Page:Scientific Memoirs, Vol. 1 (1837).djvu/383

From the experiments made by several philosophers we are enabled to calculate the values corresponding to the boiling point of $k$ and ${\frac {p}{d\,t}}$, for different liquids; we can therefore deduce from them the corresponding values of ${\frac {1}{C}}$.

NAMES of Liquids.	Value in atmospheres of ${\frac {d\,p}{d\,t}}$ at the temperature of ebullition.	Density of the vapour at the temp. of ebullition, the density of the air being 1.	Quantity of latent heat contained in a kilogramme of vapour.	Temperature of ebullition.	Corresponding values of ${\frac {1}{C}}$
Sulphuric Ether	${\frac {1}{28.12}}$	$2.280$	$90.8$	$35.5$	$1.365$
Alcohol	${\frac {1}{25.19}}$	$1.258$	$207.7$	$78.8$	$1.208$
Water	${\frac {1}{29.1}}$	$0.451$	$543.0$	$100.$	$1.115$
Essence of Turpentine	${\frac {1}{30}}$	$3.207$	$76.8$	$156.8$	$1.076$

These results confirm, in a striking manner, the theory that we are explaining; they show that $C$ is slowly augmented with the temperature, as has been already stated: we have seen that for $t=o$, ${\frac {1}{C}}=1.41$, whence $C=0.7092$; this result is deduced from experiments upon the velocity of sound.

We here find, starting from experiments upon the vapour of water, for $t=100^{\circ }$, ${\frac {1}{C}}=1.115$, whence $C=0.8969$; $C$ is therefore increased from 0 at 100° to $0.187$, which gives as the mean of the differential coefficient between these two limits

${\frac {d\,C}{d\,t}}=0.00187.$

The mean of the two experiments performed by MM. De Laroche and Bérard gives us, between the limits $22^{\circ }\centerdot 83$ and $96\centerdot 90$, for the mean value of ${\frac {d\,C}{d\,t}}$ the quantity $0.002565$.

These two results differ little from each other, and their divergence will be sufficiently explained, by reflecting on the number and the variety of the experiments whence the data on which they are founded are derived.