334 Dr. R. D. Kleeman on Relations between the 

 We may express this equation in the form of two thus : 



dPT 



dT 



Pi' 



Pi 



+ 



dP 



T 



P 





dT 



Ps 



~>2 



+ 



5-25RT, 



• (6) 



mp t 



1/3 



P f+t 2 (T). 



Now it was found that the value of ^ 2 (T) is approximately 

 constant for the same suhstance. This is shown for two 

 substances in Table V., ^ 2 (T) being calculated by means of 

 the latter of the above equations from the data given in the 

 table. 



Table V. 



Pentane. 



Hexane. 



T. 



P2- 



P 



in mm. of Hg. 



d? 

 dT' 



* 2 (T). 



932 



T. 



Pr 



P 



in mm. of Hg. 



dF 



* 2 (T). 



313 



•003390 



865-3 



28'81 



343 



•00337 



784-8 



24-73 



89-7 



333 



•006024 



1601-8 



4619 



901 



363 



•00585 



1409 



38-80 



87-2 



353 



•01013 



2742-1 



69-37 



93-5 



383 



•00952 



2358 



57-20 



86-8 



373 



•01627 



44091 



99-05 



91-9 



403 



•01502 



3723 



80-55 



85-9 



393 



•02503 



6740-5 



13602 



921 



423 



•02299 



5606 



109-2 



85-2 



413 



■03861 



9890 



181*1 



91-4 



443 



•03172 



8123 



144-0 



84-2 



433 



•05910 



14032 



235-4 



91-0 



|463 



•05155 



11407 



186-3 



841 



453 



•09354 



19362 



300-2 



906 



483 



•07900 



15619 



237 4 



83-6 



The constancy of ^(T) can be tested more conveniently 



from equations (6). We thus obtain 



5-25RT c 



V(pf-Pr)=p-P2, where C = 



m p r.+(Ty 



It follows, therefore, that if it is found that C is independent 

 of the temperature for a substance, then ^ 2 (T) must possess 

 the same property. Now this is approximately realized, as 

 will appear from Table VI., which contains the values of C 

 at different temperatures for a number of substances. 



We can find another expression for the value of C, which 

 enables us to obtain an expression for the value of ^ 2 (T). 

 Let us write p 2 — ^p 1 in the above equation, and the value of 



