158 
OX EVAPORATIOX AND DISSOCIATIOX. 
It will be seen that the results by the statical method are uniformly a very little 
higher than by the dynamical method. The behaviour of the substance resembles 
that of an imperfectly purified stable substance more closely than that of a dissociating 
body. 
A considerable number of determinations of vapour-density were made under 
varying conditions of temperature and pressure. It was proved, however, that 
condensation—probably of water—took place on the sides of the tube, and the 
results at the same temperature and pressure could be made to vary considerably 
by altering the conditions in such a manner as to increase or diminish the chance 
of such condensation taking place. The rise of vapour-density at low temperatures or 
high pressures was in no case greater than could be accounted for by premature 
condensation of liquid, and the only conclusion to be drawn from the results is that 
combination of propyl alcohol and water does not take j^lace in the gaseous state. 
The contraction on mixing propyl alcohol and water at 0°, in the ratio of 71*46 per 
cent, of alcohol to 28*54 of water, was ascertained by determining the specific 
gravities of the alcohol and of the mixture, that of water being known. For 
1 grm. of the mixture the contraction was 0*0215 c.c., or 1*857 per cent. With 
ethyl alcohol and methyl alcohol the contraction is considerably greater. 
It may be stated, in conclusion, that we have obtained no experimental evidence of 
chemical combination between propyl alcohol and water. 
