or ARTS AND SCIENCES. 23 



Cobalto-nitrite of Roseocohalt. — When a solution of (•ol)alto-iiitrite 

 of sodium, Co^,(NOJ,.,Na„, in excess of sodic nitrite is added to one of 

 the soluble sulphate of roseocohalt, heautiful brown-orange prismatic 

 crystals are thrown down, which are readily soluble in hot water vvitii- 

 out decomposition. Of these crystals dried in plena ovt-r sulphuric 

 acid, — 



0-2820 gr. gave 0-1822 gr. SO, Co = 24-60% cobalt. 



The formula of the anhydrous salt, Co,,(NH3),o(NO,)„+Co,(NO,)„, 

 requires exactly the percentage found. The solution of this salt gives 

 with salts of luteocobalt a beautiful crystalline precipitate of the co- 

 balto-nitrite of that base, Co2(NII,)j,(N03)y-|-Co2(NO.Jj. With salts 

 of strychnia and brucia, it gives the cobalto-nitrites of those alkaloids. 

 The preparation of this suit, like that of all similar compounds, is 

 somewhat uncertain, and often fails entirely in consec^uence of the for- 

 mation of salts of xanthocobalt by the action of the excess of sodic 

 nitrite on the sulphate of roseocohalt. By the action of a solution of 

 cobalto-nitrite of sodium upon chloride of purpureocobalt, Sadtler ob- 

 tained a yellow crystalline salt much more soluble than the luteocobalt 

 salt, Co2(NH3)j3(NO.,),.-[-Co^(NOo)5, and to which he assigns the prob- 

 able formula Co2(NH3),o(N02),4-Co,(NO,),+01l2. Farther study 

 is needed, however, in the case of this salt. It may be identical with 

 that described above. 



Dickromate of Roseocohalt. — When a solution of potassic dichro- 

 mate is added to one of nitrate of roseocohalt, a dark red precipitate is 

 formed, which, after re-solution in water with a few drops of acetic acid, 

 separates in beautiful red scales with bronze-yellow reflections. This 

 salt is identical with that formed in Mr. Mills's process for preparing 

 salts of roseocohalt, to which I have already alluded, and in which I 

 found five atoms of water of crystallization. When digested at a 

 gentle heat with a solution of baric nitrate, the salt yields baric chro- 

 mate and nitrate of roseocohalt only, so that it certainly belongs to this 

 series, and not to that of i^urpureocobalt. 



Sulphite of Roseocohalt. — I obtained the sj^ecimen of this salt 

 vphich I examined from Dr. Genth who prepared it by boiling chlo- 

 ride of purpureocobalt with a solution of neutral ammonic sulphite. 



The salt was recrystallized from its solution in ammonic carbonate, 

 and contained only a trace of chlorine. It forms granular brownish- 

 orange crystals, slightly soluble in cold, and readily decomposed by 

 hot water. Heated in a tube, it gave off water, ammonia, and amnionic 

 sulphite. When sulphuric acid is poured upon the sulphite, some sul- 



