542 Mr Satterly, Radium- content of Cambridge Waters. 



(1), (2), (8) were collected on separate days, (4) and (5) were 

 collected at different times on the same day from the Cam at 

 Sheep's Green just above the flood-gates, and (6) on another day 

 from below the flood-gates. The water is broken up into foam 

 on passing through the gates, so that it is quite natural that (6) 

 should contain less emanation than (4) or (5). 



There is not enough radium in a litre of water to grow 

 sufficient emanation to give a readable leak. Therefore in order 

 to test for the actual radium-content of the water larger quantities 

 of water were taken. Two large clean tin cans were filled with 

 nine litres of Cam water and tap water respectively. The water 

 was then boiled, the dissolved emanation cleared out, the cans 

 corked up and the water allowed to rest. After an interval of 

 some days the water was boiled again and the emanation given 

 off collected and tested. From the amount accumulated in the 

 given period the amount accumulated in the first 24 hours was 

 calculated*. 



The results are given in Table II together with some results 

 obtained with hydrochloric and sulphuric acids. 



Table II. 



To express the radium-content of the water in terms of gms, 

 of radium it was now necessary to use radium solutions of known 

 strength. A radium solution containing 1-57 x 10~^ gm. radium 

 was kindly presented to the author by Professor Rutherford. This 

 was divided into two parts, one containing fths and the other 

 fths and placed in two bottles. Each of these parts was treated 

 in a manner similar to the above. Instead however of boiling 

 the solutions, which was impossible as the solutions were in bottles, 

 the bottles were heated in a bath of boiling brine (b.p. = 105° C). 

 The results are given in Table III. 



* Suitable tables for this work are given by Kolowrat. Le Radium, 1909. 



