90 



G. K Li n< ho. r<j<'r — Relations between the Surface 



labelled chemically pure. I made no special tests for their 

 purity, as for ray purpose they might be considered pure 

 enough. 



The results are given in Table I. In the first column are 

 given the names, in the second the formulae of the substances, 

 while in the third are recorded their densities at 20° as found 

 in the literature. The fourth column contains the weights in 

 grams of drops of the respective hydrocarbons in water, and 

 the fifth the weights of drops of water in the hydrocarbons. 



I have not calculated the surface tension, as I did not know 

 the radius of the orifice of the pipette ; as it deals here of 

 relative rather than absolute values, that is of little moment. 





Table II. 









I. 



II. 



III. 



IV. ■ 



V. 



Benzene 



C 6 H 6 



0-879 



0-0405 



0-1932 



Toluene 



C.B..CH, 



0-865 



0-0403 



0-1920 



o-xylene 



C B H 4 .(CH 3 ) 2 l-2 



0-75 



0-0405 



0-2010 



m-xylene 



C 6 H 4 (UH 3 ) 2 -l-3 



0-87 



0-0406 



0-1910 



^-xylene 



C 6 H 4 (CH 3 ) 2 -l-4 



0-862 



0-0318 



0-1579 



Cumene 



C 6 H 3 -CH(CH 3 ), 



0-87 



0-0262 



0-1263 



Pseudocumene 



C 6 H 3 .(CH 3 ) 3 . 1-3-4 



0-86 



0-0314 



0-1536 



Ethylbenzene 



C.H..C.H. 



0-866 



0-0178 



0-0826 



Mesitylene 



C 6 H 3 .(CH 3 ) 3 . 1-3-5 





0-0141 



0-0725 



"We notice first that the determinations of the size of the 

 drops of the hydrocarbons in water and of water in the hydro- 

 carbons give relatively the same results. If the numbers in 

 the fourth column be multiplied by Jwe, the numbers in the 

 fifth column are approximately obtained. This shows that the 

 two methods give strictly comparable results. 



The weights of the drops of benzene, toluene, c-xylene and 

 m-xylene in water, as well as the weights of water-drops in 

 them, are the same, if due allowance be made for unavoidable 

 errors of observation. The superficial tensions of these organic 

 liquids in contact with water have then equal values. In pas- 

 sing to />xylene, there is a considerable decrease in the weights 

 of the drops. This is evidently due to the para-position of one 

 of the methyl groups, for pseudocumene, which contains a 

 meta- as well as para-methyl group, has the same drop-size 

 asj?-xylene. While the introduction of a mete-methyl group 

 in benzene derivatives seems without influence upon the super- 

 ficial tension, the introduction of a, para-methyl group exer- 

 cises, on the contrary, a decided influence. Yet three meta- 

 methyl groups, as in mesitylene, cause the surface tension to 

 decrease greatly Again it is to be observed how different are 

 the drop-sizes in the case of toluene or methyl-benzene and 

 ethyl-benzene. Cumene or isopropylbenzene also has a sur- 



