diathermal

For this reason, another statement of the law is "All diathermal walls are equivalent."

Such a wall is called diathermal.

All diathermal walls are equivalent."

In discussions of thermodynamics, such a diathermal wall and process of transfer of energy as heat is not usually intended unless they are explicitly expressed.

A diathermal wall is a connection of contiguity between two bodies that allows the passage of heat by conduction between them.

This physical idea is also expressed by Bailyn as a possible version of the zeroth law of thermodynamics: "All diathermal walls are equivalent."

Then from the viewpoint of states of thermal equilibrium, all diathermal walls are equivalent; this is proposed as a possible statement of the zeroth law of thermodynamics.

If heat is considered with respect to diathermal walls, then, because all diathermal walls are equivalent, all heat is of the same kind.

For theoretical purposes, a boundary may be declared adiabatic, isothermal, diathermal, insulating, permeable, or semipermeable-but actual physical materials that provide such idealized properties are not always readily available.

For example the glass bulb of a thermometer will act as a diathermal wall whether exposed to a gas or to a liquid, provided they do not corrode it or melt it.

It is sometimes allowed that the diathermal wall is substantial and has properties of its own including a temperature of its own, and it is considered that the wall is a body in its own right, but is still considered as a closed system not permitted to exchange matter.