OF GASES AND VAPOURS. 203 
instead of which we may also write 
74804 .t, 
236-22 + t, 
p = 4529°10. 
This formula differs but very little, by somewhat different co- 
efficients, from that of Magnus. I might also have set out from 
this formula. 
17. From the formula advanced, we find the coefficient of ex- 
Sane * = referred to the volume at boiling-point. 
If it be desired to refer the expansion of steam to the volume 
at 0°, we find this for each degree of heat equal 
1 
23602 — 0'004233, 
consequently greater than the expansion of air, as was to be ex- 
pected. ‘This coefficient is now determined for the first time, it 
awaits its confirmation by experiment. 
The accuracy to which this determination lays claim must not 
be overrated. The formula (2.) in No. 15 is so plastic, that the 
number 336°22 may be altered by several units without a corre- 
sponding change being made in B, the differences of the results 
of the formula from those of observation becoming considerably 
larger, so that the coefficient of expansion, such as was given, 
appears to be trustworthy only to about 4, of its value. 
18. The density of steam is found with the coefficient of ex- 
pansion 2, as is known by the formula 
Opie tae i! 
Cw A cing gr 
For ¢’ = 0 (the boiling-point) and p’ = 1 atmosphere = g, is, 
according to Gay-Lussac’s determination, 
pansion of steam = 
pte Bde, 
¢ ~ 16964 
consequently 1 336°22 p 
EpLGGGe:: 23622 in esl te Ok? 
in which p is the pressure and ¢ the temperature of the steam. 
If it be desired, as is generally done, to take the temperature 
from the freezing-point of water, we have 
Bind 33622 op 
76964 23622 +2 p, 
19819 p 
= 93692 +2,” Soups ' (5%) 
