Solubility of Radium Emanation. 849 



pressures of air and about the same concentration of emana- 

 tion, the same values of the coefficient were obtained within 

 the error of experiment. Table I. gives a number of results 

 showing that pressure and concentration of emanation can 

 be changed together without altering the result. Most of 

 the experiments were carried out by Method 1 described 

 further back, but a few were by Method 2. 



In the above the coefficient remained constant within ex- 

 perimental error, although the air-pressures varied from 183 

 to 9 cm. Hg, a ratio of 20 to 1, and the concentrations varied 

 irregularly from 1*81 to 0*017 millicuries per c.c., a ratio of 

 108 to 1. 



It will be noticed in Table I. that with one or two excep- 

 tions the coefficients appear to be lowest in the case of the 

 highest pressures. This is probably accidental, and no special 

 inference can be drawn, since the values shown do not differ 

 from the mean by more than the experimental error. 



With regard to the concentrations mentioned above, it is 

 interesting to calculate the partial pressures of emanation 

 they denote. The volume of 1 curie of emanation is 0"G 

 cubic mm. at N.T.P. Assuming Boyle's law, the above con- 

 centrations mean a variation of partial pressure of emanation 

 from 0-0008 mm. Hg to 0'000008 mm. Hg. Taking the 

 number of molecules per c.c. of a gas at atmospheric pressure 

 to be 2'8 X 10 19 , these concentrations are equivalent to a 

 variation from 3 x 10 13 to 3 x 10 11 molecules of emanation 

 per c.c. With any ordinary gas it would be impossible to 

 perform corresponding experiments at such extreme tenuities. 



Experiments were also performed with other gases con- 

 taining the emanation. Since the attraction by the small 

 mass of a gas is not comparable with that of the greater 

 mass of a liquid no differences in the coefficient should be 

 found provided that the gas does not change materially the 

 nature of the absorbent. The results of one experiment with 

 each gas are given in Table II. 



Table II. 

 Temperature 14° C. 





Gas. 



Pressure. 



Coefficient. 



Pure 

 Gases 



Oxygen 

 Hydrogen 

 Carbon dioxide | 



80 cm. Hg 



m „ 



77 „ 



0-304 

 0-308 



0-307 



Mixtures 



Coal gas 



Coal gas and air 



76 „ 



70 „ 



0-306 

 0-i!99 



