16 PROCEEDINGS OF THE AMERICAN ACADEMY 



of ammonic nitrite was poured upon finely pulverized cobaltic chloride, 

 and acetic acid was added in small excess, I consider the formation of 

 these two salts to be represented by the equations: — 



2C0CI2 + 1 ONH, . NO2 + 30 = Co,(NO.Oio(NH,), + 6NH3 + 30H„ 

 2Coa-i- 12NH, • N02 + 30= Co,(NO,)i,(NH,),-f8NH3-|- 3OH2. 



Professor Sadtler has shown that in these cases also an absorption of 

 oxygen from the air takes place. When a solution of ammonic nitrite 

 is added to a strong alcoholic solution of cobaltic chloride, Erdmann's 

 ammonium salt, Co^(NH3)^(N02)8(NHJ2, is chiefly formed, and only 

 a small quantity of the four and six atom salts. The compound formed 

 crystallizes from the alcoholic solution in very beautiful and well defined 

 prismatic forms. 



From the above it will be seen that at least four distinct compounds 

 are formed by the action of ammonic nitrite upon solutions of cobaltic 

 chloride in presence of a weak acid and of the oxygen of the air. It 

 is at least probable that all four are formed at the same time, though in 

 varying proportions. I have already shown that, in the presence of 

 free ammonia and of ammonic nitrate, cobaltic chloride and ammonic 

 nitrite yield the nitrate of the octamin series. Of the action of ammo- 

 nic nitrite upon cobaltic salts in the presence of free ammonia, I shall 

 speak in treating of the formation of the salts of xanthocobalt. 



7. I have stated above that P^rdmann obtained the hexamin nitrite, 

 Co2(NH3)q(N02)65 by the joint action of potassic nitrite and ammonia 

 upon cobaltic chloride. On repeating his experiments, I found that 

 small quantities of this salt were formed, but that the chief products of 

 the action were salts of xanthocobalt, the formation of which Erdmann 

 does not appear to have noticed. Small quantities of salts of the octa- 

 min series are also formed. The filtered solution obtained in this reac- 

 tion was precijjitated by potassic dichromate, and the orange-red needles 

 obtained recrystallized for analysis. Of these crystals, 



0-6145 gr. gave 6-7393 gr. CrO,Ba = 51-40 per cent Cr^O^. 

 0-7712 gr. gave 0-9277 gr. CrO,Ba = 51-40 per cent Cr^ol 

 0-5615 gr. gave 96*5 c.c. nitrogen (moist) at 15° C. and 763-1°"" = 



20-12 per cent nitrogen. 

 0-5028 gr. gave 86 c.c. nitrogen (moist) at 15° C. and 763-1""" = 



20*05 per cent nitrogen. 



The formula Co2(NH3)j„(NO,,)oCr207 re'quires 53-22 per cent Cr,©^ 

 and 20-67 per cent nitrogen, while the formula of the octamin salt, 

 Co2(NH3),(NO,),Cr20., requires 32-91 per cent Cr20^ and 19-30 per 

 cent nitrogen, so that the analyses leave no reasonable doubt that the 



