BETWEEN ONE ATMOSPHERE AND HALF AN ATMOSPHERE OP PRESSURE. 309 



this appears to correspond to C. The third column in the above table gives for 

 this temperature 2'0029. The agreement here may be regarded as very good. 



In correcting the densities directly observed at C., in order to deduce molecular 

 weights, we must use the third column of the alx>ve table.* Oxygen being taken as 

 32, the densities of the various gases at C., and at atmospheric and very small 

 pressures, as deduced from my own observations.t are : 



From the researches of M. LEDUC and Professor MORLEY it is probable that the 

 above numbers for hydrogen are a little, perhaps nearly one thousandth part, too 

 high. The correction to very small pressures has to be made in a different manner 

 for hydrogen and for the other gases, in consequence of the fact that the observed 

 ratio of densities corresponded not to C., but to 16 C.j Now the observed values 

 of B for hydrogen and oxygen relate to about 11 C., so that if we correct a to C., 

 we are, in fact, altering it in the wrong direction. I have employed as the correcting 

 factor to 16 C. the value 1 '00 11 8. 



It may be noticed that the discrepancy between my ratio of hydrogen to oxygen 

 and that of M. LEDUC is partially explained by the fact that my comparisons were at 

 16 C., and his at C. 



The unconnected number for nitrogen (14 '003 corresponding to O = 16) has already 

 been given, and contrasted with the 14 '05 obtained by STAS. This question 

 deserves the attention of chemists. If AVAGADRO'S law be strictly true, it seems 

 impossible that the atomic weight of nitrogen can be 14 '05. 



The atomic weight of carbon can be derived in three ways from these results. 

 First from CO and O :- 



CO = 28-003 

 O = 16-000 



C = 12-003 



The correction for temperature was neglected in the Preliminary Notice. 



t 'Roy. Soc. Proc.,' vol. 53, p. 134, 1893; vol. 62, p. 204, 1897. 'Scientific Papers,' voL 4, pp. 39, 

 352. Also for Nitrous Oxide, ' Roy. Soc. Proc,,' voL 74, p. 181, J 904. 



J See 'Roy. Soc. Proc.,' vol. 50, p. 448, 1892 ; Scientific Papers,' vol. 3, p. 533. 

 RAYLEIGII and RAMSAY, ' Phil. Trans.,' A, vol. 186, p. 187, 1895 ; ' Scientific Papers,' vol. 4, p. 133. 

 VOL. CCIV. A. ;{ B 



