From: Helmut =?iso-8859-1?Q?C=F6lfen?= <coelfen@MPIKG-GOLM.MPG.DE>
  To  : rasmb@bbri.harvard.edu
  Date: Thu, 04 Oct 2001 23:14:11 +0200

Hi my friends out there,

I seem to have a quite trivial problem but nevertheless seek your advivice if
you are aware of more recent theories.

I  have a close look at strongly charged colloids - all of them are more or 
less the ideal of a
monodisperse solid hard sphere. The sedimentation behaviour of their 
uncharged counterparts is precicisely
known as all of you will aggree. OK, I know the VBAR, the molar mass from 
their diameter from
dynamic light scattering, Field flow fractionation and transmission 
electron microscopy.
The world should be fine to describe everything so far.
But as you can imagine, there are strong charge influences on sedimentation 
and I wonder
if this "ideal" case has not yet been treated in dependence of particle charge.

Now the charge comes into play. I have started reading the classical AUC 
textbooks and
surprisingly, I found the best answer in Svedberg/Pedersens classical book. 
But this is almost
70 years old so  I guess there are more recent theories of charge influence 
on sedimentation
underway. OK, there are many papers treating the sedimentation of 
polyelectrolytes but the thing
I look for is: Can I determine the average particle charge QUANTITATIVELY 
once I know
the VBAR and particle dimension ???

I have the feeling that the answer is trivial but nevertheless, I believe 
that there must be a more
recent treatment than that of Svedberg in 1940's.

Any hints towards more recent theories for SOLID CHARGED SPHERES are highly 
appreciated.

Thanx a lot

Helmut








_______________________________________________________________
Dr. Helmut Cölfen
Max-Planck-Institute of Colloids and Interfaces
Colloid Chemistry
Am Mühlenberg 2
14424 Potsdam
Germany

Tel: --49 331 567-9513
Fax: --49 331 567-9502
http://www.mpikg-golm.mpg.de/kc/coelfen/
_______________________________________________________________