From: Richard Sullivan (richsul@earthlink.net)
Date: 02/19/03-09:12:13 AM Z
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
At 03:42 PM 2/19/2003 +0100, you wrote:
>Hi Bob,
>
>You don't need a pH meter. You just need your nose.
>Starting with a solution of citric acid, when agitating, pour slowly
>ammonia in it. Step by step. At each step, if you smell above the beaker,
>it won't smell ammonia at all. When it starts smelling ammonia, ad a pinch
>a citric acid to neutralize the smell of ammonia. You have perfectly pure
>ammonium citrate. (As the by-product is water).
>You don't need to know the concentrations of ammonia neither with this method,
>
>Cheers,
>
>Philippe
>
>|-----Original Message-----
>|From: Bob Kiss [mailto:bobkiss@caribsurf.com]
>|Sent: Wednesday, February 19, 2003 15:27
>|To: ALT PHO PROC.
>|Subject: DUMB QUESTIONS #107 & 108
>|
>|
>|DEAR LIST,
>| I have been getting great results processing my Pt/Pd
>|prints in Ammonium
>|Citrate and I want to continue with the same results for a
>|show where the
>|deadline is looming. I am running short on Am Cit developer
>|(I top up the
>|volume at the end of each printing session). We have many
>|things here in
>|B'dos but I cannot seem to find Ammonium Citrate and it is
>|either expensive
>|or a long wait to ship it in.
>|Dumb Q #107: Is it possible to titrate clear ammonia from the
>|grocery store
>|(no soap or anything else in it, just ammonia and water) with
>|citric acid
>|until my blue litmus paper turns just red? Won't this give me ammonium
>|citrate with just the slight acidity that Pt/Pd likes? Is the
>|store bought
>|ammonia too weak? Will this cause heating, boiling, toxic
>|gasses, and other
>|nasty results?
>|Dumb Q #108: I can get Sodium Citrate which I know is another Pt/Pd
>|developer but I believe it will yield different tones and I
>|don't want to
>|change horses in mid stream. If I cannot do #107 above, is
>|there anything I
>|can add to Sodium Citrate (I can get Ammonium Carbonate) to
>|produce Ammonium
>|Citrate? I was worried that Sodium Citrate plus Ammonium
>|Carbonate would
>|yield Ammonium Citrate plus Sodium Carbonate but that the
>|Sodium Carbonate
>|would leave the solution too alkaline to be a good Pt/Pd developer.
>|****Please give me suggested volumes and masses of the
>|ingredients. Please
>|consider that it will be a 30 km drive here in Barbados to the
>|nearest pH
>|meter.
>| So I am hoping that I can rough it suggested amounts and
>|litmus paper.
>| CHEERS!
>| BOB
>|
>|Please check out my website:
>|www.bobkiss.com
>|
>|
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