Surface- Tension with Temperature. 



Table III. 



Carbon tetrachloride {T = T (1- -003553 (9) 1206 [. 



41 



(Cent.). 



T (obs.). 



A. 



F. 



V. d 



. W. 



T calc. 



Diff. 



T calc. 



Diff. 



0° 





28-02 









20 



2f» V 68 



25-63 



-6-05 



25-80 



+6*12 



80 



18-71 



18-72 



+0 01 



18-77 



+0 06 



100 



16-48 



16-50 



+0-02 



16-53 



+0-05 



120 



1432 



14-33 



4-001 



14-34 



+0-02 



140 



1222 



12-22 



+ 0-00 



12-21 



-o-oi 



160 



10-22 



10-17 



-005 



10-15 



-0-07 



180 



8-26 



8-19 



-0-07 



8-16 



-o-io 



200 



6-34 



6 28 



-0-06 



6-26 



-0-Qfi 



220 



4-47 



4-47 



+0 00 



4-46 



-o-oi 



240 



2-74 



2-78 



+0-04 



2-79 



+ 0-05 



260 



1-20 



1-26 



+ 01)6 



130 



+ 0-10 



The above tables show that, whilst equations (iii.) and (v.) 

 both fit the experimental values very closely, equation (iii.) 

 is distinctly superior in point of accuracy. On the average, 

 the differences between the observed and calculated values 

 given by equation (iii.) are about half those given by 

 equation (v.). 



Several attempts have been made to express the critical 

 temperature of a liquid in terms of the temperature coefficient 

 of its surface-tension, perhaps the most widely known being 



Assuming a linear law for both 



Tand 



that given by Walden 



/ 2T\ 



la 2 = — I, and writing them in the form 



T = T o (l-a0) and a 2 = a 2 (l-K6>), 



he finds empirically, from a consideration of the observed 

 values of u } K, and 6 C , that 



a c =l-16 and K0 C = O"94. . 



(viii.) 



As a matter of fact 1-16 and 94 are the means of rather 

 variable numbers, and the values of C given by these equa- 

 tions are not very close to the true values, although the 

 mean of the two values given by equations (viii.) is usually 

 better than either value taken separately. Table IV. below, 

 which gives the data for some of the substances discussed 

 in this paper and is extracted from a long table given by 

 Walden, serves to show the kind of agreement that may be 

 expected. 



* Zeit. Phys. Ckem. Ixv. p. 129 (1909). 



