290 Gooch and Blake — Estimation of Bromic Acid 











Table III. 





















Error in 





KBrOs 



AS2O3 



H2SO4 



Time 



AS2O3 



AS2O3 



terms of 





taken. 



taken. 



(1:1). 



in 



unchanged. 



oxidized. 



KBrOs. 





grm. 



grm. 



cm^. 



minutes 



grm. 



grm. 



grm. 



( 1) 



0-0701 



0-1881 



5 



10 



0-0661 



0-1220 



0-0014— 



( 2) 



0-0701 



0-1881 



5 



10 



0-0650 



0-1231 



0-0009— 



( 3) 



0-0701 



0-2475 



5 



10 



0-1232 



0-1243 



0-0002— 



(4) 



0.0701 



0-2475 



5 



10 



0-1236 



0-1239 



0-0004- 



(5) 



0-0701 



0-2475 



5 



25 



0-1234 



0-1241 



0-0003— 



( 6 



0-0701 



0-2475 



5 



25 



0-1234 



0-1241 



0.0003— 



( 7) 



0-1402 



0-4950 



3 



15 



0-2479 



0-2471 



0-0012— 



( 8) 



0-1402 



0-4950 



3 



15 



0-2476 



0-2474 



0-0010— 



(9) 



0-1400 



0-6188 





20 



0-3708 



0-2480 



0-0004— 



(10) 



0-1400 



0-6188 





20 



0-3710 



0-2478 



0-0005- 



(11) 



0-1400 



0-6188 





20 



0-3706 



0-2482 



0-0003— 



(12) 



0-1400 



0-6188 





30 



0-3708 



0-2480 



0-0004— 



(13) 



0-1400 



0-6188 





45 



0-3711 



0-2477 



0-0006— 



Here again, as in the experiments of Table I, the indications 

 of the process of reduction of the bromate by arsenious acid, 

 point to a slight deficiency in the oxidizing power of the 

 bromate. The mean deficiency, 0-0006 grm., differs from the 

 indications of the process of reduction of the same sample by 

 the potassium-iodide method by about 0-0003 4- grm. 



The question now arises as to what is the impurity in the 

 bromate. In a product recrystallized several times, and in one 

 in which no chloride can be detected, as w^as the case with 

 the bromate of these experiments, the impurity most natural 

 to look for is potassium chlorate, which, might resist removal 

 in the process of purification by recrystallization. The pre- 

 paration of bromate upon which these last experiments were 

 made was therefore tested by igniting it and treating the resi- 

 due with potassium bichromate and sulphuric acid, volatiliz- 

 ing and collecting any chloro-chromic anhydride thus formed, 

 and converting the last into lead chromate.* Traces of 

 chlorine were thus found, which, not appearing in a similar 

 test upon the unignited bromate, must have had their origin in 

 chlorate intercrystallized with the bromate. In a former paper 

 from this laboratoryf it has been shown that a chlorate 

 may be determined by adding to it in solution potas- 

 sium iodide in known amount and an excess of an arse- 

 niate and sulphuric acid, boiling the mixture between definite 

 limits of concentration, determining by titration with iodine 

 the amount of arsenious oxide produced, and calculating 

 the amount of chlorate present, from the difference between 

 the amount of arsenious oxide thus produced and that which 



* Goocli and Brooks, this Journal, xl, p. 287 (1890). 

 t Gooch and Smith, this Journal, xlii, p. 220(1891). 



