George E. Cawthon wrote:

By the way, the inches of water measure is based on 4 deg C
and mercury is based on 0 C.

Andy replies:

You know, I had never thought of that. It's obvious from
the state table that this temp is the max density of water at standard
pressure.......

Thanks for pointing it out. It seems there are a number
of things that I haven't run into before.......
Andy