Manchester Memoirs, Vol. Ixv. (1921), No. 4 3 



(a) General considerations, with a review of those methods which are 

 most likely to prove suitable for the measurement of interfacial 

 tensions. 

 (/3) Improvements in the capillary-rise method. 



(y) An experimental study of the limits of accuracy of Jaeger's method. 

 (8) A comparative experimental study of the other principal methods, 

 elucidating the sources of error in, and the consistency of these 

 methods, 

 (c) The development of methods suitable for the measurement of 

 (i) Interfacial tensions, 

 (ii) The surface tensions of substances only obtainable in small 



quantities, and of substances such as molten metals, 

 (iii) Contact angles. 

 (£) The systematic measurement of 



(i) The surface tensions of selected classes of organic compounds, 



paying special attention to temperature coefficients, 

 (ii) Interfacial tensions, 



(iii) Contact-angles of liquids in contact with glass and with other 

 solids. 

 The present paper deals with the first section of the above scheme, and 

 the paper immediately following describes certain improvements in the capil- 

 lary-rise method which, without loss of accuracy, considerably simplify its 

 technique. 



Much difference of opinion exists concerning the reliability of the 

 " Jaeger " method for the measurement of surface tensions. The method, 

 as is well known, depends on the measurement of the maximum pressure 

 required to release a bubble of air from a small capillary tube plunged 

 vertically into the liquid under observation. Experiments are now in 

 progress in which the extruded bubble is photographed under various 

 pressures ; the information thus acquired should serve as a criterion of 

 the reliability of the method. 



The Measurement of the Tension in a Liquid-gas Surface. 



Turn now to a brief consideration of the value of the various methods 

 that have been proposed, from time to time, for the measurements of 

 surface tensions. Some schematic form of set-out is necessary to avoid 

 confusion, and the accompanying genealogical tree, whose structure ex- 

 plains itself, is perhaps as clear as any. 



I do not propose to discuss these various methods at great length ; 

 I have, in another paper, 1 attempted some estimate of their relative value, 

 and in a recent number of Science Progress 2 a very detailed analysis of 

 the capillary-rise and of the drop-weight method has been given. 



1 Ferguson, Science Progress, Jan. 1915, p. 428. 



2 Oct. 1920, p. 223. 



