r. Meconic acid throws down nitrate

the state of a white powder.††

cre.

Braconnot. #Ibid.

§ Scheele, ii. 80.

tt John.

¶ Wenzel's Verwand. p. 245.

, Ann de Chim. xi. 313.

37. Boletate of silver. When boletic acid is dropped into Sect. XXXII. nitrate of silver, a precipitate falls easily soluble in nitric acid.*

38. Camphorate of silver. When camphorate of potash is mixed with nitrate of silver, a white precipitate falls, which becomes blue when exposed to the light. When heated it melts and is decomposed, leaving metallic silver. Its constituents, according to the analysis of Brandes, are

39. Suberate of silver. When nitrate of silver and suberate of ammonia are mixed, a white powder falls, composed, according to Brandes, of

When

In the light it becomes violet, especially if moist.
heated it melts, becomes first yellow, then black, is decomposed,
and leaves silver. It is but little soluble in water.‡

40. Pinate of silver. Obtained by mixing together solutions of pinate of potash and nitrate of silver. A yellow powder, which melts when rather strongly heated. It blackens when exposed to the sun. It is insoluble in water, and very little soluble in absolute alcohol. It dissolves readily in ether and in oil of turpentine.§

41. Silvate of silver. It may be prepared by a process similar to the preparation of the preceding salt. It is soluble in 15 times its weight of cold absolute alcohol, and in a still smaller quantity of the same alcohol when hot. Has so great an affinity for ether that it will separate it from water. When the alcoholic solution is left to spontaneous evaporation, the salt crystallizes in small grains.||

42. Carbazotate of silver. Carbazotic acid dissolves oxide of silver with facility, when heated with it in water. By gentle evaporation the solution yields crystals in very fine needles, having the lustre of gold, and grouped in stars. The salt is

• Braconnot.

+ Schweigger's Jour. xxxviii. 298.

Brandes, ibid. xxxiii. 94. § Unverdorben, Poggendorf's Annalen, xi. 238. Ibid. p. 401.

Class I.

Characters.

reason. Almost the only solution of platinum which we can procure is the chloride. The characters by which a solution of platinum may be distinguished are the following:

1. The chloride has a fine reddish-brown colour, and is transparent.

2. Potash occasions a yellow precipitate, which is not sensibly soluble in acids; but it dissolves when heated in an excess of potash, and does not again precipitate when the liquid cools. 3. With ammonia the phenomena are exactly the same as with potash.

4. Carbonates of potash and of ammonia produce similar effects. But the precipitates are not re-dissolved when heated in an excess of the alkaline carbonates.

5. Neither soda nor its carbonates throw down any precipitate.

6. Nitrated suboxide of mercury throws down a yellowish red precipitate.

7. Neither oxalic acid nor phosphate of soda occasion any precipitate.

8. Sulphuretted hydrogen changes the colour to brown, and by degrees a brown precipitate falls, which becomes gradually black. Hydrosulphuret of ammonia produces the same effect; but the precipitate is re-dissolved when an excess of the hydrosulphuret is added.

9. A plate of zine precipitates platinum from its solutions in the state of a black metallic powder.

1. Sulphated peroxide of platinum. This salt is formed when moist sulphuret of platinum is exposed to the air, or still better when it is heated with nitric acid.

It is

Sulphated peroxide of platinum, thus formed, has a very darkbrown colour, approaching black. It is obtained in the form of a porous crust, similar to the carbonaceous matter left when sugar is decomposed by heat. It is very brittle and easily reduced to powder. Its lustre is somewhat similar to that of crystallized blende. Its taste is acid and metallic, with some degree of causticity. It slightly reddens litmus paper. very deliquescent, and of course very soluble in water. soluble in alcohol, ether, muriatic acid, nitric acid, and phosphoric acid. The alkalies form triple compounds with it. Its selution in water has a dark-brown colour of great intensity. Sal ammoniac does not occasion a precipitate when dropped into it; but, if the solution be boiled to dryness, the ammoniomuriate is formed. The sulphuric acid cannot be separated

It is

from this salt by any of the usual methods, in consequence of Sect, XXXIV. the disposition which the salt has of entering into triple compounds. When heated to redness, it is entirely decomposed, and metallic platinum obtained. Oxygen gas, and some sulphurous acid gas is obtained, and a liquid similar to the smoking sulphuric acid of the Germans. From the analysis of Mr. E. Davy, it appears that this sulphate is composed of

Sulphuric acid

Peroxide of platinum

26.3

73.7

100.0

2. Nitrated peroxide of platinum. This salt may be obtained by mixing sulphated peroxide of platinum and nitrate of barytes in the atomic proportions, and filtering. If saltpetre be added to chloride of platinum, as long as potash-chloride of platinum precipitates, a dark-brown liquid will remain, which after evaporation leaves a mass which is partially soluble in water, leaving a subsalt. The properties of these salts are still unknown.

3. Iodated peroxide of platinum. Iodic acid gives with chloride of platinum a yellow precipitate, somewhat soluble in

water.

4. Arseniated peroxide of platinum. Arseniate of soda, when added to nitrated peroxide of platinum, throws down a lightbrown precipitate, soluble in nitric acid.

5. Chromated peroxide of platinum. Chromate of potash, when dropt into chloride of platinum, throws down a dark-red precipitate, which becomes tile-red when dried.

6. Oxalated peroxide of platinum. When the precipitate thrown down from chloride of platinum by soda is digested in oxalic acid, a yellow-coloured solution is obtained, which yields yellow crystals.‡

7. Benzoated peroxide of platinum. Obtained by dissolving oxide of platinum in the acid. Yellow stelliform crystals are obtained, which are not altered by exposure to the air, diffi

Berzelius.

+ Pleischl.

Bergman.

Le in water, and not at all in alcohol.* Benzoate ma does not precipitate solutions of platinum.†

grated peroxide of platinum. Camphorate of soda. Het with chloride of platinum, throws down a white Tate, somewhat soluble in water.‡

SECTION XXXV. SALTS OF PROTOXIDE OF PLATINUM.

s genus of salts is almost quite unknown, owing chiefly culty of procuring protoxide of platinum in a sepaIt is probable that their saline characters would be dded than those of the salts described in the last sectests of platinum described at the beginning of the would probably apply also to the salts of the protI have not myself made any experiments on the

platinum. When a mixture of subchloride. sulphuric acid is exposed to the continued til it no longer precipitates nitrate of silver. vaporated to dryness, we obtain a matter which in the air, and which dissolved in a little water is a great deal of water it forms a yellowish-green W. et potash or soda is added to this liquid, it bedarker, but in a few days it loses its colour, the itating in the state of a hydrated protoxide.§ 2 Nere of platovan. Hydrated protoxide of platinum es in dilute nitric acid with a greenish-brown colour. When the solution is evaporated nearly to dryness, it is almost But this salt is mixed with a good deal of nitrated vende of platinum."

A state of platinom. This salt may be obtained by dismoist hydrated protoxide of platinum in acetic acid. non has a greenish colour. It may be dried into a ish brown mass, which may be again dissolved in a little protoxide which is left behind undis

N XXXVI-SALTS OF OXIDE OF PALLADIUM.

great difficulty of procuring palladium, has hitherto Lemists from investigating its salts. Hence this