8 



FERGUSON AND DOWSON, Studies in Capillarity 



in addition, we made several fractional crystallisations of the specimen, 

 and then immediately determined the surface tension, that the lower figures 

 were obtained. On allowing the benzene to stand for a few days its 

 surface tension reverted to the higher value. 



Whatever be the apparatus employed for the determination of surface 

 tensions, it is clearly advantageous to have at hand a standard liquid 

 which can be used to test the apparatus. We ourselves feel that benzene 

 is far from being the ideal liquid ; for it in several respects falls short of 

 such a standard, which should 



(i) be easily prepared ; 

 (ii) be easily purified ; 

 (iii) be non-hygroscopic ; 



(iv) not be liable (like water) to surface contamination ; 

 (v) not attack glass. 

 In Table IV. above, the first, third, and fifth results were in each case 

 taken immediately after three fractional crystallisations of different speci- 

 mens of purified benzene. The mean of these gives 



dynes 



T 15 = 29-66 



cm. 



In Table V. below are given a few of the results obtained by other ex- 

 perimenters. 



TABLE V. 



Experimenter. 



Method. 



Tig. 



Volkmann 



Harkins and Brown . 

 Ramsay and Aston . 

 Renard and Guye 

 Richards and Coombs 



Capillary rise . 

 >> >» 

 n »» 



)» 11 

 11 11 



29-51 



29*59 

 28-68 

 28-45 

 29*61 



Ferguson . 

 Feustel 



Jaeger's method 



29-65 

 30-9 



It seems then that, with the exception of Renard and Guye's value, 1 

 the value we have obtained is in very close agreement with the values given 

 by the ordinary technique of the capillary rise method. The latest and most 

 careful experiments are those of Harkins and Brown, and of Richards and 

 Coombs, and our mean value agrees with theirs to about 1 part in 500. 



These experiments were carried out in the Physical Laboratories of 



the Manchester College of Technology, and it is our pleasant duty to 



thank Professor Gee for the assistance which he has given us, and for 



the facilities which he has placed at our disposal. 



College of Technology, 

 Manchester. 



December, 1920. 



1 Ramsay and Aston's value is for the surface tension of benzene in contact with 

 its saturated vapour. 



A General Discussion in Capillarity and Surface Tension followed the reading of 

 these papers. The Discussion is published in the Transactions of the Faraday 

 Society, Vol. xvii., part 1, 1921. 



