[MURRAY] 



HELIUM CONTENT 



31 



Mixtures were made of (a) helium and oxygen, (b) helium and 

 nitrogen, (c) helium and air, (d) helium, oxygen and nitrogen. 



The oxygen for (o) was prepared from potassium permanganate 

 in the usual manner; the nitrogen for (b) from sodium nitrite and am- 

 monium chloride with a purifying train of red-hot copper, potassium 

 hydroxide, sulphuric acid and phosphorus pentoxide. 



The results obtained are plotted in Fig. 3 as percentage helium 

 against instrument reading, the various mixtures being distinguished 

 according to the legend. 



^^This calibration was carried out at room temperature about 

 16°C. 



70 72 7* 7S 78 So 82 %-\ 86 BS SO 



I n$tkument Ri:/\oifK3. /A.RL. 231. 



A straight line has been drawn from which the variations are 

 slight, and according to this line 



% Helium = • 7537 X instrument reading + 32-1 

 Thus if the instrument indicates 82, the corresponding percentage 

 helium = • 753 X 82 + 32 • 1 = 93 • 8, which can be read direct from Fig. 3. 



Calibration of Indicator with Explorer No. 39273 



For purposes of calibration the explorer was screwed into a brass 

 chamber. The inside dimensions of this cylindrical chamber were 

 lJ/8 inches diameter and 1^ inches high. Inlet and outlet tubes for 

 the mixture under examination were provided, diametrically opposed, 



