Determination of the Surface Tensions of Liquids. 109 



of are surface actions, at least, in part. For example, the solu- 

 tion of a solid in a liquid may be regarded as occurring in two 

 phases : (1) the action of the liquid and solid on each other at 

 the surface resulting in the passing of particles of the solid 

 through the separating surface over into the liquid, and (2) the 

 action between the dissolved particles and the liquid, the effect 

 of which is to bring about their equal distribution throughout 

 all parts of the liquid system ; many other examples easily 

 present themselves. 



The surface tensions and energies of liquids and solids being 

 of such importance in the elucidation of the nature of liquids 

 and solids in general, it is self-evident that the determination 

 of the values of these constants for as many liquids and solids 

 as possible is very desirable. No experimental methods have 

 yet been devised for the measurement of the surface tensions 

 of solids, and those employed in the investigation of the capil- 

 lary constants of liquids are generally not capable of giving 

 very accurate results ; their degree of accuracy rarely exceeds 

 one part in ten thousand. Furthermore, the apparatus necessary 

 to attain this accuracy requires very careful manipulation in 

 every detail, and a not inconsiderable period of time is needed 

 for each determination. These circumstances stand in the way 

 of the multiplication of data, a study of which may lead to 

 important and far-reaching theoretic results. There is accord- 

 ingly a demand for a rapid and at the same time accurate 

 method of determining the capillary constants of liquids. 



Among the various methods employed in the determination 

 of the surface tension of liquids there is one that undoubtedly 

 meets the requirement of rapidity of execution. Simon, "^ the 

 inventor of the method, measured the pressure needed to force 

 bubbles of air out of a capillary tube plunged in a liquid. 

 This pressure he assumed to be equal to the sum of (1) the 

 hydrostatic pressure which the liquid exerts at the mouth of 

 the tube, and (2) to the pressure corresponding to the height 

 to which the liquid would rise in the tube because of its sur- 

 face tension. This latter assumption is strictly true, however, 

 only in case the form of the issuing bubble of air is identical 

 with that of the meniscus within the tube, and in this circum- 

 stance lies the objection to the method, otherwise so simple 

 and rapid. 



G. Jager f modified this method by employing two capillary 

 tubes of different bores and measuring the difference of the 

 depths to which they were plunged in a liquid when air forced 

 out of them was at the same pressure. An examination of the 

 apparatus showed that it met the condition of rapidity admira- 



* Ann. de Chim. et de Phys., Ill, xxxii, p. 1, 

 f Wien. Ak. Ber. c, p. 245, 1891. 



