On the Radium Content of Some Nova Scotian Minerals. — 

 By Carl Kenty, M. Sc, formerly MacGregor Fellow in 

 Physics, Dalhousie University, Halifax, N. S. 



^Read 18 January, 1926) 



An attempt was made to develop a more sensitive method 

 for measuring the radium content of minerals and in the process 

 the occasion arose to make some measurements on a few Nova 

 Scotian minerals, the results of which seem worth recording. 



Method 



Only a resume of the method used need be given in this 

 note. The radium emanation was boiled off from a solution of 

 the mineral as usual. Instead of a gold leaf electroscope, the 

 measuring instrument was a quadrant electrometer used ballis- 

 tically. The emanation was introduced into an ionization 

 chamber having a quartz insulated electrode. This electrode 

 was made to charge up from earth potential, for a known time, 

 by a suitably applied electric field, and then connected to a 

 previously earthed quadrant of the electrometer. The magni- 

 tude of the resulting ballistic kick was then observed. 



The ballistic method possessed several advantages over 

 the ordinary rate of deflection method. In the first place, the 

 natural leak was considerably decreased. This was very im- 

 portant in the present work, which was done in the summer 

 when the leak over the amber supports of the quadrants was 

 very large. Secondly, all shift of the zero during the charging 

 period was eliminated. 



The minerals were obtained in solution by grinding in a 

 mortar and boiling with aqua regia. The solutions thus ob- 

 tained were sealed up and left for the emanation to accumulate 

 for a period of four or more days. 



Results 



The apparatus was calibrated with standard carnotite 

 solutions. Blank tests made it possible to correct for natural 

 ionization in the chamber. The sensitivity of the electro- 

 meter used was about 450 divisions per volt, while that of the 



