From: Richard M Thomas <rthomas@ifp.mat.ethz.ch>
  To  : RASMB@bbri.harvard.edu
  Date: Wed, 03 Dec 1997 12:44:16 +0100

A dentist writes......

Fluoridation.
	A couple of points in addition to those made recently by Jack.
The alkali metal flourides, as salts of a relatively weak acid increase the
pH when added to water or poorly buffered systems. This is, of course,
particularly apparent at 'kosmotropic' concentrations (>>1M). We have made
equilibrium runs in a low-strength pH7.2 buffer which had a measured pH of
9 after the addition of 3.5M KF. There was no apparent damage to any of the
cell components (ie they haven't fallen to pieces subsequently).
	Fluorides are particularly useful for establishing ionic strength in
solutions for spectroscopic studies because of their high UV transmission
(relative to chloride) and for this reason are favoured by CD
spectroscopists. As you might find them in samples from your clients, check
the pH first. 
	As a work of devotion to the RASMB community we have measured the
concentration dependence of the density of aqueous KF from 0-4.5M (DON'T
TRY THIS AT HOME). These measurements had no effect on the calibration
factors of the Paar densimeter and the data are currently 'in press'. If
anyone is interested in advance, let me know and I'll try to find them.
All the best
Richard
Richard M Thomas
Inst. für Polymere
ETH-Zentrum
CH-8092 Zürich
Switzerland
(tel) +41 1 632 5540
(fax) +41 1 632 1073