20 PROCEEDINGS OF THE AMERICAN ACADEMY 



The yellow mollification 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%. 

 0-2fi57 gr. gave 0-0856 gr. gold and 0.186G gr. silver = 32-25 c;^ gold 



and 23-11^ chlorine. 

 The formula, Co.(NH,)i„(SO,),,Cl,+2AuCl3-l-40H„ requires : — 



Calculated. Found. 



Cobalt, 9-59 9-63 



Gold, 32-04 82-25 ■ 



Chlorine, 23-09 23-11 



ChJoro-hydrargyrate of Roseocohalt. — Under the head of purpureo- 

 cobalt I have described two salts having respectively the formulas 

 Co,(NH,),oCl6+6HgCl2, and Co2(NH3),„Cl6+4HgCl2. The six-atom 

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

 Carstanjen, t 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^Naj, 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.,(NIl3),QCl,;-f-6PIgCl.„ is 

 formed 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,,),oCl(j-{- 

 6HgCl+4C)H2 crystallizes in lilac-red prismatic forms, which are 

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



Co,(x\n3),„ci„+20n,),- 



1-7840 gr. gave 1-1522 gr. HgCl2 = 54-86p^ mercurv. 

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

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



* Phil. Mag. II. p. 253. 



t De Connubiis ammoniaco-cobalticis. Berlin, 1861. 



