«.! 



CHAPTER III 



THE LIQUEFACTION OF GASES AND THE 

 ABSOLUTE ZERO OF TEMPERATURE 



"Scientia et potentia humana in idem coincidunt, quia 

 ignoratio causae destituit efifectum." — Bacon, Novum Orga7ium, 



Matter is known to us in three states — as solid, 

 as liquid, and as gas. The relations between 

 these three states have been the subject of 

 investigation throughout the history of Physical 

 Science, and, indeed, almost throughout the 

 history of the human race. The solidification of 

 water in a frost, and its evaporation by the sun 

 or a fire, have been familiar to mankind from the 

 earliest times. But water shows these changes 

 of state under too favourable an aspect to be 

 taken as a general example. It has by no means 

 always been clear that such transformations were 

 possible to all kinds of matter, and it has been 

 necessary to exhaust the resources of modern 

 civilisation to liquefy the more permanent gases. 



Ice, when heat is supplied, begins to melt at 

 a definite temperature, which is called o° on the 

 Centigrade scale, and 32^ on the scale devised by 

 Fahrenheit. While any ice remains, no change 

 of temperature occurs in the mixture of ice and 

 water. Heat is still absorbed, but its energy is 

 used to effect a change of state, not to raise the 



41 



