1817.] Dilatation of Liquids at all Temperatures. 433 
ef D much less favourable than in the. case of alcohol. It would 
have been much more advantageous if we could have employed ex- 
periments made at higher temperatures. But the extreme care of 
the experimenters in a great measure competisates for this disadvan- 
tage ; for the two values of D obtained from these equations agree 
very well with each other. ‘The first gives 
D = 0:0439595 
D = 0:042859 
This is the apparent dilatation of water in glass from 0 to 80°. 
To obtain the true dilatation within these limits, we must employ 
the formula 
The second— 
ll 
% = 80K + {1 + sok? D 
Substituting for K and D their values, we get 
%, = 0046601 
This is the true dilatation from 0 to 80° Réaumur. ‘ 
The only experiments with which T am acquainted to which we 
can compare this result are those of Nollet. ‘This philosopher says 
that common water in a graduated tube of glass, when heated from 
the freezing point to the boiling point, expands a little more than 
rave Of the volume which it occupied at the first of these tempera- 
tures ; and he adds that it acquires this dilatation in a minute and 
some seconds. The apparent dilatation which we have found is 
greater than that of Nollet by 0006, or —*... of the primitive 
volume. But, from the short time that Nollet kept the graduated 
tube in boiling water, it is very probable that it did not quite reach 
the boiling temperature ; and,. besides, the escape of vapour ought 
to have prevented it from acquiring as much heat as it would have 
done in a close tube like the thermometers of Deluc, according to 
which we have regulated our formulas. A proof that some cause of 
this nature influenced the observations of Nollet is, that he gives 
also the apparent dilatation of mercury in his instrument, and finds 
it amount to +14, from the temperature of freezing water to the 
boiling temperature of the same liquid. But from the very exact 
experiments of Lavoisier and Laplace it amounts to +ti5,. Ad- 
mitting our value of D as quite exact, the temperature of the water 
in Nollet’s tube would have been 74° R., instead of 80°, wica he 
observed the dilatation of water ; and, according to the experiments 
of Lavoisier and Laplace, it would have been 71° when he observed 
the dilatation of mercury. Pethaps, likewise, there was some inac- 
curacy in the graduation of his instrument. * 
We can with more certainty compare our formula with the expe- 
riments of Blagden and Gilpin. For this purpose we must calculate 
the values of the true dilatation 0, for the temperatures which we 
* Our result is equally confirmed hy the experiments of Dalton, as will he 
seen hereafter, 
Vor, 1X, N° VJ. 2k 
