The relationship (δT / δP)h = 0 holds good for

1. An ideal gas at any state
2. A real gas at any state
3. Any gas at its critical state
4. Any gas at its inversion point
5. A and B both

=			δT			_h
			δP

is Joule-Thompson coefficient (μ)

=			δT			_h
			δP

= 0 for an ideal gas, at any state for any gas at its inversion point. Inversion curve is the locus of all the point at which μ is zero.