1918 Shelf ord; on Acidity Affecting Fishes 101 



apparently only a rough one as indicated by the more delicate methods 

 of hydrogen ion determination. 



3. Presentation of the results 



A. Siilphuric acid 



When sulphuric acid is introduced into water containing carbonate, 

 no free mineral acid remains in the water until all the carbonates have 

 been transformed into sulphates with a liberation of carbon dioxide, and 

 this presumably occurs when the pH is about 5.0. Accordingly in most 

 of the tests made the acidity produced by the addition of sulphuric acid 

 was due to carbon dioxide liberated. On account of this fact and the 

 rapid escape of the carbon dioxide, it is important that experiments be 

 performed in running water. Also it is obvious that since average sea- 

 water is about .002 normal carbonate a large amount of acid can be 

 introduced before any marked change in hydrogen ion concentration can 

 take place. Thus it will be seen from table 1 that the introduction of 

 30 parts per million only lowered the pH to 7.25. It will be noted 

 further that up to nearly 32 parts of acid added per million no injurious 

 results were noted on small herring, and that probably with 39 parts per 

 million the injury noted was due to mechanical injury of the fish which 

 died. Fishes often die soon after being seined and occasional deaths in 

 such fresh material are by no means due to the poison. It will be noted 

 that death among the young herring occurred only with the addition of 

 39 parts of acid per million, which brought the pH down to 6.85 or just 

 on the acid side of true neutrality. This appeared to be fatal to the 

 young herring after 8 hours exposure and is little less than the concen- 

 tration which Whitley (1905) found would injure the eggs of the plaice 

 immediately after fertilization; for further work on the effects of acid 

 see cited works of Loeb, ]\Iedes and Moore. The herring is a pelagic 

 fish living near the surface in the open waters, frequently at some distance 

 from shore, and coming to shore to breed. Its remarkable sensitivity to 

 differences in hydrogen ion concentration as shown by the action in the 

 gradient tank have already been discussed by the writer and Powers 

 (1915). In a few gradient experiments, in which a very slight difference 

 in pH was produced by the addition of a very small amount of sulphuric 

 acid to the water running into one end, the herring showed an ability 

 to recognize the differences between pH 8.1 and pH 8.2 at the two ends 

 of the tank. The graph of one of these reactions is shown in chart 1, 

 graph 1, from which it would appear that the herring is able to recognize 

 differences in hydrogen ion concentration correspondng to differences in 



