352 



also to be corrected by amounts proportional to a' and to the pres- 

 sure expressed as a fraction of 76 cms. 



J3ul/) ivitJi butane vapour. 



The following table gives the results of the 6 weighings. 



I. 



II. 



III. 



Temp. Pressure 



16°.63 



.00 



21 .02 



IV. 19 .94 



V. .00 



VI. .00 



76.08 cm. 



75.68 



40.42 



18.57 



23.48 



48.89 



Weight. 



0.98219 Gram 



1.04400 



0.50339 



0.22935 



0.31244 



0.66184 



Weight 

 corrected. 

 0.98513 

 1.04733 

 0.50469 

 0.23016 

 0.31347 

 0.66398 



Volume. 



390.1 ccm. 

 390.1 



388.9 

 388.1 

 388.3 

 389.2 



Empikicai, rkduckd equation of statk. 



The equation of stale was taken in the form (Comm. Leiden, 

 Suppl. 23) 



B C n E F 



V V V V V 



(1) 



where p is the pressure in atmospheres at 45° latitude, v the volume 

 of 1 gramme expressed in the theoretical normal volume as unit ; 

 further : 



A — RT; B = "^i C = d; etc. 



Pk Pk' 



^, (i, etc. represent the "reduced virial coefficients", quantities 

 which depend on T only and must be. equal for different substances, 

 except for small individual deviations. ^ 



D and the subsequent coefficients may be neglected for pressures 

 smaller than V?/^/-- 



By introducing p as the independent variable instead of v equation 

 (1) assumes the form: 



pv 



= i27' 1 + 



B C - B^ , 



(2) 



The theoretical normal volume of pure butane is 

 22412:58.08 = 386.0 

 where 22412 is the normal volume of one gramme-molecule and 

 58.08 the molar weight of butane. When the constants were calcu- 

 lated on this basis, large deviations from the reduced equation of 

 slate were found. This finds a ready explanation in the fact, that 



