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chemeq - Chemical Equation Parser and Renderer


chemeq [-M] [-m] [-l] [-c] [-w] [-C] [-e] [-s] [-n] [-W]

chemeq [-h] [-v]


chemeq is a chemical equation analyzer. It is a fast lexical and syntaxic analyser which
helps to find out chemical informations embedded in source chemical equations. Data can be
output in various sophisticated formats, depending on options. 'chemeq' defaults to
'chemeq -mlcwCn'.


Outputs al list of space separated molecular weights.

Outputs a minimal output. It allows chemeq to be idempotent, i.e. the command 'chemeq
| chemeq' is equivalent to 'chemeq'.

Outputs a LaTeX string representing the chemical equation.

Outputs a message giving informations about the Conservation of elements and charges
in the equation. 'OK' means that both elements and electric charges are balanced.

Outputs the LaTeX string representing the Gulder-Waage equation related to the input
chemical equation, or the Nernst equation, if the input equation is a redox

Outputs a detailed Count of the molecules and atoms contained in each member of the
chemical equation. For example for the equation "H2_g + 1/2 O2_g --> H2O" it outputs:
"H2_g|H:1*2, 1/2 O2_g|O:1/2*2; H2O|H:1*2 O:1*1"

Outputs a detailed count of the Electrical charges.

Outputs a list of the chemical Species.

Outputs a Normalized string accounting for the input equation. Two chemical equations
having the same normalized string are chemically equivalent, even if the molecules are
scrambled around and the coefficient are not equal but proportionnal.

Changes the behavior of the renderer for some versions of Wims : works around a bug
whith the macro \rightarrow.

Displays Help.

Displays the Version number


chemeq_input, w_chemeq_input
if set, this variables's value overrides the standard input. If this variable is not
set, the variable w_chemeq_input is taken in account (useful for the WIMS server).
See above (useful for the WIMS server).

if set, this variable's value overrides the options.If this variable is not set, the
variable w_chemeq_option is taken in account (useful for the WIMS server).

See above (useful for the WIMS server).


echo "1/2 Cu^2+ + OH- -> 1/2Cu(OH)2s" | chemeq
will display informations about the reaction of hydroxyde and Cu II ions.

echo "MnO4^- + 8H3O^+ + 5e- --> Mn^2+ + 12 H2O" | chemeq
will display informations about the reaction of reduction of permanganate ions in an
acid environment.

echo "MnO4^- + 8H3O^+ + 5e- --> Mn^2+ + 12 H2O" | chemeq -w
will display the LaTeX format for the Nernst law related to the reduction of
permanganate ions in an acid environment.

echo "MnO4^- + 8H3O^+ + 5e- --> Mn^2+ + 8 H2O" | chemeq -c
will highlight the lack of conservation of elements H and O (water molecules are not
well balanced).


syntax of ions
allthough in some cases, shorter expressions are sucessfully parsed, it is safer to
consider that an "up arrow" (^) must be put before the charge symbols of an ion.
Examples : H3O^+, Fe(CN)6^4-, OH^-

Composing chemical equations
Two operators are defined, # as an additive oprator and ~ (tilde) as a substractive
operator: they allow to compose several chemical equations

echo "MnO4^- + 8H3O^+ + 5e- --> Mn^2+ + 8 H2O ~ 5Fe^3+ + 5e- -> 5Fe^2+" | chemeq

will display the pure redox equation from the first equation, minus the second one.
Electrons are simplified. So it will be equivalent to:

echo "MnO4^- + 8H3O^+ + 5Fe^2+--> Mn^2+ + 8 H2O + 5Fe^3+" | chemeq which is their

Mutiplying a chemical equation by one coefficient
The operator * permits to multiply a whole equation by one coefficient which may be a
fraction. Here is an example:

echo "5 * Fe^3+ + e- -> Fe^2+" | chemeq

will be equivalent to

echo "5Fe^3+ + 5e- -> 5Fe^2+" | chemeq

Combining chemical equations, with coefficients
The two previous techniques can be used at the same time, which enables you to make
more comlicated combinations, like this one:

echo "Fe^3+ + e^- -> Fe^2+ (0.77 V) # Fe^2+ + 6CN^- -> Fe(CN)6^4- (Kfa=1e24) ~ Fe^3+
+ 6CN^- -> Fe(CN)6^3- (Kfb=1e31)" | chemeq

which will work as expected, and yeld a good value for the stan‐ dard potential of the
redox couple of hexacyanoferrate II and III ions.


When not specified, chemical entities coming from the standard input are believed to be in
aqueous solutions. Water is considered by default as the main solvent. Only one liquid
(aqueous) phase is currently taken in account. All solid chemical entities are considered
as parts of separated phases. Suffixes _s, _g and _aq can be used to enforce the type of
some chemical entities. There may be problemes when you write a standard potential with no
decimal dot. For example, the entry Mn^2+ + 2e^- -> Mn_s (-1 V) would trigger an error.
Then write Mn^2+ + 2e^- -> Mn_s (-1.0 V) or the more accurate value Mn^2+ + 2e^- -> Mn_s
(-1.18 V) and there will be no error.

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