30 THE ROYAL SOCIETY OF CANADA 



Here the ionisation current appeared to be constant, as the time- 

 measurement of the movement of the gold-leaf showed a slightly 

 oscillating value of less than one per cent, which was thus the probable 

 error in taking the time of a single reading. 



The theory of the work is well known. The natural leak was 

 taken before introducing the emanation, and deducted from the 

 value obtained when the ionisation current had reached a maximum. 

 This value was corrected for atmospheric pressure, reducing all results 

 to standard pressure. Finally, the number of divisions per minute 

 for 10~^ curie of radium emanation, could be calculated by using the 

 value of l-e"'^^ directly from the tables given by Rutherford, inter- 

 polating for a fraction of a day: this value we call a "figure of merit." 

 By comparing the "figures of merit," and finally reducing to per- 

 centages, we can obtain the relative values of the two standards. 



Section 3. — Difficulties and their Solution. — Results. 



A number of sets of results were obtained, and practically all 

 showed a very close agreement between the two solutions compared. 

 As the work proceeded, a deterioration in values of the "figure 

 of merit" occurred, as if boiling had a weakening effect. Each 

 value was less than the preceding one. This suggested that some 

 of the radium might have been deposited with boiling, and so a qual- 

 itative experiment was carried out with a solution which had been 

 boiled a number of times, by adding some HCl to see if it would 

 dissolve the supposed radium deposit, and hence cause a rise in the 

 value of the "figure of merit." This is precisely what occurred. 

 A higher value, however, was now obtained than any previous one. 

 This suggested the probability of radioactive matter in the HCl 

 which had been added. To test this, a "blank" solution was pre- 

 pared, consisting of 50 c.c. of approximately 19% strength HCl, 

 obtained by diluting 38% commercial HCl to half strength. After 

 eight days it was tested, and on deducting the natural leak, which 

 was -083, it gave 2-71 divisions per minute. Two c.c. of this same 

 preparation had been added previously to the Rutherford solution 

 standard, which had been boiled fourteen times. A reading was 

 taken previous to adding the HCl, and it showed the steady decline 

 due to boiling. On next boiling, however, a rise of 12-2% occurred 

 in the "figure of merit." By calculation, 2% of this was due to the 

 radioactive matter in the acid which was added; the remainder 

 must therefore be due to the re-dissolved radium, which had been 

 deposited by boiling or otherwise rendered "de-emanating." This 

 quantitative experiment amplifies and confirms the behaviour of the 



