1899-im] Prof. Kuenen on Absorption of a Gas. 315 
coefficient of absorption relatively high, and there must, therefore 
be a minimum somewhere. With strongly soluble gases (for 
which the condensation curve is a narrow loop) this minimum will 
probably occur at a relatively high temperature not far from the 
critical point. For sparingly soluble gases on the other hand we 
may expect a well-marked minimum at lower temperature. The 
minimum will therefore occur at low temperature for helium, 
hydrogen and nitrogen in water, at a higher temperature for oxy- 
gen and argon, conclusions which are borne out by the experiments 
referred to. 
It is incorrect to say 2 that the coefficient becomes infinite at the 
critical point. The partial pressure does not and cannot approach 
zero, and the coefficient of absorption remains finite. That this 
assertion is true even if we apply the correct definition which holds 
up to the critical point may be shown as follows. We may treat 
the lower branch of the condensation-curve in the same manner as 
we have treated the upper — i.e., we may consider the partial pres- 
sure of the gas in the vapour-mixture and introduce a coefficient of 
absorption of the gas in the vapour — viz., the ratio of the mass 
of the gas contained in the vapour-mixture in the saturated con- 
dition per unit mass of the solvent and the partial pressure of the 
gas. If we call the density of the saturated vapour of the solvent 
d v the density of the gas at one atmosphere c?, its partial pressure 
p and the mass mixed with unit mass of vapour m , we have by 
Dalton’s law 
1 _ m 
d\ dp 
or 
m d 
p ~ d x 
Approximately, therefore, this new coefficient of absorption is 
equal to the ratio of d and di : as the temperature rises d 
diminishes as (1 + a if) -1 and d x increases, so that the coefficient 
is steadily diminishing with increasing rapidity. It is easily 
seen that this conclusion holds even if we take the limiting ratio 
of m and p. Owing to the existence of the condensation-loop the 
coefficient of absorption in the vapour ultimately approaches and 
1 Estreicher, loc. cit., p. 186. 
