470 Goocli and Blumenthal — Iodic Acid Process. 



idized by more iodic acid, with the result that the bromine 

 determination by calculation from the amount of iodic acid 

 remaining will be high rather than low. Andrews' results for 

 bromine were high to the extent of 1 per cent to 1*5 per cent. 

 The differences in experience and view of these investigators 

 have led vis to further investigation of the reaction. 



Suitable solutions of sodium chloride and potassium bromide* 

 were prepared and standardized gravimetrically by silver pre- 

 cipitation. An iodine solution, approximately N/10, standard- 

 ized against N/10 arsenite, and N/10 sodium thiosulphate, 

 standardized against the iodine solution, were used. Finally, 

 a solution of potassium iodatef (3'5670 grams per liter) was 

 prepared, and its iodine value was determined by titrating 

 with the thiosulphate the iodine liberated from 50™ 3 portions 

 by the action of potassium iodide in presence of sulphuric acid. 

 To avoid errors of titration due to an indefinite end point, the 

 gravimetric determination of chlorine was substituted for the 

 Yolhard process. Gaseous nitrogen trioxide, liberated from 

 sodium nitrite and washed by nitric acid, was used instead of 

 the sodium nitrite or potassium nitrite used by Bugarsky. 



The method of carrying out determinations was as follows : 

 To 50 cm3 of the solution, containing known amounts of sodium 

 chloride and potassium bromide, 50 cm3 of the iodide solution of 

 known value and 10 cm3 of 20 per cent sulphuric acid were added 

 and the solution was diluted to 200 om , in a 500 c '" 3 Erlenmeyer 

 flask. A few bits of platinum foil were added, to prevent 

 bumping, and the solution was boiled down to about 80 cm3 , 

 some 30 minutes being required. After cooling, the solution 

 was transferred to a carefully calibrated 100 cm3 flask and made 

 up to the mark. 



Half the solution was pipetted into an Erlenmeyer flask fitted 

 with an inverted mushroom trap, through which potassium 

 iodide was added. The liberated iodine was titrated with thio- 

 sulphate, and 1/6 of it was taken as the equivalent of the excess 

 iodate in the portion. 



The remaining half of the solution was transferred to a 

 beaker, the flask and stopper being carefully rinsed, and an 

 excess of gaseous sulphur dioxide (vaporized from the liquid) 

 was passed in. Gaseous nitrogen trioxide (liberated from 

 sodium nitrite or potassium nitrite by nitric acid, and washed 

 by the same) was passed into the solution to destroy the excess of 

 sulphur dioxide acid and to liberate the iodine.:}: The solution 

 was boiled until free from iodine, and the chlorine of the resid- 



* The "analyzed" C. P. article, free from chloride, so far as could be 

 determined by qualitative tests, (this Journal (3), xl, 289). 



fKI0 3 . 



\ The nitrogen trioxide prepared in the manner described produced no 

 turbidity in a solution of silver nitrate acidulated with nitric acid. 



