on the Angle of Contact. 457 



in this respect (Z. PJu/s. Ckem. xii. p. 452, 1893), and that 

 of sulphur by Kellas (Journ. Chem. Soo.cxiii. p. 911, 1918), 

 and both liquids appear to have a zero angle of contact. No 

 doubt some of the discrepancies between the results of 

 different observers are due to the difficulty of obtaining 

 liquid and solid surfaces free from contamination. 



The experiments described in the following paper con- 

 sisted : — 



(1) In a comparison of the values for the angle of contact 

 between water and solid paraffin, determined directly and by 

 measuring the capillary depression of water in a paraffin 

 tube : 



(2) in a determination of the angle of contact with glass 

 of the liquids stated by Magie to give a finite angle of 

 contact : 



(3) in a search for a solid which has a finite acute angle 

 of contact with water, and in the measurement of this angle 

 in the case of azobenzene. 



Angle of Contact between Para^in and Water. 



Ordinary paraffin wax was purified by boiling several 

 times with conductivity water and filtering. Transparent 

 tubes were prepared from it by introducing small quantities 

 into a glass capillary tube, which was then spun on a lathe 

 and warmed, the wax being driven through the tube by a 

 current of air. The rotation and air-blast were continued 

 until the tube was cold, and in this way tubes were prepared 

 with a fairly uniform transparent lining of wax. 



The tubes were cut into short lengths and the internal 

 diameter of the wax lining was measured with a micrometer, 

 which was focussed on a point several millimetres down the 

 tube where the wax had not been disturbed when the tube 

 was cut. 



The capillary depression of freshly distilled conductivity 

 water was then measured in the tubes by means of a travelling 

 microscope. It was necessary always to work with a rising 

 meniscus, the tube being tapped until no further rise was 

 observable. With a falling meniscus discordant results 

 were obtained, as the meniscus could be made to stand above 

 or below the outside level of the water. 



As the meniscus was very flat, the correction to be math 4 

 to the observed depression was equal to half the height of 

 the meniscus, and this correction was made by eye in setting 

 the cross-wire of the reading telescope. 



Four tubes of different diameters were used, and six to ten 



