Gooch and Blumenthal — Use of Selenic Acid. 55 



Gooch and Evans* find, however, that no chlorine is liberated 

 from solutions of small amounts of selenic acid at the boiling 

 temperature unless the hydrochloric acid present, reckoned as 

 concentrated aqueous acid, amounts to more than ten per cent 

 of the entire volume. Gooch and Scovillef show that the 

 interaction between selenic acid and potassium bromide in the 

 presence of sulphuric acid is proportional to the acid concen- 

 tration, to the bromide concentration, and to the elevation of 

 temperature. The present paper is an account of an attempt 

 to find conditions under which the reaction of selenic acid with 

 chlorides shall be inappreciable while the oxidizing action 

 upon bromides shall go to the end with the least possible 

 reversal. 



Fig. 1. 



. Selenic acid, now obtainable commercially, was at first used 

 in free condition, since it is capable of performing a twofold 

 service, that of acid, and that of oxidizing agent. Later it was 

 found convenient to substitute a selenate with sulphuric acid 

 to set the selenic acid free. 



Solutions of iodine and sodium thiosulphate of approximately 

 N/10 strength were carefully standardized, the iodine against 

 the arsenic solution and the thiosulphate against the iodine, 

 with the use of starch as the indicator. For nearly all these 

 experiments a solution containing 3*9673 grams per liter of 

 purest commercial potassium bromide, and 3*8974 grms. per liter 

 of the best sodium chloride, purified by fractional precipitation 

 from alcohol, were used in the preliminary analyses. In a few 

 cases, the salts were weighed directly. The selenic acid 

 employed was a commercial article of specific gravity 1*387 

 at 22°-23°, corresponding to that of 40*66 per cent pure selenic 

 acid.:}; 



* This Journal, [3], 1, 400. flbid., [3], 1, 402. 



"fDiemer and Lenher, J. Phys. Chem., xiii, p. 505. 



