
( 441 
XXVIIL—On the Computation of the Specific Heat of Liquid Water at various 
Temperatures, from the Experiments of M. Regnault. By Witi1am Joun 
Macquorn Ranxine, Civil Engineer, F.R.S.E., F.R.S.S.A., &c. 
(Read December 15, 1851.) 
Correction of M. Regnault's Experiments for the Effect of Agitation. 
The discovery by Mr Joute of the fact, that mechanical power expended in 
the agitation of liquids is converted into heat as the visible agitation subsides, 
renders a certain correction necessary in calculating the results of experiments 
on specific heat in which such agitation has occurred. 
Of this kind are the experiments of M. Reagnautt on the apparent specific 
heat of liquid water at different temperatures. Water at a high temperature, T,, 
was emitted from a boiler into a calorimeter containing water at a low tempera- 
ture, T,, and the resulting intermediate temperature of the whole mass, T,, was 
used as the means of calculating the ratio of the mean specific heat of water be- 
tween T, and T,, to its mean specific heat between T, and T,. Now, the upper 
part of the boiler contained steam at a high pressure, so that the hot water was 
expelled with great force. The vis-viva thus communicated to the water, having 
been converted by fluid friction into heat, ought to be allowed for in computing 
the results of the experiments, 
Let W, be the weight of water originally contained in the calorimeter, at the 
temperature T, : 
W,, The weight of water introduced into the calorimeter from the boiler, at 
the temperature T, ; 
T,, the resulting temperature, corrected, as has been done by M. Reenautr, 
for the effect of conduction. 
Let K,, , be the mean dynamical specific heat of water between the tempera- 
_ tures T, and T,,— 
K,, ,. its mean dynamical specific heat between T, and T,. 
Let P be the pressure of steam of saturation at the temperature T,,— 
zw, the pressure of the atmosphere,— 
And 2, the volume of unity of weight of water at the temperature T,,. 
Then the following equation must be fulfilled ;— 
W,K,,, (T,—T,)—W, K,, , (T;-T,)— W, (P—@)v=0: 
Consequently, 
Kenge Wi (—T)  _ (P=O)e i epemay 
K,, 2 Ww, (T,—T,) K,, 2 (T,—T,) 
VOL. XX. PART III. 6c 

