BETWEEN THE VISCOSITY OF LIQUIDS AND THEIR CHEMICAL NATURE. G21 
General Conclusions relating to Molecular Viscosity and Molecular Viscosity Worh 
at the Boiling-jyoint. 
On taking a general survey of the comparisons at the boiling-point, it is evident 
that for the majority of the substances examined—the paraffins and their mono¬ 
halogen derivatives, the sulphides, the ketones, the oxides, and most of the acids and 
aromatic hydrocarbons—molecular viscosity and molecular viscosity work may, with 
moderate exactness, be quantitatively connected with chemical nature. 
The remaining substances—unsaturated hydrocarbons, di- and polyhalogen com¬ 
pounds, formic acid, benzene, water, and the alcohols—present marked exceptions to 
the foregoing regnilarities. Most of these substances have already been shown, both 
in the graphical and algebraical portions of this memoir, to be peculiar ; hydroxy 
compounds, and, in particular, the alcohols, exhibiting in all cases the most pronounced 
deviations from regularity. 
B. Comparison of Viscosity Magnitudes at the corresponding Temperatupe of ffi. 
Tables similar to those already given were constructed showing the various viscosity 
magnitudes at the corresponding temperature ‘6. When satisfactory observed or 
calculated data could not be obtained, the critical temperature was deduced by means 
of the formula of Thorpe and Kucker (Jour. Chem. Soc., vol. 45, p. 135, 1884) 
_ i t + 273) V - 273 
l-9ti5(\h-l) 
0 is the absolute critical temperature, V^ is the volume that unit-volume of liquid 
measured at 0° occu})ies at f. 
From the values of the critical temperatures thus obtained, T, the corresponding 
temperature of ‘6 on the ordinary scale, was given by T = ’6 (0) — 273. 
Thorpe and Rucker’s formula is inapplicable to the case of water. To make the 
calculated critical temperature for water harmonise with the observed value, a instead 
of being 1’995 would require to be 4’2. The alcohols in general give values of a 
which are also larger than 2 by about 10 per cent. 
The critical data are too unsatisfactory to warrant us in laying any particular stress 
on the relationships obtained under this condition of comparison. We think, therefore, 
that no useful purpose can be served by reproducing the tables. Partial and imperfect 
as the available data are, the I’elationships however are similar to, even if less definite 
than, those obtained at the boiling-point. For a property like viscosity, which alters 
so rapidly with temperature, a corresponding temperature is certainly no better as a 
condition of comparison than the boiling-point. 
