22 PROCEEDINGS OF THE AMERICAN ACADEMY 



and added to a hot solution of potassic nitrite in excess. The dark 

 brown-red solution was evaporated at a gentle heat to half its volume. 

 On cooling, a small quantity of Fischer's salt, Co2(N02)j2Kc~l~^^'^2' 

 separated ; afterward sherry-wine-colored prismatic crystals were 

 formed in abundance. After recrystallization, these were analyzed. 



0-2824 gr. gave 0-1519 gr. CoSO^= 20-47 per cent cobalt. 

 0.5557 gr. gave 0-2092 gr. silver= 12-37 per cent chlorine. 



The same experiment was made wdth sodic nitrite, and with similar 

 results. After two recrystallizations the salt formed was analyzed. 



0-4163 gr. gave 0-2235 gr. CoSO^= 20-43 per cent cobalt. 

 0-2332 gr. gave 0-0876 gr. silver= 12-38 per cent chlorine. 

 0-6625 gr. gave 192-12 c.c. nitrogen (moist) at 14° C. and 764-l"'" = 



34-29 per cent. 

 1-2310 gr. gave 0-5825 gr. water = 5-24 per cent hydrogen. 

 1-6542 gr. gave 0-7996 gr. water = 5-37 per cent hydrogen. 



The salt being found to lose no water on heating, the analyses 

 agree with the formula : — 



Co2(NH3),„(N02),(N03)2Cl2, 

 which requires : — 



Cobalt, 

 Chlorine, 

 Hydrogen, 

 Nitrogen, 



and which is fully sustained by other considerations, as I shall show- 

 As the solutions of the alkaline nitrites employed also contained 

 nitrates, the formation of the new salt may be represented by the 

 equation : — 



Co2(NH3)ioCl6 + 2KN0„ + 2KNO3 = 4KC1 + 



Co2(NH3),„(Nd)2(N03)2Cl2. 



The salt itself is then a nitroso-chloro-nitrate, and belongs probably to 

 the a-decamin or purpureocobalt series ; but it may be more con- 

 veniently regarded as the chloro-nitrate of xanthocobalt. It has the 

 wine color of the salts of the so-called xanthocobalt series, and crystal- 

 lizes usually in prismatic forms, which are moderately soluble in hot 

 water, and separate readily from the solution. With neutral potassic 

 chromate the salt gives the beautiful yellow crystalline chromate of 



xanthocobalt : — 



Co,(NH3),„(N02),(CrO,)2+ 2OH2. 



