d PROCEEDINGS OP THE AMERICAN ACADEMY 



Chloride. — The chloride of this series cannot be readily obtained by 

 the action of a mixture of ammonia and potassic nitrite upon cobaltic 

 chloride, since, as I shall show hereafter, other products are formed 

 under these circumstances in much the larger quantities, salts of xan- 

 thocobalt predominating. It may, however, be easily prepared in quan- 

 tity by boiling the crude sulphate with baric chloride and a very small 

 quantity of chlorhydric acid. To avoid loss, the baric sulphate must 

 be repeatedly and carefully washed with boiling water and a trace of 

 free acid. The chloride then crystallizes fx-om the filtrate in beautiful 

 iridescent crystals. The forms of these crystals, together with those 

 of other salts of this series, I hope hereafter to be able to give in detail. 

 The chloride has the characteristic sherry-wine color of the salts of this 

 series, and the small crystals are very brilliant and exhibit a remarka- 

 ble iridescence. 



The chloride is more soluble than the sulphate, but still belongs to 

 the class of slightly soluble salts, and crystallizes almost completely 

 from hot solutions as these become cold. The salt possesses in a high 

 degree the sharply defined crystalline character of the members of this 

 series, and forms a large number of compounds with metallic chlorides, 

 many of which are of great beauty. The constitution of the chloride 

 is represented by the formula 



Co,(NH3),(NO,),Cl„ 



as the following analyses show : — 



0-5164 gr. gave 0.3152 gr. 0080^ = 23-24 per cent cobalt. 



0-6048 gr. gave 0-3683 gr. CoSO^ = 23-18 „ „ 



0-7188 gr. gave 0-3027 gr. silver =13-84 „ chlorine. 



0-4846 gr. gave 0-2152 gr. water = 4-92 „ hydrogen. 



0-6160 gr. gave 172-5 c.c. nitrogen at 16° C. and 768-2""" = 

 32-91 per cent. 



Calculated. Found. 



Cobalt 2 118 23-18 23-18 23.24 



Chlorine 2 71 13-94 13-84 



Hydrogen 24 24 4-71 4-90 



Nitrogen 12 168 33-00 32-91 



Oxygen 8 128 25-17 



509 100-00 



The corresponding bromide, Coo(NH„)g(N02)4Br2, resembles the chlo- 

 ride so closel)' that no special description is necessary. \ In this salt, 



0-3944 gr. gave 0-2059 gr. CoS04= 19-87. 

 The formula requires 19-73 per cent. 



