From: Sandy King (sanking@clemson.edu)
Date: 02/19/03-04:27:36 PM Z
There is one thing about the recipe I did not understand. If you make
the ammonium citrate following Philippe's recipe, what percent
solution of ammonium citrate do you wind up with?
Sandy King
>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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