ABSTRACT
The carbon dioxide solubility coefficient, 
, and the apparent carbonic acid dissociation constants, 
and 
, were estimated in the serum of the crab Carcinus maenas at various temperatures and ionic strengths.
At 15 °C, the indirectly determined 
value is 0·0499 m-mole 1−1 torr−1 for crabs living in normal sea water (salinity ca. 35 ‰). It is apparently independent of the serum protein concentration and of the stage of the moulting cycle.
For crabs living in undiluted sea water, the mean 
value, determined either gasometrically or titrimetrically, is 6·027 at 15 °C. At the same temperature, 
. These values approximate to those of sea water at 35‰ salinity. 
drops as temperature rises; the measured 
is –0·0053 pH unit °C−1 between 10 and 30 °C. 
rises as the ionic strength is lowered.
Alignment nomograms have been constructed for the determination of 
and 
values in relation to various conditions of temperature and salinity.
