32 PROCEEDINCxS OF THE AMERICAN ACADEMY 



Nitrate, Co,(Nll,),,(NO,),(NO,}^ 



Nitrite, Co2(NH,)io(N02)2(N02), + 4OH2 



Sulphate, Co,{lSili,)J^O,),{80^), 



lodo-sulphate, Co2(NH3)io(N02)2(SOjl2 + 2OH2 



Hyperiodo-sulphate, Co2(NH3)j(,(N02)2(SO,)I, 



Auro-chloride, Co,(NU,),,{NO^,C\ -f 2 AuClg + OHg 



Platino-chloride, Co2(NH3)io(No52Cl, -f PtCl, + OH^ 



Hydrargo-chloride, Co,(NH3)io(NO,)2CI, + 4HgCl2 + OHj 



Oxalate, Co,(NU,)^,(NOl),{C.fi^)2 



Chromate, Co2(NH3)io(N02)2(CrOj2 + 20H2 



Dichromate, Co^(Nll.^\^{N0.^.2{Cr.p.)^ 

 Ammonia-cobalt nitrite, ^ Co2(NH3)io(N02).^ ^Co2(NH3)^(N02)j2 



Ferrocyanide, Co2(NH3)io(N02)'2(FeCy6) + GOH^.' 



I have collected them for the purpose of convenience of reference 

 and comparison. 



purpureocobalt: 



12. In the first part of this memoir Genth and I have endeavored 

 to show that purpureocobalt and roseocobalt form two distinct series of 

 salts ; that chloride of roseocobalt, for instance, Co2(NH3)jpClg -|- 2OH2, 

 cannot be regarded as differing from chloride of purpureocobalt only 

 by water of crystallization. This view has been adopted by some 

 chemists, rejected and even ridiculed by others. I shall endeavor to 

 show, by a more extended study and comparison of the two series of 

 salts, that they are essentially different, and, furthermore, that, as the 

 theory of these compounds proposed by Blomstrand suggests, there are 

 more than two series containing the group Co2(NH8)jq. Reserving 

 the discussion for the present, I proceed to the description of the salts 

 which serve to throw light upon the question. 



Auro-chloride of Purpureocobalt. — When a solution of chloro-aurate 

 of sodium is added to a hot solution of chloride of purpureocobalt, con- 

 taining a little free chlorhydric acid, no precipitate is formed at first, 

 but after standing a few hours crystals of a new salt are deposited. The 

 crystals in question present flat prismatic forms. They have a dark 

 ruby-red color. Math a dull violet lustre, and after standing exhibit a 

 distinct superficial reduction of gold. Of these crystals 



0-9028 gr. gave 0-3206 gr. gold, and 1-0560 gr. silver = 35-50 per 



cent gold, and 38-45 per cent chlorine. 

 0-6840 gr. gave 0-1896 gr. SO^Co and 0*2425 gr. gold =10*55 per 



cent cobalt, and 35-45 per cent gold. 



