558 
MESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
affected by the great difficulty of obtaining dietliyl ketone in a condition of sufficient 
purity. 
Fatty Acids. 
Five members of this series were investigated, viz., formic acid, acetic acid, propionic 
acid, isobutyric acid, butyric acid. Fig. 15 represents the results obtained, on a 
scale two and a half times as close as that usually employed. 
Fig. l.'S. 
The character of the curves for the acids presents a marked difference from that of 
the paraffins and such of their derivatives as have hitherto been considered. One of 
the most important features is seen in the largely increased effect of temperature on 
the value of the viscosity coefficients of all the acids. In the case of formic acid, 
which most clearly indicates this point, the change in the coefficient between 0° and 
100° is ‘0244 ; whilst in the case of heptane, which has about the same boiling-point 
as formic acid, the change is only about ‘0032, or about one-eighth of the change in 
the case of formic acid. 
The most striking feature, however, in connection with the curves for the acids, is 
their relative disposition, which is exceptional, the anomaly being due to the peculiar 
behaviour of the lowest members of the series. Except at temperatures close to the 
