316 Prof. E. Rutherford and Mr. H. Robinson on the 



§1. 



Distribution of the Heat Emission between the Emanation 

 and its Products. 



A quantity of emanation of about 50 millicuries was intro- 

 duced into a thin-walled glass tube T (fig. 2) connected by 

 a capillary tube C to a small stopcock S. The tube was 

 attached to a mercury-pump by the aid of which the ema- 

 nation could be purified and compressed into the emanation- 

 tube. The position of the latter was adjusted to lie in the 

 centre of one of the platinum coils. 



As it was necessary to leave the emanation for about 

 5 hours in the tube for equilibrium to be reached with its 

 successive products, it was desirable to arrange that the 

 emanation-tube could be removed outside the water-bath at 

 intervals to test for any change in the balance. The ema- 

 nation-tube was kept fixed to the pump, but the water-bath 

 was moved backwards along the direction of the axis of the 

 emanation-tube. For this purpose, the water-bath was- 

 mounted on metal guides, and was moved backwards or 

 forwards by means of a screw. 



The general procedure of an experiment was as follows. 

 The balance was adjusted as nearly as possible and the tube, 

 which had been filled with emanation for more than five 

 hours, was introduced within the platinum coil. In about 

 ten minutes a steady deflexion of the galvanometer was 

 obtained, proportional to the heating effect of the emanation. 

 The emanation was then suddenly expanded into the exhausted 

 pump by opening the stopcock S, and condensed in a U- tube- 

 by liquid air. The removal of the emanation caused a rapid 

 decrease of the deflexion, followed by a slower decrease due 

 to the decay of activity of the deposit. Observations of the 

 deflexion were continued in some experiments for over two 

 hours. In this time the heating effect had decayed to about 

 6 per cent, of the initial value. At the conclusion of the expe- 

 riment, the emanation-tube was removed and the balance point 



