Evaporation of different Liquids at their Boiling-points. 51 



Appendix. 



I. Calculation of L from the thermodynamic equation ; 

 worked out for the case of Methyl Acetate from experimental 

 data given by Prof. Young (J. C. S, lxiii. p. 1191): — 



L=(S'-S). ^.~. 

 at o 



(i.) To find -^-, by means of Biot's formula 

 log p = a + &«'. 



P. 

 588-2 millim. 

 837-5 „ 

 1167-0 ■„- 



t. 



50° 

 60° 

 70° 



hence log p= 5-2852200-2-515695 x (*9937262)'- 50 



at57°-0 . . . p = 755-0043 millim. 

 at57°-2 . . . ^ = 760-2895 „ 



.-. ^ =26-4260 millim. per 1° at 57°'l. 



J£ = 2-64260 x 13-596 x 980-94 dynes per sq. cm. per 1°. 



(ii.) S'=vol. of 1 gr. vapour at 57°'l = 350*6 c.c. 



S=vol. of 1 gr. liquid at 57°*1 = 1*1 c.c. 

 .-. (S' -S) = 349-5 c.c. 



T = 273-7-f57-l = 330-8. 

 *J=4*199xl0 7 . 

 Hence L= 96*81 thermal units. 



II. Regarding the Purity of the Liquids employed. — 

 The benzene was bought from Messrs. Kahlbaum, of Berlin, 

 and guaranteed free from thiophene. It was distilled twice 

 from phosphoric anhydride until its boiling-point remained 

 constant. 



* The value of J given here is that determined by Griffiths (Phil. 

 Trans, vol. clxxxiv. 1893 A), and used in working out the experiments 

 on benzene ; even if not correct, it is still the right value to use here, 

 because it was determined by means of the same standards as those by 

 which the quantity of heat developed in the benzene experiments was 

 determined ; so that any errors would eliminate. 



This assumption as to the value of J is the only one that enters into 

 the calculation ; all the other data were obtained by direct experiment. 



E 2 



