( 379 ) 



{Cl Me.) 



dB 'Ci^te.) 



73, "b, and found y- = O.OOOJ 194, so that B^^^ = — 0.02026, 



wliile .1 ^=:l-\-Wa^. Thus wc liud 



.T^-/, = 0.01814 (K. O. and Z.) 

 while :i' .^. = 0.0195 (L.) 



f) 7? 

 Avas found bv Leduc; (I.e.)- Tlie nncertahitv of — contributes 



ot 



probably bul little to the diiference. It is noteworthy that in con- 

 tradiction with our result the value of B derived from Leduc's 



{Cl Me) 



observations B = — 0.0215 perfectly agrees with that according 



to the law of corresponding states: — 0.0216. 



Measurements on the com})ressibility of CO.^ have been made by 

 Chappuis ^) at 20° C. He found (mean from some determinations with 

 about the same pressure each time) : 



I y; = 1260.670 mm. y>/' = 1312485 



II 1117.228 „ 1313826 



III 992.911 „ 1314981 



liy third approximation yield 



(CO.,) 



B 



I and II : _J^° = _ 0.005309 



a' 



20° , 



assumed mean — 0.005296, 



II and III „ — 0.005282 

 I and III „ —0.005297 



(CO.) 



from ^vhi('ll follows B = — 0.006100, whereas according to 



i<'0,) 



Keesom B,,- = — 0.()()646. 



From the observations of Lkdlc on carbon dioxide Keesom derived 



(CO..) 



7i.,„° =1 — 0.0059. 



II. Conditions of coexistence, at lom temperatures. 



§ 7. Deterniination of tlw betjin conclensatioii pressure at — 25°. 

 In the inti'oduction we mentioned a determination of the begin 

 condensation pi'essure at — 25° for testing the results obtained 

 with the i|'-surface. This tletei-mination was made with a mixture 

 with the composition ,/' = 0.5042 of methylchloride. 



1) Trav. et Méni. du Buieaii Intern, dcs I'oid.-^ v\ Mcsiucs, t. 13, 1903. 



26 

 Proceedings Royal Acad. Amsterdam. Vol. VII. 



