86 SCIENCE PROGRESS 



radium emanation. These all give points lying on straight lines, 

 and the curves closely resemble those for the decomposition of 

 the emanation itself. These examples can be taken as typical. 



The following table shows the period of half decay, and the 

 values for X. In the case of experiments 5 — 7, the measuring 

 tube contained phosphorus pentoxide to absorb the water as 

 fast as it was formed. 



In most cases the total pressure change was small. A slight 

 error of the final readings — due to leakage or any other cause — 

 materially affects the half time as determined from the curve. 

 In view of these facts the truth of equation (2) must be held 

 as established. 



The authors point cut that it follows from this that the 

 amount of chemical action taking place in any time is strictly 

 proportional to the amount ot emanation which decays in that 

 time. From this it can be deduced that other conditions being 

 the same, each atom of emanation, as it disintegrates, produces 

 a certain definite chemical effect. 



In the seventh column are given the amounts of emanation 

 used in each experiment, calculated on the assumption that E is 

 the quantity of emanation obtained from one gram of radium 

 (as metal) dissolved in water, in 3-86 days. The eighth column 

 shows the total volume change which E c.c. of emanation would 

 effect. In experiments 5 — 7 the conditions were similar ; the 

 effect of E varies from 5-01 — 12*61 c.c. gas combined. It follows 

 therefore that some other factor besides the amount of emanation 

 present determines the total amount of chemical action. In all 

 probability there is a surface effect ; but the present data do 

 not allow its determination. Since in any single experiment 



