Goooh and Blumenthal — Iodic Acid Process. 473 



duced in the main reaction, previously cited) iodine raono- 

 broraide will be similarly formed, according to the equation 



HI0 3 +- 2l a + 5HBr = 3H 2 + lOlBr. 



When the acidulated solution containing an excess of iodic 

 acid with more or less iodine monochloride, or monobromide, 

 is treated with potassium iodide for the purpose of determin- 

 ing the excess of iodic acid by means of the iodine liberated, 



HI0 3 + 5HI = 3H 2 + 3l 2 , 



the iodine compounds of the halogens will contribute to the 

 amount of the free iodine which measures the iodic acid, 



KI + IC1 = KC1 -1- I 2 , 

 KI + IBr = KBr + I 2 , 



and this increase in free iodine will produce a corresponding 

 deficiency in the bromide, which is estimated from the amount 

 of iodate which has disappeared. 



When, on the other hand, the excess of iodate is reduced by 

 sulphur dioxide preparatory to determining the chloride, the 

 iodine monochloride is converted to hydriodic acid and hydro- 

 chloric acid, and the iodine monobromide to hydriodic acid 

 and hydrobromic acid. The hydriodic acid is destroyed, and 

 the iodine removed, in the subsequent treatment with nitrogen 

 trioxide ; the hydrochloric acid is regularly estimated as silver 

 chloride ; but the hydrobromic acid remains to produce silver 

 bromide, which contaminates the silver chloride and causes an 

 error of excess in the chloride determination. 



These hypothetical effects are in precise accordance with the 

 observed phenomena. It is conceivable, and even probable, 

 that chloric acid and bromic acid may appear also as products 

 of the hydrolysis of the halogen compounds in presence of 

 water and iodic acid. Thus the hydrolysis of iodine mono- 

 bromide may proceed according to the expression 



15 IBr + 5HIO3 + I5ll 2 



= 5HBr0 3 + 5Br 2 + 10l 2 + 15H 2 



and that of iodine monochloride according to the equation 



15 IC1 + 3HI0 3 + 15H 2 



= 5HC10 3 + 10HC1 + 9I 2 + 9H 2 0. 



The production of bromic acid by hydrolysis of iodine bromide, 

 with elimination of the free halogens and substitution of 

 bromic acid for an equivalent amount of iodic acid, will tend 

 to reduce the tendency to negative errors in the determination 

 of bromine ; but the bromine of the bromic acid will still be 



