CAPILLARY ATTRACTION IN RELATION TO CHEMICAL COMPOSITION. 267 



fully corroborates it. When a ring with a very thin edge is used, the 

 configuration for maximum surface-tension is most probably attained 

 when i—o, so that the correction for the contact angle is not required. 

 I have tested a few liquids by this method with a very thin circular 

 platinum ring", and have obtained the following results : 



Traction on the Eins 



m grammes 



AVater L.668 



Alcohol .526 



Chloroform .6215 



Benzene .6535 



Water 1. 



1.000 

 .315 

 .373 

 .392 



Capillary Height x Specific 

 Gravity 

 t her- 



mometer 



Grade ■ Bp. 



Gr. 



136.8 



t2.5 

 48.4 

 45.1 



Contact Angle 

 Water=1.000. Temperature 27<-28\ 



1.000 Supposed to be zero. 

 .311 



.357 

 .395 



18° 

 Supposed to be zero. 



These are bul rough determinations, the substances used being only 

 tolerably pure ; still the difference between the results obtained by the 

 tube method and by the ring method is very significant. The 

 capillary tube used in these experiments was a broken thermometer of 

 a good bore, which showed no difference in the length of a mercury 

 thread about the places used for the measurements. As the bore is very 

 small (about l / 6 of a millimetre), no correction has been made for the 

 meniscus. The ring had a périmètre of 69.8 m.m., and as it was very 

 thin no correction lias been made for hydrostatic pressure. The 

 contact angle of benzene seems to be zero, while that of chloroform is 

 rather large. Tr seems, therefore, advisable to use this method of 

 measuring surface tension. As air is said to have considerable in- 

 fluence in depressing the capillary height in the ease of water, it is 

 desirable to conduct the experiment in vacuum, and as organic 

 liquids dissolve gases with greater readiness than water does, the error 



