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+%%% ====================================================================
+%%% @LaTeX3-article{ LaTeX3-LTX3-002a,
+%%% filename = "l3d002a.tex",
+%%% archived = "ctan:/tex-archive/info/ltx3pub/",
+%%% related-files = "part of l3d002.tex",
+%%% author = "David Rhead",
+%%% doc-group = "Project core team",
+%%% title = "Some ideas for improving {\LaTeX}\\ General",
+%%% version = "1.1",
+%%% date = "18-Mar-1993",
+%%% time = "20:19:36 GMT",
+%%% status = "public, official",
+%%% abstract = "Ideas and suggestions from David Rhead for
+%%% improving various areas in LaTeX",
+%%% note = "prepared for the workshop at Dedham 91",
+%%% keywords = "",
+%%% project-address = "LaTeX3 Project \\
+%%% c/o Dr. Chris Rowley \\
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+
+\chapter{Could \LaTeX\ do more for chemists?}
+
+This appendix is based on a \lq\lq paper'' that I e-mailed a while
+back. It also contains some e-mailed comments.
+
+
+\section{Motivation}
+
+\begin{footnotesize}\begin{verbatim}
+From: Rainer Schoepf <Schoepf@DE.DBP.ZIB-BERLIN.SC>
+Date: Mon, 15 Oct 90 13:09:23 +0100
+
+I got the following message a while ago, as a reaction to a discussion
+I had with John Simmie after the talk at Cork. He's a chemist, so his
+focus of interest is different from the mathematicians one. I think it's
+interesting to pass this on to the list.
+
+ - Rainer
+
+----------------------original message follows ------------------------------
+
+... I would like to see ...
+a user-definable environment which would parallel displaymath-mode.
+
+For example, in printing chemical equations the conventions are that
+the text is in roman not math-italic---ok this is easily done via
+\def\chem{\rm\everymath={\rm}}
+and \chem can now be included inside $...$ or \[ ... \] or $$ ... $$ etc
+or outside as for {\chem\begin{eqnarray} ... \end{eqnarray}}
+Your virtual fonts approach will also work.
+Problems arise if mathematical and chemical equations are mixed in the sense
+text
+text
+\begin{equation} pV = nRT \end{equation}
+text
+\begin{equation}\chem
+ 2 H_2 + 2O_2 = 2H_2O \end{equation}
+text
+because the automatic numbering schemes assigns (1) to the first eqn
+and (2) to the second. Whereas one wants to number maths eqns and
+chemical eqns (reactions) independently---for example,
+(2.1) eqn 1 of chapter 2 and (1) reaction number 1, maybe in bold or
+oldstyle and maybe with <> brackets.
+
+At the moment the only solution is to hack into latex.tex
+and duplicate LL's \equation and \eqnarray environments with new
+counters and parameters---this I have done and it works fine for
+simple examples but failed for cases where the number of stacked
+eqnarray's exceeded the page size (hash size and other mysterious errors).
+
+You suggested that AMSTEX might do but on reflection that involves
+even more maths---and what us chemists want is less!
+
+Another feature is the lack of a construct to do the following:
+
+ catalyst
+ 2H_ + O_2 -------------> 2 H_2O
+ 300 K; 4 bar
+where the length of the arrow (---> or <--- or <===>) is
+determined by the amount of text over and under it.
+
+Note that we do not want to disable the equation environment just
+have a second customisable one.
+
+Regards, John.
+\end{verbatim}\end{footnotesize}
+
+\section{Typesetting and artwork}
+
+It may help to consider the division of labour
+within a traditional publishing house. A ``copy-editor''
+\cite[p.\ 236]{butcher-81} might divide the
+work on chemical formulae up between ``the printer'' and ``the draughtsman''.
+Thus, some formulae can be typeset, but others are treated as ``artwork''
+and are drawn.
+
+Although there have been valiant attempts \cite{haas+okane,ramek-90}
+to define \TeX\ macros for
+drawing chemical structure diagrams,
+I think it is inevitable that, whatever \TeX\ macros
+are defined, there will be chemists who come along with requirements that
+are beyond the abilities of the macro packages. Therefore, it seems sensible
+to retain the traditional division between typesetting and artwork: to
+typeset those formulae that can be typeset easily and to get the other
+formulae drawn in some way.
+
+In \TeX\ terms, artwork can be treated as ``graphics'' to be
+``pasted'' into a typeset document via \verb+\special+.
+For example,
+{\sc chemdraw}
+\cite{CSC} can produce ``encapsulated {\sc PostScript}'',
+so a \LaTeX-ed document with {\sc chemdraw} diagrams can be printed on
+a {\sc PostScript} printer.
+
+\section{Desirable facilities for chemists in the new \protect\LaTeX}
+
+\LaTeX\ is never going to be a system for producing ``artwork'',
+so it seems to me that it would be unwise to attempt to provide comprehensive
+facilities for ``chemical artwork'' in \LaTeX.
+However, it does seem worth providing a limited number of
+facilities to make it easier to produce the chemical
+formulae that should be treated as ``typesetting''.
+
+\subsection{Environments}
+
+Chemists' problems start when they use \LaTeX's ``mathematics''
+environments for ``chemistry''. Chemistry is not mathematics, and
+the conventions for typesetting chemistry are different from those for
+typesetting mathematics. In terms of the \LaTeX\ philosophy
+\cite[p.\ 6]{lamport-86}
+``mathematics'' and ``chemistry'' represent ``logically distinct structural
+elements''.
+
+It would seem natural to:
+\begin{itemize}
+\item define environments for chemists that are
+ analogous to the environments that are available for mathematicians
+\item within these ``chemistry'' environments, aim to keep to
+ whatever typesetting conventions are usual in chemistry.
+\end{itemize}
+How about defining {\tt chem}, {\tt displaychem} and {\tt chemequation} environments,
+by analogy with {\tt math}, {\tt displaymath} and {\tt equation}?
+
+If such environments were defined, the style-file writer would then
+have control over ``mathematics'' and ``chemistry'' separately.
+In particular:
+\begin{itemize}
+\item The default would be \verb+\rm+ for chemistry (although
+ a designer could change the default in a {\tt .sty} file).
+ Individual
+ authors would no longer have to search through
+ ``double bend'' sections of the \TeX book themselves
+ \cite[pp.\ 163 \& 179]{knuth-90}.
+\item A designer could implement a house-style in which
+ mathematical and chemical equations are numbered in separate
+ sequences
+ \cite[p.\ 224]{butcher-81} or a house-style in which there is only one
+ sequence of numbers \cite[p.\ 132]{dodd-86}.
+\item It might be possible to arrange that subscripts will normally be
+ at the same level \cite[p.\ 179]{knuth-90} inside the environments
+ for chemistry.
+\end{itemize}
+
+\subsection{Commands}
+
+At first sight, the \LaTeX\ manual \cite[ch.\ 3]{lamport-86} gives
+the impression that \LaTeX\ 2.09 provides the
+``building blocks'' to give all the arrows, harpoons and annotation that
+a chemist could want. However, it is often difficult to get these
+building blocks arranged in the ways required.
+For example:
+\begin{itemize}
+\item How does one obtain CH${_3}$(C=O)OCl
+ \cite[p.\ 235]{butcher-81} in ``math mode''?
+ We can't simply
+ use ``=''
+ to mean ``double bond'', since \TeX\ puts space
+ around it.
+\item To represent a reversible reaction with rate constants above/below
+ a pair of harpoons, I ended up with
+ \begin{verbatim}
+ \[
+ \renewcommand{\arraystretch}{0.5}
+ A \begin{array}{c}
+ \scriptstyle k\_1 \\ [1mm]
+ \rightleftharpoons \\
+ \scriptstyle k\_{-1}
+ \end{array} B
+ \]
+ \end{verbatim}
+ before it looked right. Surely individual \LaTeX\ users shouldn't have
+ to re-do the ``tuning'' needed to get these things right?
+\item As in the above example,
+ arrows and harpoons are often labelled to show reaction conditions.
+ It is not clear how to get arrows/harpoons that expand to the
+ width of the labels.
+\end{itemize}
+Many of these difficulties are another consequence of trying to use,
+for chemistry,
+the structural elements that were designed for mathematics.
+
+So what commands might usefully be made available inside some future
+``chemistry'' environments?
+\begin{itemize}
+\item
+It seems desirable \cite[p.\ 237]{butcher-81}
+to have documented facilities for
+single and double bonds. Triple bonds might also be needed
+\cite{chemsoc-61}.
+Documented facilities would also be useful for representing
+\begin{itemize}
+\item single bonds by raised dots \cite[p.\ 59]{hart-83}
+\item ``association of an unspecified type'' by three centred dots
+ \cite[p.\ 96]{dodd-86}.
+\end{itemize}
+
+Might commands such as \\
+\verb+\bond+, \verb+\doublebond+,
+\verb+\triplebond+ and \verb+\association+ \\
+be appropriate?
+\item
+It seems desirable to have specific commands for arrows/harpoons
+with labels above/below (to indicate conditions or rate
+constants). We can obtain an indication of the combinations
+of arrows/harpoons that might have traditionally been typeset from
+\cite[p.\ 371]{chicago-82}.
+Thus, as well as providing simple arrows for one-way reactions, it might
+be worth aiming to provide commands for: equilibrium reactions (beginning
+at left and right); reversible reactions (beginning at left and right);
+reactions beginning at left/right and completed to left/right.
+Might it be worth defining some commands such as \\
+\verb+\oneway+,
+\verb+\equilibriumR+,
+\verb+\equilibriumL+,
+\verb+\reversibleR+, \\
+\verb+\reversibleL+,
+\verb+\rightright+,
+\verb+\rightleft+,
+\verb+\leftright+,
+\verb+\leftleft+, \\
+that each accept two parameters: one to give a label
+above the symbol, the other to give a label below the symbol?
+For example,
+
+\begin{footnotesize}\begin{verbatim}
+\begin{displaychem}
+ 2H\_2 + O\_2 \oneway{catalyst}{300 K; 4 bar} 2 H\_2O
+\end{displaychem}
+\end{verbatim}\end{footnotesize}
+
+might be a natural way to specify
+\marginpar{\it But oneway, etc.\
+ should ensure that symbol width exceeds label width}
+\[ \rm
+2H_2 + O_2
+ \renewcommand{\arraystretch}{0.5}
+ \begin{array}{c}
+ \scriptstyle\rm catalyst \\ [1mm]
+ \longrightarrow \\
+ \scriptstyle\rm 300\ K;\ 4\ bar
+ \end{array}
+ 2H_2O
+\]
+\end{itemize}
+
+\section{Work involved}
+
+I'd guess that my suggestions about environments could be implemented
+by slight modications of the code that implements the corresponding
+environments for mathematics.
+
+Some new work would be required for commands such as
+\verb+\bond+, \dots~, \verb+\association+,
+\verb+\oneway+, \dots~, \verb+\leftleft+. (The only facility
+like \verb+\oneway+, \dots~, \verb+\leftleft+
+that I've found
+in an existing macro package is that for arrows in \AmSTeX\
+\cite[p.\ 140]{spivak-86}
+but, from a chemist's point-of-view, this doesn't provide sufficient
+choice of symbols.)
+
+It might be worth seeking advice about objectives
+from people who typeset chemistry professionally.
+% Perhaps the UK's Royal Society of Chemistry would be prepared to advise
+% about details. I've been in e-mail correspondence with their Publications
+% Manager about authors submitting manuscripts electronically to them,
+% although they seem to be going the wordprocessor + chemdraw + SGML route.
+
+\section{Documentation}
+
+If the facilities that I've outlined above were provided, I would
+be inclined to give them less prominence in the documentation than
+the analogous facilities for mathematicians. This would help
+give the impression that, whereas mathematicians can expect \LaTeX\
+to do everything they want, chemists can only expect \LaTeX\ to do a certain
+proportion of what they want.
+For example, in the successor to \cite{lamport-86},
+the description of facilities for
+chemists might be relegated to an appendix, which could start with a
+paragraph explaining that the facilities are intended to support ``typesetting''
+but not ``artwork''.
+
+\section{Some e-mail comments}
+
+\begin{footnotesize}\begin{verbatim}
+From: CA_ROWLEY@UK.AC.OPEN.ACS.VAX
+Date: Mon, 22 Oct 90 13:51:21 GMT
+
+This is a comment on the message from John Simmie, passed on by Rainer:
+
+Whilst I think that the typesetting of chemical formulas, etc, is an
+important area for any TeX-based system to provide. I think that, in
+common with maths, it should be provided by an add-on package (as
+AMS-LaTeX does for maths). This should be written in close
+cooperation with experts in such typesetting.
+
+Nevertheless, we should attempt to ensure that we dot make any
+decisions about "basic LaTeX" which make such an add-on dificult to
+produce. It is not clear to me how we can achieve this in general
+(since it applies to many other specialist areas of typeseting)
+but I cannot see anything in John's requests that requires any changes
+to basic LaTeX.
+\end{verbatim}\end{footnotesize}
+\begin{center} --- \end{center}
+\begin{footnotesize}\begin{verbatim}
+From: David Rhead ...
+Date: 24 Oct 90 14:10:44
+
+% A LaTeX input file
+\documentstyle[11pt]{article}
+
+
+\begin{document}
+
+% A chemist might hope to typeset single/double/triple bonds in
+% the following "obvious" ways. However, none of them will give
+% what is required (because, although the bonds are visually
+% similar to some mathematical sybols, they are logically different).
+
+A single bond? $X-Y$
+
+A single bond? $X.Y$
+
+A single bond? $X\cdot Y$
+
+A double bond? $X=Y$
+
+A triple bond? $X\equiv Y$
+
+\end{document}
+\end{verbatim}\end{footnotesize}
+\begin{center} --- \end{center}
+\begin{footnotesize}\begin{verbatim}
+Subject: Re: Facilities for chemists. A LaTeX example file.
+From: bbeeton <BNB@COM.AMS.MATH>
+Date: Wed, 24 Oct 90 18:14:13 CET
+
+
+in looking at david rhead's chemistry example, i find two distinct
+notions presented:
+ (a) "the bonds are visually similar to some mathematical symbols"
+and
+ (b) "they are logically different"
+
+why is it necessary to use the existing notation, just because of (a)?
+why isn't it possible, yea almost trivial!, to define new names and
+structures for these that are logically distinct? tex, after all, is
+a powerful macro language -- one of its main, perhaps most important,
+selling points.
+
+i offer another example to illustrate what i'm suggesting.
+ $\vector a$ (or $\vector{a}$ )
+assume this will be used only in math mode.
+if you're a mathematician this becomes
+ \def\vector#1{\vec{#1}}
+if you're a physicist, it becomes
+ \def\vector#1{{\bf#1}}
+here the logical notion is the same, but the representation is different.
+
+seems to me that this is what sgml is trying to tell us. teach the
+user to capture the logic, and let the representation be taken care of
+behind the scenes.
+
+i don't say that the available fonts and structures are adequate for
+chemistry (they're almost certainly not), but that doesn't mean that
+suitable new ones can't be constructed.
+\end{verbatim}\end{footnotesize}
+\begin{center} --- \end{center}
+\begin{footnotesize}\begin{verbatim}
+From: David Rhead ...
+Date: 25 Oct 90 14:08:11
+
+...
+
+... with reference to Barbara's message, there may be no difference
+between what she's suggesting and what I'm suggesting. ...
+... I just intended
+to show what a chemist might actually do on seeing the current LaTeX
+manual (before the chemist found that it didn't give him/her what s/he
+wanted), not to show what I think chemists should do in future.
+I agree with Barbara that, in an ideal world (to which we are working with
+LaTeX 3.0), the user should not use the existing notation ...
+\end{verbatim}\end{footnotesize}