Powers. — Antagonism in Polluted Waters 295 



In the experiments with a 0.297 N. sodium chloride solu- 

 tion, to which varying amounts of calcium chloride were 

 added, there was a greater antagonistic effect than the ad- 

 ditive effect of the calcium chloride. The antagonistic effect of 

 the introduced calcium chloride increased over that of its addi- 

 tive effect until the calcium chloride in the solution amounted 

 to approximately 10 per cent of that of the sodium chloride. 

 From this point on the survival time of the fish fell continu- 

 ously, up to the highest concentration of calcium chloride 

 employed, equalling that of the pure sodium chloride when 

 about 1.156 N. calcium chloride had been added. Follow- 

 ing this the antagonistic effect of the calcium chloride 

 amounted to less than its additive effect. 



These experiments show that there is no relation between 

 the antagonism and toxicity curves. They also show that the 

 antagonistic effect of calcium chloride and sodium chloride is 

 most pronounced when they are present in the ratio in nor- 

 malities of about one to ten. These results agree fairly well 

 with those of Osterhout (1914) who found the most effective 

 ratio for the antagonism of these two chlorides to be one of 

 calcium chloride to twenty of sodium chloride. 



These experiments show, in addition to the fact that a 

 definite ratio must exist between two antagonistic salts to be 

 most effective, that if this ratio is not approximated, the addi- 

 tion of the antagonistic salt to a toxic salt solution may be detri- 

 mental rather than beneficial. That is, if a toxic salt solution 

 requires more than an equivalent amount of another approxi- 

 mately equally toxic salt to have the greatest antagonistic 

 value, any amount, no matter how small, of this salt when added 

 to the solution will be detrimental rather than beneficial. On 

 the other hand a toxic salt solution can be benefited by an ad- 

 dition of another approximately equally toxic salt, provided 

 that it requires less than an equivalent amount of the second 

 salt to have the greatest antagonistic value. Thus in all treat- 

 ments of natural waters contaminated with a toxic substance, 

 the ratio for the greatest antagonistic value of the substance 



