FUNDAMENTAL EQUATIONS OF IDEAL GASES 

 AND GAS MIXTURES 



[Gibbs, I, pp. 150-184; 372-403] 



F. G. KEYES 



I. General Considerations {Gihhs, I, 150-164) 



1. Pure Ideal Gases. The response of gases to changes of 

 pressure, temperature and volume was a subject of the greatest 

 interest during the latter half of the 17th century and con- 

 tinuing through the 18th and 19th centuries. Boyle's work, 

 appearing in 1660, and Mariotte's investigations (1676) estab- 

 lished as a property of several gases the constancy of the pres- 

 sure-volume product at constant temperature. Not until the 

 beginning of the 19th century, however, was definite and 

 sufficiently exact information secured regarding the volume- 

 expansion law with temperature for constant pressure, and the 

 pressure-increase law with temperature for constant volume. 

 A knowledge of the latter laws, now known under the name 

 of Gay-Lussac^'2 as well as the Boyle-Mariotte law, was 

 necessary to understand experiments on the relations of the 

 volumes of chemically combining gases, — experiments the 

 interpretation of which proved of such incisive importance to 

 chemistry as a whole. It remained for Amed^o Avogadro^ 

 to draw the important inference from these investigations that 

 the number of particles or molecules is the same for different 

 gases of equal volume, the temperature and pressure being the 

 same for all. There results then the remarkably simple expres- 

 sion for the physical behavior of pure gases 



— = universal constant, (1) 



Q 



337 



