[MURRAY] HELIUM CONTENT 33 



1 inch from the bottom of the chamber and }/$ inch inside diameter. 

 The explorer was screwed in up to the shoulder and the junction 

 made tight with Chatterton's Compound. 



Mixtures of helium and air only were used in this case and the 

 procedure was as previously outlined for the Purity Meter. 



The results at room temperature of about 16°C are given in Fig. 4. 



According to the straight line drawn in the figure 

 % Helium = -799 Instrument Reading+27'2 

 Thus, if the instrument indicates 82, the corresponding percentage 

 Helium = • 799X 82 + 27 • 2 = 92 • 7, which can be read direct from Fig. 4. 



Calibration of Indicator with Explorer No. 39272 



This explorer was calibrated with mixtures of helium and air 

 only at a temperature of about 15-5°C. 



Hj^ Mixtures were made up by volume from dry helium and dry air; 

 and the percentage calculated. 



The results are plotted in Fig. 5, from which it is evident that 

 % Helium = 1 • 56 X Instrument Reading. 



Calibration of Permeameter Explorer No, 39275 



This explorer was used in conjunction with a reflecting galva- 

 nometer, Tinsley, No. 5753, N. P. L. 39016. 



The total scale deflection at 1 metre distance was 500 mms., the 

 scale being divided in mms. 



The deflection for 1% Hydrogen in air was given by the Cam- 

 bridge Scientific Instrument Co., Ltd. as 259 mms. 



The explorer was calibrated for 



1. Hydrogen-air mixtures; 



2. Helium-air mixtures 



at IS'S^C, the mixtures being made by volume. 



Percentages of hydrogen are plotted against scale deflection in 

 mms. in Fig. 6; and percentages helium against scale deflection in 

 Fig. 7. 



The deflection for 1% helium in air was taken from the straight 

 line drawn in Fig. 7 as 165 mms. at 15-5°C. 



From Figs. 6 and 7 it is evident that % HeHum = 1 • 57 X Hydrogen 

 percentage for the same scale deflection ; or in other words, more helium 

 than hydrogen has to be present to produce the same movement of 

 the spot of light. 



