204 HOLTZMANN ON THE HEAT AND ELASTICITY 
The density of the atmospheric air is, under the same circum- 
stances, 
rs 1:299 Dp 
$1 ~ 7 + 0:003668.¢ * p,’ 
The density of steam compared to that of atmospheric air of 
equal temperature and pressure is therefore 
198°19 1 + 0:003668.¢ 
1°299 °  236°22 + ¢ ’ 
or : 272°63 +t 
= 055964. 5. ps tt 6) 
for which may be substituted with lower temperatures the ap- 
proximate formula 
0°6459 . (1—0°000652.#). ....... (7) 
Consequently at 0° the density of steam is to that of air 
as 1 to 0°6459. Munke* found for low temperatures, on an ave- 
rage, the density 0°6568, viz. 15394" 
At 20° C. the density of steam is, according to formula (7.), 
equal 0°6329. Schmeddingk+ obtained on an average for this 
temperature the density 0°63. 
Finally, at 100°C. the density of steam is found to equal 0°6207 
from the accurate formula (6.).. The approximate formula gives 
in this case only 0°5807, and should consequently no longer be 
employed for such high temperatures. The density found ap- 
proaches closely to that deduced from the chemical composition 
=0°6217, and differs from that of Gay-Lussac’s determination 
only because in this place the coefficient of expansion 0°3668, 
discovered by Magnus, was employed instead of Gay-Lussac’s 
0°375. 
I imagine that the coincidence with these three results of ob- 
servation is as great as can be expected in such difficult determi- 
nations. 
19. The-coefficient B=5*2555 in the formulze (2.) and in (3.) 
is equal to M. ue (No. 15). In this 
M is the modulus of Briggs’s logarithms. 
a the mechanical action which the unit’ of heat is capable of 
producing = 374 (No. 8). 
* Gehler’s Worterbuch. Neue Bearb. x. Warme, S. me 
+ Dove, Repertorium der Physik, 1. S. 52. 
