﻿Attraction of Unlike Molecules. L93 



oxide, treating the petroleum as a single Liquid. Arranging 

 the data and results as before, we have : — 



Rectified Mixture Mixture Mixture 



petroleum. I. II. Ill- CIIC1 3 . 



p. 10 -633 378 -1575 00 



» 00 -367 622 -8425 10 



p -767 -034 1-100 1-300 1494 



a 2-59 2-73 282 280 2-78 



,A u /(A,y- H 1U l ' 06 



Ordinary Mixture Mixture 



petroleum. I. II. (CaH,)./). 



p, 10 -723 -401 00 



j>, 0-0 * -277 -539 10 



p -803 -780 -700 -727 



« 266 241 2-22 183 



A/dA^A.,)* -96 -99 



In these cases the theoretical formula (6) is again verified 

 by the approximate constancy of iA 2 /dA 12 A 2 )*, and again 

 the ratio iA 2 /(iA 12 A 2 )* has values close to 1. 



In my own experiments the method adopted for measuring 

 surface-tensions was by means of the rise in capillary tubes, 

 but carried out in a special manner. Elsworthy (Journ. 

 Chem. Soc. liii.) suggested inclining the capillary tube at a 

 large angle to the vertical, say 6, so that a liquid which would 

 rise a height h in the tube when vertical, while still rising 

 only h vertically, in the inclined tube rises a distance A/ cos 6 

 measured along the tube ; so that the accuracy of reading is 

 increased in the ratio 1 to cos 6. It seemed to me that the 

 best way to take advantage of this method for a number of 

 liquids was to engrave a fixed mark on the tube, and then in 

 each case to vary the inclination till the liquid rose as nearly 

 as possible to the mark, reading the inclination in each case. 

 The advantage of this method is that it makes one almost 

 independent of variation in the bore of the capillary tube. It 

 would have improved the accuracy of the method if a fine 

 scale had been engraved on the tube near the fixed mark, so 

 that one could read in each case the small departure from the 

 fixed mark and allow for it in the calculations, but this was 

 not done. The capillary tube was fitted tightly into one leg 

 of a V-tube of 6 millim. internal diameter, the joint being 

 protected by a piece of india-rubber tube slipped over it : the 

 angle of the V was such that the other leg was nearly vertical 

 in the experiments with most liquids. A second mark was 

 engraved on the capillary a little above where it entered the 

 V-tube, and at a distance of 184 millim. from the other fixed 

 mark ; the level of the free surface of the liquid in the V-tube 



Phil. Mag. S. 5. Vol. 38. No. 231. Aug. 1894. O 



