20 PROCEEDINGS OF THE AMERICAN ACADEMY 



XANTHO COBALT. 



9. Gentli and I have shown in our memoir that the salts of xantho- 

 cobalt may be formed either directly by the action of nitrous acid 

 vapors upon salts of cobalt, or by the action of the same acid upon 

 salts of purpureocobalt and roseocobalt, in each case in the presence of 

 free ammonia. I propose now to give the results of a more detailed 

 study of the subject. 



With respect to the constitution of this class of salts, I may remark, 

 in the first place, that Genth and I left it undecided whether the salts 

 in question contain NO or NO^, pointing out the fact that the analyses 

 do not decide in favor of either view, and adopting the former pro- 

 visionally. Braun first proved conclusively that the salts of xantho- 

 cobalt contain NOg, and this view has since been generally adopted. 

 I have already shown (§1) that when cobal tic chloride, CoClj, is mixed 

 with ammonia and amnionic nitrite and nitrate, the solution absorbs 

 oxygen from the air, while the nitrate of the octamin series, Co2(NH3)g 

 (NO.,)^(NO.j).„ is formed. I have not observed in this reaction the 

 formation of a salt of xanthocobalt. If present at all, such salts must 

 be formed in very small relative quantity. Genth and I have shown, 

 on the other hand, that when the red gases resulting from the action 

 of nitric acid upon starch, sawdust, or arsenous oxide are passed into 

 solutions of cobaltic salts in presence of an excess of ammonia, salts of 

 xanthocobalt are formed in a very short time, and in large quantity. 



If we consider the red gas to consist of hyponitric oxide, N^O^, we 

 may have 



2Co(N03), + 10NH, + NA = Co,(NH3),„(NO,),(N03),. 



In preparing sulphate and nitrate of xanthocobalt by this process, 1 

 have on several occasions been able to detect only salts of this base 

 among the products of the reaction. In one case, however, in which I 

 employed cobaltic sulphate and added so large a quantity of ammonic 

 sulphate that the solution gave no precipitate with ammonia, I obtained 

 a very large relative quantity of Erdmann's salt Co2(NH3)y(N02)i;. 

 In other cases in which cobaltic chloride was present I detected crystals 

 of the chloro-nitrate Co2(XH3),(,(N02)2(N03)2Cl2. The solutions after 

 the action of the red gases also contain small quantities of the am- 

 monia-cobalt-nitrite of ammoni^^m, Co2(NH3)^(N02)8(NH^)2, as well 

 as ammonic nitrite and nitrate. 



On the other hand, however, I have already shown (§ 3) that salts 

 of this radical are fonned in large quantity, together with a smaller 



