Mathematica 9 is now available
Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2009

[Date Index] [Thread Index] [Author Index]

Search the Archive

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
> 
> 


  • Prev by Date: Re: using predefined expressions in functions [newbie question]
  • Next by Date: Re: simultaneous equations for chemical speciation
  • Previous by thread: Re: simultaneous equations for chemical speciation
  • Next by thread: Re: simultaneous equations for chemical speciation