340 Mr. Gervaise Le Bas 



on 



a further examination of the molecular volumes of 

 the Paraffin Hydrocarbons under identically 

 reduced conditions. 



A more complete examination of the molecular volumes of 

 the paraffin hydrocarbons and other compounds under corre- 

 sponding conditions, is made possible by the very thorough 

 researches of Young (Trans. Chem. Soc. 1895, lxvii. p. 1075 ; 

 1897, lxxi. p. 466; 1898, lxxiii. p. 675; 1900, Ixxvii. 

 p. 1145). 



The above investigator has examined the volumes of a 

 number of organic substances under the identically reduced 

 conditions of pressure and temperature, that is to say, at 

 equal fractions of the critical vapour-pressure and the critical 

 temperature respectively. It was found that, while the 

 volumes of liquids approximately obey the law of correspond- 

 ing states at identically reduced pressures, it fails to a greater 

 extent at corresponding temperatures. 



It is proposed in this section to show, that the law of corre- 

 sponding states and the additive law are interdependent, and 

 that therefore they may be accounted for similarly. Those 

 features of the physical behaviour of liquids that depend on 

 the one are without doubt intimately connected with the 

 other. 



(a) At identically reduced Pressures. 



It will be convenient first of all to show that the law of 

 additivity is very closely followed at corresponding pressures. 

 Use is made in the following table of the valency numbers 

 W, of the four hydrocarbons pentane, hexane, heptane, and 

 octane, which are respectively 32, 38, 41, & 50. As before, 

 the ratio V/W represents the molecular volumes divided by 

 the valency numbers (see columns 4, 7, 10, 13). Columns 

 2, 5, 8, 11 give the corresponding fractions of the critical 

 temperatures at which the volumes are taken. 



The evidence of Table XIV. is very much in favour of 

 the significance of the valency numbers W for the respective 

 hydrocarbons, and there cannot be much doubt that under 

 strictly corresponding conditions, the 4 : 1 rule is very closely 

 followed. If this characteristic relation can be demonstrated 

 from a consideration of four consecutive members of the 

 series, is is likely to he true within very narroio limits for 

 every individual compound under all circumstances. 



