254 Mr. r. Claudet on a Class of 



the fomi of regular octohedi'ons, small, sparkling, and of a ruby- 

 red colour, veiy much resembling small ciystals of chrome-alum. 



This salt, which is an intense colouring matter, is sparingly 

 soluble in cold water, 1 part requiring at 60"^ F. 244 parts of water; 

 it is soluble to a much larger extent in water at the boiling-point, 

 to which it imparts a very deep red colour ; it is however slightly 

 decomposed, and altogether so on boiling the solution ; but this 

 may be prevented by keeping the solution slightly acid with 

 hydi-ochloric acid. 



Hydrochloric acid, saturated solutions of chloride of ammo- 

 nium and sodium, completely precipitate the new salt from its 

 solution ; alcohol acts in the same way. The salt is not decom- 

 posed by boiling hydrochloric acid. Sulphuric acid evolves hy- 

 drochloric acid, a corresponding sulphmic salt being formed; 

 the reaction, however, is not complete, for at the end of the 

 operation chlorine comes off from some decomposition. Nitric 

 acid partially transfoims the salt into the nitrate of the base. 

 Potash and soda decompose the solution of the salt, a hydrated 

 peroxide of cobalt being thrown down and ammonia evolved in 

 considerable quantity. Hydrate of baryta decomposes the salt 

 in the same way with the aid of heat, but not in the cold. Car- 

 bonate of potash or soda has no effect. Yellow prussiate of 

 potash gives with a solution of the salt a dirty brown precipitate, 

 red prussiate none ; but on standing, bright yellow needles cry- 

 stallize from the solution. 



Sulphuretted hydrogen precipitates the whole of the cobalt as 

 a bisulphide of that metal, ammonia being liberated at the same 

 time. The analysis of three different preparations of this sul- 

 phide gave — 

 ii Found. 



Calculated. _.___> . 



Cobalt . . 29-5 47-96 



Sulphur . . 32__ 52-04 



61-5 100-00 



On boiling a solution of the new salt, it is decomposed into 

 ammonia, which escapes, and a superior hydrated oxide of cobalt, 

 containing a certain amount of a nitride of cobalt which is pre- 

 cipitated, nothing but chloride of ammonium remaining in solu- 

 tion. The composition of the precipitated oxide of cobalt appears 

 tobe CoSO'^-fSHO. 



Dried in the air, the salt contains no water of crystallization, 

 neither does it contain oxygen. When heated to low redness in 

 a glass tube, a large quantity of ammonia is disengaged, a cer- 

 tain quantity of chloride of ammonium subhmed, and a residue 

 of common protochloridc of cobalt remains. In this reaction no 



