MadSci Network: Chemistry

Re: I can not coat Fe and Co ions on Tungsten wire, why?

Date: Wed Sep 22 03:06:09 1999
Posted By: Matthew B. Weyerich, Technical Coordinator,ES&R Dept., CPI Corp.
Area of science: Chemistry
ID: 934841282.Ch

Dear Friend:

It seems my computer has just "trashed" about two hours worth of response 
to you. I want to give you "some kind" of answer, so, here goes...

My company develops photographic film. There is a lot of silver involved in 
the processing. We try to save every penny so we can pass that savings on 
to our customers, so, it is to our benefit to "save" every bit of silver we 
can, and recycle it. We use processes very similar to the experiment you 
describe...except, think of everything magnified by a factor of 10 to 1000!

I can't tell you exactly what is wrong with your test set-up, as I don't 
have all the details. I asked a lot of people who know about this kind of 
thing, though, and they suggested the following:

1) Yes, increasing current could, at least, speed up your process. But do 
you have sufficient ionic concentration to do the job? 

2) Make sure your solution is pure. We have a rather complex set of 
processes dumping into the same tank. There are several diluents. These 
actually slow the plating process when we increase the amps [we're talking 
over a hundered, from what I understand!]because they suck up energy 
otherwise used to transport "valuable" ions. We actually find we do better 
by DECREASING the current after a certain point...more "art" than 
"science"...which differentially slows the "side-reactions" and "prefers" 
the main reaction.

3) STIR! We use a rotating cathode, in a huge bath, in a huge current. It 
does the trick, apparently, because it moves through a "field" of ions. 
(Even so, we have to pay people to "tweak" it. They often can't explain why 
it is working better, or worse, than yesterday. Like I said, "art" vs. 

4)If all else fails, try what my chemist friend said: add a pinch of salt!
I think this is goofy, as I'd assume you'd just attract the wrong ions, and 
ruin you results. But, she's a chemist, and I'm NOT, right! She says it 
sometimes helps.

I hope I've been of some little help. If you figure it out, please tell me 
what was in your way, as, everyone I've talked to says you should be seeing 

Your MadSci,

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