1817.) Dilatation of Liquids at all Temperatures. 377 
These only differ from each other --,2, of the primitive volume at 
0. Itake the mean of them, and thus obtain 
D = 0°122536 
This is the apparent dilatation of alcohol in glass from 0° to 80° R. 
To obtain the true dilatation, we must deduce it from the formula 
i, = KT + {14+ KT? 4A, 
which, making T = 80, gives 
3 = 80K + {1 + 80K} D 
Substituting for D its value obtained above, we have for strong 
alcohol 
Qe = 091254852 
or very nearly1. This is the true dilatation from 0° to 80°. Iam 
not acquainted with any other indication on this subject, except that 
of Nollet, who in his Lessons de Physique, tom. 4, p. 379, says 
that alcohol dilates 0°087 in passing from the freezing temperature 
to that of boiling water. In order to compare this result with ours, 
we must remark that Nollet observed the dilatation of the liquid in 
atube of glass, at the extremity of which he had blown a ball, so 
that the value which he gives is the apparent dilatation, which ap- 
proaches to the value of our D. There is an obvious reason why 
the dilatation should appear to him less than we have found it here. 
His tube was open, and his alcohol not freed from air. This would 
cause it to boil before it reached the temperature of boiling water ; 
but as soon as it began to boil it would not become hotter, and of 
course would not dilate any further. Hence it never dilated so much 
as the alcohol did in Deluc’s experiments, in which it was inclosed 
in a vessel hermetically sealed and freed from air. What fully con- 
firms this consideration is, that if we calculate the value of D, cor- 
responding to the apparent dilatation A; = 0°087, which may be 
done in this manner :— 
DD, = . A; 
we obtain 
D, = 56°79 
that is to say, that at this dilatation the alcohol thermometer void 
of air marks 56°79° on its own scale; which, according to the 
table of Deluc and our formula corresponds with 60°7° of the mer- 
curial thermometer; and this is nearly the temperature at which 
alcohol boils in the open air.* 
* Since this paper was written, M. Berthollet has shown me the Philosophical 
Chemistry of Mr. Dalton, I there found an experiment made by that skilful phi- 
losopher which fully confirms the value given in the text of the absolute dilatation 
ef alcohol. I shall give the calculation hereafter, 
(To be continued.) 
