RE: Lithium palladium vs. "normal" palladium
Hello Eric, It is good that you mention this. I did some reading again last week on the available chemistry publications and there is something my eye fell on. Mike Ware states that the molar ratio of ammonia ferric oxalate to ammonia tetra chloro palladate is 2 :1 to complete the reaction: Reaction 1 hv = 2[Fe(C2O4)3]3 => 2[Fe(C2O4)2]2- + C2O42- + 2CO2 Reaction 2 [PdCl4]2- + 2[Fe(C2O4)2]2 => Pd + 2[Fe(C2O4)2]- + 4Cl- But, if you read the manual of Jeffrey Matthias (which I took for a long time as my guide) you will see that he uses a ratio of 1:1 (NH4)3Fe(C2O4)3.3H2O >exposure> Fe(C2O4)2 + 3(NH4) + 3H2O + 2CO2 3Fe(C2O4)2 + 3Li2PdCl4 + 3(NH4) + 3H2O => (NH4)3Fe(C2O4)3.3H2O + 2(FeCl3) + 6LiCl + 3Pd + 3(C2O4) And Jeffrey states also : 'Or other metallic salts could be substituted. Every three sensitizer molecules will pair with three metallic double salt molecules, a one-to-one ratio (1 metal salt for 1 sensitizer).' This difference is substantial. I asked Mike Ware about it and Jeffrey Matthias. Jeffrey replied me as follows : 'Remember that my work is based on empirical study, not theoretical. This means that I am explaining things as they show themselves to behave through experimentation, not by the science of what they should or are doing. I realized that I do not have the training and experience in ionic theory as others, but I did have the time and patience to carefully run some calibrated experiments. If the suggestion is that a print can be made with less metal than the threshold, the result will be a weak print. Additional metal will just be wasted. The statement: "The correct stoicheiometry for trisoxalatoferrate(III) to chloropalladate(II) in the sensitizer is indeed 2:1."(quoting Mike Ware in an e mail to me) " is hard for me to understand. This is why I like to use the compound's formulae rather than its name. I suspect that what is being called 2:1 is the same as I have called 1:1. The bottom line is figuring how much of each substance to put into the solutions. What I call 1:1 is consistent with historic formulas and works. If this is really 2:1 then so be it. But, if it is suggested that twice or half as much sensitizer is to be used or twice or half as much metal solution, I know that will produce a problem in the print.' Of course my suggestion to Jeffrey was not 'that a print can be made with less metal than the threshold' but that you loose a lot of metal if the ratio of the reacting compounds is not right. My suggestion is to run a series of new tests with the different (2:1) ratio's. I have not calculated the B&S concentrations so I can't say from what equations they start. Maybe Richard can tell us some more about it? Witho -----Oorspronkelijk bericht----- Van: Eric Neilsen [mailto:ejnphoto@sbcglobal.net] Verzonden: woensdag 17 januari 2007 0:52 Aan: alt-photo-process-l@usask.ca Onderwerp: RE: Lithium palladium vs. "normal" palladium > Eric, > > Thanks for the information; it's amazing how much there is to learn about > pt/pd printing. > > > > 2 Moles of [Li, NH4, Na] Cl, to 1 mole of > > PdCl2. How you decide to dilute it is up to you. > > How do different dilutions affect the print (color, dmax, etc.)? Just out > of curiosity, which dilutions do you (and others) use? > The idea is to match the solution strength of the metal salts with that of the Ferric; either AFO or FO. One can get bad Dmax or extra contrast depending on which way the equation is set. > > > How does one make there AFO, or FO is equally > > important. The numbers are not etched in stone but the results nearly > are > > :) > > Not sure I'm following you here. Are you saying that there is an "ideal" > dilution of AFO/FO for a given dilution of pd, or are you simply saying > that the AFO/FO dilution, whatever it may be, plays a significant role in > print results? > Yes, equal to required needs. When you look at % solutions and matching them with molar solutions, that can be an easily lost battle unless you know the equivalent for each. What is a molar solution? A 1 molar solution is the formula weight to make 1 liter of solution. Note I did not say add to 1 liter different solution. You can see in Ware/Malde there is a .7M solution of both the ammonium based palladium and platinum salts. The AFO is mixed at 1.4M. And I see the mixing of solution / reactants like this, If you are going to error on one side or the other you should error on the side of too much of the catalyst. So for mixing your metal salts, the extra would come in the form of a little extra chloride cation _ the sodium, ammonium, lithium, because with out it, the PdCl2 can not get into solution. And like wise, add extra AFO,FO because without it the precious solution of PT / PD will sit in the paper with no enough available Ferric to convert it into the new "black" state that forms your print. I mix my solutions as close to .7 M as possible. The B&S solution are quite a bit less than .7 M. That is not to say that they are wrong, but it might be a possible reason that many seem to require and extra coating to get good Dmax. Jeffrey Mathis has an extensive write up about optimizing the solutions. I might not agree with everything there, the idea is a good one. Coat a variety of amounts, and see what gives you the best Dmax, color, contrast. Find out what this ingredients really do, not just what someone else has settled on. Eric Neilsen Photography 4101 Commerce Street Suite 9 Dallas, TX 75226 http://e.neilsen.home.att.net http://ericneilsenphotography.com Skype ejprinter
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