Chemeq - Chemical Equation Analyzer
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
Options are active only if chemeq parses an equation of chemical
reaction. If chemeq parses the formula of a simple chemical, no option
is taken in account, the output is just a straightforward TeX string
representing the simple chemical.
-h Displays Help.
-v Displays the Version number
-M Outputs al list of space separated molecular weights.
-m Outputs a Minimal output. It allows chemeq to be idempotent,
i.e. the command ’chemeq | chemeq’ is equivalent to ’chemeq’.
-l Outputs a LaTeX string representing the chemical equation.
-c 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.
-w 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 semi-equation.
-C 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"
-e Outputs a detailed count of the Electrical charges.
-s Outputs a list of the chemical Species.
-n 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.
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).
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).
echo "1/2 Cu^2+ + OH- -> 1/2Cu(OH)2s" | chemeq
will display informations about the reaction of hydroxyde and Cu
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).
NOTE: 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+"
will display the pure redox equation from the first equation,
minus the second one. Electrons are simplified. So it will be
echo "MnO4^- + 8H3O^+ + 5Fe^2+--> Mn^2+ + 8 H2O + 5Fe^3+" | chemeq
which is their combination.
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
standard 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
4 june 2000 chemeq(1)