ATOMIC WEIGHTS 45 



Corrected for the compression of the empty globe, this mean becomes 

 2.30005. The weight of an equal volume of oxygen was found to be 

 2.63760, ±.00004. Hence the ratio is 16: 14.0055, ±.0015. 



Two determinations of density for " chemical nitrogen " are given by 

 Leduc.^ In mean, the value found, referred to air as unity, is 0.96717, 

 ±.00008. This, combined with the figure already cited for oxygen gives, 

 as the value for the ratio under discussion, 16: 14.0025, ±.0012. There 

 are also two determinations by Gray,^ whose comparative weights at 0° 

 and 760 mm., are as follows : 



Nitrogen. Oxygen. 



.32286 .36889 



.32275 .36879 



Mean, .322805, ± .00004 Mean, .36884, ± .00003 



Hence the ratio 16 : 14.0030, ±.0021. 



It is evident here that the data given by Leduc and Gray are over- 

 valued in comparison with Eayleigh's much larger series of determina- 

 tions. The general mean, however, as shown in the following combination, 

 cannot be far from the truth : 



Rayleigh 14.0055, ± .0015 



Leduc 14.0025, ± .0012 



Gray 14.0030, ± .0021 



General mean 14.0036, ± .00085 



Hence the normal litre of nitrogen weighs 1.25066 grammes. 

 For the density of nitrous oxide there are several series of measure- 

 ments. Leduc ^ gives three figures, as follov/s, referred to air as unity : 



1.5304 

 1.5298 

 1.5301 



Mean, 1.5301, ± .00012 



Combined with Leduc's value for oxygen, this gives the density ratio 

 0„ : N.O : : 32 : 44.3050, ± .0037. 



By Eayleigh there are two series of determinations,* made at different 

 times. In the earlier series the gas was possibly contaminated by traces 

 of nitrogen, in the second series the nitrous oxide was purified by con- 

 densation at the temperature of liquid air. The weights of nitrous oxide 

 filling his standard globe are subjoined. 



^Ann. Chirti. Phys. (7), 15, 33. 1898. 



-Journ. Chem. Soc, 87, 1601. 1905. 



3 Ann. Chim. Phys. (7), 15, 35. 1898. 



*Proc. Roy. Soc, 62, 204, 1897, and 74, 181, 1004. 



