TEMPERATURE AND THE PROPERTIES 



OF GASES 



By FRANCIS HYNDMAN, B.Sc. 



In every branch of human activity there are distinct periods 

 which are marked either by some new discover}'' or by the 

 termination of a definite line of work. The study of the 

 thermodynamic properties of gases and the relation of the 

 gaseous to the other states of matter has now reached the con- 

 clusion of such a period. It may be said that the modern study 

 and theory of gases dates from the publication at Leiden in 1873, 

 by J. D. van der Waals, of his famous treatise on the continuity 

 of the liquid and gaseous states. Since that time a large army of 

 workers have been occupied in striving to reduce the then 

 unliquefied gases to the liquid and ultimately to the solid state, 

 and in determining the various constants which define them. 

 The honour of conquering the last of the known gases which 

 remained unliquefied owing to the extremely low temperature 

 required has fallen to Prof. H. Kamerlingh Onnes of Leiden, 

 who has been for twenty-five years building up the most 

 perfect and efficient cryogenic laboratory in the world. 



This gas, helium, which was unknown fifteen years ago 

 except spectroscopically in the sun, has now been found to occur 

 in minute quantities in every radioactive portion of the earth's 

 crust which has been tested, with one or two trifling exceptions. 

 Its presence is closely connected with the radioactivity which 

 nearly all substances possess, and it appears to be one of the 

 decomposition products of radium and of similar substances. It 

 occurs in the atmosphere but in very small quantity, and is 

 obtained in practice by heating certain minerals, preferably 

 monazite sand. It is hence a very remarkable substance, besides 

 being the gas which is the most difficult to liquefy. As all 

 the known gases have now been liquefied, this line of work must 

 stand still until the chemists discover some other and possibly 

 even more refractory gas. 



It is interesting to note that Prof, van der Waals retired 



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