Manchester Memoirs, Vol. Hi. (1908), No. 14. 



5 



Effect of Light on Iodine Titrations. 



The retarding effect of the presence of iodine on 

 further change would indicate that but little alteration 

 would take place in the short time required for titrating 

 the iodine when carrying out " oxygen absorption " tests. 

 At the same time it is obvious that solutions containing 

 potassium iodide in presence of sulphuric acid should be 

 kept as far as possible out of direct sunlight, and the 

 titration of the iodine should take place without loss of 

 time after the addition of potassium iodide to the mixture 

 of permanganate and sulphuric acid, A possible loss of 

 iodine may occur if the solution stands any length of time 

 in an open vessel, owing to escape of iodine vapour at the 

 high temperature of a tropical laboratory. 



Effect of Dilution. 



Finally, it was important to investigate the effect of 

 diliLtion, as it might be assumed that the retarding effect 

 of the liberated iodine would be less in dilute solution. 

 Consequently two bottles were exposed, the one con- 

 taining the normal mixture, the other the same mixture 

 diluted with an equal volume (20 c.c.) of distilled water. 

 The following results were obtained : — 



Table II. 

 Effect of Dilution. 



