Conservation of caloric

Eighteenth-century and early nineteenth-century views of the nature of heat were founded on the principle of conservation of caloric. This principle is an eminently attractive basis for rationalizing simple observations such as temperature changes that occur when a cold object is placed in contact with a hot one. The cold object seems to have extracted something (caloric) from the hot one. Furthermore,... 

Carnot used in his development the erroneous - but strongly held then - axiom of the conservation of caloric (he did have, however, some doubts about it later, but never articulated them). He died young, of cholera, and his work laid dormant until it was revived a few years later by Clapeyron. 

But how could Carnot using the false axiom of the conservation of caloric arrive at the correct conclusions For the first two, the proof is independent of the conversion of heat to work. As for the third, this is one case where two wrongs make a right. Again from Cardwell, p.205 "The conclusion was drawn from an argument based on the false assumption of the conservation of heat and from misleading experimental evidence that the specific heat of gases increases with volume. Nevertheless the conclusion happens to be correct."... 

Lavoisier summarized his ideas developed over the previous twenty years in his seminal 1789 book Traite Elementaire de Chimie (Elements of Chemistry). This work presented his findings on gases and the role of heat in chemical reactions. He explained his oxygen theory and how this theory was superior to phlogiston theory. Lavoisier established the concept of a chemical element as a substance that could not be broken down by chemical means or made from other chemicals. Lavoisier also presented a table of thirty-three elements. The thirty-three elements mistakenly included light and caloric (heat). Lavoisier put forth the modern concept of a chemical reaction, the importance of quantitative measurement, and the principle of conservation of mass. The final part of Lavoisier s book presented chemical methods, a sort of cookbook for performing experiments. 

Though Sadi Carnot used the caloric theory of heat to reach his conclusions, his later scientific notes reveal his realization that the caloric theory was not supported by experiments. In fact, Camot understood the mechanical equivalence of heat and even estimated the conversion factor to be approximately 3.7 joules per calorie (the more accurate value being 4.18 J/cal) [1-3]. Unfortunately, Sadi Carnot s brother, Hippolyte Camot, who was in possession of Sadi s scientific notes from the time of his death in 1832, did not make them known to the scientific community until 1878 [3]. That was the year in which Joule published his last paper. By then the equivalence between heat and work and the law of conservation of energy were well known through the work of Joule, Helmholtz, Mayer and others. (It was also in 1878 that Gibbs published his famous work On the Equilibrium of Heterogeneous Substances). 

We should notice here that Carnot had accepted the axiom of the conservation of heat. Hence, when he talks about a fall of caloric he means that all caloric that left the heat reservoir finds itself in the heat sink, just as all the water that falls through a hydraulic engine arrives at the bottom. Work is produced because of the fall of caloric, not through conversion of it. 

Second, the idea of a loss of caloric (heat) by conversion to work was against the aforementioned conservation of heat axiom. 

Homeostatic regulation of metabolic efficiency (i.e., caloric intake required to maintain body weight constant to maintain constant ratios of energy expenditure/ conservation). 

Rumford s studies (along with those of Humphrey Davy see Section 3.4) contributed to gradual decline of the caloric theory of heat and its replacement by the modem kinetic molecular theory. By about 1840, the interconversion of heat and work was clearly understood, as well as the association of heat with molecular motion. However, there was as yet no clear statement of the conservation principle for the total heat plus work. 

The differential forms of the conservation equations derived in the appendixes for reacting mixtures of ideal gases are summarized in Section 1.1. From the macroscopic viewpoint (Appendix C), the governing equations (excluding the equation of state and the caloric equation of state) are not restricted to ideal gases. Most of the topics considered in this book involve the solutions of these equations for special flows. The forms that the equations assume for (steady-state and unsteady) one-dimensional flows in orthogonal, curvilinear coordinate systems are derived in Section 1.2, where specializations accurate for a number of combustion problems are developed. Simplified forms of the conservation equations applicable to steady-state problems in three dimensions are discussed in Section 1.3. The specialized equations given in this chapter describe the flow for most of the combustion processes that have been analyzed satisfactorily. 

Withdrawal of most, or all, caloric intake has been used to treat certain cases of obesity. Such withdrawal provokes many metabolic responses. The body attempts to conserve protein at the expense of other sources of energy, such as fat. The blood glucose concentration decreases by as much as ISmg/dL (1 mmol/L) within the first 3 days of the start of a fast in spite of the body s attempts to maintain glucose production. Insulin secretion is greatly reduced, whereas glucagon secretion may double in an attempt to maintain normal glucose concentration. Lipolysis and hepatic keto-... 

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