Secrion III, 1912. [109] Trans. R. S. C 
The Heat of Solution of Radium Emanation. 
By R. W. Bortz, M.Sc., Pa.D. 
Presented by Dr. A. 8. Eve, F.R.S.C. 
(Read May 16, 1912). 
Some time ago the writer! determined the solubility of radium 
emanation in water at temperatures from 0° C. to 40° C. The results were 
expressed in the form of the ratio of concentrations in the liquid and 
vapour phases, and are in substantial agreement with those determined 
at a few points of temperature by Mdle. Ramstedt.? From the variation 
of the solubility with temperature, it is possible to deduce the heat of 
solution on thermodynamical considerations; the point is of theoretical 
interest only, since, of course, it is impossible to test it experimentally. 
Henry’s law of solution of gases was found to hold exactly in the 
case of the emanation. The partial pressures experimented with were 
of necessity extremely minute, they varied in the experiments from 
about 107 to 10° mm. of mercury; but the distribution between liquid 
and vapour phases does not depend on the pressure or on the presence 
of other gases. 
Assuming that the solubility coefficient (S) at any temperature, 
for the low pressures just mentioned, would also be the coefficient at 
the same temperature for ordinary pressures, if it were possible to 
obtain them, we can find the volume of emanation at N.T.P. which unit 
volume of water would absorb from an atmosphere of the emanation. 
This quantity is the Bunsen absorption coefficient (a), and is connected 
with the solubility coefficient by the relation 
SRE 0200366 1), 
where t is the temperature in degrees Centigrade. Also, it is possible 
to calculate the heat of solution of the emanation, 1.e., the heat pro- 
duced by the solution of 1 gm-molecule in a quantity of water sufficiently 
large for the solution to be considered dilute. Except for the reserva- 
tion made above the emanation is a good case to consider, for we are 
dealing with a gas of simple composition, which does not dissociate, and 
does not enter into any chemical combination. 
Van Hoff’s equation gives us:— 
d log, Ix —q 
dT dev Les 
! Phil. Mag., December, 1911. 
? Le Radium, July, 1911. 

