From: Philippe Monnoyer (philippe.monnoyer@skynet.be)
Date: 02/19/03-01:00:28 PM Z
What percentage ammonium citrate do you want as starting one ?
Philippe
----- Original Message -----
From: "Pay" <payral@club-internet.fr>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Wednesday, February 19, 2003 7:09 PM
Subject: Re: DUMB QUESTIONS #107 & 108
> What percentage citric acid solution do you use as starting one ?
>
>
>
> Richard Sullivan a *crit :
> >
> > Yes,
> >
> > Philippe is correct.
> >
> > I might also add that ammonium citrate is strongly buffered and this
might
> > cause some confusion when making it.
> >
> > What happens is as you add ammonia the pH will gradually go up step by
step
> > more or less linearly to the amount of ammonia being added. When you get
to
> > 6.5 it will stop moving and at that point you can add a quite a quantity
of
> > ammonia without seeing a move in the pH and then suddenly the pH will
start
> > to move up again. It's a slope up, a flat spot and a slop up. As most
paper
> > will be alkaline today it is best as Philippe says to be on the acid
side
> > of the buffer point. Ammonium citrate is nice in this regard as it holds
it
> > pH pretty steady due to the buffer action. Philippe has a far more
> > knowledge of chemistry than I do so if I've not explained this quite
right
> > my apologies.
> >
> > --Dick Sullivan
> >
>
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