Of' ARTS AND SCIENCES. 3 



separation and recn'stallization, these crystals may be separated and the 

 two salts obtained pure for analysis. In this manner I found the octa- 

 hedral salt to be nitrate of xanthocobalt, while the prismatic crystals 

 are the nitrate of the octamin series above mentioned. In one experi- 

 ment, of the octahedral salt, 



0-3833 gr. gave 0-1890 gr. CoSO^ = 18-77 per cent cobalt. 



The formula of nitrate of xanthocobalt, Co2(NH3)jq(N02)2(N03)^, re- 

 quires 18-73 per cent. Of the prismatic salt, 



0-7369 gr. gave 0-4050 gr. €080^= 20-92 per cent cobalt 

 The formula of the nitrate of the new series, 



Co2(NH8)^(NO,),(N03)2, requires 20-99 per cent. 

 For greater certainty I made also a nitrogen determination in this 

 nitrate : — 



0-5668 gr. gave 168-5 c.c. nitrogen at 13-5° C. and 756-1"" = 

 34-79 per cent nitrogen. 

 The formula cited requires 34-88 per cent. The two salts were further 

 readily recognized by their characteristic reactions. In my experi- 

 ments the proportion of xanthocobalt salt formed was much the greater. 

 The formation of the new nitrate may in this case be represented by 

 the equation : — 



2Co(N03)., + 8NH8 + 4KN0., + OH. + 0= 

 Co2(NH3)s(N02),(N03)2 + 2KN03+20KH; 



and the formation of the nitrate of xanthocobalt by the equation: — 



2Co(N03)o + IONH3 + 2KN0., + OH. + O = 

 CJ,(NH3),„(N02),(N03);+ 20KH. 



The green flocky matter which accompanies the formation of the 

 above-mentioned nitrates and sulphate is cobaltic hydrate, Co(OH)., -(- 

 20H.„ and is of course due to the action of the potassic hydrate uj)on 

 the solution of cobalt in excess. I varied the above process by adding 

 ammonia first to the solution of cobaltic nitrate, and afterward the 

 solution of potassic nitrite, but the results were the same. 



4. Action of Ammonia and Potassic Nitrite upon a Mixture of Cobal- 

 tic and Ammonic Sulphates. — In this case as in the others the solution 

 becomes brown and deposits an orange crystalline mass. If the mass 

 is dissolved in water and a solution of potassic bromide is added, after 

 standing, fine crystals are formed, which, after a single recrystallization, 

 are pure bromide of xanthocobalt. In one experiment : — 



0-5634 gr. gave 0-2496 gr. CoSO^ = 16-87 per cent cobalt. 

 0-7294 gr. gave 0-4496 gr. silver = 45-65 per cent bromine. 



