ATOMIC WEIGHTS 57 



For the calculation of the true molecular weight of carbon monoxide 

 from this crude density ratio, the critical data cited by Guye ' are 

 available. The mean of two sets of critical constants gives (1 + a) 

 (1_&) =1.00109, and T = 132.7°. Applying these figures by the formula 

 given under nitrogen, the molecular weight becomes 



CO = 12.0031, ±.00077. 



The density of carbon dioxide has been determined by many investi- 

 gators,^ but the earliest measurements have now only historical interest. 

 In 1845 Regnault ' published five determinations of the density, referred 

 to air as unity, and they were the first to be worth consideration now 

 His figures are as follows : 



1.52915 



1.52900 



1.52915 



1.52906 



1.52915 



Mean, 1.52910, ± .000032 



Corrected by Crafts,* for compression of the empty globe, this becomes 

 1.52897, ±.000033. For the density of oxygen, Eegnault's corrected 

 value is 1.10562, ±.000008. 



Hence 0, : CO, : : 32 : 44.2530, ± .00098. 



In three concordant measurements, which are not given separately, 

 Leduc ^ found for CO, the density 1.52874. This figure, combined with 

 his value for oxygen, already cited, gives for CO, the density ratio 33 : 

 44.2667. Eayleigh" gives a single figure for the density of CO,, namely, 

 1.52909. For oxygen he found 1.10535. Hence the ratio 33:44.3673. 

 ^ The three determinations by Guye and Pintza ^ are stated in the form 

 of normal litre-Aveights, as follows: 



1.97684 

 1.97676 

 1.97681 



Mean, 1.97680, ± .0000176 



With Morley's figure for the weight of a litre of oxygen, 1.48896, ± 

 .000038, the ratio becomes 



0„:C0o: : 32: 44.2683, ± .00097. 



1 Journ. Chim. Phys., 3, 342. 1905. 



^ The early determinations are well summarized in Van Geun's monograph. 



=> Compt. Rend., 20, 993. 1S45. 



^ Compt. Rend., 106, 1664. 



° Ann. Chim. Phys. (7), 15, 34. 1898. 



«Proc. Roy. Soc, 62, 204. 1897. 



"Conipt. Rend., 141, 51. 1905. 



