240 MORRIS M. WELLS. 



tion of this acid in distilled water, at which the fishes in question 

 live as well as though in tap water. Higher concentrations of 

 acid are fatal, the time required to kill the fishes being propor- 

 tional to the hydrogen ion concentration. 



2. Resistance to Alkalies. 



In a .001 N solution of KOH in distilled water, a 3 gram blue- 

 gill lived 4 hrs. and 25 min. In a .0005 N solution, a fish of the 

 same size was alive at the end of 10 days. Titration at this time 

 showed that the water had become acid to phenolphthalein from 

 the CO 2 given off in the metabolism of the fish. The experi- 

 ment was discontinued. To make sure that the fish in the first 

 experiment had not been killed by the toxic potassium ion, 

 another 3 gram blue-gill was placed in a .01 N solution of 

 NaHCOs in distilled water. At the beginning, this solution was 

 neutral, but it was expected that the bicarbonate would dissociate 

 and the solution would become slightly alkaline from the 

 carbonate thus formed. A blank control, containing the same 

 amount of bicarbonate, but no fish, was run. The fish in the 

 experiment died on the third day. Titration showed that the 

 water had become .0009 N alkaline. The control was .001 N 

 alkaline. Blue-gills therefore do not live well in water which is 

 even very slightly alkaline. 



3. Resistance to Neutrality. 



The foregoing experiments, together with many facts recorded 

 in the literature, suggested the possibility that the fact that it is 

 neutral may have something to do with the toxicity of distilled 

 water. Thirteen experiments were performed to test this pos- 

 sibility in a preliminary way. The facilities available did not 

 make it possible to experiment with absolutely neutral water, 

 but the results obtained are suggestive, as neutrality was ap- 

 proached very closely in some cases. Most of the experiments 

 were performed with water that came from a copper still and 

 will be referred to as once-distilled water. A few experiments 

 were performed with a much purer water which was the once- 

 distilled water redistilled in a better still and coming in contact 

 with little copper. In neither kind of water could the amount 



