[m'lennan à KENNEDY] RADIOACTIVITY OF POTASSIUM 23 



TABLE VII. 

 Absorption Experiments — (Reduced Values). 



From the form of the curves it is evident that the radia- 

 tions from the different potassium salts were not identical in their 

 composition. The absorption curves for the sulphate and the chloride 

 were very similar but that for the cyanide was markedly different 

 and indicated by its shape that the rays from the salt besides being 

 heterogeneous in character contained a predominating proportion of 

 the more penetrating types. 



It is of interest to note too that the absorption curves in Fig. 6 

 shew no irregularities in their initial portions such as one should have 

 expected if the radiations had consisted, amongst others, of a type 

 possessing the characteristics of the ex radiations from the known 

 radioactive elements. 



These results it will be seen are in accordance with Campbell and 

 Wood's observations and confirm the conclusions reached by them 

 that the radioactivity exhibited by the potassium salts possesses the 

 characteristics of either a /5 or an easily absorbed y radiation rather 

 than those of the a type of radiation. 



In a second series of measurements on the absorption of the 

 potassium rays the tray was filled with a quantity of potassium 

 sulphate and then placed in the ionising chamber resting on the bottom. 

 The salt was covered successively with an increasing number of sheets 

 of tinfoil and the saturation current measured for each set of the 

 absorbing sheets. The foil used was 0.0089 mm. in thickness. The 

 values of the currents corresponding to the different thicknesses of 

 tinfoil are given in Table VIII and the manner in which the values 

 of the currents decreased is indicated by the curve in Fig. 7. In 

 arriving at the numbers recorded in Table VIII corrections were made 



