Re: simultaneous equations for chemical speciation

*To*: mathgroup at smc.vnet.net*Subject*: [mg100214] Re: simultaneous equations for chemical speciation*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Thu, 28 May 2009 06:48:54 -0400 (EDT)*Organization*: Uni Leipzig*References*: <gvk9v0$ono$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de

Hi, and we can look on you post for ages, but we will never find out *what* variables you wish to eliminate, so we will not found out *what* error message or what's wrong. And more over whe I try eqn = {a == b + c + d, e == f + g + c + 2 d, h == c/(b*g), i == d/(c*g), h*i == d/(b*g^2), j == m*g/f, k == l*m, n + m + b + c == g + l} syms = Cases[eqn, _Symbol, Infinity, Heads -> False] // Union Eliminate[eqn, #] & /@ syms all work fine with out an error message. Regards Jens Jem & Tracy wrote: > Hi, I am a postgrad student and completely new to mathematica, I am just > starting to realise the possibilities. > > I am trying to do a chemical speciation calculation. > I have a set of simultaneous equations which represents the equilibria, > mass balance, and charge balance in the system. > > I want to eliminate some of the variables, and then be able to solve for > the remaining ones. > My system of equations looks like this: > a=b+c+d > e=f+g+c+2d > h=c/(bg) > i=d/(cg) > hi=d/(bg^2) > j=mg/f > k=lm > n+m+b+c=g+l > > Basically, I can solve for the variable I want, but I am having trouble > eliminating the ones I don't want (ie. I am getting an answer that is in > terms of the wrong variables) > Sofar my formula looks like: > > Solve[{a == b + c + d, e == f + g + c + 2 d, h == c/(b*g), > i == d/(c*g), h*i == d/(b*g^2), j == m*g/f, k == l*m, > n + m + b + c == g + l}, {g}] > > If I use a similar formula for the "Eliminate" function, I get error > mesages. > > I have been in the help files for ages, and don't really understand how > to do this. > I would really appreciate some pointers!! > Thanks > >