30 



THE ROYAL SOCIETY OF CANADA 





Mencury ;45|=i'alôr SeT. 



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USEO lis ^Al.i0«tAT<O(X 



Procedure 

 The apparatus between taps A and C (the volume of which was 

 about 250 ces.) was exhausted through tap B by a Fleuss pump. 

 This procedure was adopted in order to economise in pure hehum, as 

 the amount available at the date of the calibration work was small. 

 Tap B being closed, the gas mixture was slowly admitted at A till the 

 pressure was atmospheric as shown by the manometer. Readings 

 were then taken by the katharometer and also when a slow flow was 

 created by slightly opening tap C. 



Per Cent. Composition of Mixtures Used 

 Two methods were employed to determine the percentage of 

 helium in the mixtures: 



1. For high percentages (85-100% helium) the mixture was made 

 approximately by volume, and a sample taken for analysis after pass- 

 ing through the apparatus. 



2. For low percentages (0-30% helium) the mixture was made 

 exactly by volume. 



The pure helium was prepared from high grade impure gas by 

 passing through cocoanut charcoal at the temperature of liquid 

 oxygen, and was stored in glass gas-tubes over mercury till required. 



The analysis referred to in 1 was made by measuring the contrac- 

 tion in volume of a sample after absorption by cocoanut charcoal at 

 the temperature of liquid oxygen. A correction of 0.2 cc. per 18 cc. 

 residual volume was made to allow for the absorption of helium itself 

 by charcoal — a figure obtained for the analysis apparatus employed. 



Calibration of Shakespear Hydrogen Purity Meter 

 This meter is a field instrument designed for measuring the 



purity of hydrogen in balloons. The indicator readings were from 



75-100 with subdivisions of 0-25 per cent. 



