Many (but, not all) MRIs and catscans are done on Dryview or other "Dry" type film. Also, they use it for "regular" x-rays. To strip this, we used 4% caustic soda at 200F and tumbled it chopped up for an hour. Even then, a special proprietary additive, that I can't divulge, was required to get 100% of the black silver layer off of the PET plastic. I don't think that oxalic acid will touch it. Check some of the older posts by Manuel. I think he mentioned that a certain solution containing some alcohol would strip it. A big problem is that, when you get a container of film these days, it is usually a mixture of common "wet" halide rare earth film and "dry" film. When developed, these 2 types look identical (almost) and are almost impossible to sort. We did have a couple of guys that could sort it (fairly well), but they had been doing it for years. I can't sort it without checking each sheet with a cigarette lighter. I've detailed that method several times on the forum.
Since each sheet of film is different, it is a worthless exercise to base film values on running one or two sheets - an average of what to expect on various type film is the only important thing. The only exception to this is the "dry" type film. Since no silver is removed during developing, each sheet of the same size will yield exactly the same, whether developed or undeveloped, assuming it is of the same type and by the same manufacturer.
Your yields show a value of 1.56% or, .227 tr.oz. of silver/pound of film. Totally impossible unless the film is (1) of an earlier variety at least 27 years old, (2) the film was custom made (extremely unlikely), (3) it was industrial x-ray and not medical x-ray film, (4) it was 4 mil litho film, which actually looks totally different than x-ray film, or (5) Production screwed up on a batch and put on too much silver and this somehow got past QC. On this link, the included chart is based on the processing yields (and my approx. 6000 assays) of about 50 million pounds of all types of film scrap from all over the US. This chart is DEAD ON and, if you're wise, you'll accept these numbers as gospel. If you use your own figures, you'll quickly go broke.
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=3735&p=50819hilit=rare+earth+litho#p50819
Also, check this earlier thread.
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=7361&hilit=litho+chart+dryview
How do I know your numbers are way too high? If this were undeveloped (green) rare earth film, 100% of the silver would still be on it and the highest value I've ever seen is .20 oz/# (1.37%) and the average is about .18 (.123%). If it's developed rare earth film, which it probably is, the worst I've seen are chest shots, which can run as low as .065 oz/# (.45%). The best I've ever seen ran .14 oz/# (.96%) and I'm thinking that was from Sri Lanka. On average, day in and day out, it will run .10 oz/# (.69%).
I have no idea how you got such big numbers but I would guess that if you were to borax melt those powders (if they will melt) and weigh the beads, it would bring things back to reality.
Please don't take offense on what I've written, kjavanb123. I just don't want others to think this stuff is worth more than it actually is and lose money on it.
