20 PROCEEDINGS OF THE AMERICAN ACADEMY 



The yellow modification of sulphate of roseocobalt gives with cliloro- 

 aurate of sodium a precipitate in yellow needles, soluble without de- 

 composition in boiling water, and crystallizing from the solution 

 unchanged. In this salt, — 

 0-19o2 gr. gave 0-0494 gr. SO,Co = 9-G3%. 

 0-2657 gr. gave 0-0856 gr. gold and 0.1866 gr. silver = 32-25r^ gold 



and 23-11^ chlorine. 

 The formula, Co2(NH„)io(SOj2Cl2+2AuCl3+40H„ requires : — 



Calculated. Found. 



Cobalt, 9-59 9-03 



Gold, 32-04 32-25 



Chlorine, 23-09 23-11 



Chloro-hydrargyrate of Roseocobalt. — Under the head of purpureo- 

 cobalt I have described two salts having respectively the formulas 

 Co,(NH3),„Cl6+6HgCl2, and Co,(NH3),„Cl,+4HgCl2. The six-atom 

 salt was first described and analyzed by Claudet,* and afterward by 

 Carstanjen, f who also first described the six-atom salts with four and 

 twelve molecules of water of crystallization. I find that the six-atom 

 salts are always formed when chloride of mercury and sodium, 

 HgCl^Na2, is added to a solution of chloride or of sulphate of roseoco- 

 balt, but that the resulting salt always contains four atoms of water of 

 crystallization, while the anhydrous salt, Co^(NH.5),„Cl,.,-|-6HgCl„ is 

 foimed when an excess of the mercuric salt is added to a solution of 

 chloride of purpureocobalt. On re-solution and recrystallization, 

 each salt separates unchanged, so that the hydrous salt does not appear 

 to be merely a hydrated form of the other. The salt Co.,(Nn,),nCl(;-}- 

 GIIgCl2-|-4()H2 crystallizes in lilac-red prismatic forms, which are 

 much more soluble than the anhydrous salt. Of this compound (from 

 Co,(NH3),„Cl,+20H,),- 



1-7840 gr. gave 1-1522 gr. HgClj^ 54-86<|^ mercury. 

 1-4373 gr. gave 1-2721 gr. silver =29-09'^ chlorine. 

 0-8430 gr. gave 0-1205 gr. SO,,Co= 5-43% cobalt. 

 0-3731 gr. (from Co,(NH8)w(SO,)3+5aq) gave 0-2373 gr. IlgS = 

 54-84''^ mercury. 



The formula requires : -^ 



