Troff preprocessor for chemical symbols

[LT. Thomas Luteran]

     Does anyone know of any available troff preprocessors, similar to eqn and
table, to provide formatting of chemical symbols and structures (such as rings,
chains,etc.)?  Does anyone have experience that they are willing to share in 
writing such a preprocessor?  The system I will be working with uses a Xerox
9700 laser printer and a formatter called xroff (troff for the Xerox printer).
Any information or comments will be appreciated.


				Tom Luteran

				(301) 671-3688