1894.] The Viscosity of Liquids and their Chemical Nature. 155 



Fundamental Viscosity Constants (molecular viscosity work at the 

 boiling point, in ergs X 10 s ). 



quantitatively connected with chemical nature. The remaining sub- 

 stances unsaturated hydrocarbons, di- and poly-halogen compounds, 



)rmic acid, benzene, water, and the alcohols present marked ex- 



jptions to the foregoing regularities. 



As regards the comparison of the viscosity magnitudes at the corre- 

 sponding temperature, it is found that, although the critical data are 

 unsatisfactory to warrant us in laying any particular stress on 

 the relationships obtained under this condition of comparison, these 

 jlationships are similar to, even if less definite than, those obtained 

 it the boiling point. For a property like viscosity, which alters so 

 ipidly with temperature, a corresponding temperature is no better 

 a condition of comparison than the boiling point. 



On comparing the viscosity curves of those substances which give 

 best physicochemical relationships at the boiling point, it was at 

 ice seen that the general shape of the curves towards the boiling 

 nnt was practically the 'same. If tangents were drawn to the 

 curves at points corresponding with the boiling points of the liquids, 

 the inclinations of the tangents to the axes, that is, the slopes of the 

 fves, varied but little. On the other hand, the curves for liquids 

 ich as the alcohols, or the lowest members of homologous series, 

 rhich gave little indication of physicochemical relationships, had in- 

 iriably a different shape ; the inclinations of tangents drawn at the 

 ailing point were markedly different from those of the majority of 

 ibstances. It seemed probable, therefore, that the discrepancies 

 rere related to this difference in the value of the slopes, and that, if 

 the temperature of comparison was chosen so as to eliminate this 

 lifference, better relationships ought to be obtained. This idea led 



