the Radioactive Emanations by Charcoal. 



370 



Using this apparatus when there is no absorbing material 

 between the thorium hydroxide and the testing-vessel, and 

 taking observations of the ionization current with varying 

 speed of the air-current, we get a curve such as is shown in 

 fig. 3 (Table I.), which has ionization (?) for ordinates, and 

 speeds of the air-current in c.c. per sec. (q) for abscissa?. 

 We shall hereafter call this the i-g curve. 



Table I. (Fig. 3.) 

 Emanation directly into testing vessel. 



Flow in cc./sec. 



Ionization Current 

 in arbitrary units. 



030 



91 



037 



174 



076 



380 



112 



441 



1-86 



464 



2-52 



433 



3-80 



291 



5-18 



238 



600 



224 



840 



192 



107 



169 



12-6 



1-19 



I'll 



5oo 



20o 







~j j 



•* 6 8 iO iz 



»"iow in cc PER sec 



The shape of this curve can be deduced from theoretical 

 considerations by the following : — 



The thorium hydroxide, in radioactive equilibrium, gives 

 off free atoms of emanation at a constant rate, and these are 



