OF THE MEADOW-SWEET. 159 



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 cheri-y-red colour to 

 appear. 



Svbspiroilide 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 agi- 

 tating 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 depo- 

 sited 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 aque- 

 ous solution of spiroilide of zinc is coloured cherry-red ^by sesquichlo- 

 ride of iron. 



Spiroilide of Lead. When pure oxide of lead is brought into contact 

 with hydrospiroilic acid no spiroilide of lead is formed. Newly pre- 

 pared hydrated oxide of lead however, when left for some time in con 

 tact 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 ac- 

 tion on red oxide of mercury when they are left together in close ves- 

 sels, even though frequently agitated. 



Spiroilide of mercuiy is however obtained when a concentrated solu- 

 tion 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 in- 

 flames with detonation in the candle, leaving behind metallic silver. 



