent flame, and with a larger addition of the acid
becomes spontaneously enameline on cooling.
in the reducing flame.
As in the oxidizing flame.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Dissolves readily to a clear glass, which, when it contains a
large proportion of the acid, is yellow while warm, but becomes
colorless on cooling.
in the reducing flame.
The glass obtained in the oxidizing flame undergoes no change,
nor does it, according to _H. Rose_, alter by the addition of
sulphate of iron.
* * * * *
26. Niobic Acid, Ni^{2}O{3}
Behavior with Borax on Platinum wire
in the oxidizing flame.
Behaves in a similar manner to tantalic acid, but the glass
requires a very large dose of the acid to render it opaque under
an intermittent flame. With an increased amount of the acid, the
glass is clear and yellow, while warm, but becomes on cooling
turbid, and when quite cold is white.
in the reducing flame.
The glass obtained in the oxidizing flame and which has become
opalescent on cooling, is rendered clear in the reducing flame.
With a larger addition of the acid, it becomes dull, and of a
bluish-grey color on cooling, and a still larger amount of
renders it opaque and bluish grey.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Dissolves in large quantities to a clear colorless glass.
in the reducing flame.
If the acid be not present in too large a proportion, the glass
remains unchanged. An additional amount of the acid renders it
violet, and a still larger quantity affords a beautiful pure
blue color, similar to that produced by tungstic acid. If to
such a bead some sulphate of iron be added, the glass becomes
blood-red. The addition of peroxide of iron renders the glass
deep yellow while warm, the color becomes paler on cooling.
* * * * *
27. Pelopic Acid, Pp^{2}O^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Behaves similarly to the preceding.
in the reducing flame.
A bead containing sufficient of the acid to render it
spontaneously opaque on cooling, has a greyish color.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Dissolves even in large quantity to a colorless glass.
in the reducing flame.
With sufficient dose of the acid, the bead becomes brown with a
violet tinge. This reaction is readily obtained upon charcoal.
Sulphate of iron renders the bead blood-red.
* * * * *
28. Oxide of Antimony, SbO^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Even when in large proportion, dissolves to a clear glass, which
is yellow when warm, but almost entirely loses its color on
cooling. On charcoal, the antimonious acid may be almost
expelled, so that tin produces no further change.
in the reducing flame.
A bead, that has only been treated for a short time in the
oxidizing flame, when submitted to the reducing flame becomes
grey and turbid from the reduced antimony. This soon volatizes
and the glass again becomes clear. The addition of tin renders
the glass ash-grey or black, according to the amount of oxide it
contains.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Dissolves with ebullition to a glass of a pale yellow color
while warm.
in the reducing flame.
On charcoal, the saturated glass becomes at first dull, but as
soon as the reduced antimony is volatilized, it again becomes
clear. With tin, the glass is at first rendered grey by the
reduced antimony, but by continued blowing is restored to
clearness. Even when the glass contains but little oxide, tin
produces this reaction.
* * * * *
29. Tungstic Acid, WO^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Dissolves readily to a clear colorless glass. In large
proportion it renders the borax yellow, while warm, and with a
still greater addition the bead may be made opaque with an
intermittent flame. If more be then added, this reaction takes
place spontaneously.
in the reducing flame.
When the oxide is present in small quantity, the glass undergoes
no change. With a larger proportion, the glass is deep yellow
while warm, and yellowish-brown when cold. This reaction takes
place upon charcoal, with a small quantity of the acid. Tin
produces a dark coloration, when the acid is not present in too
great a quantity.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Dissolves to a clear glass, which, when saturated, is yellow in
the hot state.
in the reducing flame.
The glass is of a pure blue. If the tungstic acid contain iron,
the glass becomes blood-red on cooling, similar to titanic acid.
In this case, tin restores the blue color, or, if iron be in
considerable quantity, renders it green.
* * * * *
30. Molydbic Acid, MO^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Dissolves readily and in large quantity. When but little is
dissolved, the glass is yellow while hot and colorless when
cold. When in larger quantity yellow while warm and opaline when
cold, and a further addition of acid renders it yellow when
warm, the color, on cooling, changing first to a pale enamel
blue, and then to an enamel white.
in the reducing flame.
The glass, which has been treated in the oxidizing flame,
becomes, when the acid is not present in too large a quantity,
brown, and when in large quantity, perfectly opaque. In a
strong flame, oxide of molybdenum is formed which is visible in
the yellow glass in the form of black flakes. If the glass
appear opaque, it should be flattened with the forceps.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Dissolves to a clear glass, which, when sufficient acid is
present, is of a yellowish-green color when warm, and becomes
nearly colorless on cooling. On charcoal, the glass becomes
dark, and when cool has a beautiful green color.
in the reducing flame.
The glass becomes of a bottle-green color, which on cooling,
changes to a brilliant green, similar to that produced by oxide
of chromium. The reaction on charcoal is precisely similar. Tin
renders the color somewhat darker.
* * * * *
31. Vanadic Acid, VaO^{8}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Dissolves to a clear glass, which is colorless when only a small
quantity of acid is present, and yellow when containing a larger
proportion.
in the reducing flame.
The yellow color of the glass changes to a brown when warm and a
chrome-green on cooling.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
As with borax.
in the reducing flame.
As with borax.
* * * * *
32. Oxide of Chromium, Cr^{2}O^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Affords an intense color, but dissolves slowly. A small
proportion colors the glass yellow when warm, and yellowish
green when cold; a larger addition produces a dark red color
when warm, which, on cooling, becomes yellow and finally a
brilliant green with a tinge of yellow.
in the reducing flame.
A small quantity of the oxide renders the glass beautifully
green both when warm and when cold. A larger addition changes it
to a darker emerald green. Tin produces no change in the color.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
Dissolves to a clear glass which has a pink tinge while warm,
but on cooling becomes dusky green, and finally brilliantly
green.
in the reducing flame.
As in the oxidizing flame, except that the colors are somewhat
darker. Tin produces no further change.
* * * * *
33. Arsenious Acid, AsO^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
No reaction.
in the reducing flame.
No reaction.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
No reaction.
in the reducing flame.
No reaction.
* * * * *
34. Tellurous Acid, TeO^{2}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Dissolves to a clear colorless glass which, when treated on
charcoal, becomes grey and dull from particles of reduced
tellurium.
in the reducing flame.
As in the oxidizing flame.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
As with borax.
in the reducing flame.
As with borax.
* * * * *
7. EXAMINATIONS WITH CARBONATE OF SODA.
The carbonate of soda is pulverized and then kneaded to a paste with
water; the substance to be examined, in fine powder, is also mixed
with it. A small portion of this paste is placed on the charcoal, and
gradually heated until the moisture is expelled, when the heat is
brought to the fusion of the bead, or as high as it can be raised.
Several phenomena will take place, which must be closely observed.
Notice whether the substance fuses with the bead, and if so, whether
there is intumescence or not. Or, whether the substance undergoes
reduction; or, whether neither of these reactions takes place, and, on
the contrary, the soda sinks into the charcoal, leaving the substance
intact upon its surface. If intumescence takes place, the presence of
either tartaric acid, molybdic acid, silicic, or tungstic acid, is
indicated. The silicic acid will fuse into a bead, which becomes clear
when it is cold. Titanic acid will fuse into the bead, but may be
easily distinguished from the silicic acid by the bead remaining
opaque when cold.
Strontia and baryta will flow into the charcoal, but lime will not.
The molybdic and tungstic acids combine with the soda, forming the
respective salts. These salts are absorbed by the charcoal. If too
great a quantity of soda is used, the bead will be quite likely to
become opaque upon cooling, while, if too small a quantity of soda is
used, a portion of the substance will remain undissolved. These can be
equally avoided by either the addition of soda, or the substance
experimented upon, as may be required.
As silica and titanic acid are the only two substances that produce a
clear bead, the student, if he gets a clear bead, may almost conclude
that he is experimenting with silica, titanic acid being a rare
substance. When soda is heated with silica, a slight effervescence
will be the first phenomenon noticed. This is the escape of the
carbonic acid of the carbonate of soda, while the silicic acid takes
its place, forming a glass with the soda. As titanic acid will not
act in the same manner as silica, it can be easily distinguished by
its bead not being perfectly pellucid. If the bead with which silica
is fused should be tinted of a hyacinth or yellow color, this may be
attributed to the presence of a small quantity of sulphur or a
sulphate, and this sometimes happens from the fact of the flux
containing sulphate of soda. The following metals, when exposed with
carbonate of soda to the reducing flame, are wholly or partially
reduced, viz. the oxides of all the noble metals, the oxides and acids
of tungsten, molybdenum, arsenic, antimony, mercury, copper,
tellurium, zinc, lead, bismuth, tin, cadmium, iron, nickel, and
cobalt. Mercury and arsenic, as soon as they are reduced, are
dissipated, while tellurium, bismuth, lead, antimony, cadmium, and
zinc, are only partially volatilized, and, therefore, form sublimates
on the charcoal. Those metals which are difficult of reduction should
be fused with oxalate of potassa, instead of the carbonate of soda.
The carbonic oxide formed from the combustion of the acid of this salt
is very efficient in the reduction of these metals. Carbonate of soda
is very efficient for the detection of minute quantities of manganese.
The mixture of the carbonate of soda with a small addition of nitrate
of potassa, and the mineral containing manganese, must be fused on
platinum foil. The fused mass, when cooled, presents a fine blue
color.
* * * * *
1. The following minerals, according to Griffin, produce beads with
soda, but do not fuse when heated alone: quartz, agalmatolyte,
dioptase, hisingerite, sideroschilosite, leucite, rutile,
pyrophyllite, wolckonskoite.
2. The following minerals produce only slags with soda: allophane,
cymophane, polymignite, æschynite, oerstedtite, titaniferous iron,
tantalite, oxides of iron, yttro-tantalite, oxides of manganese,
peroxide of tin (is reduced), hydrate of alumina, hydrate of magnesia,
spinel, gahnite, worthite, carbonate of zinc, pechuran, zircon,
thorite, andalusite, staurolite, gehlenite, chlorite spar, chrome
ochre, uwarowite, chromate of iron, carbonates of the earths,
carbonates of the metallic oxides, basic phosphate of yttria, do. of
alumina, do. of lime, persulphate of iron, sulphate of alumina,
aluminite, alumstone, fluoride of cerium, yttrocerite, topaz,
corundum, pleonaste, chondrodite.
3. The following minerals produce beads with a small quantity of soda,
but produce slags if too much soda is added: phenakite, pierosmine,
olivine, cerite, cyanite, talc, gadolinite, lithium-tourmaline.
* * * * *
1. The following minerals, when fused alone, produce beads. Of these
minerals the following produce beads with soda: the zeolites,
spodumene, soda-spodumene, labrador, scapolite, sodalite (Greenland),
elæolite, mica from primitive lime-stone, black talc, acmite,
krokidolite, lievrite, cronstedtite, garnet, cerine, helvine,
gadolinite, boracic acid, hydroboracite, tincal, boracite, datholite,
botryolite, axinite, lapis lazuli, eudialyte, pyrosmalite, cryolite.
2. The following minerals produce beads with a small quantity of soda,
but if too much is added they produce slags: okenite, pectolite, red
silicate of manganese, black hydro-silicate of manganese, idocrase,
manganesian garnets, orthite, pyrorthite, sordawalite, sodalite,
fluorspar.
3. The following minerals produce a slag with soda: brevicite,
amphodelite, chlorite, fahlunite, pyrope, soap-stone (Cornish) red
dichroite, pyrargillite, black potash tourmaline, wolfram,
pharmacolite, scorodite, arseniate of iron, tetraphyline, hetepozite,
uranite, phosphate of iron, do. of strontia, do. of magnesia,
polyhalite, hauyne.
4. The following metals are reduced by soda: tungstate of lead,
molybdate of lead, vanadate of lead, chromate of lead, vauquelinite,
cobalt bloom, nickel ochre, phosphate of copper, sulphate of lead,
chloride of lead, and chloride of silver.
* * * * *
The following minerals fuse on the edges alone, when heated in the
blowpipe flame:
1. The following produce beads with soda: steatite, meerschaum,
felspar, albite, petalite, nepheline, anorthite, emerald, euclase,
turquois, sodalite (Vesuvius).
2. The following minerals produce beads with a small quantity of
soda, but with the addition of more produce slags: tabular spar,
diallage, hypersthene, epidote, zoisite.
3. The following minerals produce slags only with soda:
stilpnosiderite, plombgomme, serpentine, silicate of manganese (from
Piedmont), mica from granite, pimelite, pinite, blue dichroite,
sphenc, karpholite, pyrochlore, tungstate of lime, green soda
tourmaline, lazulite, heavy spar, gypsum.
* * * * *
The reactions of substances, when fused with soda in the flame of
oxidation may be of use to the student. A few of them are therefore
given. Silica gives a clear glass.
The oxide of tellurium and telluric acid gives a clear bead when it is
hot, but white after it is cooled.
Titanic acid gives a yellow bead when hot.
The oxide of chromium gives also a clear yellow glass when hot, but is
opaque when cold.
Molybdic acid gives a clear bead when hot, but is turbid and white
after cooling.
The oxides and acids of antimony give a clear and colorless bead while
hot, and white after cooling.
Vanadic acid is absorbed by the charcoal, although it is not reduced.
Tungstic acid gives a dark yellow clear bead while hot, but is opaque
and yellow when cold.
The oxides of manganese give to the soda bead a fine characteristic
green color. This is the case with a very small quantity. This
reaction is best exhibited on platinum foil.
Oxide of cobalt gives to the bead while hot a red color, which, upon
being cooled, becomes grey.
The oxide of copper gives a clear green bead while hot.
The oxide of lead gives a clear colorless bead while hot, which
becomes, upon cooling, of a dirty yellow color and opaque.
* * * * *
The following metals, when they are fused with soda on charcoal, in
the flame of reduction, produce volatile oxides, and leave an
incrustation around the assay, viz. bismuth, zinc, lead, cadmium,
antimony, selenium, tellurium, and arsenic.
_Bismuth_, under the reduction flame, yields small particles of metal,
which are brittle and easily crushed. The incrustation is of a flesh
color, or orange, when hot, but gets lighter as it cools. The
sublimate may be driven about the charcoal from place to place, by
either flame, but is finally dissipated. While antimony and tellurium,
in the act of dissipation, give color to the flame, bismuth does not,
and may thus be distinguished from them.
_Zinc_ deposits an incrustation about the assay, which is yellow while
hot, but fades to white when cold. The reduction flame dissipates this
deposit, but not that of oxidation. All the zinc minerals deposit the
oxide incrustation about the assay, which, when moistened with a
solution of cobalt and heated, changes to green.
_Lead_ is very easily reduced, in small particles, and may be easily
distinguished by its flattening under the hammer, unlike bismuth. It
leaves an incrustation around the assay resembling that of bismuth, in
the color of it, and in the peculiar manner in which it lies around
the assay.
_Cadmium_ deposits a dull reddish incrustation around the assay.
Either of the flames dissipate the sublimate with the greatest
readiness.
_Antimony_ reduces with readiness. At the same time it yields
considerable vapor, and deposits an incrustation around the assay.
This deposit can be driven about on the charcoal by either of the
flames. The flame of reduction, however, produces the light blue color
of the antimony.
_Selenium_ is deposited on the charcoal as a grey metallic-looking
sublimate, but sometimes appearing purple or blue. If the reduction
flame is directed on this deposit, it is dissipated with a blue light.
_Tellurium_ is deposited on the charcoal as a white sublimate,
sometimes changing at the margin to an orange or red color. The
oxidation flame drives the deposit over the charcoal, while the
reduction-flame dissipates it with a greenish color.
_Arsenic_ is vaporized rapidly, while there is deposited around the
assay a white incrustation of arsenious acid. This deposit will extend
to some distance from the assay, and is readily volatilized, the
reducing flame producing the characteristic alliaceous color.
* * * * *
The following metals, or their compounds, are reduced when fused with
soda on charcoal, in the flame of reduction. They are reduced to
metallic particles, but give no incrustation, viz. nickel, cobalt,
iron, tin, copper, gold, silver, platinum, tungsten, and molybdenum.
The particles of iron, nickel, and cobalt, it should be borne in mind,
are attracted by the magnet.
The following substances are neither fused nor reduced in soda, viz.
alumina, magnesia, lime, baryta, strontia, the oxide of uranium, the
oxides of cerium, zirconia, tantalic acid, thorina, glucina, and
yttria. Neither are the alkalies, as they sink into the charcoal. The
carbonates of the earths, strontia, and baryta fuse.
* * * * *
Part III
SPECIAL REACTIONS; OR, THE BEHAVIOR OF SUBSTANCES BEFORE THE BLOWPIPE.
Analytical chemistry may be termed the art of converting the unknown
constituents of substances, by means of certain operations, into new
combinations which we recognize through the physical and chemical
properties which they manifest.
It is, therefore, indispensably necessary, not only to be cognizant of
the peculiar conditions by which these operations can be effected, but
it is absolutely necessary to be acquainted with the forms and
combinations of the resulting product, and with every modification
which may be produced by altering the conditions of the analysis.
We shall first give the behavior of simple substances before the
blowpipe; and the student should study this part thoroughly, by
repeating each reaction, so that he can acquire a knowledge of the
color, form, and physical properties in general, of the resulting
combination. There is nothing, perhaps, which will contribute more
readily to the progress of the pupil, than thorough practice with the
reactions recommended in this part of the work, for when once the
student shall have acquired a practical eye in the discernment of the
peculiar appearances of substances after they have undergone the
decompositions produced by the strong heat of the blowpipe flame,
together with the reactions incident to these changes, then he will
have greatly progressed in his study, and the rest will be
comparatively simple.
A. METALLIC OXIDES.
GROUP FIRST.--THE ALKALIES: POTASSA, SODA, AMMONIA, AND LITHIA.
The alkalies, in their pure, or carbonated state, render reddened
litmus paper blue. This is likewise the case with the sulphides of the
alkalies. The neutral salts of the alkalies, formed with the strong
acids, do not change litmus paper, but the salts formed with the weak
acids, render the red litmus paper blue; for instance, the alkaline
salts with boracic acid. Fused with borax, soda, or microcosmic salt,
they give a clear bead. The alkalies and their salts melt at a low red
heat. The alkalies cannot be reduced to the metallic state before the
blowpipe. They are not volatile when red hot, except the alkali
ammonia, but they are volatile at a white heat.
(_a._) _Potassa._(KO).--It is not found free, but in combination with
inorganic and organic acids, as well in the animal as in the vegetable
organism, as in the mineral kingdom. In the pure, or anhydrous state,
or as the carbonate, potassa absorbs moisture, and becomes fluid, or
is deliquescent, as it is termed. By exposing potassa, or its easily
fusible salts (except the phosphate or borate), upon platinum wire, to
the point of the blue flame, there is communicated to the external
flame a violet color, in consequence of a reduction and reoxidation.
This color, though characteristic of all the potassa compounds, is
scarcely visible with the phosphate or borate salts of that alkali.
The admixture of a very little soda (1/300th) destroys the color
imparted by the potassa, while the flame assumes a yellow color,
characteristic of the soda. The presence of lithia changes the violet
color of the potash into red. The silicates of potassa must exist in
pretty large proportion before they can be detected by the violet
color of the flame, and those minerals must melt easily at the edges.
The presence of a little soda in these instances conceals the reaction
in the potassa entirely.
If alcohol is poured over potassa compounds which are powdered, and
then set on fire, the external flame appears violet-colored,
particularly when stirred with a glass rod, and when the alcohol is
really consumed. The presence of soda in lithia will, in this case
likewise, hide by their own characteristic color, that of the potassa.
The salts of potassa are absorbed when fused upon charcoal. The
sulphur, bromine, chlorine, and iodine compounds of potassa give a
white, but easily volatile sublimate upon the charcoal, around the
place where the fused substance reposed. This white sublimate
manifests itself only when the substance is melted and absorbed within
the charcoal, and ceases to be visible as soon as it is submitted to
the reducing flame, while the external flame is colored violet;
sulphate of potassa, for instance, is reduced by the glowing charcoal
into the sulphide. This latter is somewhat volatile, but by passing
through the oxidation flame, it is again oxidized into the sulphate.
This, being less volatile, sublimes upon the charcoal, but by exposing
it again to the flame of reduction, it is reduced and carried off to
be again oxidized by its passage through the oxidation flame.
Potassa and its compounds give, with soda, borax or microcosmic salt,
as well when hot as cold, colorless beads, unless the acid associated
with the alkali should itself produce a color. When borax is fused
with some pure boracic acid, and sufficient of the oxide of nickel is
added, so that the beads appear of a brown color after being cooled,
and then the bead thus produced fused with the substance suspected to
contain potassa, in the oxidation flame, the brown color is changed to
blue. The presence of the other alkalies does not prevent this
reaction. As it is not possible to detect potassa compounds with
unerring certainty by the blowpipe flame, the the wet method should
be resorted to for the purpose of confirming it.
The _silicates of potassa_ must be prepared as follows, for analytical
purposes by the wet way. Mix one part of the finely powdered substance
with two parts of soda (free from potassa), and one part of borax.
Fuse the mixture upon charcoal in the oxidation flame to a clear,
transparent bead. This is to be exposed again with the pincers to the
oxidation flame, to burn off the adhering coal particles. Then
pulverize and dissolve in hydrochloric acid to separate the silica;
evaporate to dryness, dissolve the residue in water, with the
admixture of a little alcohol, and test the filtrate with chloride of
platinum for potassa.
(_b._) _Soda_ (NaO).--This is one of the most abundant substances,
although seldom found free, but combined with chlorine or some other
less abundant compound. Soda, its hydrate and salts manifest in
general the same properties as their respective potash compounds; but
the salts of soda mostly contain crystal water, which leaves the salts
if they are exposed to the air, and the salts effervesce.
By exposing soda or its compounds upon a platinum wire to the blue
flame, a reddish-yellow color is communicated to the external flame,
which appears as a long brilliant stream and considerably increased in
volume. The presence of potash does not prevent this reaction of soda.
If there is too large a quantity of potash, the flame near to the
substance is violet-colored, but the edge of the flame exhibits the
characteristic tint of the soda. The presence of lithia changes the
yellow color to a shade of red.
When alcohol is poured over powdered soda compounds and lighted, the
flame exhibits a reddish-yellow color, particularly if the alcohol is
stirred up with a glass rod, or if the alcohol is nearly consumed.
Fused upon charcoal, soda compounds are absorbed by the coal. The
sulphide, chloride, iodide, and bromide of soda yield a white
sublimate around the spot where the substance is laid, but this
sublimate is not so copious as that of the potash compounds, and
disappears when touched with the reduction flame, communicating a
yellow color to the external flame. The presence of soda in compounds
must likewise be confined by reactions in the wet way.
(_c._) _Ammonia_ (NH^{4}O).--In the fused state, and at the usual
temperature, ammonia is a pungent gas, and exerts a reaction upon
litmus paper similar to potash and soda. Ammonium is considered by
chemists as a metal, from the nature of its behavior with other
substances. It has not been isolated, but its existence is now
generally conceded by all chemists. The ammonia salts are volatile,
and many of them sublimate without being decomposed.
The salts of ammonia, on being heated in the point of the blue flame,
produce a feeble green color in the external flame, just previous to
their being converted into vapor. But this color is scarcely visible,
and presents nothing characteristic. When the ammonia salts are mixed
with the carbonate of soda, and heated in a glass tube closed at one
end, carbonate of ammonia is sublimed, which can be readily recognized
by its penetrating smell of spirits of hartshorn.
This sublimate will render blue a slip of red litmus paper. This can
be easily done by moistening the litmus paper, and then inserting the
end of it in the tube. By holding a glass rod, moistened with dilute
hydrochloric acid, over the mouth of the tube, a white vapor is
instantly rendered visible (sal ammoniac).
(_d._) _Lithia_ (LiO).--In the pure state, lithia is white and
crystalline, not easily soluble in water, and does not absorb
moisture. It changes red litmus to blue, and at a low red heat it
melts. Lithia or its salts, exposed to the point of the blue flame,
communicates a red color to the external or oxidation flame, in
consequence of a reduction, sublimation, and re-oxidation of the
lithia. An admixture of potash communicates to this flame a
reddish-violet color, and the presence of soda that of a yellowish-red
or orange. If the soda, however, is in too great proportion, then its
intense yellow hides the red of the lithia. In the latter case the
substance under test must be only imperfectly fused in the oxidation
flame, and then dipped in wax or tallow. By exposing it now to the
reduction flame, the red color imparted to the external flame by the
lithia becomes visible, even if a considerable quantity of soda be
present. A particular phenomenon appears with the phosphate of lithia,
viz., the phosphoric acid itself possesses the property of
communicating to the flame a bluish-green color. By its combination
with lithia it still exhibits its characteristic color, while the
latter presents likewise its peculiar tint. Then we perceive a green
flame in the centre of the flame, while the red color of lithia
surrounds it.
The _silicates_, which contain only a little lithia, produce only a
slight hue in the flame, and often none at all. We have to mix one
part of the silicate with two parts of a mixture composed of one part
of fluorspar and one and a half parts of bisulphate of potassa.
Moisten the mass with water so that the mass will adhere, and then
melt it upon a platinum wire in the reduction flame, when that of
oxidation will present the red color of lithia.
The _Borates of lithia_ produce at first a green color, but it soon
yields to the red of lithia. When alcohol is poured over lithia or its
compounds, and inflamed, it burns with a deep red color, particularly
if the fluid is stirred up with a glass rod, or when the alcohol is
nearly consumed. This color presents the same modifications as the
corresponding ones communicated to the blowpipe as mentioned above.
The salts of lithia are absorbed by charcoal when fused upon it. The
sulphide, bromide, iodide, and chloride of lithia produce upon the
charcoal a greyish-white sublimate, although not so copiously as the
corresponding compounds of potash and soda. This sublimate disappears
when touched by the reduction flame, while the oxidation flame gives
the characteristic color of lithia.
SECOND GROUP.--THE ALKALINE EARTHS, BARYTA, STRONTIA, LIME, AND
MAGNESIA.
In the pure state, the alkaline earths are caustic, cause red litmus
paper to become blue, and are more or less soluble in water. Their
sulphides are also soluble. The carbonates and phosphates of the
alkaline earths are insoluble in water. By igniting the carbonates,
their carbonic acid is expelled, and the alkaline earths are left in
the caustic state. The alkaline earths are not volatile, and their
organic salts are converted, by ignition, into carbonates.
(_a._) _Baryta._ (BaO).--This alkaline earth does not occur free in
nature, but combined with acids, particularly with carbonic and
sulphuric acids. In the pure state, baryta is of a greyish-white
color, presents an earthy appearance, and is easily powdered. When
sparingly moistened with water, it slakes, becomes heated, and forms a
dry, white powder. With still more water it forms a crystalline mass,
the hydrate of baryta, which is completely soluble in hot water. Pure
baryta is infusible; the hydrate fuses at a red heat, without the loss
of its hydratic water; if caustic baryta is exposed for too great a
length of time to the flame, it absorbs water, originated by the
combustion, and becomes a hydrate, when it will melt. Salts of baryta,
formed with most acids, are insoluble in water; for instance, the
salts with sulphuric, carbonic, arsenic, phosphoric, and boracic
acids. The salts of baryta, soluble in water, are decomposed by
ignition, except the chloride.
Carbonate of baryta loses its carbonic acid at a red heat, becomes
caustic, and colors red litmus paper blue.
By exposing baryta or its compounds upon a platinum wire, or a
splinter of the substance held with the platinum tongs, to the point
of the blue flame, a pale apple-green color is communicated to the
external flame. This color appears at first very pale, but soon
becomes more intense. This color is most visible if the substance is
operated with in small quantities. The chloride of barium produces the
deepest color. This color is less intense if the carbonate or sulphate
is used. The presence of strontia, lime, or magnesia, does not
suppress the reaction of the baryta, unless they greatly predominate.
When alcohol is poured over baryta or its salts, and inflamed, a
feeble green color is communicated to the flame, but this color should
not be considered a characteristic of the salt.
Baryta and its compounds give, when fused with carbonate of soda upon
platinum foil, a clear bead. Fused with soda upon charcoal, it is
absorbed. The sulphate fuses at first to a clear bead, which soon
spreads, and is absorbed and converted while boiling into a hepatic
mass. If this mass is taken out, placed upon a piece of polished
silver and moistened with a little water, a black spot of sulphide of
silver is left after washing off the mass with water.
Borax dissolves baryta and its compounds with a hissing noise, as well
in the flame of oxidation as in that of reduction. There is formed a
clear bead which, with a certain degree of saturation, is clear when
cold, but appears milk-white when overcharged, and of an opal, enamel
appearance, when heated intermittingly, or with a vacillating flame,
that changes frequently from the oxidating to the reducing flame.
Baryta and its compounds produce the same reactions with microcosmic
salt.
Baryta and its compounds fuse when exposed to ignition in the
oxidizing flame. Moistened with the solution of nitrate of cobalt, and
heated in the oxidation flame, it presents a bead, colored from
brick-red to brown, according to the quantity used. This color
disappears when cold, and the bead falls to a pale grey powder after
being exposed awhile to the air. When heated again, the color does not
appear until fusion is effected. If carbonate of soda is fused upon
platinum wire with so much of the sesquioxide of manganese that a
green bead is produced, this bead, when fused with a sufficient
quantity of baryta, or its compounds, after cooling, will appear of a
bluish-green, or light blue color.
(_b._) _Strontia_ (SrO).--Strontia and its compounds are analogous to
the respective ones of baryta. The hydrate of strontia has the same
properties as the hydrate of baryta, except that it is less soluble in
water. The carbonate of strontia fuses a little at a red heat, swells,
and bubbles up like cauliflower. This produces, in the blowpipe flame,
an intense and splendid light, and now produces an alkaline reaction
upon red litmus paper. The sulphate of strontia melts in the oxidation
flame upon platinum foil, or upon charcoal, to a milk-white globule.
This fuses upon charcoal, spreads and is reduced to the sulphide,
which is absorbed by the charcoal. It now produces the same reactions
upon polished silver as the sulphate of baryta under the same
conditions. By exposing strontia and its compounds upon platinum wire,
or as a splinter with the platinum tongs, to the point of the blue
flame, the external flame appears of an intense crimson color. The
deepest red color is produced by the chloride of strontium,
particularly at the first moment of applying the heat. After the salt
is fused, the red color ceases to be visible in the flame, by which it
is distinguished from the chloride of lithium. The carbonate of
strontia swells up and produces a splendid white light, while the
external flame is colored of a fine purple-red. The color produced by
the sulphate of strontia is less intense. The presence of baryta
destroys the reaction of the strontia, the flame presenting the light
green color of the baryta.
If alcohol is poured over powdered strontia and inflamed, the flame
appears purple or deep crimson, particularly if the fluid is stirred
with a glass rod, and when the alcohol is nearly consumed.
The insoluble salts of strontia do not produce a very intense color.
Baryta does not prevent the reaction of the soluble salts of strontia,
unless it exists greatly in excess. In the presence of baryta,
strontia can be detected by the following process: mix some of the
substance under examination with some pure graphite and water, by
grinding in an agate mortar. Place the mixture upon charcoal, and
expose it for a while to the reduction flame. The substance becomes
reduced to sulphide of barium and sulphide of strontium, when it
should be dissolved in hydrochloric acid. The solution should be
evaporated to dryness, redissolved in a little water, and enough
alcohol added that a spirit of 80 per cent. is produced. Inflame the
spirit, and if strontia is present, the flame is tinged of a red
color. This color can be discerned more distinctly by moistening some
cotton with this spirit and inflaming it.
If strontia or its compounds are fused with a green bead of carbonate
of soda and sesquioxide of manganese, as described under the head of
baryta, a bead of a brown, brownish-green, or dark grey color is
produced. Carbonate of soda does not dissolve pure strontia. The
carbonate and sulphate of strontia melt with soda upon platinum foil
to a bead, which is milk-white when cold, but fused upon charcoal they
are absorbed. Strontia or its compounds produce with borax, or
microcosmic salt, the same reactions as baryta. When they are
moistened with nitrate of cobalt, and ignited in the oxidizing flame,
a black, or grey infusible mass is produced.
(_c._) _Lime, Oxide of Calcium _(CaO).--Lime does not occur free in
nature, but in combination with acids, chiefly the carbonic and
sulphuric. The phosphate occurs principally in bones. The hydrate and
the salts of lime are in their properties similar to those of the two
preceding alkaline earths. In the pure state, the oxide of calcium is
white; it slakes, produces a high temperature, and falls into a white
powder when sprinkled with a little water. It is now a hydrate, and
has greatly increased in volume. The hydrate of lime is far less
soluble in water than either those of baryta or strontia, and is less
soluble in hot water than in cold. Lime, its hydrate and sulphide of
calcium, have a strong alkaline reaction upon red litmus paper. Lime
and its hydrate are infusible, but produce at a strong red heat a very
intense and splendid white light, while the hydrate loses its water.
The carbonate of lime is also infusible, but at a red heat the
carbonic acid is expelled, and the residue becomes caustic, appears
whiter, and produces an intenser light. The sulphate of lime melts
with difficulty, and presents the appearance of an enamelled mass when
cold. By heating it upon charcoal it fuses in the reducing flame, and
is reduced to a sulphide. This has a strong hepatic odor, and exerts
an alkaline reaction upon red litmus paper. By exposing lime, or its
compounds, upon platinum wire--or as a small splinter of the mineral
in the platinum tongs--to the point of the blue flame, a purple color,
similar to that of lithia and strontia, is communicated to the
external flame, but this color is not so intense as that produced by
strontia, and appears mixed with a slight tinge of yellow. This color
is most intense with the chloride of calcium, while the carbonate of
lime produces at first a yellowish color, which becomes red, after the
expulsion of the carbonic acid. Sulphate of lime produces the same
color, but not so intense. Among the silicates of lime only the
tablespar (3CaO, 2SiO^{3}) produces a red color. Fluorspar (CaFl)
produces a red as intense as pure lime, and fuses into a bead.
Phosphate and borate of lime produce a green flame which is only
characteristic of their acids. The presence of baryta communicates a
green color to the flame. The presence of soda produces only a yellow
color in the external flame.
If alcohol is poured over lime or its compounds and inflamed, a red
color is communicated to the flame. The presence of baryta or soda
prevents this reaction. Lime and its compounds do not dissolve much by
fusion with carbonate of soda. If this fusion is effected on charcoal,
the carbonate of soda is absorbed and the lime remains as a
half-globular infusible mass on the charcoal. This is what
distinguishes lime from baryta and strontia, and is a good method of
separating the former from the latter. Lime and its compounds fuse
with borax in the oxidizing and reducing flames to a clear bead, which
remains clear when cold, but when overcharged with an excess or heated
intermittingly, the bead appears, when cold, crystalline and uneven,
and is not so milk-white as the bead of baryta or strontia, produced
under the same circumstances. The carbonate of lime is dissolved with
a peculiar hissing noise. Microcosmic salt dissolves a large quantity
of lime into a clear bead, which is milky when cold. When the bead has
been overcharged with lime, by a less excess, or by an intermittent
flame, we will perceive in the bead, when cold, fine crystals in the
form of needles. Lime and its compounds form by ignition with nitrate
of cobalt, a black or greyish-black infusible mass.
(_d._) _Magnesia_ (MgO).--Magnesia occurs in nature in several
minerals. It exists in considerable quantity combined with carbonic,
sulphuric, phosphoric, and silicic acids, etc. Magnesia and its
hydrate are white and very voluminous, scarcely soluble in hot or cold
water, and restores moistened red litmus paper to its original blue
color. Magnesia and its hydrate are infusible, the latter losing its
water by ignition. The carbonate of magnesia is infusible, loses its
carbonic acid at a red heat, and shrinks a little. It now exerts upon
red litmus paper an alkaline reaction. The sulphate of magnesia, at a
red heat, loses its water and sulphuric acid, is entirely infusible,
and gives now an alkaline reaction. The artificial Astrachanit (NaO,
SO^{3} + MgO, SO^{3} + 4HO) fuses easily. When fused on charcoal, the
greater part of the sulphate of soda is absorbed, and there remains an
infusible mass.
Magnesia and its compounds do not produce any color in the external
flame, when heated in the point of the blue flame. The most of the
magnesia minerals yield some water when heated in a glass tube closed
at one end.
Magnesia, in the pure state, or as the hydrate, does not fuse with
soda. Some of its compounds are infusible likewise with soda, and
swell up slightly, while others of them melt with soda to a slightly
opaque mass. Some few (such as the borate of magnesia) give a clear
bead with soda, though it becomes slightly turbid by cooling when
saturated with magnesia, and crystallizes in large facets.
Magnesia and its compounds give beads with borax and microcosmic salt
similar to those of lime. By igniting magnesia or its compounds very
strongly in the oxidizing flame, moistening with nitrate of cobalt,
and re-igniting in the oxidation flame, they present, after a
continued blowing, a pale flesh-color, which is more visible when
cold. It is indispensable that the magnesia compounds should be
completely white and free of colored substances, or the color referred
to cannot be discerned. In general the reactions of magnesia before
the blowpipe are not sufficient, and it will be necessary to confirm
its presence or absence by aid of reagents applied in the wet way.
THIRD GROUP.--THE EARTHS, ALUMINA, GLUCINA, YTTRIA, THORINA, AND
ZIRCONIA.
The substances of this group are distinguished from the preceding by
their insolubility in water, in their pure or hydrated state--that
they have no alkaline reaction upon litmus paper, nor form salts with
carbonic acid. The earths are not volatile, and, in the pure state,
are infusible. They cannot be reduced to the metallic state before the
blowpipe. The organic salts are destroyed by ignition, while the
earths are left in the pure state, mixed with charcoal, from the
organic acids. The most of their neutral salts are insoluble in water;
the soluble neutral salts change blue litmus paper to red, and lose
their acids when ignited.
(_a._) _Alumina_ (Al^{2}O^{3}).--This earth is one of our most common
minerals. It occurs free in nature in many minerals, as sapphire,
etc.; or in combination with sulphuric acid, phosphoric acid, and
fluorine, and chiefly silicates. Pure alumina is a white crystalline
powder, or yellowish-white, and amorphous when produced by drying the
hydrate, separated chemically from its salts. Alumina is quite
unalterable in the fire; the hydrate, however, losing its water at a
low red heat. The neutral salts of alumina, with most acids, are
insoluble in water. Those soluble in it have an acid reaction upon
litmus paper, changing the blue into red.
The sulphates of alumina eliminate water when heated in a glass tube
closed at one end. By ignition, sulphurous acid (SO^{2}) is given off,
which can be recognized by its smell, and by its acid reaction upon
blue litmus paper, when a small strip of it moistened is brought
within the orifice of the tube; an infusible residue is left in the
tube.
The greater part of the alumina compounds give off water with heat;
the most of them are also infusible, except a few phosphates and
silicates.
Pure alumina does not fuse with carbonate of soda. The sulphates, when
exposed upon charcoal with soda to the reducing flame, leave a hepatic
residue. The phosphates melt with a little soda, with a hissing noise,
to a semi-transparent mass, but they are infusible with the addition
of soda, and give only a tough mass. This is the case, likewise, with
the silicates of alumina. Fluoride of aluminium melts with carbonate
of soda to a clear bead, spreads by cooling, and appears then
milk-white. Borax dissolves the alumina compounds slowly in the
oxidizing and reducing flames to a clear bead, which is also clear
when cold, or heated intermittingly with a vacillating flame. The bead
is turbid, as well in the heat as the cold, when an excess of alumina
is present. When the alumina compound is added to excess in the
powdered form, the bead appears crystalline upon cooling, and melts
again with great difficulty.
Alumina and its compounds are slowly dissolved in the microcosmic salt
to a bead, clear in both flames, and when hot or cold. When alumina is
added to excess, the undissolved portion appears semi-transparent.
Alumina melts with bisulphate of potash into a mass soluble in water.
When the powdered alumina compounds are strongly ignited in the
oxidizing flame, then moistened with nitrate of cobalt, and re-ignited
in the oxidizing flame, an infusible mass is left, which appears, when
cooled, of an intense blue color. The presence of colored metallic
oxides, in considerable quantity, will alter or suppress this
reaction. The silicates of the alkalies produce, in a very strong
heat, or continued heat, with nitrate of cobalt, a pale blue color.
The blue color produced by alumina is only distinctly visible by
daylight; by candle-light it appears of a dirty violet color.
(_b._) _Glucina._ (G^{2}O^{3}).--Glucina only occurs in a few rare
minerals, in combination with silica and alumina. It is white and
insoluble in the pure state, and its properties generally are similar
to those of alumina. The most of its compounds are infusible, and
yield water by distillation. Carbonate of soda does not dissolve
glucina by ignition. Silicate of glucina melts with carbonate of soda
to a colorless globule. Borax and microcosmic salt dissolve glucina
and its compounds to a colorless bead which, when overcharged with
glucina, or heated with the intermittent flame appears, after cooling,
turbid or milk-white. Glucina yields, by ignition with nitrate of
cobalt, a black, or dark grey infusible mass.
(_c._) _Yttria_ (YO) occurs only in a few rare minerals, and usually
in company with terbium and erbium. Its reactions before the blowpipe
are similar to the preceding, but for its detection in compounds it
will be necessary to resort to analysis in the wet way.
(_d._) _Zirconia_ (Zr^{2}O^{3}).--This substance resembles alumina in
appearance, though it occurs only in a few rare minerals. It is in the
pure state infusible, and at a red heat produces such a splendid and
vivid white light that the eyes can scarcely endure it. Its other
reactions before the blowpipe are analogous to glucina. Microcosmic
salt does not dissolve so much zirconia as glucina, and is more prone
to give a turbid bead. Zirconia yields with nitrate of cobalt, when
ignited, an infusible black mass. To recognize zirconia in compounds
we must resort to fluid analysis.
(_e._) _Thorina_ (ThO).--This is the rarest among the rare minerals.
In the pure state it is white and infusible, and will not melt with
the carbonate of soda. Borax dissolves thorina slowly to a colorless,
transparent bead, which will remain so when heated with the
intermittent flame. If overcharged with the thorina, the bead
presents, on cooling, a milky hue. Microcosmic salt dissolves the
thorina very tardily. By ignition with nitrate of cobalt, thorina is
converted into an infusible black mass,
CLASS II.
FOURTH GROUP. CERIUM, LANTHANIUM, DIDYMIUM, COLUMBIUM, NIOBIUM,
PELOPIUM, TITANIUM, URANIUM, VANADIUM, CHROMIUM, MANGANESE.
The substances of this group cannot be reduced to the metallic state,
neither by heating them _per se_, nor by fusing them with reagents.
They give by fusion with borax or microcosmic salt, colored beads,
while the preceding groups give colorless beads.
(_a._) _Cerium_ (Ce).--This metal occurs in the oxidated state in a
few rare minerals, and is associated with lanthanium and didymium,
combined with fluorine, phosphoric acid, carbonic acid, silica, etc.
When reduced artificially, it forms a grey metallic powder.
(_a._) _Protoxide of Cerium_ (CeO).--It exists in the pure state as
the hydrate, and is of a white color. It soon oxidizes and becomes
yellow, when placed in contact with the air. When heated in the
oxidation flame, it is converted into the sesquioxide, and then is
changed into light brick-red color. In the oxidation flame it is
dissolved by borax into a clear bead, which appears of an orange or
red while hot, but becomes yellow upon cooling. When highly saturated
with the metal, or when heated with a fluctuating flame, the bead
appears enamelled as when cold. In the reduction flame it is dissolved
by borax to a clear yellow bead, which is colorless when cold. If too
much of the metal exists in the bead, it then appears enamelled when
cooled.
Microcosmic salt dissolves it, in the oxidation flame, to a clear
bead, which is colored dark yellow or orange, but loses its color when
cold. In the reduction flame the bead is colorless when either hot or
cold. Even if highly saturated with the metal, the bead remains
colorless when cold. By fusing it with carbonate of soda upon charcoal
in the reduction flame, the soda is absorbed by the charcoal, while
the protoxide of the metal remains as a light grey powder.
(_B._) _Sesquioxide of Cerium_ (Ce^{2}O^{3}).--This oxide, in the pure
state, is a red powder. When heated with hydrochloric acid, it
produces chlorine gas, and is dissolved to a salt of the protoxide. It
is not affected by either the flame of oxidation or of reduction; when
fused with borax or microcosmic salt, it acts like the protoxide. It
does not fuse with soda upon charcoal. In the reduction flame it is
reduced to the protoxide, which remains of a light grey color, while
the soda is absorbed by the charcoal.
(_b._) _Lanthanium_ (La.)--This metal is invariably associated with
cerium. It presents, in its metallic state, a dark grey powder, which
by compression acquires the metallic lustre.
The _oxide of lanthanium_ (LaO) is white, and its salts are colorless.
Heated upon charcoal, it does not change either in the oxidation flame
or that of reduction. With borax, in the flame of oxidation or
reduction, it gives a clear colorless bead. This bead, if saturated,
and when hot, presents a yellow appearance, but is clouded or
enamelled when cold. With microcosmic salt the same appearance is
indicated. It does not fuse with carbonate of soda, but the soda is
absorbed by the charcoal, while the oxide remains of a grey color.
(_c._) _Didymium_ (D).--This metal occurs only in combination with the
preceding ones, and it is therefore, like them, a rare one.
_Oxide of Didymium_ (DO).--This oxide is of a brown color, while its
salts present a reddish-violet or amethyst color. The oxide is
infusible in the oxidation flame, and in that of reduction it loses
its brown color and changes to grey. With borax in the oxidation
flame, it fuses to a clear dark red or violet bead, which retains its
clearness when highly saturated with the oxide, or if heated with a
fluctuating flame.
The reactions with microcosmic salt are the same as with borax.
It does not melt with carbonate of soda upon charcoal, but the oxide
remains with a grey color, while the soda is absorbed by the charcoal.
(_d._) _Columbium,_ (_Tantalum_--Ta).--This rare metal occurs quite
sparingly in the minerals _tantalite_, _yttrotantalite_, etc., as
columbic acid. In the metallic state, it presents the appearance of a
black powder, which, when compressed, exhibits the metallic lustre.
When heated in the air it is oxidized into columbic acid, and is only
soluble in hydrofluoric acid, yielding hydrogen. It is oxidized by
fusion with carbonate of soda or potash.
_Columbic Acid_ (Ta^{2}O^{3}) is a white powder, and is infusible.
When heated in the flame of oxidation or reduction, it appears of a
light yellow while hot, but becomes colorless when cold. With borax,
in the flames of oxidation and reduction, it fuses to a clear bead,
which appears by a certain degree of saturation, of a yellow color so
long as it continues hot, but becomes colorless when cold. If
overcharged, or heated with an intermittent flame, it presents an
enamel white when cool.
It melts with microcosmic salt quite readily in both of the flames, to
a clear bead, which appears, if a considerable quantity of columbic
acid be present, of a yellow color while hot, but colorless when cold,
and does not become clouded if the intermittent flame be applied to
it.
With carbonate of soda it fuses with effervescence to a bead which
spreads over the charcoal. Melted with more soda, it becomes absorbed
by the charcoal.
It yields, moistened with a solution of nitrate of cobalt, and exposed
to the oxidation flame after continued blowing, an infusible mass,
presenting while hot a light grey color, but after being cooled that
of a light red, similar to the color presented by magnesia under the
same circumstances. But if there be some alkali mixed with it, a
fusion at the edges will be manifest, and it will yield by cooling a
bluish-black mass.
(_e._) _Niobium_ (Ni).--This metal occurs as niobic acid in columbite
(tantalite). Niobic acid is in its properties similar to columbic
acid. It is white and infusible. By heating it either in the flames of
reduction or oxidation, it presents as long as it continues hot, a
greenish-yellow color, but becomes white when cool. Borax dissolves it
in the oxidation flame quite readily to a clear bead, which, with a
considerable quantity of niobic acid, is yellow when hot, but
transparent and colorless when cold. A saturated bead is clear when
either hot or cold, but becomes opaque when heated intermittingly.
In the flame of reduction, borax is capable of dissolving more of the
niobic acid, so that a bead overcharged and opaque in the oxidation
flame appears quite clear when heated in the flame of reduction. A
bead overcharged in the flame of reduction, appears by cooling dim and
bluish-grey.
Microcosmic salt dissolves in the flame of oxidation a great quantity
of it to a clear bead, which is yellow while hot, but colorless when
cold.
In the flame of reduction, and in presence of a considerable quantity
of niobic acid, the bead appears while hot of a light dirty blue
color, and when cold, of a violet hue; but by the addition of more
niobic acid, the bead, when hot, is of a dirty dark blue color, and
when cold, of a transparent blue. In the presence of the oxides of
iron, the bead is, while hot, of a brownish-red color, but changing
when cool to a dark yellow.
This acid fuses with an equal quantity of carbonate of soda upon
charcoal, to a bead which spreads very quickly, and is then infusible.
When fused with still more soda, it is absorbed.
When moistened with nitrate of cobalt, and heated in the flame of
oxidation, it yields an infusible mass which appears grey when hot,
and dirty green when cold; but if the heat has been too strong, it is
fused a little at the edges, which present a dark bluish-grey color.
_Pelopium_ (Pe).--This metal occurs as an acid in the mineral
columbite (tantalite), and is very similar to the two preceding
metals.
(_f._) _Pelopic Acid_ (PeO^{3}).--This acid is white, and appears
yellow when heated, but resumes its white color when cold. Borax
dissolves it in the oxidation flame to a clear colorless bead, which
appears, when overcharged and heated intermittingly, enamel-white when
cold. This is likewise the case in the flame of reduction, but when
overcharged the color is light grey, when the bead is cooled.
Microcosmic salt dissolves it in the flame of oxidation, to a clear
yellow bead, which loses its color when cold. In the reduction flame,
when the bead is highly saturated, a violet-brown color is produced.
In presence of the oxides of iron, the reactions are like those of
niobic acid. With carbonate of soda, the reactions are similar to
those of niobic acid. By heating with nitrate of cobalt, it yields a
light grey infusible mass.
(_g._) _Titanium_ (Ti).--This metal occurs occasionally in the slags
of iron works, in the metallic state, as small cubical crystals of a
red color. It is a very hard metal, and very infusible. Titanic acid
occurs in nature crystallized in _anatase_, _arkansite_, _brookite_,
and _rutile_. Titanium is harder than agate, entirely infusible, and
loses only a little of its lustre, which can be regained by fusion
with borax. It does not melt with carbonate of soda, borax, or
microcosmic salt, and is insoluble in every acid except the
hydrofluoric. By ignition with saltpetre it is converted into titanic
acid, which combines with the potassium, forming the titanate of
potassium.
_Titanic Acid_ (TiO^{2}) is white, insoluble, and, when heated, it
appears yellow while hot, but resumes upon cooling its white color.
Borax dissolves it in the oxidation flame to a clear yellow bead,
which when cool is colorless. When overcharged, or heated with the
intermitting flame, it is enamel-white after being cooled. In the
reduction flame, the bead appears yellow, if the acid exists in small
quantity, but if more be added, then it is of an orange, or dark
yellow, or even brown. The saturated bead, when heated intermittingly,
appears when cold of an enamelled blue. By addition of the acid, and
by heating the bead on charcoal in the reduction flame, it becomes
dark yellow while hot, but dark blue, or black and opaque when cold.
This bead appears, when heated intermittingly, of a light blue, and
when cold, enamelled.
Microcosmic salt fuses with it in the oxidation flame to a clear
colorless bead, which appears yellow only in the presence of a
quantity of titanic acid, though by cooling it loses its color. In the
reduction flame this bead exhibits a yellow color when hot, but is red
while cooling, and when cold of a beautiful bluish-violet. If the bead
is overcharged, the color becomes so dark that the bead appears
opaque, though not presenting an enamel appearance. By heating the
bead again in the oxidation flame the color disappears. The addition
of some tin promotes the reduction. If the titanic acid contains oxide
of iron, or if some is added, the bead appears, when cold,
brownish-yellow, or brownish-red.
By fusion with carbonate of soda, titanic acid is dissolved with
effervescence to a clear dark yellow bead, which crystallizes by
cooling, whereby so much heat is eliminated, that the bead, at the
instant of its crystallization, glows with great brightness. A
reduction to a metal cannot, however, be effected. By ignition with a
solution of nitrate of cobalt in the oxidation flame, it yields an
infusible yellowish-green mass.
(_h._) _Uranium_ (U).--This rare metal occurs in the form of protoxide
along with other oxides, in the mineral _pitch-blende_; as peroxide in
_uranite_ and _uran-mica_, associated with phosphoric acid and lime.
In the metallic state it presents the appearance of a dark grey mass,
which is infusible, and remains unchanged when under water, or when
exposed to dry air, but, when heated in the oxidation flame, it
becomes oxidized, with lively sparkling, to a dark green mass,
composed of the protoxide and peroxide.
The _protoxide of uranium_ (UO) is black, uncrystalline, or forms a
brown powder. When exposed to heat it is converted partially into
peroxide, when it has a dark green color.
The _peroxide of uranium_ (U^{2}O^{3}) is of an orange color, while
its hydrate is of a fine yellow color, and in the form of a powder.
The salts are yellow.
By heating it in the oxidation flame, it acquires a dark green color,
and is partly reduced to protoxide. In the reduction flame it presents
a black appearance, and is there completely reduced to protoxide.
Borax dissolves it in the oxidation flame to a clear dark yellow bead,
which is colorless when cold, if the metal is not present in great
quantity. If more of the metal, or peroxide, be added, the bead
changes to orange when hot, and light yellow when cold. When heated
with the intermittent flame, it requires a large quantity of the
peroxide to produce an enamel appearance in the cooled bead.
In the flame of reduction the bead becomes of a dirty green color,
being partly reduced to protoxide, and appears, with a certain degree
of saturation, black, when heated intermittingly, but never enamelled.
The bead appears on charcoal, and with the addition of tin, of a dark
green color.
It fuses with microcosmic salt in the oxidation flame to a clear
yellow bead, which is greenish-yellow when cold. In the reduction
flame it produces a beautiful green bead, which increases when cold.
When fused upon charcoal with the addition of tin, its color is
darker. Carbonate of soda does not dissolve it, although with a very
small portion of soda it gives indications of fusion, but with still
more of the soda it forms a yellow, or light-brown mass, which is
absorbed by the charcoal, but it is not reduced to the metallic state.
(_i._) _Vanadium_ (V).--This very rare mineral is found in small
quantity in iron-ores, in Sweden, and as vanadic acid in a few rare
minerals. The metal presents the appearance of an iron-grey powder,
and sometimes that of a silver-white mass. It is not oxidized either
by air or water, and is infusible.
_Vanadic Acid_ (VO^{3}) fuses upon platinum foil to a deep orange
liquid, which becomes crystalline after cooling. When fused upon
charcoal, one part of it is absorbed, while the rest remains upon the
charcoal and is reduced to protoxide similar in appearance to
graphite.
A small portion of it fuses with borax in the oxidation flame to a
clear colorless bead, which appears, with the addition of more vanadic
acid, of a yellow color, but changes to green when cold.
In the reduction flame the bead is brown while hot, but changes, upon
cooling, to a beautiful sapphire-green. At the moment of
crystallization, and at a degree of heat by which at daylight no
glowing of the heated mass is visible it begins to glow again. The
glow spreads from the periphery to the centre of the mass, and is
caused by the heat liberated by the sudden crystallization of the
mass. It now exhibits an orange color, and is composed of needle
crystals in a compact mass.
Microcosmic salt and vanadic acid fuse in the oxidation flame to a
dark yellow bead which, upon cooling, loses much of its color.
In the reduction flame the bead is brown while hot, but, upon cooling,
acquires a beautiful green color.
Vanadic acid fuses with carbonate of soda upon charcoal, and is
absorbed.
(_k._) _Chromium_ (Cr) occurs in the metallic state only in a very
small quantity in meteoric iron, but is frequently found in union with
oxygen, as oxide in chrome iron ore, and as chromic acid in some lead
ores.
In the metallic state it is of a light grey color, with but little
metallic lustre, very hard, and not very fusible. Acids do not act
upon it, except the hydrofluoric; fused with nitre, it forms chromate
of potassa. It is unaltered in the blowpipe flame.
_Sesquioxide of Chromium_ (Cr^{2}O^{3}).--This oxide forms black
crystals of great hardness, and is sometimes seen as a green powder.
Its hydrate (Cr^{2}O^{3} + 6HO) is of a bluish-grey color. It forms
with acids two classes of isomeric salts, some of which are of a
green color, and the others violet-red or amethyst. The neutral and
soluble salts have an acid reaction upon blue litmus paper, and are
decomposed by ignition.
Sesquioxide of chromium in the oxidation and reduction flames is
unchangable. When exposed to heat, the hydrate loses its water, and
gives a peculiarly beautiful flame. In the oxidation flame borax
dissolves the sesquioxide of chromium slowly to a yellow bead (chromic
acid) which is yellowish green when cold. Upon the addition of more of
the oxide, the bead is dark red while hot, but changes to green as it
becomes cold.
In the reduction flame the bead is of a beautiful green color, both
while hot and when cold. It is here distinguished from vanadic acid,
which gives a brownish or yellow bead while hot.
With microcosmic salt it fuses in the oxidation flame to a clear
yellow bead, which appears, as it cools, of a dirty-green, color, but
upon being cool is of a fine green color. If there be a superabundance
of the oxide, so that the microcosmic salt cannot dissolve it, the
bead swells up, and is converted into a foamy mass, in consequence of
the development of gases.
In the reduction flame it fuses to a fine green bead. The addition of
a little tin renders the green still deeper.
Sesquioxide of chromium fuses with carbonate of soda upon platinum
foil to a brown or yellow bead, which, upon cooling, appears of a
lighter color and transparent (chromate of sodium).
When fused with soda upon charcoal, the soda is absorbed, and the
green oxide is left upon it, but is never reduced to the metallic
state.
_Chromic Acid_ (CrO^{3}) crystallizes in the form of deep ruby red
needles. It is decomposed into sesquioxide and oxygen when heated.
This decomposition is attended with a very lively emission of light,
but this is not the case if the chromic acid has been attained by the
coöperation of an aqueous solution, unless the reduction is effected
in the vapor of ammonia. Before the blowpipe chromic acid produces the
same reactions as the sesquioxide.
(_l._) _Manganese_ (Mn).--This metal occurs in considerable abundance,
principally as oxides, less frequently as salts, and sometimes in
combination with sulphur and arsenic. It is found in plants, and
passes with them into the animal body. In the metallic state, it is
found frequently in cast iron and steel. It is a hard, brittle metal,
fusible with difficulty, and of a light grey color. It tarnishes upon
exposure to the air and under water, and falls into a powder.
_Protoxide of Manganese_ exists as a green powder; as hydrate
separated by caustic alkalies, it is white, but oxidizes very speedily
upon exposure to the air. The protoxide is the base of the salts of
manganese. These salts, which are soluble in water, are decomposed
when heated in the presence of the air--except the sulphate (MnO,
SO^{3}), but if the latter is exposed to ignition for awhile, it then
ceases to be soluble in water, or at least only sparingly so.
_Sesquioxide of Manganese_ (Mn^{2}O^{3}) Occurs very sparingly in
nature as small black crystals (_Braunite_) which give, when ground, a
brown powder. When prepared by chemical process, it is in the form of
a black powder. The hydrate occurs sometimes in nature as black
crystals (_manganite_). By digestion with acids, it is dissolved into
salts of the protoxide. With hydrochloric acid, it yields chlorine.
The _prot-sesquioxide of manganese_ (MnO + Mn^{2}O^{3}) occurs
sometimes in black _crystals_ (_hausmannite_). Prepared artificially,
it is in the form of a brown powder.
_Peroxide of Manganese_ (MnO^{2}) occurs in considerable abundance as
a soft black amorphous mass, or crystallized as pyrolusite, also
reniform and fibrous. It is deprived of a part of its oxygen when
exposed to ignition. It eliminates a considerable quantity of chlorine
from hydrochloric acid, and is thereby converted into chloride of
manganese (ClMn).
Most of the manganese compounds which occur in nature yield water when
heated in a glass tube closed at one end. The sesquioxide and peroxide
give out oxygen when strongly heated, which can be readily detected by
the increased glow which it causes, if a piece of lighted wood or
paper is brought to the mouth of the tube. The residue left in the
tube is a brown mass (MnO + Mn^{2}O^{3}).
When exposed to ignition with free access of air, all manganese oxides
are converted into (MnO + Mn^{2}O^{3}), but without fusion. Such, at
least, is the statement of some of the German chemists, although it
will admit perhaps of further investigation.
Manganese oxides fuse with borax in the oxidation flame to a clear and
intensely colored bead, of a violet hue while hot, but changing to red
as it cools. If a considerable quantity of the oxide is added, the
bead acquires a color so dark as to become opaque. If such be the
case, we have to press it flat, by which its proper color will become
manifest.
In the reduction flame the bead is colorless. A very dark colored bead
must be fused upon charcoal with the addition of some tin. The bead
must be cooled very suddenly, for if it cools too slowly, it then has
time to oxidize again. This may be effected by pushing it off the
platinum wire, or the charcoal, and pressing it flat with the forceps.
The oxides of manganese fuse with microcosmic salt in the oxidation
flame, to a clear brownish-violet bead, which appears reddish-violet
while cooling. This bead does not become opaque when overcharged with
manganese. As long as it is kept in fusion a continued boiling or
effervescence takes place, produced by the expulsion of oxygen, in
consequence of the fact that the microcosmic salt cannot dissolve much
sesquioxide, while the rest is reduced to protoxide, is re-oxidated,
and instantly again reduced. If the manganese is present in such a
minute quantity as not to perceptibly tinge the bead, the color may be
made to appear by the contact of a crystal of nitre while hot. The
bead foams up upon the addition of the nitre, and the foam appears,
after cooling, of a rose-red or violet color. In the reduction flame
the bead sometimes becomes colorless.
The oxides of manganese fuse with carbonate of soda upon platinum
foil or wire, to a clear green bead, which appears bluish-green and
partially opaque when cold (manganate of soda NaO + MnO^{3}). A very
minute trace of manganese will produce this green color. The oxides of
manganese cannot be reduced upon charcoal with carbonate of soda
before the blowpipe. The soda is absorbed, and (MnO + Mn^{2}O^{3}) is
left.
GROUP FIFTH.--IRON, COBALT, NICKEL.
The oxides of this group are reduced to the metallic state when fused
with carbonate of soda upon charcoal in the reduction flame. Metals
when thus reduced form powders, are not fusible or volatile in the
blowpipe flame, but they are attracted by the magnet.
Furthermore, these oxides are not dissolved by carbonate of soda in
the oxidation flame, but they produce colored beads with borax and
microcosmic salt.
(_a._) _Iron._--It occurs in great abundance in nature. It is found in
several places in America in the metallic state, and it likewise
occurs in the same state in meteors. It occurs chiefly as the oxide
(red hematite, brown hematite, magnetic oxide, etc.), and frequently
in combination with sulphur. Iron also forms a constituent of the
blood.
Metallic iron is of a grey color, and presents the metallic lustre
vividly when polished. It is very ductile, malleable, and tenacious.
It is very hard at common temperatures, but soft and yielding at a red
heat.
In dry and cold air, iron does not oxidize, but when the air is dry
and moist, it oxidizes rapidly. This likewise takes place with great
rapidity when the metal is heated to redness. When submitted to a
white heat iron burns with brilliant scintillations.
_Protoxide of Iron_ (FeO).--This oxide does not occur pure in nature,
but in union with the peroxide of iron and other substances. It
presents the form of a black powder, and has some metallic lustre, is
brittle, and fuses at a high temperature to a vitreous looking mass.
It is attracted by the magnet, and of course is susceptible of
becoming magnetic itself. It forms with water a hydrate, but this
passes so rapidly into a state of higher oxidation, that it is
difficult to keep it in the pure state.
_Magnetic Oxide of Iron_ (FeO + Fe^{2}O^{3}).--This peculiar oxide is
of a dark color, and is magnetic, so that tacks or small nails adhere
to it when brought in contact with it. It is the variety of the oxide
termed "loadstone." It is found frequently crystallized in octahedrons
in Scandinavia and other places. Magnetic oxide of iron is produced
when red-hot iron is hammered.
_Sesquioxide of Iron_ (Fe^{2}O^{3}).--This oxide is found native in
great abundance as red hematite and specular iron, crystallized in the
rhombic form. In the crystalline state it is of a blackish-grey color,
and possessed of the metallic lustre. When powdered, it forms a
brownish-red mass. When artificially prepared, it presents the
appearance of a blood-red powder. It is not magnetic, and has less
affinity for acids than the protoxide. Its hydrate is found native as
brown hematite.
By exposing the peroxide of iron to the oxidation flame, it is not
acted upon, but in the reduction flame it becomes reduced to the
magnetic oxide.
The oxides of iron are dissolved by borax in the oxidation flame to a
clear dark-yellow or dark-red bead, which appears lighter while
cooling, and yellowish when cold. In the presence of a very small
quantity of iron, the bead appears colorless when cold. If the iron is
increased, the bead is opaque while cooling, and of a dirty
dark-yellow color when cold. In the reduction flame, and fused upon
platinum wire, the bead appears dark green (FeO + Fe^{2}O^{3}). By the
addition of some tin, and fused upon charcoal, the bead appears
bluish-green, or not unlike that of sulphate of iron.
Microcosmic salt dissolves the oxides of iron in the oxidation flame
to a clear bead, which, by the addition of a considerable quantity of
iron, becomes of an orange color while hot, but gets lighter while
cooling, presenting finally a greenish hue, and gradually becoming
lighter, till, when cold, it is colorless. If the iron is increased,
the hot bead presents a dark red color, but while cooling a
brownish-red, which changes to a dirty-green, and, when cold, to a
brownish-red color. The decrease of the color during the transition
from the hot to the cold state is still greater in the bead formed by
the microcosmic salt.
In the reduction flame no change is visible if the quantity of iron be
small. By the addition of more iron, the hot bead appears red, and
while cooling, changes to yellow, then green, and, when cold, is of a
dull red. By fusing the bead on charcoal with a small addition of tin,
it exhibits, while cooling, a bluish-green color, but, when cold, is
colorless.
The oxides of iron are not dissolved in the oxidation flame by fusion
with carbonate of soda. By ignition with soda upon charcoal in the
reduction flame, they are absorbed and reduced to the metallic state.
Cut out this portion of the charcoal; grind it with the addition of
some water in an agate mortar, for the purpose of washing off the
carbon particles, when the iron will remain as a grey magnetic powder.
(_b._) _Cobalt_ (Co) occurs in combination with arsenic and sulphur,
and associated with nickel and iron. It is found occasionally in
combination with selenium, and there are a traces of it in meteoric
iron. In the metallic state it is of a light, reddish-grey color,
rather brittle, and only fusible at a strong white heat; at common
temperatures it is unalterable by air or water. At a red heat, it
oxidizes slowly and decomposes water; at a white heat it burns with a
red flame. Cobalt is soluble in dilute sulphuric or hydrochloric acid
by the aid of heat, whereby hydrogen is eliminated. These solutions
have a fine red color.
_Protoxide of Cobalt_ (CoO).--It is an olive-green powder, but, by
exposure to the air, it becomes gradually brown. Its hydrate is a rich
red powder. The solution of its salts is red, but the aqueous solution
is often blue.
When heated in the oxidation flame, the protoxide is converted into
the black proto-sesquioxide (CoO + Co^{2}O^{3}). In the reduction
flame it shrinks and is reduced without fusion to the metallic state.
It is now attracted by the magnet and acquires lustre by compression.
Borax dissolves it in the oxidation flame, and produces a clear,
intensely colored blue bead, which remains transparent and of the same
beautiful blue when cold. This blue is likewise manifest even if the
bead be heated intermittingly. If the cobalt exists in considerable
quantity, the color of the bead is so intense as to appear almost
black.
This reaction of cobalt is so characteristic and sensitive that it can
detect a minute trace.
With microcosmic salt the same reaction is exhibited, but not so
sensitive, nor is the bead so intensely colored when cold as that with
borax.
By fusion with carbonate of soda upon a platinum wire, with a very
small portion of cobalt, a bright red colored mass is produced which
appears grey, or slightly green when cold. By fusion upon platinum
foil the fused portion floats down from the sides, and the foil is
coated around the undissolved part, with a thin, dark-red sublimate.
When fused upon charcoal, and in the reduction flame, it is reduced
with soda to a grey powder, which is attracted by the magnet, and
exhibits the metallic lustre by compression.
_Sesquioxide of Cobalt_ (Co^{2}O^{3}).--It is a dark brown powder. Its
hydrate (2HO + Co^{2}O^{3}) is a brown powder. It is soluble only in
acetic acid as the acetate of the sesquioxide. All other acids
dissolve its salts to protoxide, the hydrochloric acid producing
chloric gas. By ignition in the oxidation flame, it is converted into
the proto-sesquioxide (CoO + Co^{2}O^{3}) and produces with reagents
before the blowpipe the same reactions as the protoxide.
(_c._) _Nickel_ (Ni).--This metal occurs invariably associated with
cobalt, and in analogous combinations, chiefly as the arsenical
nickel. In the metallic state it is greyish, silver-white, has a high
lustre, is hard, and malleable both cold and hot. At common
temperatures, it is unalterable either in dry or moist air. When
ignited, it tarnishes. It is easily dissolved by nitric acid, but very
slowly by dilute sulphuric or hydrochloric acid, producing hydrogen.
_Protoxide of Nickel _(NiO).--It is in the form of small greyish-black
octahedrons, or a dark, greenish-grey powder. Its hydrate is a green
powder. Both are unalterable in the air, and are soluble in nitric,
sulphuric, and hydrochloric acids, to a green liquid. The protoxide is
the base of the salts of nickel, which in the anhydrous state are
yellow, and when hydrated are green. The soluble neutral salts change
blue litmus paper to red. By ignition in the oxidation flame,
protoxide of nickel is unaltered. In the reduction flame and upon
charcoal, it becomes reduced, and forms a grey adherent powder, which
is infusible, and presents the metallic lustre by compression, and is
magnetic. Borax dissolves it in the oxidation flame very readily to a
clear bead, of a reddish-violet or dark yellow color, but yellow or
light red when cold. If there is but a small quantity of the oxide
present, it is colorless. If more of the oxide be present, the bead is
opaque and dark brown, and appears, while cooling, transparent and
dark red. By the addition of a salt of potassa (the nitrate or
carbonate) a blue or a dark purple colored bead is produced. The borax
bead, in the reduction flame, is grey, turbid, or completely opaque
from the reduced metallic particles. After a continued blast, the bead
becomes colorless, although the particles are not fused. If the nickel
contains cobalt, it will now be visible with its peculiar blue color.
Upon charcoal, and by the addition of some tin, the reduction of the
oxide of nickel is easily effected, while the reduced nickel fuses
with the tin.
The oxide of nickel is dissolved by microcosmic salt in the oxidation
flame to a clear bead, which appears reddish while hot, but yellow and
sometimes colorless when cooling. If a considerable quantity of nickel
be present the heated bead is of a brown color, but orange when
cooled. In the reduction flame, and upon platinum wire, the color of
the bead is orange when cold; but upon charcoal, and with the addition
of a little tin, the bead appears grey and opaque. After being
submitted to the blowpipe flame all the nickel is reduced, and the
bead becomes colorless.
Carbonate of soda does not affect it in the oxidation flame, but in
the reduction flame and upon charcoal, it is absorbed and reduced, and
remains, after washing off the carbon, as a white metallic powder,
which is infusible, and has a greater attraction for the magnet than
iron.
_Sesquioxide of Nickel_ (Ni^{2}O^{3}).--It is in the form of a black
powder, and does not combine with other substances, unless it is
reduced to the protoxide. It exhibits before the blowpipe the same
behavior as the protoxide.
GROUP SIXTH.--ZINC, CADMIUM, ANTIMONY, TELLURIUM.
The substances of this group can be reduced upon charcoal by fusion
with carbonate of soda, but the reduced metals are volatilized, and
cover the charcoal with sublimates.
(_a._) _Zinc_ (Zn).--This metal is found in considerable abundance,
but never occurs in the pure metallic state, but in combination with
other substances, chiefly as sulphide in zinc blende, as carbonate in
calamine, and as the silicate in the kieselzinc ore; also, with
sulphuric acid, the "vitriol of zinc."
Zinc is of a bluish-white color and metallic lustre, is crystalline
and brittle when heated 400°F., but malleable and ductile between 200°
and 300°. It will not oxidize in dry air, but tarnishes if exposed to
air containing moisture, first becomes grey, and then passes into the
white carbonate. It decomposes in water at a glowing heat. It is
dissolved by diluted acids, while hydrogen is eliminated. It melts at
about 775°, and distills when exposed to a white heat in a close
vessel. When heated over 1000° in the open air, it takes fire, and
burns with a bluish-white light, and with a thick white smoke of oxide
of zinc.
_Oxide of Zinc_ (ZnO).--In the pure state, oxide of zinc is a white
powder, infusible, and not volatile. It is readily soluble in acids
after being heated strongly. Its soluble neutral salts, when dissolved
in water, change blue litmus paper to red. Its salts, with organic
acids, are decomposed by ignition, and the carbonate of zinc remains.
The oxide of zinc turns yellow by being ignited in the oxidation
flame, but it is only visible by daylight; this color changes to white
when cold. It does not melt, but produces a strong light, and it is
not volatile.
It disappears gradually in the flame of reduction, while a white smoke
sublimates upon the charcoal. This sublimate is yellow while hot, but
changes to white when cold. The cause of this is, that the oxide is
reduced, is volatilized, and re-oxidized, by going through the
external flame in the form of a metallic vapor.
Borax dissolves oxide of zinc in the flame of oxidation easily to a
clear bead, which is yellow while hot, and colorless when cold. The
bead becomes, by the addition of more oxide, enamelled, while cooling.
If the bead is heated with the intermittent flame, it is milk-white
when cold. When heated in the flame of reduction upon platinum wire,
the bead at first appears opaque, and of a greyish color, but becomes
clear again after a continued blast.
When heated upon charcoal in the reduction flame, it is reduced to a
metal; but, at the same moment, is volatilized, and sublimes as oxide
of zinc upon the charcoal, about one line's distance from the assay.
This is likewise the case with the microcosmic salt, except that it is
more easily volatilized in the reduction flame.
Carbonate of soda does not dissolve the oxide of zinc in the flame of
oxidation. In the reduction flame and upon charcoal, the oxide of zinc
is reduced to the metallic state, and is volatilized with a white
vapor of the zinc oxide, which sublimes on the charcoal and exhibits a
yellow color while hot, and which changes to white when cold. By a
strong heat the reduced zinc burns with a white flame.
Moistened with a solution of cobalt oxide, and heated strongly in the
flame of oxidation, zinc oxide becomes of a yellowish-green color
while hot, and changes to a beautiful green color when cold.
(_b._) _Cadmium_ (Cd).--This is one of the rare metals. It occurs in
combination with sulphur in _greenockite_, and in some ores of zinc.
It was detected first in the year 1818, and presents itself as a
tin-white metal of great lustre, and susceptible of a fine polish. It
has a fibrous structure, crystallizes easily in regular octahedrons,
presenting often the peculiar arborescent appearance of the fern. It
is soft, but harder and more tenacious than tin; it can be bent,
filed, and easily cut: it imparts to paper a color like that of lead.
It is very malleable and ductile, and can be hammered into thin
leaves. It is easily fused, and melts before it glows (450°). At a
temperature not much over the boiling point of mercury, it begins to
boil, and distills, the vapor of the metal possessing no peculiar
odor. It is unalterable in the air for a long time, but at length it
tarnishes and presents a greyish-white, half metallic color. This
metal easily takes fire when heated in the air, and burns with a
brownish-yellow vapor, while it deposits a yellow sublimate upon
surrounding bodies. It is easily soluble in acids with the escape of
hydrogen, the solutions being colorless. Its salts, soluble in water,
are decomposed by ignition in free air. Its soluble neutral salts
change blue litmus paper to red. The salts, insoluble in water, are
readily dissolved in acids.
_Oxide of Cadmium_ (CdO).--This oxide is of a dark orange color. It
does not melt, and is not volatile, not even at a very high
temperature. Its hydrate is white, loses in the heat its hydratic
water, and absorbs carbonic acid from the air when it is kept in open
vessels.
Cadmium oxide is unaltered when exposed upon platinum wire in the
flame of oxidation. When heated upon charcoal in the flame of
reduction it disappears in a very short time, while the charcoal is
coated with a dark orange or yellow powder, the color of which is more
visible after it is cooled. The portions of this sublimate furthest
from the assay present a visible iridescent appearance. This reaction
of cadmium is so characteristic and sensitive that minerals (for
instance, calamine, carbonate of zinc) which contains from one to five
per cent. of carbonate of cadmium, will give a dark yellowish ring of
cadmium oxide, a little distance from the assay, after being exposed
for a few moments to the flame of reduction. This sublimate is more
visible when cold, and is produced some time previous to the reduction
of the zinc oxide. If a vapor of the latter should appear, it
indicates that it has been exposed too great a length of time to the
flame.
Borax dissolves a considerable quantity of cadmium oxide upon a
platinum wire to a clear yellow bead, which, when cold, is almost
colorless. If the bead is nearly saturated with the cadmium oxide, it
appears milk-white when intermittingly heated. If the bead is
completely saturated, it retains its opalescent appearance. Upon
charcoal, and in the flame of reduction, the bead intumesces, the
cadmium oxide becomes reduced to metal; this becomes volatilized and
re-oxidized, and sublimes upon the charcoal as the yellow cadmium
oxide.
In the oxidation flame, microcosmic salt dissolves a large quantity of
it to a clear bead, which, when highly saturated and while hot, is
yellowish colored, but colorless when cold. By complete saturation,
the bead is enamel-white when cold.
Upon charcoal, in the flame of reduction, the bead is slowly and only
partially reduced, a scanty sublimate being produced on the charcoal.
The addition of tin promotes the reduction.
Carbonate of soda does not dissolve cadmium oxide in the oxidation
flame. In the reduction flame, upon charcoal, it is reduced to metal,
and is volatilized to a red-brown or dark, red sublimate of cadmium
oxide upon the charcoal, at a little distance from the assay the
charcoal presenting the characteristic iridescent appearance. This
reaction is still more sensitive if the cadmium oxide is heated _per
se_ in the reduction flame.
_Antimony_ (Sb).--This metal is found in almost every country. It
principally occurs as the tersulphide (SbS^{3}), either pure or
combined with other sulphides, particularly with basic sulphides.
Sometimes it occurs as the pure metal, and rarer in a state of
oxidation as an antimonious acid and as the oxysulphide.
In the pure state, antimony has a silver-white color, with much
lustre, and presents a crystalline structure. The commercial and
impure metal is of a tin-white color, and may frequently be split in
parallel strata. It is brittle and easily pulverized. It melts at a
low red heat (810°), is volatilized at a white heat, and can be
distilled. At common temperatures it is not affected by the air. At a
glowing heat it takes fire, and burns with a white flame, and with
white fumes, forming volatile antimonious acid. Common acids oxidize
antimony, but dissolve it slightly. It is soluble in aqua regia
(nitro-hydrochloric acid).
_Sesquioxide of Antimony_ (Sb^{2}O^{3}).--In the pure state this oxide
is a white powder, is fusible at a dull red heat to a yellow liquid,
which, after cooling, is greyish-white and crystalline. If it is
heated excluded from the air, it can be volatilized completely; it
sublimes in bright crystals having the form of needles. It occurs
sometimes in nature as white and very bright crystals. It takes fire
when heated in the open air, and burns with a white vapor to
antimonious acid. It fuses with the ter-sulphide of antimony to a red
bead. It is distinguished from the other oxides of antimony by the
readiness with which it is reduced to the metallic state upon
charcoal, and by its easy fusibility and volatility.
The sesquioxide is the base of some salts--for instance, the tartar
emetic. It is not soluble in nitric acid, but is soluble in
hydrochloric acid. This solution becomes milky by the addition of
water. A part of the salts of the sesquioxide of antimony are
decomposed by ignition. The haloid salts are easily volatilized,
without decomposition. Its soluble neutral salts change blue litmus
paper to red, and are converted, by admixture of water, into
insoluble basic and soluble acid salts.
Antimonious acid (antimoniate of sesquioxide of antimony, Sb^{2}O^{3}
+ Sb^{2}O^{5}) is of a white color, but, when heated, of a light
yellow color, but changes to white again when cold. It is infusible
and unaltered by heat. It forms a white hydrate, and both are
insoluble in water and nitric acid. It is partly soluble in
hydrochloric acid, with the application of heat. The addition of water
causes a precipitate in this solution.
_Antimonic Acid _(Sb^{2}O^{5}).--In the pure state this acid is a
light yellow-colored powder. Its hydrate is white, and is insoluble in
water and nitric acid. It is sparingly soluble in hot concentrated
hydrochloric acid. It forms salts with every base, some of which are
insoluble, and others sparingly so. Notwithstanding that antimonic
acid is insoluble in water, it expels the carbonic acid from the
solutions of the carbonates of the alkalies. Antimonic acid and its
hydrate changes moistened blue litmus paper to red.
_Behavior of Antimony and its Oxides before the Blowpipe._
_Metallic Antimony_ fuses easily upon charcoal. When heated to
glowing, and then removed from the flame, it continues to glow for
awhile, and produces a thick white smoke. The vapor crystallizes
gradually, and coats the assay with small crystals which iridesce like
mother of pearl (sesquioxide of antimony). It is not volatile at the
temperature of melted glass. Ignited in an open glass tube, it burns
slowly with a white vapor, which condenses upon the cool part of the
tube, and exhibits some indications of crystallization. This vapor
consists of the sesquioxide, and can be driven by heat from one place
to another, without leaving a residue. If the metallic antimony
contains sulphide of antimony, there is a corresponding portion of
antimonious acid produced, which remains as a white sublimate after
the sesquioxide is removed.
_Sesquioxide of antimony_ melts easily, and sublimes as a white vapor.
It may be prepared by precipitating and drying. When heated, it takes
fire previous to melting, glows like tinder, and is converted into
antimonious acid, which is now infusible. When heated upon charcoal in
the flame of reduction, it is reduced to the metallic state, and
partly volatilized. A white vapor sublimates upon the charcoal, while
the external flame exhibits a greenish-blue color. Antimonious acid is
infusible, produces a strong light, and is diminished in volume when
heated in the external flame, during which time a dense white vapor
sublimes upon the charcoal. It is not, however, in this manner reduced
to the metallic state like the sesquioxide.
_Antimonic acid_, when first heated, becomes white, and is converted
into antimonious acid. Hydrated antimonic acid, which is originally
white, appears at first yellow while giving off water, and then
becomes white again, while oxygen is expelled, and it is converted
into antimonious acid.
The oxides of antimony produce, with blowpipe reagents, the following
reactions: borax dissolves oxides of antimony in the oxidation flame
in considerable quantity to a clear bead, which is yellow while hot,
but colorless when cold. If the bead is saturated, a part of the oxide
is volatilized as a white vapor. Upon charcoal, in the oxidation
flame, it is completely volatilized, and the charcoal is covered with
a white sublimate. Heated upon charcoal in the reducing flame, the
bead is of a greyish color, and partially, if not wholly opaque, from
the presence of reduced metallic particles. A continued heat will
volatilize them, and the bead becomes clear. The addition of tin
promotes the reduction.
Microcosmic salt dissolves the compounds of antimony in the flame of
oxidation with intumescence, to a clear light-yellow colored bead,
which when cold is colorless. Heated upon charcoal in the reduction
flame, the bead is first turbid, but soon becomes transparent. The
addition of tin renders the bead greyish while cooling, but a
continued blast renders it transparent. Soda dissolves the compounds
of antimony upon platinum wire in the oxidation flame, to a clear
colorless bead, which is white when cold.
Upon charcoal, both in the oxidation and reduction flames, the
antimony compounds are readily reduced to the metal, which is
immediately volatilized, and produces a white incrustation of oxide of
antimony upon the charcoal. If the antimony compounds are heated upon
charcoal in the flame of reduction, with a mixture of carbonate of
soda and cyanide of potassium (KCy), there are produced small globules
of metallic antimony. At the same time, a part of the reduced metal is
volatilized (this continues after the assay is removed from the flame)
and re-oxidized. A white incrustation appears upon the charcoal, and
the metallic globules are covered with small white crystals. If this
white sublimate upon the charcoal is moistened with a solution of
cobalt-oxide, and exposed to the reduction flame, a part of it is
volatilized, while the other part passes into higher oxidation, and
remains, after cooling, of a dirty dark-green color.
(_d._) _Tellurium_ (Te).--This is one of the rare metals. It occurs
very seldom in the metallic state, but often with bismuth, lead,
silver, and gold. Tellurium, in the pure state, is silver-white, very
bright, of a foliated or lamellar structure, brittle, and easily
triturated. It is inclined to crystallize. It is soluble in
concentrated sulphuric acid without oxidation. The solution is of a
fine purple color, and gives a precipitate with the addition of water.
_Tellurium in the Metallic form._--By the aid of heat it is oxidized
in sulphuric acid, a portion of the oxygen of the acid oxidizing the
metal, while sulphurous acid gas escapes. This solution is colorless,
and is tellurous acid, dissolved in sulphuric acid. It melts at a low
red heat, and volatilizes at a higher temperature. If tellurium is
heated with free access of air, it takes fire, and burns with a blue
color, the flame being greenish at the edges, while a thick white
vapor escapes, which has a feeble acidulous odor.
_Tellurous Acid_ (TeO^{2}) is of a fine, granulous, crystalline or
white earthy mass, which is partly soluble in water. The solution has
a strong metallic taste, and an acid reaction upon litmus paper.
Heated in a tube closed at one end until it begins to glow, it fuses
to a yellow liquid which is colorless, crystalline, and opaque when
cold. Beads of it remain usually transparent like glass. Heated upon
platinum wire in the flame of oxidation, it melts, and is volatilized
as a white vapor. When heated upon charcoal in the oxidation flame, it
melts, and is reduced to the metallic state, but volatilizes and a
sublimate of white tellurous acid is formed upon the charcoal. The
edge of this deposit is usually red or dark-yellow.
Heated upon charcoal in the flame of reduction, it is rapidly reduced,
the external flame exhibiting a bluish-green color.
Borax dissolves it in the oxidation flame upon platinum wire to a
clear colorless bead which turns grey when heated upon charcoal,
through the presence of reduced metallic particles. Upon charcoal, in
the reduction flame, the bead is grey, caused by the reduced metal.
After a continued blast, tellurium is completely volatilized, and the
bead appears clear again, while a white sublimate is deposited upon
the charcoal.
With microcosmic salt, the same reactions are produced.
With carbonate of soda, tellurous acid fuses upon platinum wire to a
clear colorless bead, which is white when cold. Upon charcoal it is
reduced, and forms _tellur-sodium_, which is absorbed by the charcoal,
and metallic tellurium, which is volatilized, and deposits upon the
charcoal a white incrustation (tellurous acid).
If tellurous acid, finely powdered charcoal, and carbonate of soda are
mixed together, and the mixture be well ignited in a closed tube,
until fusion is effected, and a few drops of boiled water are brought
into the tube, they are colored purple, indicating the presence of
_tellur-sodium._
_Telluric Acid _(TeO^{3}) forms six-sided prismatic crystals. It has
not an acid, but rather a metallic taste. It changes blue litmus paper
to red; is slowly soluble in water, and rather sparingly. Exposed to
a high temperature, but not until glowing, the crystalline acid loses
its water, and acquires an orange color, but still it preserves its
crystalline form, although no longer soluble in water, and is in fact
so much changed in its properties as to present the instance of an
isomeric modification.
If telluric acid is heated gently in a closed tube, it loses water and
turns yellow. Heated still more strongly, it becomes milk-white,
oxygen is expelled, and it is converted into tellurous acid. The
presence of oxygen can be recognized by the more lively combustion
which an ignited splinter of wood undergoes when held in it. Telluric
acid produces the same reactions with the blowpipe reagents as
tellurous acid.
SEVENTH GROUP.--LEAD, BISMUTH, TIN.
The oxides of these metals are also reduced to the metallic state by
fusion with soda upon charcoal in the flame of reduction, but they are
volatilized only after a continued blast, and a sublimate is thrown
upon the charcoal.
(_a._) _Lead_ (Pb).--This metal occurs in considerable quantity in
nature, chiefly as galena or lead-glance (sulphide of lead). Likewise,
but more rarely, as a carbonate; also as a sulphate, and sometimes
combined with other acids and metals.
In the metallic state, lead is of a bluish-grey color, high lustre,
and sp. gr. 11.4. It is soft, and communicates a stain to paper. It is
malleable, ductile, but has very little tenacity. It melts at about
612°. Exposed to the air it soon tarnishes, being covered with a grey
matter, which some regard as a suboxide (Pb^{2}O), and others as
simply a mixture of lead and protoxide. At a glowing heat it is
oxidized to a protoxide, and at a white heat it is volatilized. It is
insoluble in most acids. It is, however, soluble in nitric acid, but
without decomposing water.
(_L._) _Protoxide of Lead_ (PbO).--It is an orange-colored powder,
which melts at a glowing temperature, and forms a lamellar mass after
cooling. Protoxide of lead absorbs oxygen from the atmosphere while
melting, which is given off again by cooling. Being exposed for a
longer while to the air, it absorbs carbonic acid and water, and
becomes white on the surface. It is soluble in nitric acid and caustic
alkalies. It forms with most acids insoluble salts. It is slightly
soluble in pure water, but not in water which contains alkaline salts.
This hydrate is white.
([beta].) _Red Oxide of Lead_ (PbO^{2}, PbO).--It forms a puce-colored
powder. It is insoluble in caustic alkalies. Hydrochloric acid
dissolves it and forms a yellow liquid, which is soon decomposed into
chloride of lead and chlorine. It is reduced by ignition to the
protoxide.
([gamma].) _Peroxide of Lead _(PbO^{2}).--It is a dark-brown powder.
It yields with hydrochloric acid the chloride of lead and chlorine
gas. When heated it liberates oxygen, and is reduced to the protoxide.