138 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Of course pbenolphthalein could not be employed as 

 an indicator in tbis case as it is attacked by carbonic 

 acid. 



The values given by this method are what seem to be 

 most probably correct from titrations with several 

 different portions of the sea waters. The titrated 

 solution was found to become alkaline again on 

 standing for some time, hence the imperfect results 

 of this method. 



(b.) — By Estimation of Excess of Acid (Tornoe's 

 method)* 



Whilst the former method seemed to give too high 

 results, this method when phenolphthalein was em- 

 ployed as indicator, seemed to err on the side of 

 lowness, which was probably due to the carbonic acid 

 not being completely driven off by boiling. 



100 cc. of sea water were boiled for about twenty 

 minutes with excess of standard sulphuric acid (about 

 T |^). Most other workers so far as I have been able to 

 find out seem usually to have employed hydrochloric 

 instead of sulphuric acid, but this latter seemed to me 

 to possess a great advantage over the former in that 

 there is practically no liability of the acid itself being 

 carried away in the steam. Even in very dilute solu- 

 tion hydrochloric acid is always more susceptible to loss 

 in this way on boiling than is sulphuric. Sulphuric 

 acid may have the disadvantage of being dibasic and so 

 forming two series of salts, whereby the excess of acid 

 might not be a direct measure of the alkalinity owing 

 to the formation in unknown proportions of acid and 

 normal salts, but as the base with which the carbonic 

 acid in sea water is almost all combined is lime, this 

 danger seemed to be almost completely done away with. 



*Den Norske Nordhaus-Expedition, 1876-1878, Chemi. Christiania. 



