14 PROCEEDINGS OF THE AMERICAN ACADEMY 



argentic nitrite and a little free acetic acid, gave argentic iodide and 

 a clear sherry-wine-colored filtrate giving with amnionic oxalate a 

 salt which I could not distinguish from the ordinary oxalate of xantho- 

 cobalt. Treated with nitric acid this oxalate gave an octahedral 

 nitrate showing all the reactions of nitrate of xanthocobalt. The rose- 

 red solution which Krok obtained as above, may prove to contain a 

 red modification of xanthocobalt, and deserves further study. 



Acid Sitlp/iate. — The acid sulphate described by Geiith and my- 

 self, and to which we gave the formula (old style) oNH3.C02O3.4SO3 

 -)-.!) no, may be formulated in various ways. We may regard it as a 

 basic disulphate with the formula, 



Co,(Nn3),o.O.(S,0,),+50H,. 



It is diflUcult to see how such a basic salt could be formed in a solution, 

 and in presence of an excess of free sulphuric acid. The fact that the 

 salt does not exhibit a strong acid taste and reaction does not in itself 

 furnish a very strong argument, Schultz-Sellack has shown that 

 disulphates of the type SjO-Rj are formed by dissolving normal sul- 

 phates in warm fuming sulphuric acid ; but it has not been shown in 

 any case that a normal sulphate by digestion vrith sulphuric acid can 

 form a pyrosulphate, — an atom of water being given off. It seems, 

 therefore, more probable that the acid sulphate has the formula, 



Co,(NH3)^,(SOj34-SO,H,+40H, ; 



but it is worthy of notice that the salt is not formed when normal sul- 

 phate of roseocobalt is boiled with dilute sulphuric acid. In this case 

 the normal sulphate crystallizes without change. The type of the acid 

 sulphate of roseocobalt is the same as that of the acid carbonate of 

 luteocobalt described by Genth and myself: — 



Co.(Nn,) ,.(C03)3-t-C03H2+50H2, 



and with that of the acid oxalo-bisulphate, which in my view has the 

 formula, 



Co,(NH3) ,„(aOJ (S0,),+C,H,0,+20II,. 



On the other hand, the acid oxalate of roseocobalt, which I shall de- 

 scribe, has the formula, 



Co,(NH3),„(CA)3+4CJI,0„ 



the type not being that of the ordinary double oxalates containing a 

 hexatomic metallic element. 



Yellow Sulpfiafe of Roseocobalt. — A small quantity of crude sul- 

 jihateof roseocobalt, which had stood for some years in my laboratory. 



