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CHEMISTRY: W. D. HARKINS 
1 Laby, London, Phil. Mag., (Ser. 6), 16, 1908, (789). 
2 Smith and Menzies, /. Amer. Chem. Soc, 32, 1910, (1434). 
3 Smith and Menzies, Ibid., 32, 1910, (1412). 
4 Pfaundler, Leipsig, Ann. Physik, (Ser. 3), 63, 1897, (36); Morley, Phil. Mag., (Ser. 6), 
7, 1904, (662); Hertz, Ann. Physik., (Ser. 3), 17, 1882, (193); Regnault, Paris, Mem. Acad. 
Sci., 21, 1847, (30, 502); 26, 1862, (506); Ramsay and Young, /. Chem. Soc., 49, 1886, (37); 
Young, Ihid., 59, 1891, (629); Cailletet, Colardeau and Riviere, Paris, C. R. Acad. Sci., 130, 
1900, (1585), etc. 
5 Knudsen, Ann. Physik, 28, 1909, (1002). 
6 Knudsen, Ibid., 29, 1909, (184). 
7 Knudsen, Ibid., 32, 1910, (809). 
8 Villiers, Ann. Chim. Phys., (Ser. 8), 30, 1913, (588). 
^ Haber and Kirschbaum, Zr. Elektrochemie. 20, 1914, (301). 
10 Langmuir, /. Amer. Chem. Soc, 35, 1913, (105). 
11 Reichsanstalt certificate dated 1914. 
12 Menzies, /. Amer. Chem. Soc, probably November, 1919. 
15 Regnault, Ann. phys chim., (Ser. 3), 15, 1845, (129); Mem. Acad. Sci., 26, 1862, (679). 
14 Campbell, Trans. Faraday Soc, 10, 1914, (197). 
1^ If these two pressures were very close, and if the gauge tubes were too narrow, the total 
pressure within the hot gauge might be appreciably greater than the pressure within the 
reservoir. 
16 Happel, Ann. Physik, (Ser. 4) 13, 1904, (340), etc. 
1^ Van Laar, Verslag. Akad. Wetenschappen, 24, 1916, (1635). 
18 Van Laar, Proc. Acad. Sci. Amsterdam, 20, 1917, (138). 
19 Aries, Paris, C. R. Acad. ScL, 166, 1918, (334). 
2° "A Lower Limit for the Critical Temperature of Mercury," presented before the 
Division of Inorganic and Physical Chemistry, 1910. 
21 Koenigsberger, Chem. Ztg., 135, 1912, (1321). 
22 Menzies, /. Amer. Chem. Soc, 35, 1913, (1065). 
23 Bender, Physik. Zr., 16, 1915, (246); 19, 1918, (410). 
COHESION, INTERNAL PRESSURE, ADHESION, TENSILE 
STRENGTH, TENSILE ENERGY, NEGATIVE SURFACE 
ENERGY, AND MOLECULAR ATTRACTION 
By William D. Harkins 
Kent Chemical Laboratory, University of Chicago 
Communicated by W. A. Noyes, October 14, 1919 
Work of adhesion. — For the past seven years I have been engaged in 
the study of molecular attraction from a new point of view, as repre- 
sented by a thermodynamic equation which does not seem to have been 
developed before, in spite of the fact that it is exceedingly simple. It 
gives what may be called the total adJiesional energy {Ej^), or the total 
energy involved in the approach of two unKke surfaces. The equation 
developed by Dupre^ in 1869 gives the adhesional work {Wa), which is 
