REACTIONS OF FISHES TO SALTS 



269 



TABLE 6 



Showing the resistance of small blue-gills {3-gram) to .OIN concentrations of the 

 , chlolide, nitrate and sulphate of ammonium dissolved in tap and 

 distilled water 



in the acidity of the solutions was marked in the case of all three 

 salts and the titrations showed that the acidity upon the day 

 of death of the fishes, had increased to nearly O.OOIN while 

 O.OOOIN is enough to kill these fishes in distilled water when no 

 salt is present. The increase in acidity was not due entirely to 

 the COo given off by the fishes, as boiling did not remove it. It 

 must, therefore, have come from the acid which had formed 

 from the hydrolysis of the salt. The ammonia formed in the 

 same process had passed off into the atmosphere. It seems 

 clear then that the three salts in question do not furnish a large 

 enough quantity of NH3 to kill the fishes, if the salts are dissolved 

 in distilled water. 



It has been pointed out in a previous paper (Wells '15 a) that 

 the tap water at the University of Illinois contains an unusually 

 large amount of the bicarbonates of Ca and Mg and that as 

 the water is aerated these bicarbonates dissociate to give the 

 normal carbonate. It was thought that the toxicity of the 

 ammonium salts in the tap water may have been due to the forma- 

 tion of ammonium carbonate and the further dissociation of this 

 salt to give NH3 in toxic quantities. To test this possibility 

 three experiments with O.OIN concentrations of (NH4)2C03 

 in distilled water, were tried. The dry salt gave a strong odor 

 of ammonia but the solution was too dilute to give any odor at 

 all. After thoroughly shaking the solution and allowing it to 

 stand for 10 minutes, a 10-gram sun-fish was placed in a liter of 

 it. A control was run in distilled water. The result of this 

 experiment, together with those obtained from a number of other 

 experiments are given in table 7. The table shows that am- 



