Jim:

I am recommending banishing the use of the term "vapor density", not the use of the concept of relative density which obviously has importance in many venues.

As explained in my original post, the term vapor density is ill-defined and leads to imprecise statements/thoughts/theories/etc.

I recommend in the alternative using the terms specific gravity or relative density (ideally with a footnote defining the reference substance and conditions if necessary or that the term is simply the ratio of molecular weights) instead, which are generally better defined and understood.

Mike Learmonth, B.A.Sc., M.B.A., M.Eng., J.D., LL.B., P.Eng., C.F.E.I
Senior Associate, Giffin Koerth Forensic Engineering and Science