PROCEEDINGS 



OF THE 



AMERICAN ACADEMY 



OF 



ARTS AND SCIENCES. 



VOL. XI. 

 PAPERS READ BEFORE THE ACADEMY, 



RESEARCHES ON THE HEXATOMIC COMPOUNDS OF 



COBALT. 



By Wolcott Gibbs, M.D. 



Presented, June 8th, 1875. 

 ( Continued from Vol. X. p. 38. ) 



Nitrates of Purpureocolalt. — In our joint memoir, Genth and I 

 assigned the anhydrous nitrate, Coo(NH,.)jq(NO,,)(;, to the roseocobalt 

 series, upon the ground that with certain reagents it forms salts iden- 

 tical with those which the hydrous nitrate, Co2(NH.,)j(|(N03)g-|-'20H2, 

 yields under the same circumstances. I am now satisfied that this 

 salt belongs in reality to the purpureocobalt series, partly because it 

 exhibits toward the hydrous nitrate relations precisely analogous to 

 those which exist between Co2(NH.,)joClg and Co2(NH.3),oCla-|-20H2, 

 and partly because, while a few of its reactions correspond with 

 those of tlie hydrous salt, the greater number agree with those of the 

 anhydrous chloride. By dissolving the normal nitrate of purpureo- 

 cobalt in water containing ammonic nitrate in large quantity, with a 

 little free ammonia, Genth and I obtained a new salt in beautiful 

 violet-red talcose scales, readily decomposed by solution in water. 

 The formula of this salt is most probably 



Co,(NH3),o.O.(N03),+GOH„ 



as the following analyses appear to show : — 



0-0675 gr. gave 0-0303 gr. SO.Co = 17-08% cobalt. 

 0-0729 gr. gave 0-0333 gr. SO,Co = 17-18% cobalt. 

 0-0769 gr. gave 0-0343 gr. SO,Co= 17-16% cobalt. 



VOL. XI. (n. S. II.) 1 



