Testing the purity of zinc

[qst42know]

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

 

[Lou]

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

 

[qst42know]

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?

 

[Anonymous]

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

 

[LittleJohnnyH2SO4]

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

 

[Harold_V]

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

 

[qst42know]

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.

 

[Harold_V]

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

 

[qst42know]

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.

 

[Platdigger]

How much do you have?

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

 

[qst42know]

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

 

[Lou]

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

 

[goldsilverpro]

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

 

[Platdigger]

I read that zinc is flamable.

 

[qst42know]

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.

 

[lazersteve]

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

 

[Platdigger]

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

 

[qst42know]

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:

 

[Lou]

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).

 

[jimdoc]

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