[satterly-patterson] 



LATENT HEATS 



125 



cylinder being placed in position , wastage was collected for 5 seconds, then 

 the current was on for 30 seconds and the wastage allowed for 

 another 25 seconds, making the total time of collection 1 minute. 

 By running the experiment in this way we get over any error caused 

 in the lag of the escape of the methane from the thermos bottle. 

 The readings were as follows : 



The density of methane gas at the time of the experiment was 

 •000664 gm. per cc. hence the latent heat of vaporization 



6-68X30X-24 



L = 



534 X -000664 

 = 136 calories per gm. 

 The experiment was repeated on a later occasion ; unfortunately, 

 the temperature of the methane was not read. The following results 

 were obtained: 



This gives L = 147 calories per gm. 



Method II. In the other method the stopper of the bottle now 

 carries only the tube TT. A piece of copper rod is attached to a 

 thread and at a given instant the copper is lowered into the liquid 



