226 ./. W. Glbbs — EqulUbrium of Ileteroyeiieoits Substances. 



the values of the potentials of the volatile components of the liquid 

 may be estimated from the density of these substances in the vapor. 

 The variations of the potentials in the liquid due to the change of 

 pressure will in general be quite trifling as compared with the 

 variations which are connected with changes of temperature or ot 

 composition, and may moreover be readily estimated by means of 

 equation (272). The same considerations will apply to volatile solids 

 with respect to the determination of the potential for the substance 

 of the solid. 



As an application of this method of determining the potentials 

 in liquids, let us make use of the law of Henry in regard to the 

 absorption of s^ases by liquids to determine the relation between 

 the quantity of the gas contained in any liquid mass audits potential. 

 Let us consider the liquid as in equilibrium with the gas, and let 

 m'-^^ denote the quantity of the gas existing as such, rn'-^^ the 

 quantity of the same substance contained in the liquid mass, yUj the 

 potential for this substance common to the gas and liquid, v^^'> and 

 v^^^ the volumes of the gas and liquid. When the absorbed gas 

 forms but a very small part of the liquid mass, we have by Henry's 

 law 



^ = .4 J-, (204) 



where ^1 is a function of the temperature ; and by (-'76) 



ni 



(G) 



;., = i?+CMog-^^, (295) 



v^ 



B and C also denoting functions of the tenq>erature. Therefore 



m 



(L) 



It will be seen (if we disregai-d the difference of notation) that this 

 equation is equivalent in form to (216), which was deduced from 

 a jorior* considerations as a probable relation between the quantity 

 and the potential of a small component. When a liquid absoi'bs 

 several gases at once, there will be sevei'al equations of the form of 

 (296), which will hold true simultaneously, and which we may regard 

 as equivalent to equations (217), (218). The quantities A and C in 

 (216), with the corresponding quantities in (21 7), (218), were regarded 

 as functions of the temperature and pressure, but since the potentials 

 in liquids are but little affected by the pressure, we might anticipate 

 that these quantities in the case of liquids miglit be regarded as func- 

 tions of the temperature alone. 



