( 551 ) 

 r. Alixluro \\'\i\\ niolcciilar projxd'lioii : ,/■ = 0.3072. 



As ;iii iiislaiicc lor the caJculalioii nvc shaJl consider (lic hisl 

 iiii.xlnrc more in detail. Firsl llie pi-essiii'es were reduced lo llie 

 mean t(Mni)era1nre 'iO'Mo ('., i)_v m(^ans of IIk' "real" coeriicienl of 



i)ressiire variation -f v' ) al 20 ; 0.0034.^). This ,^-avc tor .1, Il 

 p\dljr 



t\ 4cS.193, 59.cS37 and 115. 74S cm. i-es|)(M-lively. If />,. T, and />.,. 



r.^ resi)ecli\elv reprcscjil a correspondin.u' |)ressnre and \olnme, 



we have (o the tirsf a})|)i-oximatioii, which for onr case is snfticieiit : 



1 i'^^-^ ^^(r> 



Pi ^'i 



(^) 



where p^ and p., are expressed in atmospheres. From this we may 



ƒ > 

 derive - . In the case considered we found; 



from .1 with 6': ^ = — 0.003579^ 



.1 



„ B „ C 



— 0.003407 



niean : —0.003493 at 20.13 C. 

 In the same way foi' carhon dioxide at 2(r.00 C'. : 



from. I with 7i: ^ = — 0.005814 



.1 



.1 



. A „ C 



0.00553G 



mean : — 0.005G75, 



and for the mixture 0.2 at 20\00 C. : 



-1^ = — 0.003847, 



If the coefticient of pressure \"ai'ialion were known (mean coel'ti- 

 cient between and 20') we could easily derixc J j,, foi' the 

 dilferent cases. For if foi- the mixlni-e 0.3 at / =3 20. 13 in the (Mpiation: 



1) Comp. p. 'Jj3. 



