OP ARTS AND SCIENCES. 13 



Iodo-siilj>/i(ite of Baseocobalt. — Wlien a solution of pottissic iodide 

 is added to one of the soluble sulphate of roseocobalt a beautiful cin- 

 nabar-red crystalline salt is thrown down, which may be dissolved 

 without much ditliculty in hot water, and crystallizes from the solution 

 in granular crystals of an intense orange-red color. This salt has 

 essentially the formula Co.^(NH8)i„(SOJJ._,-|-20IL, which is that of 

 the iodo-suli)hate described by Krok, and obtained by the action of 

 iodine upon a boiling solution of ammonia and cobaltic sulphate. 

 Krok's analyses agree fairly well with the requirements of the formula. 

 I found, however, that the salt precipitated as above varied in different 

 preparations not inconsiderabl}'. I prepared the salt also from the 

 onliuary sulj)hate of roseocobalt for the sake of comparison, but could 

 detect no really essential difference between the two. The following 

 are the results of my analyses : — 



Of the iodo-sulphate from the ordinary red sulphate of roseocobalt : — • 



I. 0-6300 gr. gave 0-2073 gr. SO.Co = lG-15% cobalt. 

 0-4284 gr. gave 0-1170 gr. silver = 32-12% iodine. 

 0-5689 gr. gave 0-3516 gr. SO,Ba= 25-46% So,. 



Of the iodo-sulphate from the soluble sulphate : — 



JI. 0-4045 gr. gave 0-1776 gr. SO,Co = 16-72% cobalt. 

 0-4045 gr. gave 0-1763 gr. SO,Co = 16-60% cobalt. 

 0-4647 gr. gave 0-1096 gr. silver =: 27-76% iodine. 

 0-4935 gr. gave 0-3027 gr. SO,Ba:= 25-27% SO,. 

 III. 0-3579 gr. gave 0-1442 gr. SO, Co = 15-33% cobalt. 

 0-7586 gr. gave 0-3816 gr. silver = 27-18% iodine. 

 0-7099 gr. gave 0-4308 gr. So,Ba = 25-32% SO,. 



The formula Co,(NH,),o(SO,),l,+20H, reqmres: — 



Calculated. i. ii. ui. 



Cobalt, 15-33 16-15 10-66 (mean) 15-33 



Iodine, 32-99 32-12 27-76 27-18 



SO,, 24-93 25-46 25-27 25-32 



These analyses show at least that the reaction between potassic iodide 

 and the soluble sulphate is less definite than in the case of the iodide 

 and the ordinary sulphate. Krok states that he did not obtain sul- 

 phate of xautliocobalt by the action of argentic nitrite u])on iodo- 

 sulphate of roseocobalt, but only a rose-red solution, giving off nitrous 

 acid with the stronger acids. I found, however, that the iodo-sul|)hate 

 obtained from the soluble sulphate of roseocobalt, when digested with 



