or globally without being straitjacketed to the (incorrect) caloric theory doctrine that
heat is a material substance. This point was made nicely by the philosopher Psillos
[3]. One example of locally non-isolated thermal system is the problem of adiabatic
compression/expansion associated with sound propagation in gases as developed by
Laplace and Poisson, which will be considered in Sect. 2.4; Sect. 6.6 will provide a
reason why the Laplace–Poisson solution works. The example of a globally
non-isolated thermal system is the problem of transformation of heat into work,
which is the central problem of the book, and the “caloric formalism” approach to
the problem taken by Carnot–Clapeyron is covered in Chap. 4; in Chap. 8 an
interpretation will be given as to what Carnot’s “caloric formalism” really means.
2.2 Direct Heating: Sensible Heat and Latent Heat
Before Lavoisier and Laplace formulated the caloric theory of heat, Black had made
the first advance in the quantitative understanding of heat. He was the first to
recognize the importance of making a distinction between temperature and quantity
of heat, between what we describe as the intensive and extensive measures of heat—
and he together with Berthelot, Lavoisier, and Laplace were the founders of the
science of calorimetry. At the time, it had been known how to read temperature
directly from the thermometer. But, how could one measure the quantity of heat?
In the earlier experiments of Black on the latent heat (see below), which required
melting ice and boiling water, the heat was applied by means of a flame. And, as the
rate of heat produced by flame was assumed to be uniform, the quantities of heat
supplied were inferred to be proportional to the time during which the supply
continued. A method of this kind was obviously very imprecise, and in order to
make it at all accurate, it would need numerous precautions and auxiliary investigations with respect to the laws of the production of heat by the flame and its heat
transmission to the body which was heated.
Instead of relying on the thermal interaction of flame and a body, Black came to
the conclusion that a more dependable research method relies on the interaction of
two thermal bodies. Since when heat is applied to or removed from a body it
produces changes of various kinds—raising its temperature, altering its volume or
its pressure, and in certain cases it changes the state of the body from solid to liquid
or from liquid to gaseous—reading of such changes provides means for inferring
the quantities of heat.
Q net ¼ Q 1 þ Q 2 ¼ 0
The principle of calorimetry is based on combining this idea with the supposition, the conservation of heat (Fig. 2.1): if two bodies of different temperature are in
thermal contact and if no external heat exchange is allowed to go out or enter into
the system of two bodies and if no chemical reactions take place in between the two
bodies then heat lost by the hotter body will be equal to the heat gained by the
2.1 Theories of Heat
27
heat is a material substance. This point was made nicely by the philosopher Psillos
[3]. One example of locally non-isolated thermal system is the problem of adiabatic
compression/expansion associated with sound propagation in gases as developed by
Laplace and Poisson, which will be considered in Sect. 2.4; Sect. 6.6 will provide a
reason why the Laplace–Poisson solution works. The example of a globally
non-isolated thermal system is the problem of transformation of heat into work,
which is the central problem of the book, and the “caloric formalism” approach to
the problem taken by Carnot–Clapeyron is covered in Chap. 4; in Chap. 8 an
interpretation will be given as to what Carnot’s “caloric formalism” really means.
2.2 Direct Heating: Sensible Heat and Latent Heat
Before Lavoisier and Laplace formulated the caloric theory of heat, Black had made
the first advance in the quantitative understanding of heat. He was the first to
recognize the importance of making a distinction between temperature and quantity
of heat, between what we describe as the intensive and extensive measures of heat—
and he together with Berthelot, Lavoisier, and Laplace were the founders of the
science of calorimetry. At the time, it had been known how to read temperature
directly from the thermometer. But, how could one measure the quantity of heat?
In the earlier experiments of Black on the latent heat (see below), which required
melting ice and boiling water, the heat was applied by means of a flame. And, as the
rate of heat produced by flame was assumed to be uniform, the quantities of heat
supplied were inferred to be proportional to the time during which the supply
continued. A method of this kind was obviously very imprecise, and in order to
make it at all accurate, it would need numerous precautions and auxiliary investigations with respect to the laws of the production of heat by the flame and its heat
transmission to the body which was heated.
Instead of relying on the thermal interaction of flame and a body, Black came to
the conclusion that a more dependable research method relies on the interaction of
two thermal bodies. Since when heat is applied to or removed from a body it
produces changes of various kinds—raising its temperature, altering its volume or
its pressure, and in certain cases it changes the state of the body from solid to liquid
or from liquid to gaseous—reading of such changes provides means for inferring
the quantities of heat.
Q net ¼ Q 1 þ Q 2 ¼ 0
The principle of calorimetry is based on combining this idea with the supposition, the conservation of heat (Fig. 2.1): if two bodies of different temperature are in
thermal contact and if no external heat exchange is allowed to go out or enter into
the system of two bodies and if no chemical reactions take place in between the two
bodies then heat lost by the hotter body will be equal to the heat gained by the
2.1 Theories of Heat
27