282 THE NEW WORLD OF SCIENCE 



of potassium, and the same amount of a one per cent, solution 

 of soluble starch and one-half per cent, of sulphate of zinc. 

 If free chlorin be present, the iodine is liberated from the 

 potassium iodide and it combines with the starch, giving the 

 characteristic blue color of starch iodide. The significance of 

 the test is clear when it is realized that the chlorin is used up 

 by the organic matter present in the water, and that there can 

 be no excess unless all the organic matter has been oxidized. 

 If the test shows no free chlorin more bleaching powder is 

 added until some is present in excess. 



The principle of chlorination in the Lyster bag is the same as 

 in the largest installations, depending as it does on the oxidiza- 

 tion of all organic matter, by the oxygen set free by the action 

 of nascent chlorin on the water molecule. The small quantities 

 treated in this method make it very difficult to adjust the 

 chloride of lime accurately, and the result is that the water 

 may be 'overdosed with chlorin, giving it an unpleasant taste. 

 The soldier may then be tempted to drink untreated water, 

 which although clear, bright and sparkling, may be heavily 

 contaminated with pathogenic bacteria, rather than the water 

 which is quite safe but less attractive in appearance and flavor. 



In the A. E. F. both large and small scale water treatment 

 was used almost everywhere the American troops were sta- 

 tioned. In the back areas, that is, on the Lines of Com- 

 munication, or rather, in the area of the Service of Supply 

 (S. O. S.) as it later came to be called, it was usually possible 

 to use the large scale methods in cooperation with the French 

 civil and military authorities. 



Chlorination of water supplies in the United States has been 

 customary for the past ten years, but until 1917 the method 

 was not known in France. It was introduced there by an army 

 chemist and water supply expert, who had been selected for 

 special work in France by the National Research Council. 

 This officer worked with the French authorities and at the 

 Laboratory of the Museum de Histoire Naturelle, Paris, in 

 conjunction with a French chemist he carried out a series of 



