Page:Scientific Memoirs, Vol. 1 (1837).djvu/171

 watery hydrospiroilic acid and hydrate of magnesia. It appears as a light yellow and almost insoluble powder.

Protospiroilide of Iron. The aqueous solution of hydrospiroilic acid has no action on protochloride of iron; on the addition of ammonia however a deep violet blue precipitate falls.

Sesquispiroilide of Iron. Sesquichloride of iron immediately changes the colour of the aqueous solution of hydrospiroilic acid to a fine deep cherry-red colour, without any precipitate.

If this fluid be exposed to the air it loses its red colour in a short time, and a pure solution of sesquichloride of iron remains, in which a fresh addition of hydrospiroilic acid again causes the cherry-red colour to appear.

Subspiroilide of Copper. Hydrospiroilic acid has no action on the subchloride of copper; a slight addition of ammonia however causes a light brown precipitate in this mixture.

Protospiroilide of Copper. This compound is best obtained by agitating together an aqueous solution of hydrospiroilic acid and newly prepared hydrated oxide of copper. This latter immediately loses its blue colour and becomes green.

If solutions of sulphate of copper and spiroilide of potassium be mixed, a voluminous precipitate falls, which however is but slowly deposited and possesses a distinct ciystalline texture.

Spiroilide of Zinc. When oxide of zinc is agitated with the aqueous solution of hydrospiroilic acid, it very soon absorbs the acid from the water, which latter acquires a yellow colour. By evaporation under the airpump, a yellow pulverulent substance is obtained. The aqueous solution of spiroilide of zinc is coloured cherry-red by sesquichloride of iron.

Spiroilide of Lead. When pure oxide of lead is brought into contact with hydrospiroilic acid no spiroilide of lead is formed. Newly prepared hydrated oxide of lead however, when left for some time in contact with the aqueous acid, becomes converted into a light yellow pow- der, consisting of small shining laminae of spiroilide of lead.

Spiroilide of Mercury. The aqueous solution of the acid has no action on red oxide of mercury when they are left together in close vessels, even though frequently agitated.

Spiroilide of mercury is however obtained when a concentrated solution of corrosive sublimate is poured over hydrospiroilate of ammonia. A pale straw-coloured flocky voluminous precipitate is formed. Spiroilide of Silver. Oxide of silver is partially dissolved by the aqueous solution of hydrospiroilic acid.

The solution is of a yellow colour, and has a bitter metallic taste. By evaporation in vacuo a brownish black residue is obtained, which inflames with detonation in the candle, leaving behind metallic silver.