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Photo Forum / Film Photography / Darkroom / September 2003measuring small quantities
Does anyone here use phenidone devlopers made from scratch? I have trouble measuring small quantities, say less than 1 gramme. Is it reasonable to measure a larger weight (say 5 grammes), in a small Paterson graduate, then see how much volume it takes up, and divide by 5? Hi Michael, I, too, have a triple beam balance - an O-Haus, and I can comfortably measure 0.1 g. on it. So that is the way I go. Your query about conversion to volumetric measure runs a greater risk of inaccuracy, I think, both because of visual limitations and because of possible compaction problems. One NON-option is making a percentage solution of a gram and using a fraction of that solution. Anchell and Troop advise that phenidone does not keep well in stock solutions. TFDC, p. 24. They do note, however, that dimezone, a phenidone substitute, does keep well in solution. So, if that is available, a 1% solution of dimezone, would allow you to take 10 ml to accurately get 0.1 g. of dimezone. Francis A. Miniter >Does anyone here use phenidone devlopers made from scratch? I have >trouble measuring small quantities, say less than 1 gramme. Is it >reasonable to measure a larger weight (say 5 grammes), in a small >Paterson graduate, then see how much volume it takes up, and divide by >5? Phenidone keeps well in water for something like three months, but it does react and lose its effectiveness, which you can track by its progressive darkening from light pink to dark red-brown. By six months it is dark pink and no longer useable. It dissolves in many organic solvents, including acetic acid, and keeps for much longer (mine is still good after about 2 years). Dimezone is difficult to source in less than 25kg drums. David Foy > Hi Michael, > [quoted text clipped - 18 lines] > >Paterson graduate, then see how much volume it takes up, and divide by > >5? > Phenidone keeps well in water for something like three months, but it does > react and lose its effectiveness, which you can track by its progressive [quoted text clipped - 4 lines] > > David Foy Patrick Dignan reaserched phenidone probably more so than any other person. He, at his own expense, saw to it that it was removed from the HazMat list of materials. He recommends the use of sodium bisulfite. From his "Classic B&W Formulas" I have extracted the following formula. Water 800 ml 125*F Phenidone 1gr Sodium bisulfite 5gr Water to make 1 liter I believe he would recommend that the bisulfite be added first to the water. A note on temperature: Room or a little above has done well in my work. I've not worked with phenidone. Dan Yes, it is stable in an acidic environment and is hydrolyzed over time in an aqueous alkaline solution. Thank you for pointing this out. My statement should have been "Phenidone keeps well in a liquid developer concentrate for something like three months...", developers being alkaline. DF > > Phenidone keeps well in water for something like three months, but it does > > react and lose its effectiveness, which you can track by its progressive [quoted text clipped - 20 lines] > A note on temperature: Room or a little above has done well in my > work. I've not worked with phenidone. Dan I'm keeping 2% phenidone solved in very pure alcohol and no problems up to now. About it in bissulfite, see: http://www.udmercy.edu/crna/agm/phenvitc.htm In alcohol it has a longer life. Jorge >> Patrick Dignan reaserched phenidone probably more so than any other >> person. He, at his own expense, saw to it that it was removed from [quoted text clipped - 11 lines] >> A note on temperature: Room or a little above has done well in my >> work. I've not worked with phenidone. Dan The author of that paper, interesting though it is, made a fundamental mistake. Phenidone in aqueous alkaline solution is hydrolyzed by the alkali, not oxidized by combined or dissolved oxygen. Phenidone powder in contact with alkali is also. Phenidone powder deteriorates with extreme slowness, if at all, due to atmospheric oxygen. Attempting to preserve a Phenidone solution by excluding oxygen will be fruitless if the solution is alkaline. This discovery was the basis for a series of papers and patents in the early or middle 1950s, without which Phenidone would have remained in the laboratory. You are correct that it is preserved extremely well in alcohol, and in other organic solvents. It also keeps well in dry form -- the paper's deterioration data for Phenidone powder looks to me like a data problem, and in fact the author speculates about that, noting how difficult it is to weigh small samples accurately. The paper also perpetuates some confusion about the identity of Phenidone A and B, stating (incorrectly) that Phenidone B is Dimezone. As far as I can tell (I am not an expert but I do try hard), the various Phenidones are: Phenidone A (CAS 92-43-3) Phenidone B (CAS 2654-57-1) The Dimezones are: Dimezone S (CAS 13047-13-7) Dimezone (CAS 2654-58-2) Details can be found at http://www.james-robinson.ltd.uk/JR/jrweb0201.nsf/UPPL?OpenPage Lastly, some over-snipping of the post quoted below has left the impression that it was I who posted the information about Patrick Dignan's work with Phenidone. It was someone else. David Foy > I'm keeping 2% phenidone solved in very pure alcohol and no problems up > to now. [quoted text clipped - 22 lines] > >> A note on temperature: Room or a little above has done well in my > >> work. I've not worked with phenidone. Dan Sorry about it. Did not notice it at the time of posting. Jorge > Lastly, some over-snipping of the post quoted below has left the > impression that it was I who posted the information about Patrick > Dignan's work with Phenidone. It was someone else. > > David Foy > ...and divide by 5? Divide by 4. In laboratory work the procedure is refered to as quartation. When measuring small quantities be sure some other weight is added to the scale. Of course "small" is relative to the scale's capacity. I never weigh out less than 1gr of any thing and that with a tare of several grams. Dan > > ...and divide by 5? > [quoted text clipped - 4 lines] > capacity. I never weigh out less than 1gr of any thing and that > with a tare of several grams. Dan I have an Ohaus triple-beam. I am going to use a small Paterson graduate and fill it to the top mark with several powders (salt, sugar, flour etc) as a test for repeatability. RE: mikescarpitti@yahoo.com (Michael Scarpitti) On the shelf is an Ohaus two pan, single beam, 2000gr. balance. Years ago I used it to weigh quantities as little as 10mg. I'm still amazed at how well it moved when very nearly nothing at all was added to such a massive structure. I forget the details. I do still have the wire loop rider which I fashoned and was used on the beam. The long pointer was used to measure as it deviated from center. The center mark is indexed both sides. I'd suppose your triple beam uses agate and steel bearings. Although it is a bit make-shift the technique may give you a 10mg, even 1mg weighing wonder. I never did test the limits. Dan A frequent method is to mix up a percentage solution of phenidone in alcohol (ethyl and isopropyl both work), say 5 grams in 100cc, then use th appropriate amount in the developer. I use an Ohaus dial-o-gram scale, and it gives me sufficient accuracy to avoid the problem. I understand the low cost electronic scales also do a good job. > Does anyone here use phenidone devlopers made from scratch? I have > trouble measuring small quantities, say less than 1 gramme. Is it > reasonable to measure a larger weight (say 5 grammes), in a small > Paterson graduate, then see how much volume it takes up, and divide by > 5? > A frequent method is to mix up a percentage solution of phenidone in alcohol > (ethyl and isopropyl both work), say 5 grams in 100cc, then use th [quoted text clipped - 7 lines] > > Paterson graduate, then see how much volume it takes up, and divide by > > 5? I have used solutions of phenidone in methanol that were more than 6 months old with good results. You can get substantially pure methanol at auto parts stores in the form of gas line antifreeze. Measure 1 gram into 100 ml of alcohol and stir for a while. Even if the solution were to go really bad before you use it all, you will not have lost much. A yellow color is not a sign of "bad". That color will stabilize very soon after mixing if you use methanol. I'm using very pure ethanol (easy to find over here) to mix 250cc of 2% sol. at a time (my paper dev is phenidone based, so I use use plenty of it). Up to now, the solution ends before any sign of exaustion. Jorge > > A frequent method is to mix up a percentage solution of phenidone in alcohol > > (ethyl and isopropyl both work), say 5 grams in 100cc, then use th [quoted text clipped - 14 lines] > all, you will not have lost much. A yellow color is not a sign of "bad". That > color will stabilize very soon after mixing if you use methanol. |
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