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acid; but by nitric acid it is converted into vanadic sulphate, which is a soluble salt.
THE CARBONATE and THE OXALATE seem to be soluble.
The Ferrocyanide is produced by the action of ferrocyanide of potassium: it is a bulky, lemon.yellow precipitate, which becomes green by exposure to the air.
THE FERRICYANIDE is produced by ferricyanide of potassium, as a gelatinous yellow-green precipitate.
THE PHOSPHATE is soluble.
In most instances the other special reagents of the present and three preceding subdivisions have been found to give no characteristic reactions with vanadic salts; the action of others has not been ascertained.
The insoluble hydrate, sulphide, and ferrocyanide are the most characteristic vanadic salts.
TER-SALTS OF VANADIUM. The oxide of this series (V,03) plays the same part as the corresponding oxide of molybdenum; and this metal occurs in nature in the form of a vanadiate, just as molybdenum occurs as a molybdate. Several salts, however, containing other salt-radicals than oxygen, belong to the ter- or pervanadic series. The vanadiates are colourless, yellow, or occasionally red,while the ter-salts are also generally red or yellow, and give solutions of the same colour: by the action of reducing agents (e.g. H, S or H, D) they become blue.
THE CHLORIDE (VC1,) is a liquid which dissolves in large excess of water, forming a pale yellow solution, which decomposes in a few days, becoming green or blue, and evolving chlorine, and forming the bichloride VCI,.
THE IODIDE and THE CHROMATE are unknown.
The Oxide is produced by the action of nitric acid on the lower oxides, or directly from the ores; it may also be obtained by the action of the hydrates of potassium or ammonium on vanadic salts. It is a reddish yellow or brickred precipitate. Its formula is V,0g. It dissolves in the hydrates of potassium and ammonium, forming vanadiates, the solutions of which are yellow or brown (most metallic vanadiates are soluble). 1 part of ter-oxide requires 1000 parts of boiling water for solution. It dissolves readily in acids.
The Sulphide is not produced by hydrosulphuric acid gas ; but by the addition of sulphydrate of ammonium a brown precipitate falls. Its formula is V, Sg. It dissolves in the hydrates, sulphides, and carbonates of the first subdivision, forming sulphovanadiates. It is not decomposed by sulphuric acid.
THE SULPHATE is soluble.
THE FERROCYANIDE is produced by ferrocyanide of potassium, as a beautiful green precipitate, which is insoluble in acids.
THE FERRICYANIDE is unknown.
The other special reagents of the present and three preceding subdivisions have generally been found to give no characteristic reactions with ter-salts of vanadium.
Ter-salts of vanadium may be recognized best by the formation and reactions of the oxide, and also of the sulphide.
SALTS OF SELENIUM AND TELLURIUM. These two bodies, which will be fully treated of in the next Chapter, are mentioned here because they are precipitated as sulphides from their acid solutions, in conjunction with the members of the fourth subdivision, by the passage of hydrosulphuric acid gas.
The Sulphide of selenium is yellow. Its formula is Sesc. It dissolves in excess of sulphydrate of ammonium.
If the sulphide be dissolved in nitrohydrochloric acid and evaporated to dryness, selenious anhydride (Seo,) will be obtained, which may be recognized by the following reactions :
a. If a portion be dissolved in water, with which it combines to form selenious acid (H, Seo,), and some hydrochloric acid and a strip of zinc be then introduced into the solution, the zinc will become coated with a coppercoloured film, and subsequently red or red-brown flocks of selenium are deposited.
B. If another portion of the selenious anhydride, or some of the precipitated selenium of experiment a. be dried at a gentle heat, and then volatilized before the blowpipe flame, a peculiar odour, resembling that of horse-radish, is perceived.
The Sulphide of tellurium is a dark brown precipitate. Its formula is Tes. It is soluble in excess of sulphydrate of ammonium, and in boiling solutions of the hydrates of potassium and sodium, yielding salts known as sulphotellurites.
We now subjoin a method for the analysis of the 2nd Section of this subdivision, supposing that we have one only of its important members present. The Table for the 1st Section has been already given (p. 190).
On pp. 246 and 247, the synopsis of reactions will be found.
Analysis of Subdivision IV. Section II.-Salts of metals which form Sulphides soluble in Sulphide of
Ammonium. The salt may be one of TIN, ANTIMONY, ARSENIC, PLATINUM, or GOLD.
If, as is probable, it is a sulphide, wash thoroughly; add hydrochloric acid; boil, and add, while boiling, a few drops of nitric acid, drop by drop, until the precipitate is dissolved. Pour the solution down the funneltube of a hydrogen apparatus fitted with an “arsenic-tube” (see p. 213). Apply the heat of a spirit-lamp, urged by a blowpipe, to the arsenic-tube. The formation of a mirror after the lapse of a few minutes indicates
the presence If no mirror is obtained when the action in the hydro
gen apparatus has ceased, brush the black powder which is Arsenic or found, carefully from the surface of the zinc; it may contain Antimony.
Tin, Antimony, Platinum, or Gold. Dissolve the Wash it by decantation, boil it with hydrochloric acid, and filter. mirror out of the tube by al Any residue indicates the Perfect solution indicates the drop of hot presence of
presence of nitric acid; Platinum or Gold. 1 Tin or Antimony: evaporate in Boil in hydrochloric acid, Boil the hydrochloric solution, a porcelain and add a drop or two of add a drop or two of nitric dish to dry- | nitric acid, just to disso
nitric acid, just to dissolve ; acid, or a crystal of chlorate ness at 100° | boil to decompose any nitric of potassium ; cool, and add C.; redissolve acid remaining, then add excess of solution of sesqui
in a drop of some concentrated solution carbonate of ammonium : water, and add of oxalic acid, and keep the formation of a precipitate nitrate of warm for some time. I insoluble in excess indicates
silver. A yellow or A brown If no pre- the presence of The solution red precipitate precipitate, cipitate occurs, Tin. may contain
indicates 1 or yellow the solution This should be Antimony.
Arsenic; metallic should be verified by re- Pass hydrono change | spangles, in- neutralized ducing this sulphuric acid indicates dicates the with ammonia; precipitate by gas into it, Antimony. | presence of a yellow 1 fusion with and then
Gold. precipitate | cyanide of | acidify with
will indicate | potassium, hydrochloric the presence of dissolving the acid : a Platinum. washed metal reddish-orange
in hydrochloric precipitate
Sb. Sb. (Stannous salts.) (Stannic salts.) (Antimonious (Antimonicsalts)
salts.) (see page 192) (see page 196) (see page 204) (see page 207)
white Hydrate......... white white Oxide...
Is white cry. U
With carbonate of sodium With carbonate of sodium in the reducing flame (on in the reducing flame (on charcoal), stannous and charcoal), antimonious and stannic salts yield a mal antimonic salts yield a leable globule of tin. The brittle globule of antiincrustation on the char- | mony, and a bluish white coal is white.
* Signifies that a precipitation occurs, but not + Signifies that the precipitate which is formed consists of
Arsenious and arsenic salts, when The metal is The metal is heated to redness on charcoal, in reduced, and reduced, and the reducing flame, emit a cha- appears as a black appears as a racteristic garlic odour, and, when or grey powder, malleableglobule, heated in a tube (closed at one end) when platinum if a sufficient with a mixture of carbonate of so- salts are heated temperature has dium and charcoal, give a black with carbonate of been attained. lustrous mirror. (See page 210.) sodium (or alone)
in either flame.
of the salt indicated in the horizontal column.