OF GASES AND VAPOURS. on4 
pik SAAaE 
108 O75 = 95842 
in which p is expressed in metres and ¢ is counted from—20°7 
C., the boiling-point observed by Bunsen with the pressure 
o™-75. We obtain with it 
ale sak 9 4 
Temperature. Elastic force in Metres. 
Difference. 
Degree C, t. Formula. Bunsen, 
—20 0-7 0:78 0:80 +0-02 
—15 5:7 0:98 1:10 +0:12 
-10 | 107 1-23 141 | 40-18 
a | 157 154 173 | +0-19 
0 | 20-7 1:90 2:07 | 40:17 
5 | 25-7 2:33 244 | 40-11 
10 | 307 2:84 288 | 40-04 
15 35-7 3°44 3°33 —0-11 
20 40:7 4:13 3°80 —0°33 
The boiling-point for the pressure 0™76 results from the 
above formula for = 1°67, therefore at— 19°03 C. 
32. The expansion of the unit of volume at 0° amounts, ac- 
cording to the advanced formula for each degree C., to 
u 
279 0°00359. 
Regnault states this expansion at 0°003682. Both statements 
agree in so far as the number 279 is trustworthy (see No. 17). 
33. Bunsen finds the boiling-point of ammonia at the pressure 
of 0™-7493 to equal — 33°7. Ifthe temperatures are measured 
from this point, the greatest force of expansion of ammonia in 
metres of mercury is obtained from the formula 
| ale eS 
0°7493° 230+¢ 
From this formula we find the forces of expansion calculated 
in the following table. 
log Porere S| 
Temperature. Elastic force in Metres. 
Difference. 
Formula. Bunsen. 
2-86 304 | 40-18 
3-49 361 | +012 
4:27 4:26 —0-01 
5:12 4:98 —014 
6:15 5:78 —0°37 
7°35 6°67 — 0°68 
The boiling-point for the pressure 0™76 is found, according 
to the above formula, at = + 0°26, therefore at—33°44 C. 
