at the Royal Institution, 1 900-1 907. 



365 



As the relation between the vohime absorbed and the temperature 

 is nearly lineal in the later stages of the condensation of hydrogen 

 and helium, it may be inferred that at a temperature of from 5^ to 6^ 

 absolute helium would be as freely absorbed by charcoal as hydrogen 

 is at its boiling point, so that, in all probability, the boihng point 

 of helium is not below 5°. That such an inference is legitimate 

 cannot be denied in view of the fact that at the boiling points of 

 liquid hydrogen, nitrogen and oxygen respectively, good charcoal 

 absorbs (at atmospheric pressure) equal volumes of each of these 

 gases, namely 260 c.c. per gramme. It is to be. noted that the rate 



Fig. 7. 



at which helium is absorbed increases far more rapidly than does that 

 of hydrogen, a degree or two making a great difference in the volume 

 absorbed. Judging from such results therefore, it was highly prob- 

 able that the boiling point of helium is about one-fourth that of 

 hydrogen just as that of hydrogen is about one-fourth that of 

 nitrogen. 



The heat values given above are those deduced from an early 

 series of experiments. Later, more refined determinations made with 

 the apparatus depicted in Fig. 7 (which is a modification of the hquid 

 air calorimeter suitable for this investigation) show that at 18° absolute 

 the molecular latent heat of absorption of helium in charcoal, 483 

 calories, is nearly equal to the molecular heat of hydrogen absorption 



