CHEMISTR Y: HARKINS AND HUMPHER Y 
585 
The accompanying table illustrates the maximal effects of the various 
drugs used on one of us, as expressed by the quantity of stimulus in 
C. G. S. units required to produce the threshold sensation of pain. 
Although by the above described method only cutaneous sensations 
could be studied, we think that our observations are of some value in 
the study of the very important subject of analgesia. This research 
has been endowed in part by a grant from the Council on Pharmacy 
and Chemistry of the American Medical Association; the complete 
data with many tables will appear in the Journal of Pharmacology and 
Experimental Therapeutics, Vol. 7, No. 5, January, 1916. 
1 Claude Bernard, Paris, C. R. Acad. Sci., 59, 406 (1864). 
2 Fronmiiller, Klin. Stud, iiher die narcot. Arzneimittel, Erlangen, 1869. 
»Baxt, Arch. Anat. Physiol.. 1869, p. 112. 
* Martin, Porter and Nice, Psychological Review, 20, 194 (1913); Grobfield and Martin, 
Amsr. J. Physiol., 31, 300 (1913) ; Martin, Bigelow and Wilbur, 33, 415 (1914); Martin, 
Wittington and Putnam, Ibid. 34, 97 (1914). 
6 Martin Grace and McGuire, /. Pharmacol. Exp. Therap., 6. 527 (1915). 
8 von Frey, Leipzig, Ahh. Ges. Wiss., 66, 186, 293 (1894); 67, 166 (1895), and /. Amer. 
Med. Ass., 47, 695 (1906). 
^Straub, Biochem. 7s., 41, 419 (1912). 
THE SURFACE-TENSION AT THE INTERFACE BETWEEN 
TWO LIQUIDS 
By William D. Harkins and E. C. Humphery 
KENT CHEMICAL LABORATORY. UNIVERSITY OF CHICAGO 
Read before the Academy, December 7. 1914. Received, October 22, 1915 
While working with Haber upon a theory of muscular motion it 
was found by Harkins that the capillary- tube method for the deter- 
mination of surface-tension is very inaccurate whenever a basic solu- 
tion is used. This method is also extremely sensitive to the action 
of dust particles and to the presence of certain impurities, since the sur- 
face involved in the measurement is very small. Of the other avail- 
able methods the two best seem to be the measurement of surface waves 
and the determination of the weight of a falling drop. Of these two the 
former requires a very elaborate and expensive apparatus if the deter- 
minations are to be made with considerable accuracy, while on the 
other hand the drop-weight method makes use of comparatively simple 
apparatus and gives results which are reproducible with considerable 
accuracy. 
The most complete treatment of the mathematical theory of the rela- 
tion between the forms of drops and surface-tension is given in a book 
published in 1883 by Bashforth and Adams.^ Much later than this, 
