244 
A. H. Church. 
(1909) that it is the carbonic acid which acts as a “buffer” in 
regulating the Hydroxyl-ion concentration of the sea; and this 
suggestion is of the greater value as bearing possibly on the primary 
relation of the carbon-compounds in the evolution of autotrophic 
pelagic life, in which the carbon atom under the influence of solar 
radiation apparently comes into a still more intimate association 
1 
with the ions of water to initiate the CHOH chains (H-C-OH), in 
i 
terms of which it has been usual to visualize the chemistry of the 
carbohydrate series. 
Thus the complex relations of the ions of carbonic acid in sea¬ 
water may be first approached by considering that: — 
(1) A portion of the C0 2 of the sea will be absorbed from the 
atmosphere, just as will any other gas, in amount depending on the 
temperature, pressure and salinity ; one litre dissolving approximately 
.3 cc, physically (3 in 10,000), giving a concentration equal to that of 
the air at 15 0 C’. 
(2) The rest of the C0 2 of the sea, 150 times as much (or more) 
may be regarded as combining chemically with the water as H 2 C0 3 
and the latter dissociating to H - and HC0 3 ', the dissociation-constant 
being H-, HCO 3 '=3xl0-* (H 2 C0 3 ) 2 . 
(3) The HCO s ' ion further dissociates to H\ C0 3 ; but the dissoc¬ 
iation-constant for this reaction is many times less than that of the 
preceding (5,000 times less, Palitzsch) 3 . 
Only a small part of the H 2 C0 3 is thus completely dissociated, 
not 1% (Ruppin), and the greater part of the C0 2 of the sea occurs as 
HCOg' ions in equilibrium with calcium ions or other kations, or as 
undissociated carbonates and bi-carbonates. There in no reason to 
suppose that any great amount of carbonate exists in molecular form 
among the 10 % residual non-ionized part of the total salts ; and 
theoretical discussions of the constants of one substance taken 
separately in pure water do not go very far in explaining the complex 
relation of such a mixture of ions as that presented in sea-water. 
Whether the plant in photosynthesis utilizes dissolved C0 2 
HC0 3 ' or CO 3 " is still disputed ; quite possibly the last as the most 
completely ionized form, to which the HCO a ' ion constitutes the 
main reserve. 
The complications that are involved in such phenomena of 
ionization may he briefly considered as follows:—Assuming a 
condition of equilibrium to be in existence, if C0 2 , physically 
absorbed by the solution, be removed from the water, as in the 
hypothetical case of the action of a photosynthetic submerged plant, 
1 Palitzsch, loc. tit., p. 242. 
2 Thiel and Strohecker (1914) give 5 x 10 ' 4 ; Gaarder, loc. tit. p. 33. 
3 Ruppin (1910) assumes a dissociation-constant for H', CO a " as 1.295 
XlO 11 : Palitzsch (1912) takes 6 x 10 -‘ 1 (Auerbach and Pick, 1911). 
