^rpo4] Mills — Molecular Attraction. 165 



SOME RELATIONS RESULTING FROM THE LATENT HEAT 

 EQUATIONS. 



By combining - equations 6 and 7 we get: 



[11] P - ^T - "'(^-^) or 



U J ST 0.0,31833 (V — ») 



[12] P=^-T 



8T YvVs-\-V%v%-\- Wsv' 



Equations 11 and 12 are not suitable for calculating- accu- 

 rately the pressure, for that value appears as the difference 

 of two comparatively equal values. We give as an example 

 of such application Table 22. Of the substances we 

 have discussed isopentane is one of the most carefully meas- 

 ured and the agreement is to within the limit of experimental 



8P 

 irror permitted by the equation. The -^^ is obtained from 



Biot's formula. ^-j-. — , Tro/ — => — r- TT1/ is given under the head- 

 VvYa -j- V%z>73 -|- \Ysv 



Ing "a". 



Equation 12 will recall the similar equation: 



13] p = bT — a, 



8 P 

 foroposed by Profs. Ramsay and Young -1 , where b = ^7=- and 



o 1 



1 = constant. The equation is applicable where the volume 



)f the gas is kept constant, "0" has a value dependent upon 



;:he volume. 



SP 

 The -j= of equation 12 shows the variation of the vapor 



pressure of a liquid with a rise in temperature, the volume of 



8P 



the liquid meanwhile undergoing change. The -^p of equa- 

 tion 13 denotes a change in pressure of a gas, the volume 



iPhil. Mag., May, 1887. Phil. Mag., August, 1887. Proc. Phys. Soc, 

 1894-95. Proc. Phys. Soc, Vol. 15. Phil. Mag., April 1899. Proc. Phys. 

 3oc.. Vol. 17. 



