68 REPORT—1849, 
The multipliers of a for the three latter combinations given in the preceding 
table are, according to Graham’s experiments, 0°72, 1°35 and 1°18. These 
numbers agree with Hess’s statement only so far as to indicate that the heat 
evolved in the combination of SO, HO with HO is nearly the same as that 
evolved in the combination of SO, 2HO with 4HO. 
The experiments of Abria were performed by the direct method and with 
a similar apparatus to that employed by Hess. Adopting the views of Hess as 
to the quantities of heat in the cases of combination being in simple relations 
to one another, he arrives nevertheless at very different numbers for the ratios. 
In the next table I have given Abria’s theoretical whole numbers, as-also the 
exact numbers which result from his experiments. 
Theory. Experiment. 
BOSE TIC ee a re Ee, Se ee ae 
SO,HO+HO .... Qa ........ 200a 
SO,2HO+HO.... a .. 0°95a 
eee LUE es OU) anon eee O'57a 
SO,4HO+HO.... 3a ........ 0°35a 
SO,5HO+HO.... 2a¢ ........ 0:22 
In the three latter cases, the simple relations in the second column are 
scarcely borne out by the experimental numbers. The only agreement with 
the ratios given by Hess is in the combination SO, 2HO with HO, which, 
according to both experimenters, sets free exactly half as much heat as the 
combination SO,HO with HO. The value of a, given by Abria, is 39°33. 
The latest experiments on this subject are those of Fabre and Silbermann, 
from which I have calculated the following multipliers for a :— 
SO, BOs HO. oilie-é 2-00a 
SO, 2HO+HO jie cece onip «u's 0:93a 
SG BHO HD Nem eatsne. 0°53a 
SO,4HO+HO 2.2... 004. 0°32a 
Se FEO 4 FO ind. moitcatcies 0:26a 
Hess has also attempted to express by simple multiple relations the quan- 
tities of heat disengaged in the formation of the hydrates of nitric acid, but 
for the details of his results I must refer to the original memoir. 
Combination of Acids and Bases.—In the same memoir Hess describes an 
extensive set of experiments on the heat evolved during the union of certain 
bases with acids of different degrees of concentration. These experiments 
serve to illustrate the general principle, that in the formation of a chemical 
compound the heat developed is a constant quantity, being the same in 
amount, whether the combination takes place directly at one time or in- 
directly at repeated times. ‘Thus he finds that on neutralizing an aqueous 
solution of ammonia with sulphuric acid, containing one, two, three and six 
atoms of water, there is a different development of heat in each case; but by 
adding to the results found by experiment in the three latter cases the quan- 
tities of heat due to the combination of the monohydrated acid, with one, 
two and five atoms of water respectively, the same number is obtained in each 
case as in the direct combination of the monohydrated acid itself. This | 
principle is correct, but it is almost self-evident and scarcely required so 
elaborate a proof. 
The bases examined by Hess were potash, soda, ammonia and lime, which 
he combined in different ways with the sulphuric, nitric and hydrochloric 
acids. The conclusion at which he arrives is, that the same acid in combining 
with equivalents of different bases produces the same quantity of heat, but at 
the same time he expresses some doubt as to the applicability of this principle 
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