# Testing the purity of zinc



## qst42know (Mar 29, 2009)

Is there a simple test that can be done with common chemicals to test the purity of zinc?


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## Lou (Mar 30, 2009)

It should dissolve in dilute sulfuric acid with much hydrogen evolution to yield a clear solution with no sediment whatsoever.

If it can do that, it is probably pure enough for use. The offending ingredient in most atomized/powdered products seems to be fumed silica. Cab-O-Sil is the trade name.


Lou


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## qst42know (Mar 30, 2009)

Thanks Lou.

I suppose now is a bad time to mention that the material in question is a cast grounding anode not a powder.  

Would any possible aluminum content dissolved in sulfuric leave a residue or color in solution?


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## Anonymous (Mar 30, 2009)

was it a sacrafical (speeeling, LOL) anode in a previous life?


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## LittleJohnnyH2SO4 (Mar 31, 2009)

I'd just buy good, clean material in bulk from a metals supplier and not have to worry about purity. It's cheap enough stuff. I've gotten some metals from this company before and they were good, except the packaging was mildly lacking for some of what I bought. It would be a non-issue for a shipment of ingots like these, though: http://www.rotometals.com/product-p/zincingots.htm


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## Harold_V (Mar 31, 2009)

qst42know said:


> Thanks Lou.
> 
> I suppose now is a bad time to mention that the material in question is a cast grounding anode not a powder.
> 
> Would any possible aluminum content dissolved in sulfuric leave a residue or color in solution?



If you'd like to determine if there's aluminum present, instead of sulfuric, dissolve a trace in nitric instead. Aluminum won't dissolve, so if you find any traces of solids, you'll know it may contain aluminum. Any discoloration of the solution is an indicator that there is something besides zinc present. Blue=copper (or nickel). 

I dissolve zinc scrap to make a spray for killing moss on our roofs. Any copper that is present remains undissolved in the end. The solution is free of color. 

Harold


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## qst42know (Mar 31, 2009)

I'll test some both ways. If it tests well enough I'll use this material for scavenging the last PM's from my stock pot. It would probably be best to buy an ingot of known purity for any critical work.

Thanks for the help.


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## Harold_V (Mar 31, 2009)

If you're worrying about your stock pot, use scrap steel. You can usually find it free, and it doesn't create problems down the road. Zinc is fine, too, but not necessary..

Harold


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## qst42know (May 25, 2009)

A small sample dissolved completely in battery fluid (sulfuric). 

Encouraged by this I tried to melt and shot a small piece. The result was just before it began to melt it ignited. :shock:  

Anyone have any use for magnesium?

A quick check on the Internet indicates high quality direct burial anodes are magnesium not zinc.


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## Platdigger (May 25, 2009)

How much do you have?

btw, that must have been startling......the stuff burns bright


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## qst42know (May 25, 2009)

One anode is 3-1/4 pounds, the other is 7-1/8 pounds.


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## Lou (May 25, 2009)

Magnesium is one heck of a reducing agent. It will work in lieu of zinc, but it will bring down everything.


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## goldsilverpro (May 25, 2009)

We used to use magnesium to drop rhodium out of Rh plating solutions.


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## Platdigger (May 25, 2009)

I read that zinc is flamable.


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## qst42know (May 25, 2009)

I understand zinc dust is flammable. 

But this burned from a solid piece. Just as it began to slump a little a couple sparkles from a corner and poof, most of it was gone. I dumped the remains still burning into the water where it danced around on the surface for a while, still burning. I found one little nugget of metal in the water the rest was ash and white smoke.


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## lazersteve (May 25, 2009)

It may be zinc after all as I recall a high school chemistry class where we lit a ribbon of magnesium and placed it in a burette of water. 

The ribbon burned under water and produced hydrogen gas which we collected from the burette.

I also remember one of my firemen friends telling me that the rims on some VWs are made of magnesium and they can not extinguish them with water.

Steve


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## Platdigger (May 25, 2009)

Thats right, I have burned magnesium and when you throw water on it it flames up even much more.


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## qst42know (May 25, 2009)

Hmm.

So back to the original question but with a twist.

Is there a simple test that can be done with common chemicals to test the purity of an unknown metal, originally cast as an anode, that resembles both zinc and/or magnesium, may be a combination of both, and dissolves completely in sulfuric? 
:lol: 

I don't think this puzzle will be solved in my driveway lab :wink:


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## Lou (May 25, 2009)

I recall a qualitative test for zinc, but I want to look it up to have the specifics. I'll post it tomorrow evening.


Steve, most high performance sportscars have a lot of magnesium in them. Mag rims are fairly common as they're some 30% lighter than regular aluminum alloy. I think the firefighter was thinking of a magnesium transmission from a VW; VW's are notorious for having magnesium transmissions (in fact I have one such myself).


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## jimdoc (May 25, 2009)

Run flat tires are supposed to have magnesium inside there, I haven't seen any. Still looking for one to come into the junkyard.
Jim


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## solar seeker (Aug 4, 2010)

I would like some magnesium how much are you selling it for ? 
By the way I would use pennies, AA,AAA,C,or D size (not alkaline) battery casings for zinc unless I could find a cheaper and or larger source for zinc metal.


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## Anonymous (Aug 4, 2010)

jimdoc said:


> Run flat tires are supposed to have magnesium inside there, I haven't seen any. Still looking for one to come into the junkyard.
> Jim




When I took that last load of aluminum into the scrap yard, there was a partial case from a 4x4 transfer case that was magnesium. Wished I had kept it now I'm on the hunt.

The old lawn boy mowers had a mag deck, some chainsaws are also made from mag especially the older ones.

Regards
G


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## jimdoc (Aug 4, 2010)

solar seeker said:


> I would like some magnesium how much are you selling it for ?
> By the way I would use pennies, AA,AAA,C,or D size (not alkaline) battery casings for zinc unless I could find a cheaper and or larger source for zinc metal.



You can try Rotometals for zinc,that is where I bought mine.They have free shipping sometimes if you spend like $99.I think I got around 60 lbs. of zinc
http://www.rotometals.com/

Jim


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## solar seeker (Aug 5, 2010)

That's a good company which I'll begin looking into when I get skilled enough at recycling e scrap that I begin making money instead of losing it on the cost of chemicals.


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## jimdoc (Aug 5, 2010)

The key is saving up enough to make a batch worth while.
I save up my fingers until I have at least a kilogram,but
usually 5 lbs.Testing is one thing,but small batches are too 
easy to not see your results,or be very disappointed in them 
and lose interest.

Jim


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## solar seeker (Aug 5, 2010)

So how much gold can be expected from 5lbs of fingers ?


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## Oz (Aug 6, 2010)

All fingers are not created equal. Even in a generic desktop computer you will get great variation just in your expansion cards. A video card will yield better than most, and double the yield of some. Speaking of fingers and desktops, if all fingers are well trimmed the ram will beat them all based on starting mass.

I have not tried to do quantitative yields so I am more than willing to accept corrections here from those that have. These are just general observations based on yields from mixed lots that have run higher or lower as to the finger source materials. I typically refine fingers on a percentage so I get mixed lots.


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## butcher (Aug 6, 2010)

Magnesium oxidizes in atmosphere dark gray, aluminum or zinc does not oxidize the same.

http://www.weld-direct.com/base.htm

http://books.google.com/books?id=jEv3FdDeu4sC&pg=PA9&lpg=PA9&dq=magnesium+tin+aluminum++identification&source=bl&ots=y-ju_vc4Ho&sig=IA4zBFb2aq2Eioi3wW97IfHmeDg&hl=en&ei=Y89bTI7XBIu6sQObq5TsDw&sa=X&oi=book_result&ct=result&resnum=8&ved=0CC8Q6AEwBzge#v=onepage&q=magnesium%20tin%20aluminum%20%20identification&f=false
see page 10


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## jimdoc (Aug 6, 2010)

solar seeker said:


> So how much gold can be expected from 5lbs of fingers ?



It has been stated at 1-3 grams per lb for clean cut fingers.
I have averaged 2 grams per lb.So for 5 lbs of fingers I would
expect about 10 grams of gold.It takes me 6 months to a year
to save up enough fingers for a batch,since they are all free.

I was saying that small batches of say a few ounces of fingers 
will not yield an amount to be worth processing.In both chemicals
and your time.Unless you are just in the testing phase.
On small amounts of some scrap,like cell phone boards you may 
not even see your gold.

Jim


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