The Alkalinity and the Carbonic Acid of the Ocean. 



A great many determinations of alkalinity and carbonic 

 acid in seawater have been made since the time of the Chal- 

 lenger-expedition but very few general results have been obtained. 

 The alkalinity and still more the quantity of carbonic acid have 

 been found to be «variable»; the carbonic acid being present, 

 as a rule, in quantities insufficient to form bicarbonates with 

 all the alkali. 



It is obvious however that neither the alkalinity nor the 

 quantity of carbonic acid can vary spontaneously, and I shall 

 now endeavour to enumerate and to exemplify the circumstances 

 which will cause alterations of these quantities. 



Causes which govern the alkalinity. 



I. Alkaline substances. When flowing along the bottom the 

 water will in many places be in close contact with alkaline sub- 

 stances: carbonate of lime, carbonate of magnesia and silicate 

 of lime. If the water contains an excess of carbonic acid it is 

 certain that it will readily dissolve these substances and that 

 the alkalinity will increase (Dittmar: op. cit. p. 130), and even 

 when the water is in its natural state it also seems to be capable 

 of dissolving carbonates. Dittmar made two experiments (p. 130 

 — 131) with water from the Irish Channel, containing 97.7 mgrs. of 

 CO. i per 1. with an alkalinity of 50.2 mgrs. (corresponding probably 

 to a tension at 16° of 4.5—5). He digested 260 cc. of this 

 water at ordinary temperature with 2 grms. of Ca CO.^ and 

 MgCO.j, respectively. In the first case he found that the 



