144 On the Substitution of the Metal in a Salt. 



becoming rose-coloured, and ultimately brown on exposure to the 

 light. Thus, according to the stage at which we stop the addi- 

 tion of hypochlorous acid, we obtain acicular or granular crys- 

 tals sensitive to the light. The granular crystals are separated 

 from the mother-liquor, washed with anhydrous acetic acid, and 

 finally dissolved in anhydrous acetic acid at 60° C. The so- 

 lution, which should be colourless, is separated from a small 

 residue of iodic acid and then allowed to cool, when it de- 

 posits prismatic crystals with very brilliant facets. 



The greatest care must be taken to avoid the action of the 

 light. Even a strong gas-light is sufficient to yellow the crystals. 

 Finally, the adherent anhydrous acetic acid must be removed 

 from the crystals by warming them to 50° C. in a current of dry 

 air. When exposed to moist air, the crystals deliquesce very 

 rapidly, iodine being set free. Water or absolute alcohol decom- 

 poses them instantly, giving iodine, iodic acid, and hydrated 

 acetic acid. In the case of alcohol there is also production of 

 acetic ether. At 100° C, even in dry air, the crystals evolve a 

 little iodine. At temperatures above 100° C. they decompose 

 rapidly, sometimes with a slight explosion, setting free much 

 iodine. Analyses of the crystals purified by three crystalliza- 

 tions and dried in a current of dry air were made as follows : — 



It was proved that chlorine was absent. 0'675 grm. of the 

 silver-salt was prepared by calcining the crystals with pure lime 

 and then dissolving in dilute nitric acid and precipitating with 

 nitrate of silver. This silver-salt, which should be iodide of silver, 

 was then heated in a current of chlorine : loss in weight 0-260 

 grm. Theory, supposing chlorine absent, 0-262 grm. It was 

 furthermore shown that the whole of the iodine exists in a pecu- 

 liar state, treatment of the crystals with water giving all the 

 iodine as free iodine and iodic acid. 





Calculated. 



. 72 23-68 

 . 9 2-96 

 . 127 41-77 

 . 6 31-59 



304 100-00 







Found. 



A 









C 6 

 H 9 

 I 

 O 6 



I. 



22-21 



2-83 



II. 



41-41 



.III IV. 



41-24 42-28 



V. 



22-78 

 2-95 



VI. 



42-83 



VII. 



22-30 

 2-83 



It will thus be seen that iodine is triatomic in acetate of iodine, 



(C 2 H'0) 3 l n 3 



jiii r u s 



being the rational formula of the substance in question. 



A very interesting reaction takes place when the product of 

 the action of chloride of iodine on acetate of soda is heated above 



