380 



S. E. Moody — Iodides and Iodates. 



shown by the subsequent slight liberation of iodine upon the 

 addition of the iodide-iodate mixture to react with the sulphuric 

 acid left behind. Yet the amount of hydrolysis which takes 

 place when the ammonium sulphate is boiled with water is 

 greater than when the ammonium sulphate and the iodide- 

 iodate mixture are allowed to stand at the ordinary room tem- 

 perature. 



The following table shows the results of these experiments : 









Table II. 







(NH 4 ) 2 S0 4 

 cm 3 . 



Time 



in 

 hours. 



KI. 



grm. 



KIOs. 



cm 3 . 



Approx. N/10 



Na 2 S 2 3 . 



cm 3 . 



I. 



grm. 



25 



3 



1-0 



10 



1-25 



0-0156 



25 



3 



1-0 



10 



1-55 



0-0193 



25 



3 



1-0 



10 



1-30 



0-0162 



25 



3 



1-0 



10 



1-47 



0-0183 



If the acid produced is eliminated as fast as it is formed, the 

 hydrolysis of the salt should proceed more rapidly. The 

 action of the iodide-iodate mixture, which reacts with the sul- 

 phuric acid to form potassium sulphate and iodine, should 

 bring this about ; and the iodine may be removed by boiling, 

 in the presence of a current of hydrogen, and collected for 

 estimation. In experiments made under these conditions it 

 was found, curiously enough, to be impossible to collect the 

 iodine in the Drexel flask used as a receiver when charged 

 with potassium iodide only, although it was evident that much 

 iodine came over. It appeared, upon investigation, that ammo- 

 nium iodide and ammonium iodate were formed by reaction in 

 the receiver between the liberated iodine and the ammonia 

 also volatilized, and to obviate the difficulty sulphuric acid was 

 added to the contents of the receiver into which the distillate 

 was passed. Under these conditions iodine is obtained in 

 amount corresponding to that which should be eliminated 

 when the ammonium sulphate is entirely hydrolyzed. 



This is shown in the subjoined table : 











Table III 









(NH 4 ) 2 S0 4 . 



KI. 



KI0 3 , 



Time 

 in 



H 2 S0 4 



(1:1) 



in the 



receiver. 



Approx. 



N/10 

 Na 2 S 2 3 . 



I. 



Diff. 



cm 3 . 



grm. 



cm 3 . 



hours 



. cm 3 . 



cm 3 . 



grm. 



grm. 



25 



1-0 



10 



3 



40 



38-25 



0*4769 



— 0-0004 



25 



1-0 



10 



3 



40 



38-25 



0-4769 



— 0-0004 



25 



1-0 



10 



3 



40 



38-30 



0-4775 



+ 00002 



25 



1-0 



10 



3 



40 



38-25 



04769 



— 0-0004 



25 



1-0 



10 



3 



40 



38-23 



0-4766 



— 0-0007 



