Ratio between Uranium and Radium in Minerals. 347 



joined to that from the ether extraction. However, we 

 found that the ether extract contains actually more thorium 

 than uranium. This was proved for the aqueous solution of 

 the evaporated ether extract, both by precipitating with 

 oxalic acid and by tests on the amount of thorium emanation 

 generated. So the thorium and other rare earths were pre- 

 cipitated with oxalic acid from both the ether extract and 

 residue. But it was found that the extraction was quite 

 unnecessary, the same results being obtained whether it was 

 employed or not. The uranium finally in some cases was 

 precipitated by ammonium sulphide, and weighed as U 3 8 

 after ignition in oxygen ; in others, as phosphate by micro- 

 cosmic salt and sodium thiosulphate (Brearley, Analytical 

 Chemistry of Uranium, p. 7). 



Five analyses were performed of the uranium which gave 

 results comprised between 19' 74 and 20*56 per cent, of 

 uranium. The mean, which agreed well with the three most 

 satisfactory determinations, wa3 20'0 per cent. 



For autunite the uranium was precipitated as phosphate 

 by microcosmic salt and sodium thiosulphate in presence of 

 free acetic acid. 



Ratio of Radium to Uranium. — The results are given in 

 the following table. In the first column is given the name 

 of the mineral, in the second the quantity of uranium in the 

 solution employed, in the third the leak of the electroscope 

 in divisions per minute, and in the last the leak per milli- 

 gram of uranium. If the ratio of uranium to radium is the 

 same for all minerals, the figures in the last column should 

 be constant. 



Mineral. 



Uranium 

 (milligrams). 



Leak. 



Leak per 

 mg. Uranium. 



Pitchblende 



0308 

 0149 



20-3 

 97 



65 9 \ Mean 

 65-1/65-5 







0613 



41-5 1 

 411/ 



6 7-7 1 P ~. ± 

 67-0 j 6 ' 4 







0834 



243 



291 





Thus the ratios for thorianite and pitchblende come out 

 very nearly the same, the thorianite being about 3 per cent, 

 higher than pitchblende ; while for autunite the ratio is 

 very low, being less than half (44*5 per cent.) of that of 

 pitchblende. 



The measurements, therefore, so far as they have gone 

 bear out those of Mile. Gleditsch, in that thev show the ratio 



2 A 2 



