AMMONIA-COBALT BASES. 27 



starch or sawdust exerts a very remarkable influence upon the chloride of Pur- 

 pureocobalt, converting it into the nitrate of a base, which will be described further 

 on under the name of Xanthocobalt. 



Sulphurous acid solution throws down from solutions of the chloride a dull orange- 

 brown precipitate, which appears to be a sulphite. By boiling with an excess of 

 the acid this is reduced, and there remains a solution of a protosalt of cobalt. 



Sulphuric acid, under certain conditions, converts chloride of Purpureocobalt 

 into the acid sulphate of the same base. 



Zinc may be boiled a long time with an acid solution of the chloride without 

 producing decomposition or reduction. Formic and oxalic acids have no reducing 

 action. Protochloride of tin simply unites with the chloride of Purpureocobalt so 

 as to form a chloro-salt. 



The chloride of Purpureocobalt exhibits a remarkable tendency to unite with 

 metallic chlorides to form chloro-salts. Such compounds are formed with the 

 chlorides of Platinum, Palladium, Mercury, Tin, Zinc, and various other metals. 

 The chloride of Purpureocobalt even dissolves chloride of silver in large quantity, 

 doubtless forming with it a double chloride. It is for this reason, that it is not 

 generally advantageous to prepare the salts of Purpureocobalt by double decompo- 

 sition between the chloride and salts of silver. 



The reactions of a pure solution of the chloride of Purpureocobalt are as follows : 



Ferrocyanide of potassium gives a yellowish precipitate which quickly becomes 

 chocolate-brown. 



Ferridcyanide of potassium gives a beautiful bright orange-red crystalline preci- 

 pitate. 



Cobaltidcyanide of potassium gives a fine red crystalline precipitate. 



Oxalate of ammonia gives a beautiful purple-red precipitate of fine needles. 



Pyrophosphate of soda gives a lilac precipitate easily soluble in an excess of the 

 precipitant. 



Neutral chromate of potash gives a brick-red precipitate. 



Bichromate of potash gives orange-yellow scales. 



Picrate of ammonia gives a beautiful yellow precipitate. 



Terchloride of gold precipitates the chloride unchanged. 



Bichloride of platinum gives a fine cinnamon-brown precipitate of crystalline 

 scales. 



Sulphide of ammonium gives a black precipitate. 



Chloride of mercury gives fine rose-red needles, easily decomposed. 



Bichloride of tin gives pale peachblossom-red silky needles. 



Molybdate of ammonia gives a pale peachblossom-red precipitate. 



Alkalies and their carbonates give no precipitate. 



Iodide and bromide of potassium give no precipitate. 



Chlorhydric acid and the alkaline chlorides throw down the chloride of Pur- 

 pureocobalt from its solutions as a violet-red powder. 



The reactions of the chloride of Purpureocobalt with the ferridcyanide and 

 cobaltidcyanide of potassium and with oxalate of ammonia are not sufficient to 

 distinguish it from the chloride of Boseocobalt, which, when pure and freshly pre- 



