OF ARTS AND SCIENCES. 7 



Hiiperiodlde. — "When a solution of iodine in potassic iodide is added 

 to one of the nitrate of this series, a magnificent crystalline cinnabar- 

 red compound is precipitated, which may be washed with cold water, 

 and afterward with a little alcohol, without decomposition. For anal- 

 ysis, the salt was dried in pleno over sulphuric acid. The crystals are 

 small scales of unusual beauty and richness of color. They are slightly 

 soluble in cold water, and are partially decomposed by boiling water 

 with evolution of iodine vajDors. Even long boiling, however, does not 

 ajipear to decompose them completely. When heated with a solution 

 of sodic sulphite, tlie salt instantly becomes yellow and is converted 

 into the normal iodide. No similar compound is formed when a solu- 

 tion of potassic hyperiodide is added to one of nitrate of xanthocobalt. 

 The formation of the hyperiodide may be represented by the equation : 



Co,(NH3),(NO,),(NO,), + 2KI3 = Co,(NH,),(NO,) J, -f 2KNO3. 



In this salt, 



0-5748 gr. gave 0-1494 gr. CoSO^ = 9-87 per cent cobalt. 

 0-4705 gr. gave 0-2550 gr. silver = 63-70 „ iodine. 

 0-3942 gr. gave 49 c.c. nitrogen at 14-5° C. and 736-8"""= 14-10 

 per cent nitrogen. 



1-200 100-00 



If we consider NO^ as in part triatomic in this salt, the constitutional 

 formula may be most simply represented by the expression : — 



NH, - NO2 



NH3-NO, =1, 

 P J NH^-NIlj-r 

 ^^2 ^ NH, - NH„ - I 



I NH. - NOr = I2 



[ nh; - no; 



Nitrate. — I have already stated that the nitrate of this series may be 

 formed by the action of a mixture of ammonia and ammonic nitrate 

 upon a solution of cobaltic chloride and ammonic nitrate. It is much 

 more convenient, however, to prepare it from the crude sulphate by 

 double decomposition with baric nitrate. The sulphate is to be boiled 

 with a small excess of baric nitrate and a little acetic acid, and the baric 



