CHEMISTRY: HENDERSON AND COHN 621 
ably chiefly silicic acid and boric acid, though the conversion of bicar- 
bonates into carbonates is also of importance. 
These buffers regulate the reaction of sea water at the present time in 
a manner quite similar to the way in which bicarbonates and phosphates 
regulate the reaction of blood. The principal effect of the products of 
metabolism upon sea water is defined by the data concerning variation in 
the carbon dioxide tension. 
5. Geographical Variation in Carbon Dioxide Tension. — Taking ac- 
count of the facts as stated above, certain conclusions regarding geo- 
graphical variations in the composition of sea water may be deduced 
from Palitzsch's data. 
First, the uniform increase in acidity of sea water with increase of 
depth, proves that the concentration of free carbonic acid everywhere 
varies in like manner. This may be illustrated by one example. 
Station 
81. 
Depth 
meters 
Temperature 
in situ 
Salinity 
% 
Hydrogen ion concentration 
at room temperature 
Relative concentration 
of free carbonic acid 
0 
17.94 
35.43 
0.060 X 10-7 
1.0 
50 
13.56 
35.52 
0.066 X 10-7 
1.3 
100 
12.56 
35.63 
0.074 X 10-7 
1.8 
400 
11.01 
35.57 
0.091 X 10-7 
2.5 
800 
11.25 
36.02 
0.098 X 10-7 
2.8 
1000 
10.84 
36.02 
0.098 X 10-7 
2.8 
1200 
9.89 
36.00 
0.104 X 10-7 
3.1 
1500 
6.97 
35.50 
0.112 X 10-7 
3.4 
2000 
4.20 
35.10 
0.112 X 10-7 
3.4 
Disregarding a conceivable effect of pressure, it seems to follow from 
these facts that, upon the whole, (i.e., in most places and at most seasons) 
carbonic acid is escaping from the sea into the air. 
Secondly, the well marked variation in hydrogen ion concentration 
with latitude and therefore according to the temperature, in the case of 
surface waters, indicates that the concentration of free carbonic acid at 
the surface steadily increases in the direction of the pole. This, no 
doubt, depends upon the variation of the absorption coefficient of the 
gas with change in temperature. And, taking account of Krogh's^ obser- 
vations upon the high tensions of carbon dioxide, and the uniformly 
greater tension of atmospheric than of surface carbon dioxide in high 
latitudes, it appears to be certain that in cold marine regions carbonic 
acid is passing from air to sea. It does not appear likely that this ab- 
sorption of carbon dioxide by the cold oceans can balance its escape 
from the warm oceans, first, because Palitzsch found, even in cold re- 
gions, an increase of hydrogen ion concentration with the depth, and, 
