32 RESEARCHES ON THE 



the other salts of Purpureocobalt. A rapid current of NO x passed into the solu- 

 tion gives, after a short time, an abundant precipitate of the nitrate of Xantho- 

 cobalt. 



The constitution of the acid sulphate might be represented by either of the 

 following formulas, besides that already given : 



5NH 3 .Co 2 3 ,3S0 3 +HO,S0 3 -i-4HO 



5NH 3 .Co 2 3 ,2S0 3 +2HO,S0 3 +3HO. 



We reject the first of these formulae because Purpureocobalt is a biacid and not 

 a triacid base. The second formula appears to us less probable than that which 

 we have adopted, in the first place, because a salt so constituted ought to be 

 strongly acid, and in the second place, because we shall presently show that there 

 exists an oxalo-sulphate of Purpureocobalt, in which two equivalents of sulphuric 

 are replaced by two of oxalic acid, and another and neutral oxalo-sulphate in which 

 one equivalent of oxalic acid replaces one equivalent of sulphuric acid. 



ACID OXALO-SULPHATE OP PURPUREOCOBALT. 



When sulphate of Roseocobalt is boiled for several hours with an excess of a 

 solution of oxalic acid, a clear red solution is formed, which on evaporation deposits 

 an abundance of crystals of a bright brick-red color, and indistinct acicular form. 

 These crystals are soluble in hot water without decomposition, and may be purified, 

 though with difficulty, by recrystallization. Their constitution is represented by 

 the formula 



5NH 3 .Co 2 3 ,2S0 3 ,2C 2 3 +3HO 



as appears from the following analyses : 



0.7433 grs. gave 0.3315 grs. sulphate of cobalt = 16.91 per cent, cobalt. 

 1.3912 grs. gave 0.9535 grs. sulphate of baryta = 23.50 " sulphuric acid. 

 1.6895 grs. gave 1.1564 grs. " " = 23.49 " sulphuric acid. 



2.7702 grs. gave 0.7070 grs. carbonic acid = 20.88 " oxalic acid. 

 2.0198 grs. gave 340 c. c. of nitrogen at 14°.5 C. and 163 n "°.01 (at 15° C.) = 318.1 c. c. at 0° 

 and 760 mm = 19.78 per cent, nitrogen. 



The formula requires 



Eqs. Calculated. Found. 



Cobalt . . . 2 17.00 16.97 



Sulphuric acid . 2 23.05 23.49 23.50 



Oxalic acid . . 2 20.74 20.88 



Nitrogen . . 5 20.17 19.78 



The reactions of this remarkable salt resemble closely those of the acid sulphate. 

 It has an acid taste and reaction, gives no precipitate with oxalate of ammonia, 

 or cobaltidcyanide of potassium, and yields chloride of Purpureocobalt by boiling 

 with an excess of chlorhydric acid. The formula of this salt may be written in 

 various ways. In the first place, we may consider it as a double salt represented 

 by the formula 



5NH 3 .CoA^0 3 +5NH s .CoA,4CA+6HQ. 



