[SHUTT & CHARLTON] VOLHARD METHOD OF CHLORINE 



69 



These data are sufficient, we think, to show the extreme sensitive- 

 ness of the Volhard method and also its superiority to the chromate 

 process, especially when very small amounts of chlorine are to be 

 determined. 



Some of our earlier trials with this method were made on upland, 

 peaty waters — a class with which, as we observed, it is very difficult to 

 obtain satisfactory results by the older process. The following series, 

 consisting of samples taken from various points on the same river, very 

 well illustrates the value of the Volhard method. All' the waters were 

 quite bro^wTi from the presence of dissolved peaty matter, but with the 

 Volhard process this high colour did not interfere with the end re- 

 action, as happened when using the chromate method. 



Analysis of Peaty Waters. 

 Eesults in Parts per Million. 



Comparing the chlorine values, it will at once be seen that the 

 Volhard results allow a much closer discrimination than is possible 

 from those of the chromate method. In this instance they were in- 

 strumental in establishing the entrance of sewage at a certain point in 

 the course of the river — a fact which the chromate data were quite in- 

 capable of showing. 



The following results have been taken seriatim from our analysis 

 book and constitute about two-thirds of the waters examined by the 

 Volhard process to date. The waters are from all sources and come 

 from all parts of the Dominion. Among them are representatives of 

 the polluted barnyard well, of pure spring waters, of river and lake 

 waters and of waters charged with saline matter and occasionally sul- 

 .phuretted hydrogen. 



