268 MORRIS M. WELLS 



ever, in that their toxicity is not due to the action of either of 

 the original ions, but to the products which are derived from the 

 breaking down of the original ammonia compound. Ammonia 

 salts in solution dissociate principally into NH4 ions and the 

 acid ion with which the ammonia is combined. There is a hy- 

 drolytic dissociation also, so that there is always present in the 

 solution a small amount of the free acid and the ammonium hy- 

 drate. In considering the reactions of fishes to ammonium hy- 

 drate (Wells, '15a, p. 236) it was pointed out that the ammonium 

 hydrate in solution is in equilibrium with and is but a small per 

 cent of the dissolved ammonia gas. In the case of an ammonia 

 salt the hydrolytic dissociation of the salt produces the hydrate, 

 which in turn dissociates to give water and ammonia gas. The 

 amount to which the salts dissociates into ammonium hydrate 

 and ammonia gas varies with the salt, being least in the sul- 

 phate and larger in the carbonate (Mathews, I.e.). Mathews 

 further states that it is probable that the action of the ammonium 

 salts is due, therefore, to the hydrate which is formed, and in 

 turn the action of the hydrate is dependent upon the action of 

 the dissociated NH3. This gas is probably in a nascent con- 

 dition just at its moment of origin, when the valencies of the 

 nitrogen are still open. 



The toxic action of the ammonium salts used in the reaction 

 experiments was found to be very marked when they were dis- 

 solved in the tap water, but was much less when the salts were 

 dissolved in distilled water. Solutions (O.OIN) of the chloride, 

 nitrate and sulphate were made up in tap and distilled water 

 and small blue-gills (3-gram) were placed in jars of the different 

 solutions. The temperature was kept constant by setting the 

 jars in running tap water. One liter of solution was contained 

 in each; the results are shown in table 6. 



The marked increase in the longevity of the fishes in the dis- 

 tilled water seemed worthy of further investigation. Death in 

 the distilled water was in part due to increasing acidity of the 

 solution, as titrations showed a concentration of hydrogen ion 

 at the end of the experiments that must soon have killed the 

 fishes even though no other factor were present. This increase 



