40 Mr. A. L. Fletcher on the Radioactivity of 



Electroscope B. 



In the case of this electroscope the tests were made 

 throughout with strongly acid solutions. 



(1) In this case the test was carried out with the tem- 

 porary addition of a U tube of CaCl 2 and KHO, and 

 with the delivery tube reaching to the bottom of tha 

 electroscope. 



Standardized with 1 m.g. uraninitein 60 c.c. strong radium- 

 free HC1 and 600 c.c. distilled water. Closure 44 hours 

 30 minutes, i. e. 30 per cent, emanation collected. 



Gain = 82*4 scale-divisions per hour. 



Here the emanation present was equivalent to a quantity 

 in equilibrium with an amount of radium = 65*28 x 10" 12 

 gram. 



Hence C - 65 ' 2 «* 10 "" = 0'792 x 10~ 12 . 

 82-4 



(2) Standardized from an acid solution of 10 grams Keuper 

 Sandstone, consisting of the precipitate insoluble in water 

 after fusion with 24 grams fusion mixture, dissolved in 

 70 c.c. distilled HC1. Solution very limpid. 



Test I. Closure 14 days. 



Total leak = 22 scale-divisions per hour 

 and gain = 16 „ ,, 



Test II. (after adding *2 m.g. uraninite from standard solu- 

 tion). Closure 14 days. Gain = 65'5 scale-divisious per hour. 



Gain due to radium = 655 — 16 = 49*5 scale-divisions per hour. 



Hence = 4Q-Q > :lQ-» = y 



49*5 



In this case the emanation present represented 4047 x 10~ 12 

 gram radium. 



(3) Standardized from the acid solution of No, 9 of the 

 Andes rocks. This had already been found to contain 

 9 x 10 ~ 12 gram radium, uAng the constant *8. To this was 

 added from a standard uraninite solution 8'84xl0~ 12 gram 

 radium. 



Hence 



total radium = 17"84 x 10~ 12 gram. 



Gain (closure 21 days) = 25 scale-divisions per hour. 



Hence r 17-84xl0" 12 71 in 12 



C = — = -71 x 10 - 2 . 



2d 



