From: Monnoyer Philippe (monnoyer@imec.be)
Date: 02/19/03-09:58:52 AM Z
Hi Dick,
You explained it rigourously right and in more details than I did.
Cheers,
Philippe
|-----Original Message-----
|From: Richard Sullivan [mailto:richsul@earthlink.net]
|Sent: Wednesday, February 19, 2003 16:12
|To: alt-photo-process-l@skyway.usask.ca
|Subject: RE: DUMB QUESTIONS #107 & 108
|
|
|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
|>|
|>|
|
|
|
This archive was generated by hypermail 2.1.5 : 03/04/03-09:19:09 AM Z CST