350 



while the alkalinity is determined by titration of the surplus 

 acid in the sample of water. 



ToRNôE expressed his results with regard to the alkalinity, 

 as well as to the quantity of carbonic acid, in units of carbonic 

 acid, and he has been followed in this respect by all subsequent 

 authors. The term alkalinity in the quantitative sense means 

 therefore the quantity of carbonic acid (now as a rule given in 

 cubic-centimeters) necessary to convert the surplus base in 1 liter 

 of seawater to normal carbonate. 



ToRNöE found as mean values for the tract of the North- 

 Atlantic investigated by him : 



Alkalinity 52.78 mgrs. = 26.86 cc. of CO2 



Total quantity of C0^_... 96.42 mgrs. M = 49.07 ce. 



The quantity of carbonic acid is insufficient to convert all 

 the alkaU present to bicarbonate but greatly in excess, on the 

 other hand, of the amount necessary for normal carbonate. 

 T0RNÔE, therefore, was of opinion that seawater contained a 

 mixture of normal with bicarbonate, but that no trace of free 

 carbonic acid could possibly be present. Accordingly, he 

 supposed that the water must absorb carbonic acid from the 

 atmosphere. 



This last-mentioned supposition was disproved by Dittmar, 

 This Author prepared an artificial seawater [op. cit. p. 109} 

 by dissolving suitable quantities of chloride of sodium and sul- 

 phate of magnesia and adding a solution of magnesium- 

 bicarbonate. The alkalinity corresponded to 53.54 mgrs. of CO.. 

 per I., and the water was found to contain 104.5 mgrs. of CO^ 

 (pp. 114 — 115). This water was shaken repeatedly; each time 

 with 5 volumes of fresh air. After n such treatments the 

 quantity of carbonic acid was found to be 



') DiTTMAR, who afterwards tested the method, found that, as a rule, the 

 results proved 1—2 mgrs. too high [op. cit. p. 107). 



