840 Dr. R. W. Boyle on the 



of increasing the amount of deposits. This, however, must 

 be due to an increase in the amount of: the emanations them- 

 selves. It may be ndded that the range of variation of the 

 amount of the radium deposit observed is practically the 

 same as that of the amount of the emanation observed by 

 Satterly. 



In conclusion, we wish to thank Professor Tanakadate for 

 placing the resources of the Laboratory at our disposal, and 

 Professor Nagaoka and the other professors in the Laboratory 

 for their valuable suggestions during the progress of this 

 investigation. 



Physical Laboratory, University of Tokyo, 

 June 1911. 



LXXXII. The Solubility of JRadium Emanation. Application 

 of Henry's Law at Low Partial Pressures, By R . W. Boyle, 

 M.Sc, Ph.D., 1851 Exhibition Science Scholar of McGill 

 University *. 



Introduction, 



MEASUREMENTS of the solubilities of radium emana- 

 tion in some common liquids have already been made 

 by a number of experimenters. The results have served to 

 give an approximate idea of the solubility of the gas, but 

 they have in themselves showed such wide variations that no 

 reliance can be placed on any particular figure. The previous 

 determinations were made with the small quantities of 

 emanation such as are measured by means of an ordinary 

 emanation electroscope, that is to say, the equilibrium quan- 

 tities of about 10 -5 or 10~ 6 mgm. of radium. The experiments 

 involved more than one transference of emanation to the 

 measuring electroscope, or electroscopes, with the consequent 

 losses of emanation in the conducting and drying tubes. 



Since large quantities of radium have become available, 

 the 7- ray electroscope has come to be used for quantitative 

 measurements of emanation. In this method the vessel 

 containing the emanation is simply brought near enough to 

 the electroscope to cause a satisfactory ionization by the 

 7 rays sent out by Ra 0, and this ionization is compared 

 with that produced by a standard quantity of radium at the 

 same distance from the electroscope. The emanation cannot 

 be measured until at least four hours after admitting it into 

 the containing vessel. Alter this period radioactive equilibrium 



* Communicated bv Prof. E. Rutherford, F.R.S. 



