With fear and trembling, I must disagree with John Kiernan here. We 
check our colloidal gold (and other metals), and gold chloride 
solutions with a pH meter. We use a gel filled electrode instead of 
the standard porous glass electrode. There are also solid-state 
electrodes available for testing the pH of anything, including mud 
and peanut butter. (Hey, it's something to do during lunch ... )

Phil

>There are a few solutions, notably those containing gold,
>that must be tested with paper because the metal ions can
>permanently damage the glass electrode of a pH meter.
>
>  John A. Kiernan,
>  Department of Anatomy & Cell Biology,
>  The University of Western Ontario,
>  LONDON,  Canada  N6A 5C1

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Philip Oshel
Supervisor, AMFSC and BBPIC
Dept. of Animal Health and Biomedical Sciences
University of Wisconsin
1656 Linden Drive
Madison,  WI  53706-1581
voice: (608) 263-4162
fax: (608) 262-7420 (dept. fax)