154 Compressibilities and Atomic Weights of Oxygen, etc. [Feb. 3, 



the application to deduce a correction to the relative densities of gases 

 as observed at atmospheric pressure, so as to determine what would be 

 the relative densities in a state of great rarefaction, to which alone 

 Avogadro's law is applicable.* 



Taking oxygen as a standard, we see that the small correcting 

 factor to be introduced in order to pass from the ratio of densities at 

 one atmosphere to that at great rarefaction, is (1 +a)/(l +a ), or 

 1 + 2 (B - B), the suffix relating to oxygen, that is, as follows : — 



Hydrogen 1-00128 



Nitrogen 1-00046 



Carbonic oxide 1 • 00024 



The double of the first number, viz., 2-0026, represents, according 

 to Avogadro's law, the volume of hydrogen which combines with one 

 volume of oxygen at atmospheric pressure to form water. Direct 

 determinations by Scott gave 2*00245, and Morley, in his later work, 

 found 2*0027, so that there is here a good agreement. 



The following table gives the densities of the various gases, referred 

 to oxygen = 16, at atmospheric pressure and at very small pressure, 

 as deduced from my own observations.! 



Atmospheric Very small 



Gas. pressure. pressure. 



Hydrogen 1-0075 1-0088 



Nitrogen 14*003 14-009 



Carbonic oxide 1 4 * 000 14 • 003 



From the researches of M. Lecluc and Professor Morley, it is 

 probable that the above numbers for hydrogen are a little, perhaps 

 one thousandth part, too high. 



The uncorrected number (14'003) for nitrogen has already been 

 given, J and contrasted with the 14-05 obtained by Stas. This question 

 deserves the attention of chemists. If Avogadro's law be strictly true, 

 it seems impossible that the atomic weight of nitrogen can be 14*05. 



From the molecular weight of CO, viz., 28-006, we deduce, as the 

 atomic weight of carbon, 12*006. 



It should be mentioned that D. Berthelot§ has, meanwhile, calculated 

 very similar numbers, based upon the observations of Leduc. 



* The application to oxygen and hydrogen was made in my paper, " On the 

 Kelative Densities of Oxygen and Hydrogen," ' Eoy. Soc. Proc.,' vol. 50, p. 448, 

 1892 ; ' Scientific Papers,' vol. 3, p. 525. 



f 'Boy. Soc. Proc.,' vol. 53, p. 134, 1893; vol. 62, p. 204, 1897; 'Scientific 

 Papers,' vol. 4, pp. 39, 352. 



t.Bayleigh and Ramsay, ' Phil. Trans.,' A, vol. 186, p. 187, 1895. 



§ ' Comptes Ren dus,'. 1898. 



