DOCBOOK-APPS: Chemistry in DocBook?

I intend to write a text that will contain many chemical formulae.  I
would like to write it in DocBook/XML.  Now DocBook by itself does not
have special tags for that.  Of course I need a stylesheet and
formatter that will render the proper numbers in sub- or super-scripts
too.  Does something like that exist?
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	Tom "thriving on chaos" Peters
		NL-1062 KD nr 149	tel.    +31-204080204
 			Amsterdam	e-mail