206 HOLTZMANN ON THE HEAT AND ELASTICITY 
The experiments of Van Rees are more accurate; he finds*, 
with an external temperature of 10°°6 from the relations of sound 
of a pipe which was first blown into with air and then with 
steam, the velocity of sound in steam to equal 369™6 reduced — 
to 0°, in which the velocity of sound in the atmosphere is as- — 
sumed to be 333™7. From these numbers pai results, calcu- 
lated in the way Dulong has done, the relation <= = 1°1213 with | 
1 
the above found density of steam. 
: 
But this number still requires a correction. Van Rees has © 
reduced the velocity of the steam to 0° with Gay-Lussac’s coeffi- 
cient, 000375. If, instead of this, the one found by me, 0°004233, — 
be employed, we have, since the temperature of the steam was 
certainly very near 100° (it is not stated in the work quoted), to : 
: 
multiply the above result by * 9 = We then obtain 
© = 10831, | 
Qj 
which agrees more closely with my determination 1:0901 than 
was to be expected, considering the nature of these experiments, © 
and the uncertainty still prevailing respecting the above calcu- 
lated value of a. 
22. De la Roche and Bérard have attempted to determine the 
specific heat of steam. They caused air which had been satu- 
rated with steam at 39°} to cool in higher degrees of tempera- 
ture, at about 56°, and observed how much heat was given off. 
The pressure under which the moist air stood was 07596 
Steam has at 39° the force of tension. . . . . O™0521 
There consequently remains the pressure of dry air 0™7075 
The quantity of heat in the air for this pressure is (No. 9 and 13) 
O° 0°7075 
0°7600 
g =A +0°267.t—0'180. igo ie 
= A + 0:273 .¢ + 0:0055 ar 
This air was cooled 56°. In this operation it gives off the hea’ 
G:273'56 = 15°29: 
At the same time an equal volume of steam is cooled the sam 
* Gehler’s Worterbuch, a. B. viii. Schall. St. 478. 
+ These statements are taken from Gehler’s Worterbuch, vol. x. Heat, P. 
693. 
