Manchester Memoirs, Vol. Ixv. (1921), No. 5 



b = 



-, and consequently nb = 0*00420. Hence, we may write, very 



approximately 



T l5 = T«{i - ni(i 5 - $)} 



(ix) 



giving a change in the surface tension of about 0*14 dynes per cm. per 

 degree. 



From the above experiment, we have, with this value of the tem- 

 perature coefficient 



T 15 — 29/65 dyne-cm. -1 . 

 In Table III. above is given a similar set of readings obtained with toluene. 



There is no need to give details of all the readings for the remaining 

 experiments ; Table IV. below gives a conspectus of the results obtained. 



TABLE IV. 



Benzene. 



e. 



Pi- 



hi. 



p- 



h. 



T*. 



Ti B . 



14-4° 



0-8551 



0-9257 



0-8832 



o'ogoo 



29-59 



29'73 



i6'i° 



0-8562 



0-8841 



0*8850 



0*0357 



30-I3 



30*05 



15-5° 



0-8555 



9210 



0*8837 



0-0864 



29*58 



29*65 



16 -o° 



0-8552 



0-8903 



0*8830 



00590 



29*46 



29-60 



14-8° 



0-8559 



0*9024 



0-8843 



00530 



29*98 



29-95 



n *o° 



0-8585 



1-0932 



0*8885 



0-0488 



30-49 



* 29-93 



Toluene. 



15-0° 



i6-o° 



0*8559 

 0*8552 



0*8656 

 0*8706 



0*8715 

 0*8704 



00402 

 0-0524 



29*29 

 1 29-05 



29-29 

 29-17 







Methyl Propionate. 







15-5° 

 iri° 



0-8555 

 0*8584 



0-7699 

 1*0280 



o*g22 

 0-926 



0-0342 

 0-1241 



26-09 

 * 26-31 



— 



(The starred results were obtained using a new tube for which r 

 therefore log A = 1-5307.) 



0-02724 cm., and 



The production of authoritative figures for the surface tensions of 

 these compounds forms no essential part of this paper ; our main object 

 is to show that the very simple modification proposed removes the chief 

 technical difficulties that beset the capillary-rise method, and that the 

 method does effect this object is almost a priori evident. But the dis- 

 cussion of one or two points connected with the above figures will, we 

 think, be of use. 



Our experience of benzene has convinced us that this liquid is, for 

 a standard liquid, more than a little treacherous. The six values for T 15 

 given above represent but a small fraction of our experimental figures, 

 which, however, group themselves into two classes — one set giving a value 



of T 15 of about 29-6 



dynes 



the other about 29-9 



dynes 



This latter 



cm. cm. 



figure is the value which we generally obtained after performing all the 

 usual rites associated with the purification of benzene. It was only when, 



