Ion pair equlibria, mathematical modelling of data - Please help

Tomas Eriksson tomas_e at LINK.Physchem.KTH.SE
Thu Mar 18 07:27:56 EST 1993

In article <1993Mar18.155857.898 at otago.ac.nz>, alastair at farli.otago.ac.nz (Alastair Thomson), University of Otago, Dunedin, New Zealand writes:
>We have been examining an ion-pair between eosin (anion) and  
>cetylpridinium chloride (cation) (a quaternary ammonium compound) by  
>spectrophotometry (542 nm) and are seeking to determine the ion-pair  
>association constant (K).


>What we want to know is the ion-pair constants for both the 1:1 (K1) and  
>1:2 (K2) complexes.  Does anyone have a mathematical model we could use to  
>calculate these constants, and if so, can we use it?

This sound like a fairly standard evaluation of stability constants of 
complex formation. (Nevertheless, the actual computation of several K's 
simulataneously can be numerically very troublesome.) There are several 
different computer programs that are used to evaluate this kind of data, 
most commonly for ligand bonding to metal ions. Since this is a typical 
inorganic chemistry thing, I would recommend you to contact the 
inorganic chemistry department closest to you. I'm sure they will know 
someone who has the appropriate complex constant evaluation programs, 
and know how to use them.

Tomas Eriksson                                          tomas_e at physchem.kth.se
            Surface Force Group, Department of Physical Chemistry,
               Royal Institute of Technology, Stockholm, Sweden

"These latter-day practitioners of surface chemistry reflect a lingering of the
adventurous spirit of the Enlightment" -- Charles Tanford

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