﻿Radium Content of Secondary Rocks. 281 



under which the standardization of the electroscopes was 

 effected. It was found that while both borax and quartz 

 powder confer fluid properties upon the melt, accompanied 

 by a brisk effervescence, the temperature required in the case 

 of the former was much lower and the reaction likely therefore 

 to be the more conplete. The marked advantage in tact in 

 working with a mixture of borax and boracic acid, added to 

 the fusion mixture of carbonates, is that, effervescence taking 

 place at a much lower temperature than with the use of pure 

 silica, renders the prolonged attainment of high temperatures 

 unnecessary and thus lengthens the life of the furnace. 



Were the expulsion of the emanation of radium from a 

 rock-melt a result attendant merely upon the attainment of 

 a condition of high temperature and independent of any 

 mechanical disturbance, we might expect a similar effect in 

 the case of thorium, t* An attempt, however, to measure 

 thorium by a measure of the emanation contained in air 

 passed over a fluid rock-melt under undisturbed conditions 

 yielded a negative result. 



Purity of tli£ Chemicals, 



The relatively low quantities of radium contained in some 

 of the rocks, and in particular in some of the limestones 

 and dolomites examined (quantities involving an increase 

 in the rate of collapse of the gold leaf of the order of 3 and 

 4 scale-divisions per hour), might have been easily masked 

 by the presence of a very small amount of radioactive 

 impurity in the chemicals, and rendered therefore a 

 knowledge of their purity imperative. 



To this end a series of six experiments were made. It 

 had been observed previously on several occasions that the 

 mere fusion of a mixture of sodium and potassium carbonates 

 failed to exert any appreciable effect on the rate of collapse 

 of the gold leaf. Fusion, however, of these carbonates with 

 varying quantities of borax and boracic acid — causing a 

 violent effervescence of the melt — produced on three 

 successive occasions on two electroscopes a small but quite 

 unmistakable, and steady gain of two scale-divisions per 

 hour, involving the minute but almost certain presence of at 

 least 0'04 x 10 -12 gram Ra per gram of mixed carbonates. 

 This effect has been observed by others, and an allowance 

 was made in rock determinations. No radium could be 

 detected in the borax glass or boracic acid used. 



Notwithstanding the precautions which were taken, ii is 

 Phil. Mag. S. 0. Vol 23. No. 134. Feb. 1512. I 



