Effects of MOLEcaLAR dissymmetry 259 



W. B. Hardy- in discussing the interfacial surface tension between 

 fluids said in 191 2: 



"If the stray field of a molecule ... be unsymmetrical, the surface layer 

 of fluids and solids, which are close packed states of matter, must differ 

 trom the interior mass in the orientation of the axis of the fields with re- 

 spect to the normal to the surface, and so form a skin on the surface of 

 a pure substance having all the molecules oriented in the same way instead 

 of purely in random ways." 



In a later paper ^ he adds : 



"The surface film must therefore have a characteristic molecular 

 architecture. . . . When the composite surface is formed its architecture 

 is determined by the interaction of the fields of force of molecules of A 

 and B under the influence of the attraction of B for A." 



In connection with a study of chemical reactions at the surfaces of 

 highly heated tungsten and carbon filaments in gases at low pressures 

 (less than o.i mm.) I came to the conclusion ^ that adsorbed carbon 

 monoxide must be regarded as oriented on the surface, so that the carbon 

 atoms are attached to the solid while the oxygen atoms form the surface 

 layer. 



Shortly thereafter, without at that time knowing of Hardy's work, I 

 saw the application of these ideas to the orientation of molecules at the 

 surfaces of liquids, and was then able to develop a theory of the effect of 

 chemical constitution on the surface tension of pure liquids as well as 

 solutions and oil films on water.* 



It is the object of the present paper to consider in a general way the 

 causes of molecular orientation and the effects produced by such orientation 

 on surface tension, solubility, vapor pressure, etc. In particular, since the 

 chemist knows a good deal about the shapes of molecules and the stray fields 

 around their different parts, it will be urged that this knowledge be used to 

 correlate, as nearly quantitatively as possible, the various so-called physical 

 properties which depend on these factors. For this purpose it will not be 

 necessary to have knowledge of the exact shapes and fields of forces of the 

 molecules, but, just as in the case of the kinetic theory, considerable 

 progress may be made even by the crudest kinds of assumptions in regard 

 to these factors. 



* A paper on this work was read before the American Chemical Society in Sep- 

 lember, 1916, and a two-page abstract was pubHshed in Met. Chem. Eng., 15, 468 

 (1916). Before the full work could be pubHshed, two papers by W. D. Harkins 

 appeared in Jour. Avicr. Chcm. Soc, 39, 354 and 541 (iQi?). which dealt in detail 

 with the surface tensions of pure liquids. In the final publication of my results, Jour. 

 Amer. Chem. Soc, jg, 1848 (1917), the part dealing with pure liquids was therefore 

 omitted. 



