$6 C. E. Linebarger — Relations between the Surface 



shaken up with an ethereal oil, although tlie liquids are re- 

 garded as insoluble in each other, yet the latter imparts its 

 odor to the former. There are, however, numbers of pairs of 

 liquids which are practically insoluble in each other ; at least, 

 we are unable by our analytical methods to detect the presence 

 of one in the other — and it is the surface tension of these 

 liquids that it is my purpose to investigate. 



At the surface of two absolutely insoluble liquids, there 

 would reign complete repulsion between the molecules ; no 

 molecule of one liquid would pass beyond a definite surface con- 

 centric with the surfaces of the liquids, and this surface would 

 form an impenetrable barrier to molecules of each liquid. 

 But in the case of liquids which dissolve one another a little, 

 complete repulsion between the molecules prevails no longer, 

 but on the contrary a slight attraction, so that now a mole- 

 cule of one liquid may pass into the other. This would 

 continue until the " tension " of solution of each liquid was 

 reached. The question arises then, whether, in searching 

 for stoichiometrical relations, the superficial tensions of liquids, 

 saturated with each other, or pure, be employed. Leaving the 

 discussion of the question for the present, we will in this paper 

 make use of those superficial tensions determined with liquids 

 uncontaminated with one another. 



It is necessary in work of this kind to select one liquid as a 

 standard of comparison, absolute measurements being less 

 reliable than comparative. Mercury, as regards insolubility, is 

 admirably adapted to the end in view, but I have not found it 

 advantageous to employ it in measurements made by the 

 method I adopted. I have therefore chosen water, the uni- 

 versal standard, as it is insoluble in a sufficient number of 

 organic compounds to receive quite an extended use. 



The method consisted in determining : — 1°, the number of 

 drops into which a certain volume of water divided in " drop- 

 ping down " through liquids lighter than water and in " drop- 

 ping up " through liquids heavier than water ; 2°, the num- 

 ber of drops of a liquid " dropping down," if heavier than 

 water, and " dropping up " if lighter, through that standard.* 



The bulb of a small pipette was so shaped and ground that 

 it fitted snugly (like a stopper in a bottle) in the neck of a 

 cylindrical vessel, provided at its lower end with a stop cock. 

 An inch above the bulb, a second much smaller bulb was 

 blown, and between it and the larger bulb as well as an inch or 

 so below the latter, marks were scratched. The lower stem of 

 the pipette was bent out so as to run down close to the side of 

 the cylindrical vessel nearly to the bottom, where it was turned 



*For an extension of the meaning of " drop," I refer to Guthrie's work (loc. 

 cit.) 



