210 HOLTZMANN ON THE HEAT AND ELASTICITY 
give the formula 
p _ 5°866.t 
O78 232247’ 
in which the force of expansion is measured by the height of 
a column of mercury in metres, and ¢ should be reckoned from — 
—10°C. The following table exhibits the comparisons of this — 
formula with the forces of expansion calculated by Bunsen. 
log Sg HH 
Temperature. | Elastic force in Metres. 
—_ —_————— Difference. 
Degree C. t. Formula. Bunsen, 
—10 0 0:78 0°78 
ate 5 1-04 111 -++0-07 j 
0 10 1:36 1:48 40-12 
+ 5 15 1-77 1-91 +014 
10 20 2:28 2-39 +011 
15 25 2-90 293 +0-03 
20 30 3°66 3°54 —O012 
25 35 4-56 4-20 —0°36 
The differences are large, but yet not too large for pressures 
measured with an air manometer; the more so as the numbers 
given by Bunsen appear to have been found by interpolation. — 
Probably the pressure 0°78, upon which I based my calculation, — 
is somewhat too small, which would render the formula better 
for representing the course of the elasticities. 
For the temperature at which the pressure becomes 0°76, we © 
find ¢ = —0°447, which gives for the boiling-point of sulphurous 
acid 10°447 C. Bunsen found with the pressure 0™744 the 
boiling-point—10°5 C *. 
30. The expansion of the unit of volume at 0° C. is, according 
1 : 
to the above, 949-9 = 0'00413, when the gas stands, according to 
the above table, under a pressure of 1°48, therefore near two 
atmospheres. According to Magnus the expansion is 0°003859_ 
under the pressure of one atmosphere ; and from Regnault’s ex- 
periments it results that this expansion increases with the pres- 
sure, so that the coefficient of expansion now found has great 
probability under those conditions for which it obtains. 
31. For the maximum of the elastic force of cyanogen gas I 
find likewise from Bunsen’s statements, the formula 
* T found this statement ouly after I had already made this calculation ; it 
gives indeed the best datum for the calculation of the coefficients of the for- 
mula. I did not however feel inclined to repeat the tedious calculation, as it 
could only yield a slightly different result, 
