582 MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
7 ; = A/(l + 
will hold for niost of the liquids. 
Fifty-five of the liquids give differences which are not greater than 5 ; in most 
cases the differences are nil. Five of the liquids give differences greater than 5, 
the largest, viz., 3‘G per cent., being given by propionic anhydride. In most of the 
cases where the differences are greater than 2 , slightly better agreement is obtained 
by introducing another term into the expansion. Since n is less than 2 for all of 
these liquids the additional term is negative, and the denominator in the formula is 
made smaller; the result is, that with the additional term the calciffated values 
are all too large, whereas with three terms, as the table shows, they are all too small. 
In the case of ethylene bromide and ortho-xylene the negative differences obtained 
on using the additional term are greater than the positive differences given by the 
formula already used. Little advantage is therefore obtained by introducing another 
term into the formula, and in any case the small differences, given by all the 
substances in the preceding table indicate that the values of the coefficient /3 and y 
closely represent the true effect of temperature upon viscosity, and that any 
connections which may be traced between the magnitudes of these coefficients and the 
chemical nature of the substances may therefore be regarded as valid relationships. 
The nature of these relationships is dealt with in what follows. 
Relationshijys hetiveen the Magnitudes of the Temperature Coefficients /3 and y. 
On taking a general survey of the table it is evident that the fatty hydrocarbons 
and their monobalogen derivatives, the sulphides, the ketones, aldehyde and ether, 
are characterized by small values of the coefficients ; in these series temperature 
exerts the smallest effect on the viscosity. The aromatic hydrocarbons and thiophen 
have larger values of the coefficients, whilst the largest of all are given by the 
alkylene dibromides, the acids, and the anhydrides, to which may also he added 
ethylene dichloride and carbon tetrachloride. 
On closer examination the following conclusions may be arrived at : 
ITomologues. —In general the coefficients increase as a homologous series is ascended. 
Exceptions to the ride occur in the case of the dibromides, formic and acetic acids, 
benzene and toluene, probably for the reasons already given when discussing the 
gi’aphical representation of the results. 
Corresponding Compounds. —In general the compound of higher molecular weight 
has the larger coefficients. This rule is obeyed by the chlorides, bromides, and 
iodides of the alkyls, by the allyl halogen compounds, and by ethylene chloride and 
bromide. The acids on the other hand, although they have smaller molecular weights, 
have much larger coefficients than the corresponding iodides. 
Substitution of Halogen for Hydrogen. —On comparing the coefficients of the 
mono-bromides with those of the corresponding dibromides, the large increase in the 
