465 
rubber tubing from the shaking vessel into the ionization chamber and back 
again to the shaking vessel until the emanation is mixed through the air of 
both chambers in the same proportion. Knowing the constants of the elec- 
troscope and the observed change of deflection of the leaf, the amount of 
emanation in the ionization chamber is known. Knowing this and the various 
volumes of air and water the amount of emanation per liter of water can be 
calculated. The shaking vessel is made of a can with two brass stop cocks 
soldered into it. One cock is placed near the top the other is placed on the 
side about half way up. For convenience the position of the lower stop cock 
can be calculated so that the vessel will hold a certain quantity of water 
when the vessel is filled full and then placed on a level stand with both stop 
cocks open. In this manner the volume of the water is determined easily 
and can be made the same in each experiment. The volume of the air above 
the water can be had by determining the total volume of the can. To pump 
the air around a rubber bulb pump such as is used in pyrography outfits 
answers well. The volume of the air in the tubes and pump must be esti- 
mated and used in the calculations. 
The formula for calculating the amount of emanation per liter, which 
can be derived easily in connection with Fig. 6, is as follows: 
I V2 == v4 Vi V> == V; ain Va 
EK =- ( ee ) e, 
Vi Vi Vi. 
Where V, = Volume of water in shaking can, expressed in liters. 
V. = Volume of air in shaking can, expressed in liters. 
V; = Volume of bulb, pump, and connection tubes. 
V. = Volume of ionization chamber. 
= Absorption coefficient of water for radium emanation. 
R 
e = Amount of emanation in chamber, V4. 
E = Amount of emanation per liter of water. 
The quantity alpha, z, has been determined experimentally and has 
been found to depend upon the temperature. The value at any temperature 
ean be had by referring to the curve (Fig. 7). The data for this curve is 
taken from M. Kofler (Akad. Wiss. Wien, Ber. 121, 2a pp. 2193; Sci. Abs. 
Vol. 16, 1742, 1913), and Boyle (Phil. Mag., 22, p. 840, 1911.) 
As a test of the above equation the following will serve (Table 4). 
Three tests were made at the spring under the ordinary conditions. The 
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