The form of magnetic work in a fundamental thermodynamic equation for a paramagnet

Magnetic work takes two forms in the thermodynamics of a paramagnet as deve loped in many textbooks. We observe that in the case when the lattice energ y is excluded, the form delta W=BdM cannot be used in a fundamental thermod ynamic equation. This shows that there are thermodynamic systems with no fu ndamental thermodynamic equation. (C) 1999 American Association of Physics Teachers.