Conservation and Innovation : Helmholtz's Struggle with Energy ...
Conservation and Innovation : Helmholtz's Struggle with Energy ...
Conservation and Innovation : Helmholtz's Struggle with Energy ...
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generate a determined equivalent of heat, however complicated the transition<br />
from one force to the other" 56. Helmholtz asserted that the empirical evidence<br />
was not very large but still he wanted to offer specific theoretical applications of<br />
the principle to the heat produced through mechanical, chemical, electrolytic <strong>and</strong><br />
electrostatic forces. The case of animal heat was now only the last of five<br />
applications of a principle that was becoming more <strong>and</strong> more general.<br />
A great difficulty immediately appeared: the most important balance, the<br />
one between heat <strong>and</strong> work, could not be written for the lack of a mechanical<br />
equivalent of heat; in fact the values offered by the theories of Carnot-Clapeyron<br />
<strong>and</strong> Holtzmann could not be accepted, being based on the caloric model <strong>and</strong> only<br />
referred to the propagation <strong>and</strong> not to the production of heat 57. Helmholtz, despite<br />
having clearly focussed the problem, lacks experimental data. In October 1846 he<br />
still did not know of Mayer's nor of Joule's work: "no experiment can be taken in<br />
account for the mechanical forces" 58. Thus all the other balances were written as<br />
equivalences based on heat units <strong>and</strong> not on work units. In the "Bericht" heat <strong>and</strong><br />
not work was the unity of measurement common to all the natural phenomena<br />
considered, not a minor difference <strong>with</strong> the subsequent Erhaltung.<br />
In the analysis of chemical transformations Hess' law of the constancy of<br />
the production of heat, whichever the intermediate stages of the reaction, was<br />
acknowledged. Here appeared the first instance of the identification of latent heat<br />
<strong>with</strong> the thermal equivalent that was to play a role in the subsequent discussion of<br />
animal heat.<br />
For the electrolytic currents the heat developed in the circuit must be<br />
equivalent to the electrochemical transformations in the galvanic chain (battery),<br />
independently of their order. The heat in the circuit could be calculated through<br />
Georg Simon Ohm's <strong>and</strong> Emily Christianovic Lenz's laws (Joule was not<br />
mentioned):<br />
frictional electricity, where a release of latent heat is inconceivable". Helmholtz: W A 1 Pp.6-<br />
7.<br />
56 Helmholtz W A 1 P.7<br />
57 It is interesting to remark that instead in the Erhaltung these data were utilised,<br />
that Clausius criticised this "improper" use, that Helmholtz accepted the criticisms, that<br />
Truesdell denies the validity of these criticisms. See below.<br />
58 Helmholtz WA 1 P.7.