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tallizes in anhydrous octohedra, KC1, SiiCl 2 ; a similar constitution
holds in the corresponding ammoniacal salt, NH 4 C1, SnCl 2 , which
is the pink salt of the dyer. An impure bichloride of tin is largely
used by the dyers under the name of nitromuriate of tin, or com-
position; it is generally prepared by dissolving tin at a gentle heat
in a mixture of nitric acid and sal ammoniac. The other salts of
tin are unimportant.

(683) CHARACTERS OF THE SALTS OF TIN. Tin forms two
series of salts, the salts of the protoxide and the salts of the
peroxide : the bichloride of tin is the only salt of the latter class
that has been minutely examined.

i . The Protosalts of Tin are nearly colourless ; they have a
powerful styptic taste ; when in solution they absorb oxygen
rapidly from the air ; when largely diluted with water the solution
becomes milky, but it is rendered clear by a small excess of hydro-
chloric acid. The fixed alkalies produce a white precipitate of
hydrated protoxide of tin, which is soluble in excess of the alkali, but
on boiling, part of the tin is deposited as a black metallic powder.



TESTS FOR TIN ESTIMATION OF TIN. 937

Ammonia gives a white hydrated oxide of tin, but the precipitate
is not redissolved by an excess of ammonia. The alkaline carbonates
give a similar precipitate, whilst carbonic acid escapes with efferves-
cence. A very characteristic reaction is the . production, with sul-
phuretted hydrogen, of a chocolate-brown precipitate of hydrated
protosulphide of tin. With sulphide of ammonium, a similar pre-
cipitate is formed, which is soluble in the alkaline sulphides. With
dilute solution of chloride of gold, they give, if used in excess, a
brown precipitate of reduced gold ; in smaller quantity, they yield a
beautiful purple precipitate, the purple of Cassius. Ferrocyanide
of potassium gives a white precipitate, soluble in hydrochloric
acid.

2. The Per salts of Tin are found to give with the caustic
alkalies a white precipitate, sol able in excess of the alkalies ; it
is not precipitated on boiling the solution. Carbonates of the alka-
lies give a white hydrated oxide with escape of carbonic acid : the
precipitate is insoluble in excess of the alkaline salt. Sulphuretted
hydrogen and hydrosulphate of ammonia both produce a dirty yellow
precipitate of hydrated sulphide of tin, which is soluble in excess
of the alkaline sulphides, and in the caustic alkalies. All the
compounds of tin before the blowpipe with soda on charcoal in the
reducing flame, give white malleable globules of the reduced metal.

(684) Estimation of Tin, and separation from, the foregoing
Metals. Tin is estimated in the form of the anhydrous peroxide ;
100 parts of which contain jS'66 of the metal.

The separation of tin from all the metals hitherto described, is
effected by means of sulphuretted hydrogen. With the exception
of cadmium, none of these metals is precipitated by the gas.
The mixed sulphides of tin and cadmium may be at once evaporated
to dryness with nitric acid : on treating the residue with water,
nitrate of cadmium will be dissolved, and the insoluble oxide of
tin will remain. The sulphide of cadmium is also easily separated
from the sulphides of tin by hydrosulphate of ammonia, which dis-
solves the sulphides of tin and leaves the sulphide of cadmium.
Both the sulphides of tin, by ignition in a current of air, are gra-
dually converted into the binoxide of tin : this change may be
accelerated by moistening them with nitric acid.

Tin may also be separated from all metals with the exception of
antimony, arsenic (and lead if sulphuric acid be present), by
evaporating the solution nearly to dryness with nitric acid, and wash-
ing the residue with water strongly acidulated with nitric acid.
The tin remains as mctastannic acid, and by ignition furnishes the
anhydrous peroxide.



938 TITANIUM,

II. TITANIUM.
Symbol, Ti; Equivalent, 24*12?.

(685) TITANIUM is a comparatively rare metal, which presents
considerable analogy with tin. Its principal ores are titaniferous
iron, and rutile, anatase, or brook it e, which are three different forms
of titanic acid, TiO 2 , coloured by variable quantities of the oxides
of iron, manganese, and chrome. When titanic acid is intensely
heated with charcoal, it is reduced, but is not fused. A remarkable
compound of the metal is frequently found, in the form of copper-
coloured cubic crystals, adhering to the slags of the Welsh iron
furnaces. These crystals are hard enough to scratch agate ; they
have a sp. gr. of 5-3. No acid, except a mixture of nitric and
hydrofluoric acids, has any action upon them, but they are oxidized
by fusion with nitre, or by ignition in a current of oxygen. These
crystals were supposed by Wollaston to be metallic titanium, but
Wohler showed that they consist of a combination of cyanide with
nitride of titanium ; they contain 18 per cent, of nitrogen, and 4
of carbon, having a formula TiCy + 3 (Ti 3 N) . Another nitride of
the metal, Ti 3 N 2 , also formerly mistaken for metallic titanium, is
procured in copper- coloured scales by igniting the ammonio-
chloride of titanium (2 H 3 N, TiCl 2 ) in close vessels, in a current
of ammonia. Pure titanium may be obtained by decomposing the
double fluoride of titanium and potassium with potassium. It then
forms a grey amorphous powder, which burns in air with scin-
tillation, and deflagrates in oxygen with dazzling brilliancy.

(686) Three Oxides of Titanium probably exist the prot-
oxide, the sesquioxide, and the deutoxide or titanic acid.

The Protoxide (TiO, Eg. 32), has not been obtained in a pure
state. It appears to be formed when titanic acid is heated in a
crucible lined with charcoal : but where the acid is actually in
contact with the charcoal, a film of metallic titanium is formed.
The protoxide is a black powder nearly insoluble in acids, and is
gradually oxidized by exposure to a high temperature in air, or
by fusion with nitre.

If a solution of titanic acid in hydrochloric acid be digested
with zinc, a purple hydrated sesquioxide of titanium is deposited,
which absorbs oxygen from the air with great rapidity, becoming
white from the formation of titanic acid. Hydrochloric acid dis-
solves it sparingly, and forms a blue solution.

Titanic Acid (TiO 2 ), Eq. 40. This compound occurs in menac-
canite and iserine as titanate of iron ; but more commonly it is
met with in the uncombined condition, constituting the principal



TITANIC ACID. 939

ore of the metal. It is found native under three distinct crystal-
line forms, each of which has a different specific gravity. Of
these, the densest and most abundant is rutile, of specific gravity
4' 25 : it occurs in long striated prisms or needles of a brown
colour, isomorphous with those of tin-stone. The second variety,
brookite, of specific gravity 4*13, is found in right rhombic prisms,
sometimes opaque, at others transparent, and of a pale brown ;
whilst the third variety, anatase, is found at Dauphiny in acute
octohedra, which are semitransparent and of a yellowish brown or
blue colour ; they have a specific gravity of 3*9. Corresponding
differences are observed in the titanic acid artificially prepared in
the laboratory. Like the oxide of tin, it may be obtained in two
isomeric forms, possessed of different properties. In fact, the
existence of two dissimilar modifications is a very usual occurrence
in the case of metallic oxides possessed of feeble acid powers.

Pure titanic acid may be obtained by reducing rutile to a
fine powder, and fusing it with thrice its weight of carbonate of
potash. On treating the mass with hot water, an impure bitita-
nate of potash remains. It is dissolved in hydrochloric acid,
next mixed with an excess of ammonia, and the precipitate is
digested in hydrosulphate of ammonia, by which the tin, iron, and
manganese are converted into sulphides, whilst the titanic acid
remains unchanged : a solution of sulphurous acid then dissolves
the sulphides, and a pure white titanic acid is left. By long
continued ignition, the colour of this white acid deepens, and its
specific gravity increases till it acquires a density equal to that of
rutile. In this state it is insoluble either in solutions of the alka-
lies, or in acids, except hydrofluoric acid, or in boiling oil of vitriol.
This modification of the acid may however be converted into the
soluble form, by heating it with a fixed alkaline carbonate, then
dissolving the residue with cold hydrochloric acid, and precipitating
the titanic acid by means of carbonate of ammonia : it thus forms
a white gelatinous hydrate, which dries into a semitransparent
mass capable of reddening litmus. The liquid long remains
turbid ; it cannot be rendered clear by filtration, unless an excess
of some ammoniacal salt be present. Hydrated titanic acid is
dissolved by the alkalies in solution, and it yields definite salts with
them. When fused with potash it forms a transparent yellowish
glass. The hydrate of titanic acid is soluble in dilute hydro-
chloric acid; it is also dissolved by sulphuric acid, and forms a
definite sulphate (TiO 2 , SO 3 ), which may be evaporated to dryness
at a low temperature without undergoing decomposition. Both
these acid solutions are decomposed by boiling them; and the



940 CHARACTERS OF THE COMPOUNDS OF TITANIUM.

insoluble variety of titanic acid is precipitated. When heated it
loses water and becomes insoluble. It becomes yellow on ignition,
but recovers its whiteness on cooling.

(687) A Bisulphide of Titanium (TiS 2 ), may be obtained in
green scales ; it is not soluble in the alkaline sulphides.

Bichloride of Titanium (TiCl 2 , Eg. 95), is a fuming volatile
liquid, resembling the bichloride of tin. It may be obtained by
decomposing pure titanic acid, intimately mixed with charcoal, and
heated to redness in a porcelain tube, by means of a current of
dry chlorine gas. It is a colourless liquid, which boils at 277 F.,
and yields a vapour of sp. gr. 6' 836 ; with a small quantity of
water it combines to form a crystallizable compound. A large
quantity of water produces its decomposition, hydrated titanic acid
being separated.

(688) CHARACTERS OF THE COMPOUNDS OF TITANIUM. The
salts of the protoxide are little known; with the alkaline carbonates
they give a blue precipitate, which becomes first brown and ulti-
mately green. The titanates of the alkalies are of a yellowish white
colour ; if neutral, they are insoluble ; hot water removes the alkali,
while most of the titanic acid remains undissolved. Hydrochloric
acid dissolves them, forming a solution, which, when boiled, becomes
turbid from deposition of titanic acid ; ammonia, when added to
this solution, produces a white precipitate. Infusion of galls pro-
duces an orange coloured precipitate in the acid solutions of the
titanates ; a precipitate of similar colour is produced by ferrocyanide
of potassium. In the reducing flame of the blowpipe the titanates
give with microcosmic salt a beautiful purple or bluish glass, which
becomes colourless in the oxidizing flame. This reaction distin-
guishes the titanates from the tantalates.

(689) Estimation of Titanium. Titanium is always estimated
in the form of titanic acid. Its solution in cold hydrochloric acid
is not precipitated by sulphuretted hydrogen, by which means it may
be separated from tin and cadmium, both of which are thrown down
as insoluble sulphides. The solution is then mixed with tartaric
acid, and supersaturated with hydrosulphate of ammonia. Iron,
nickel, cobalt, manganese, and zinc are thus separated in the form
of sulphides. The solution is then evaporated to dry ness, and the
carbon is burned off; titanic acid is left, mixed with the earthy
and alkaline salts of the mixture ; the residue is fused with potash,
redissolved in the cold with hydrochloric acid, and on boiling the
liquid, to which a little dilute sulphuric acid has been added, the



COLUMBIUM NIOBIUM ILMENIUM MOLYBDENUM. 941

titanic acid is precipitated. This process, however, is not very accu-
rate ; indeed the exact determination of the quantity of titanium
in its compounds is a matter of considerable difficulty.

III. COLUMBIUM, NIOBIUM, ILMENIUM.

(690) COLUMBIUM or tantalum occurs in the tantalite of Bo-
hemia, and niobium is a metal found by H. Rose in the American
tantalite. These metals have been as yet but imperfectly studied,
and are too rare to need a detailed notice here ; they have a
considerable analogy with silicon. According to M. Hermann
the yttro-tantalite of Siberia contains a new metal analogous to
colurnbium, to which he has given the name of ilmenium.

IV. MOLYBDENUM.
Symbol, Mo ; Equivalent, 46*0; Specific Gravity, 8-615 to $'636-

(691) The principal ore of molybdenum is the bisulphide, a
mineral in appearance much resembling plumbago, and which occurs
chiefly in Bohemia and in Sweden. Molybdenum is also occasion-
ally found oxidized, in combination with oxide of lead as molybdate
of lead. The metal may be obtained by roasting the pure native sul-
phide in a free current of air ; the sulphur passes off as sulphurous
acid, whilst the molybdenum also combines with oxygen, and re-
mains behind in the form of molybdic acid. If this be mixed into a
paste with oil and charcoal, and exposed to the heat of a smith's
forge, in a crucible lined with charcoal, it is reduced to the me-
tallic state. In this form molybdenum is white, brittle, and very
difficult of fusion. The acid may also be reduced by heating it to
redness in a. porcelain tube in a current of hydrogen : when the
pulverulent metal is heated in the open air it is gradually oxidized,
and finally converted into molybdic acid. It is also oxidized by
nitric acid ; if the metal be in excess, a soluble nitrate of the
binoxide is obtained ; if the acid predominate the oxidation pro-
ceeds further, and molybdic acid is formed ; aqua regia produces
similar results. Molybdenum is also oxidized when fused with
nitre, and molybdate of potash is produced.

(691 bis) Oxides of Molybdenum. Molybdenum forms 3 oxides j
the protoxide (MoO), and the deutoxide (MoO 2 ) are both possessed
of basic characters : the third (MoO 3 ) is a powerful metallic acid.

The protoxide (MoO, eq. 56,) is precipitated as a black hydrate
from the protochloride by means of ammonia; it is soluble in

3 P



942 DEUTOXIDE OF MOLYBDENUM MOLYBDIC ACID.

solutions of carbonate of ammonia, but not in those of the fixed
alkalies or their carbonates. It may also be obtained in the
anhydrous form, by digesting molybdic acid with zinc and hydro-
chloric acid.

The deutoxide (MoO 2 ), eg. 62,) may be prepared by igniting a
mixture of 2 parts of molybdate of soda and i part of sal ammoniac,
and digesting the mass in solution of potash, to remove any unde-
composed molybdic acid. The residue when well washed is the
pure oxide, which has been reduced from molybdic acid by the
hydrogen of the ammonia. It is of a dark brown colour, but it
becomes purple if exposed to solar light ; it is nearly insoluble in
acids. The hydrated binoxide may be obtained by digesting
molybdic acid, mixed with copper filings, in hydrochloric acid ;
an excess of ammonia precipitates the oxide of a rusty brown
colour, whilst the copper is retained in solution. Hydrated bin-
oxide of molybdenum is soluble in pure water, but is precipitated by
the addition of any salt. The solution gelatinizes on keeping. The
salts which this oxide forms with acids are of a reddish-brown
colour, or if anhydrous, are nearly black. If a solution of bichloride
of molybdenum be added, drop by drop, to a concentrated solution
of bimolybdate of ammonia, a deep blue precipitate of molybdate of
molybdenum (MoO 2 , 4 MoO 3 ) takes place. This compound is soluble
in water, but is precipitated by the addition of any saline body.
The addition of a small quantity of a protosalt of tin to a soluble
molybdate reduces it, and produces this beautiful blue compound,
which may serve as a test of the presence of molybdic acid : care
must be taken not to add the tin salt in excess. Another com-
pound of the binoxide of molybdenum with molybdic acid
(MoO 2 , 2 MoO 3 ) has a green colour.

(692) Molybdic Acid (MoO 3 ), Eg. 70, is obtained^in an impure
state by roasting the sulphide of molybdenum at a low red heat ;
it remains behind as a dirty yellow powder ; caustic ammonia
dissolves the acid, leaving oxide of iron and other impurities.
The ammoniacal solution crystallizes on evaporation, and by a low
red heat the ammonia is expelled, leaving the acid behind, of a
pale buff colour. It reddens moistened litmus paper, and is
sparingly soluble in water, forming a yellow solution. At a red
heat it fuses to a straw-coloured glass of sp. gr. 3*49 : it undergoes
volatilization in open vessels, and the acid is deposited on cool sur-
faces in brilliant transparent needles. No definite hydrate of
molybdic acid is known. When precipitated from its salts by the
addition of an acid, it may be redissolved, if the acid be added in



THE MOLYB DATES SULPHIDES OF MOLYBDENUM. 913

excess. It is also freely soluble in cream of tartar. Molybdic
acid unites with bases, and forms well characterized salts, both
neutral and acid. Those of the alkalies are soluble. Neutral
molybdate of ammonia crystallizes in colourless square prisms.
An acid molybdate of ammonia (2 H 4 NO, 5 MoO 3 , 3 aq) crystal-
lizes readily in six-sided prisms. Other acid molybdates of the
alkalies have been formed, which contain as many as 3, 4, and even
5 equivalents of the acid to i of base. Molybdate of lead (PbO,
MoO 3 ) occurs native in crystals of a yellow colour ; it is soluble in
nitric acid, and in solution of potash if the alkali be in large excess.

Solution of molybdate of ammonia may be advantageously
employed in certain cases to detect the presence of very small
quantities of phosphoric acid in solution. The solution suspected
to contain the phosphate must be acidulated with hydrochloric
acid, and the molybdate then added. The liquid becomes yellow,
and gradually deposits a yellow crystalline precipitate, consist-
ing of molybdic and phosphoric acids in combination with am-
monia. According to Sonnenschein it contains 6*747 per cent, of
ammonia.

Sonnenschein takes advantage of the insolubility of this salt to
detect small quantities of ammonia by its means. In order to
prepare the test solution, he first procures the yellow precipitate, by
adding molybdate of ammonia to an acidulated solution of phos-
phate of soda, ignites the precipitate to expel the ammonia, adds
nitric acid to the residue, in order completely to reoxidize any
reduced molybdic acid, evaporates to dryness, and expels the
nitric acid by ignition. A solution of carbonate of soda is em-
ployed to dissolve the remaining mixture of phosphoric and molybdic
acids, and the solution is supersaturated with hydrochloric acid.
This liquid, it is stated, will easily detect the presence of I part
of sal ammoniac in 10,000 of water. Salts of soda are not affected
by it, but strong solutions of the salts of potash yield a similar
yellow precipitate.

(693) Three sulphides of molybdenum are known, MoS 2 ,
MoS 3 , and MoS 4 .

Bisulphide of Molybdenum (MoS 2 ), Eg. 78; Sp. Gr. 4*138.
This sulphide is the principal ore of the metal : it is unchanged
by heat in close vessels, but if roasted in the open air, sulphurous
acid is formed and is volatilized, while molybdic acid remains.
This sulphide may be formed artificially by heating molybdic acid
in the vapour of sulphur.

The Tersulphide (MoS 3 , Eq. 94), is precipitated by transmitting

3 P 2



944 CHARACTERS OF THE SALTS OF MOLYBDENUM.

sulphuretted hydrogen through a solution of a molybdate, and add-
ing hydrochloric acid. It is of a dark brown colour, and forms
sulphur salts with the sulphides of the alkaline metals. The potash
salt crystallizes in magnificent iridescent crystals (KS, MoS 3 ). The
quadrisulphide of molybdenum also combines readily with the
alkaline sulphides.

A Protochloride of Molybdenum (Mod, Eg. 81-5), is obtained
by dissolving the protoxide in hydrochloric acid. A bichloride
(MoCl 2 ) is procured in deliquescent, fusible, volatile crystals, in
appearance resembling those of iodine, by heating the metal in a
current of dry chlorine. It is obtained in solution by dissolving
the deutoxide in hydrochloric acid.

A Chloromolybdic Acid sublimes in yellowish scales when the
deutoxide is heated in a current of chlorine. It is soluble both in
water and in alcohol, and consists of (MoCl 3 , 2 MoO 3 ), or (MoO 2 Cl).
Similar compounds may be formed with many aeidifiable metals,
such, for example, as tungsten, chromium, and vanadium.

(694) CHARACTERS OF THE SALTS OF MOLYBDENUM :

1. Little is known of the protosalts of molybdenum. They
yield a dark brown precipitate with the alkalies and their car-
bonates ; the precipitate is soluble in excess of carbonate of
ammonia; sulphuretted hydrogen slowly produces a brown preci-
pitate of hydrated sulphide which is soluble in hydrosulphate of
ammonia.

2. The salts of the deutoxide have a dark colour, and a metallic
astringent taste. Infusion of galls produces a brownish-yellow
solution ; ferrocyanide of potassium gives a dark brown precipitate ;
ammonia a rusty brown precipitate of the deutoxide.

3. The reactions of zinc, tin, and copper, on the molybdates
are characteristic. With zinc, in dilute acid solutions, the liquid
becomes first blue, then green, and finally black, after which the
addition of ammonia produces a deposit of protoxide of molybde-
num. The addition of a small quantity of protochloride of tin in
solution to a liquid containing a molybdate, produces a beautiful blue
molybdate of molybdenum (MoO 2J 4 MoO 3 ), but care must be taken
not to have the tin salt in excess, or the precipitate becomes dull
green. Copper filings in similar solutions reduce the molybdic acid
to the deutoxide, which is precipitated as a brown hydrate by
ammonia.

Molybdenum is usually estimated in the form of the bisul-
phide, of which 100 parts contain 58-97 of the metal.



TUNGSTEN ITS OXIDES. 94-5

V. TUNGSTEN.
Symbol, W; Equivalent, 92; Specific Gravity, 17 '6.

(695) TUNGSTEN is a metal found in small quantities in the
form of an acid combined with lime, in the mineral known as
Scheelite or tungstate of lime (CaO, WO 3 ) : or else in wolfram as
a tungstate of iron and manganese (MnO, WO 3 )+3 (FeO, WO 3 ).
It is easily obtained from the tungstate of lime, by digesting the
powdered mineral in hydrochloric acid, which combines with and
dissolves the lime, but leaves the insoluble tungstic acid behind :
from this compound the metal itself is procured, by heating it to
bright redness in a current of hydrogen gas. It is thus left of a
dark grey colour, but it assumes a metallic lustre under the burn-
isher. If the acid be made into a paste with oil and heated intensely
in a crucible lined with charcoal for some hours, tungsten is obtained
as a heavy, iron-grey metal, which is very hard, and difficult of
fusion. It may be heated in the air whilst in the compact state
without sensible change, but in the pulverulent form it burns
easily into tungstic acid. Aqua regia and nitric acid convert it
into tungstic acid, and the same change is produced by heating it
in contact with the alkalies or with nitre.

(696) Two oxides of tungsten are known, viz., a binoxide
which does not form salts with acids, and an acid teroxide.

The Binoxide (WO 2 ) is obtained as a brown powder by heating
tungstic acid to low redness in a stream of hydrogen; or in copper-
coloured scales by adding tungstic acid to dilute hydrochloric acid
in which some pieces of zinc have been placed. In the latter form
it rapidly attracts oxygen from the air and dissolves in a solution
of potash with evolution of hydrogen and formation of tungstate
of potash. Wohler obtains it from wolfram by fusing I part of this
mineral with 2 parts of carbonate of potash : the melted mass is
treated with boiling water, filtered, and mixed with a solution of
ii part of chloride of ammonium. The solution is evaporated to
dryness and the residue ignited. Upon treating the mass with
boiling water, the oxide of tungsten remains as a heavy black
powder, which must be washed, first with a weak solution of potash,
and afterwards with water. The hydrogen of the ammoniacal
salt partially reduces the tungstic acid of the mineral.

With soda the oxide of tungsten forms a remarkable com-
pound of a yellow colour and metallic lustre. It crystallizes in
cubes, and is not acted upon by any acid or mixture of acids except



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