28 RESEARCHES ON THE 



pared, gives also precipitates with these reagents. The character of the precipi- 

 tates with oxalate of ammonia, bichloride of platinum, and bichromate of potash 

 enable us, however, readily to distinguish the chloride of Purpureocobalt from 

 chloride of Roseocobalt, with which, however, it is not likely to be confounded. 



CHLORPLATINATE OF PURPUREOCOBALT. 



When a solution of bichloride of platinum is added to one of the chloride of 

 Purpureocobalt, a brown-red precipitate is thrown down, which is a combination of 

 the two chlorides. When dried it has a fine rich brown-red color and high lustre. 

 The crystals seen under the microscope are usually aggregations of flat pale reddish- 

 brown needles. They are very distinctly dichrous, the ordinary image being pale 

 . violet-rose, while the extraordinary image is rich orange-red. 



The chlorplatinate is nearly insoluble in cold, and with great difficulty soluble 

 in hot water. It resists the action of reducing agents much more powerfully than 

 the chlorplatinates of the alkaline metals. Thus it must be boiled for a very long 

 time with zinc and chlorhydric acid before a complete reduction of the platinum is 

 effected. If the process be interrupted before the reduction is complete, brilliant 

 yellow granular crystals are often formed in the liquid. We have not determined 

 the constitution of these crystals, but they are not chlorplatinate of ammonium. 

 Sulphurous acid reduces this double chloride readily, and yields a red solution 

 containing the protochlorides of platinum and of cobalt. We may here remark, 

 that so far as our observation has hitherto extended, the action of a reducing agent 

 upon any constituent of a compound containing an ammonia-cobalt base extends 

 invariably to the ammonia-cobalt base itself. 



The chlorplatinate of Purpureocobalt has the formula 



5NH 3 .Co 2 Cl 3 +2PtCl 2 

 as the following analyses show : 



0. 6*165 grs. (reduced by boiling with S0 3 and the platinum precipitated as sulphide by NaO.S 3 3 



after adding HC1) gave 0.2267 grs. of platinum = 33.51 per cent. 

 0.9521 grs. gave 0.3169 grs. of platinum and 0.2483 grs. sulphate of cobalt = 9.93 per cent, cobalt. 

 grs. gave grs. of chloride of silver= 41.80 per cent, chlorine. 



The formula requires 



Eqs. Calculated. Found. 



Cobalt ... 2 10.10 9.93 



Platinum . . 2 33.50 33.51 



Chlorine . ~ . . 1 42.01 41.80 



This salt is identical with the chlorplatinate described and analyzed by 

 Claudet, and for which that chemist found the same formula, with the exception 

 of the hydrogen, which he makes 16 in place of 15 equivalents. We have 

 also obtained it from a chloride which gave the reactions of chloride of Roseo- 

 cobalt, but we must leave it for the present undecided whether in this case 

 there was a conversion of Roseocobalt into the isomeric Purpureocobalt, by the 



