AMMONIA-COBALT BASES. 29 



action of the chloride of platinum, or whether the chloride of Roseocobalt had 

 already undergone the change. We consider it certain that the salt in question is 

 a salt of Purpureocobalt, because it contains two in place of three equivalents 

 of bichloride of platinum. We shall show further on, that the oxygen salts of this 

 base contain either hco or four equivalents of acid, and it is well known that in 

 the chlorplatinates there is — we believe invariably — but one equivalent of bichlo- 

 ride of platinum for each equivalent of chlorine in the chloride with which it is 

 united. Since there are three equivalents of chlorine in this chloride of Purpureo- 

 cobalt, we infer that two of them are differently combined from the other two, so 

 that the rational formula of the chlorplatinate is 



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

 We shall develop this view more fully when speaking of the oxygen salts of 

 Purpureocobalt. 



OXALATE OF PURPUREOCOBALT. 



This most beautiful salt is readily prepared by adding a solution of oxalate of 

 ammonia to one of chloride of Purpureocobalt. After a short time violet-red 

 needles are thrown down, which may be washed with cold water. As thus pre- 

 pared, the salt is almost chemically pure. The color of the oxalate of Purpureo- 

 cobalt is the violet T ^ of the first circle of Chevreul's scale ; the crystals are not 

 sensibly dichrous. We have not, as yet, obtained measurable crystals of this salt. 

 Under the microscope four- and six-sided acicular prisms are distinguishable, but 

 without characterizing terminal planes. 



The oxalate of Purpureocobalt has the formula 



5NH 3 .Co 2 3 ,2CA+3HO 



as the following analyses show : 



0.2723 grs. gave 0.1574 grs. sulphate of cobalt = 22.00 per cent, of cobalt. 

 0.3545 grs. gave 0.2045 grs. " " = 21.95 " 



0.8970 grs. burnt with oxide of copper gave 0.2973 grs. carbonic acid = 27.11 per cent, of 

 oxalic acid. 

 The formula requires 



Eqs. Calculated. Found. 



Cobalt ... 2 22.09 22.00 21.95. 



Oxalic acid . . 2 26.96 27.11 — 



The oxalate is nearly insoluble in cold water, and not very soluble in boiling 

 water, even after addition of free oxalic acid. The salt does not crystallize 

 Avell from its solutions, and we have always obtained it in the most beautiful form 

 by direct precipitation from the chloride. The salt is neutral to test paper, and is 

 the only neutral oxysalt of Purpureocobalt which we have yet obtained. It will 

 appear from what follows, extremely probable that there is an acid oxalate of Pur- 

 pureocobalt containing four equivalents of oxalic acid. We have not obtained such 

 a salt, however, in one or two experiments made for the purpose. 



