[satterly] partial CONDENSATION 111 



for a while we should expect the gauge H to read the vapour pressure 

 of methane at liquid air temperature. This reading is about 6 to 7 cm. 

 of mercury. The reading directly after exhaustion through P is 

 usually much less than this, somewhere about 3 to 4 cm. Apparently, 

 the pumping causes evaporation from the condensate with consequent 

 cooling. 



Behaviour of Contents of Condenser. 



In this series of experiments observations were made on the con- 

 densate in G, on its vapour pressure as registered by the gauge H, 

 and the behaviour of this pressure under different temperature con- 

 ditions. The condensate is usually solid with western Canadian 

 gases and Texas gas, but liquid with most of the Ontario gases. The 

 liquidity is due to the presence of dissolved ethane with consequent 

 lowering of the freezing point. 



The temperature of the liquid air was not taken. Sometimes the 

 air was fresh, in which case the temperature would be about— 190°C 

 other times it was old and its temperature would approximate to 

 — 183°C. As an example of how the temperature may be obtained, the 

 following may be quoted. One day pure dry air at 20°C was sent 

 into the apparatus, all the taps turned off and the pressure read. It 

 was 752 mm. Liquid air about 18 hours old was then placed around G 

 and the final air pressure read. It was 242 mm. Calculating from 

 temperatures and assuming the gas laws, the final pressure should have 

 been 



79 

 752 X — =203 mm. 

 293 



Conversely calculating the temperature from the pressures we find 

 the effective temperature to be 



293X^ =94°A or-179°C. 



752 



A reading at another time gave a pressure reduction from 758 to 252 

 corresponding to — 176°C. 



It follows from these readings that if at any time when liquid air 

 is around G, a gas pressure is recorded as p cm. the volume of this gas 

 at 75 cm. pressure and room pressure = 



400X^X ^ =\6p 

 96 73 



nearly. This is a useful equation. 



If successive units of pure methane are passed into G, the methane, 



having a boiling point of — 164°C. at atmospheric pressure, should 



