Favre and
Silbermann adopted the plan of ascertaining the weight of the
substances consumed by calculation from the weight of the products of
combustion. Carbonic acid was absorbed by caustic potash, as also was
carbonic oxide, after having been oxidized to carbonic acid by heated
oxide of copper, and the vapor of water was absorbed by concentrated
sulphuric acid. The adoption of this system showed that it was in any
case necessary to analyze the products of combustion in order to
detect imperfect action. Thus, in the case of substances containing
carbon, carbonic oxide was always present to a variable extent with
the carbonic acid, and corrections were necessary in order to
determine the total heat due to the complete combination of the
substance with oxygen. Another advantage gained was that the
absorption of the products of combustion prevents any sensible
alteration in the volumes during the process, so that corrections for
the heat absorbed in the work of displacing the atmosphere were not
required. The experiments on various substances were repeated many
times. The mean results for those in which we are immediately
interested are given in Table I., next column.
Comparison with later determinations have established their
substantial accuracy. The general conclusion arrived at is thus
stated:
"As a rule there is an equality between the heat disengaged or
absorbed in the acts, respectively, of chemical combination or
decomposition of the same elements, so that the heat evolved during
the combination of two simple or com-pound substances is equal to the
heat absorbed at the time of their chemical segregation.
Pages:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25