The Hydrogen-ion Concentration, etc., of Sea-Water. 



33 



If the sea-water contains more than normal non-volatile buffer, 

 the CO2 content will be less than that read from the table, and vice 

 versa, but the quantitative side of this relation has not been thoroughly 

 investigated. We may picture it in the following manner: Suppose 

 the water is sealed in an air-tight container so that CO2 can not escape. 

 If we add boric acid part of it will remain free and increase the number 

 of H ions; but since it is so weak an acid, this change will be slight. 

 Part of the boric acid will displace CO2 from bicarbonates and some of 

 the CO2 will dissociate and increase the number of H ions still more. 

 Since boric acid is weaker than CO2 it will not decrease the Pg as much 

 as the same number of molecules of CO2; hence the error in estimating 

 the CO2 will not be as great as the same molecular concentration of 

 boric acid. Si02 would have even less effect than boric acid, but 

 phosphoric acid would have a relatively greater effect. We know of 

 no determinations of AS2O3 in sea-water, but Bang found 4 mg. per 

 kilogram of fish. 



The conversion table in figure 5 has a very limited range, and the 

 further it is extended graphically the greater the error. We did this 

 for the Princeton aquarium water because it had the very abnormal 

 excess base of about 44.5. We determined the total CO2 and Ph on a 

 portion of it and Dr. L. R. Gary determined the Ph of another portion 

 and the change in Ph on further additions of CO2. The results are: 



The difference of 6.2 c.c. CO2 at Ph 8.1 is only 0.0004 m, but the 

 difference at Ph 6.6 is probably partly due to an error in the extended 

 table or the experimental data. It may be remarked that the history 

 of this abnormal water does not completely solve the question of the 

 origin of the difference in excess base. It is possible that some con- 

 crete may have been dissolved, although it was said to have been par- 

 affined. Concrete may possibly have been dissolved by the rain-water 

 used to compensate for evaporation, or limestone dust may have gotten 

 into the rain-water by being blown onto the roofs. These character- 

 istics of the water were not investigated when it was first received. 



In using the conversion table in figure 5 for the study of the respira- 

 tion of marine organisms, only relative values are necessary, and it is 

 thought wholly adequate for the purpose. It would be of little advan- 

 tage to extend the table to a greater Ph range unless it is first absolutely 

 established that the abnormal Ph does not make the organisms physio- 

 logically abnormal and that oxygen is still present in the water (see 



