Absorption of ft Rays by Liquids, 



189 



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5-0 5-5 



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7. One more experiment must be described. An attempt 

 was made to discover whether the same mass of substance pos- 

 sessed the same absorption in the solid and liquid states. 

 A certain volume of water was poured into the tray (without 

 filter-paper) and frozen by pouring liquid air into a metal 

 vessel covering the tray. The tray was then placed under 

 the ionization-vessel and the readings of the electroscope 

 taken while the ice melted. Similar observations were taken 

 by pouring melted paraffin- wax into the tray and taking 

 readings while it solidified. The measurements were not 

 very reliable because the temperature changes of the walls 

 and the air of the ionization-vessel undoubtedly produce 

 small changes in the current through it ; but no certain 

 change in the current could be detected while the substance 

 changed from the solid to the liquid state or vice versa. 

 Such a conclusion is to be expected. It is very improbable 

 that the complications of the absorption of the rays by liquids 

 are due to some peculiarity in the condition of the molecules 

 of the substances, for if absorption were a property dependent 

 on the state of the molecules, it would not follow the atomic 

 law stated by Crowther for solids. It is much more probable 

 that they are due to some peculiarity of the distribution 

 of the liquid in the tray, and this distribution would not be 

 altered greatly by the solidification of the substance in situ. 

 The detailed investigation of the absorption of any substance 

 in two different states involves the measurement of ionization 

 currents at different temperatures. The accuracy obtainable 

 in such measurements at any temperature other than atmo- 



