EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: Refrigerator on May 05, 2021, 11:44:50 am
-
Found this weird chunk of metal in the garage, no idea what metal it is.
All i know is that some 15 years ago when me and my brother were kids he told me that you rub this metal on the bench grinder stone to clean it.
But i doubt that's true. ;D
The metal is non magnetic and feels quite dense. The structure is very crystalline and it's very brittle, the crystals are huge and very long.
It seems very resistant to tarnishing, this piece is many years old but despite dirt still has shiny spots where it was broken long ago.
I tried breaking a piece off with pliers but it seems the metal is quite hard and breaking a piece off is not that easy.
Once i managed to knock a corner off it revealed some very shiny metal underneath.
It leaves me wondering what metal or alloy of metals this is, my closest guess would be bismuth but i'm not sure.
I have not yet tried melting the metal.
Any guesses? :)
-
Interesting. :-//
-
Could be many things! If it is a "wheel dressing stick" it will be a composite of a very hard material, e.g. tungsten carbide or even diamond, sintered into a solid block. Norten make a proprietry stick that has a grey-ish appearance - sintered boron carbide - look up "Norbide wheel dresser".
-
Are you sure it's a metal? Did you measure the electrical resistance? Does it read near zero, when measured with a DVM set to Ohms? Note you might need to stab it quite hard with probes, to break the oxide layer.
-
Can you get an idea of specific gravity (weigh it, weigh its water displacement)? Does it dissolve in HCl or H2SO4? NaOH solution? And if so, what color is the solution?
The long crystals resemble either a cross section from the Van Arkel–De Boer process, or condensed/sublimated material. I suppose it could be directionally solidified and fractured too.
Tim
-
Are you sure it's a metal? Did you measure the electrical resistance? Does it read near zero, when measured with a DVM set to Ohms? Note you might need to stab it quite hard with probes, to break the oxide layer.
Didn't need to stab at all, only the dirty spots resisted some but that's just because i had to poke through the dirt.
DMM beeps with very little probe pressure.
-
Can you get an idea of specific gravity (weigh it, weigh its water displacement)? Does it dissolve in HCl or H2SO4? NaOH solution? And if so, what color is the solution?
The long crystals resemble either a cross section from the Van Arkel–De Boer process, or condensed/sublimated material. I suppose it could be directionally solidified and fractured too.
Tim
I'd have to find my scale first. Funny how i bump into it all the time but when i need it the damn thing is gone, nowhere to be found.
I boxed most of my stuff when renovating the lab so i'll go look in the boxes.
Buti agree, a specific gravity measurement would be a good start.
I have some battery acid on hand i'll try dropping a few pieces in, a great opportunity to try out my ebay test-tubes.
-
The metal reacts quite actively with sulphuric acid since there's quite some bubbling.
The solution appears to remain clear besides some floaties at the top, which may be just dirt from the surface since i didn't clean the metal before dropping it in.
The reaction is undoubtebly between the metal and the acid, not the dirt because the reaction has been going for quite a few minutes now and seems to have only sped up.
-
Calcium? See https://www.wikiwand.com/nl/Calcium (https://www.wikiwand.com/nl/Calcium) .
Burn a bit of the cleaned-up stuff and see what color the flame is. Compare to attached.
-
Calcium? See https://www.wikiwand.com/nl/Calcium (https://www.wikiwand.com/nl/Calcium) .
Burn a bit of the cleaned-up stuff and see what color the flame is. Compare to attached.
Well it's not calcium for sure, from wikipedia:
calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air
This chunk has been exposed to air for years.
-
Calcium oxidizes slowly in air. Magnesium? Neither is very heavy nor hard.
Suspecting something top-left transition metals, especially scandium, titanium, chromium, manganese, yttrium, zirconium. And of those, titanium should give a pink to purple Ti(3+) solution in sulfuric, chromium blue or green I think (but colored in any case), zirconium probably doesn't react at all, and scandium is very rare indeed. Manganese I think tarnishes more in air, but if not, may be a good candidate; it has a very pale pink color in solution, so it could be easy to mistake. Zinc, aluminum and other right-side transition and common metals aren't hard enough. Unless it's something really oddball like tellurium, which is also colorless in solution; but that's still not very hard, AFAIK.
We can certainly rule out iron, nickel and PGMs, which aren't colorless in solution, and besides iron, dissolve very slowly if at all in acid.
Once that metal stops bubbling much, if you can filter and neutralize it to get some hydroxide or carbonate (preferably use dilute NaOH, but baking soda will do), that may be informative. Also if the hydroxide dissolves in NaOH (amphoteric), or changes color over time (oxidation -- for example Mn(OH)2 is very pale, but quickly oxidizes to the brown Mn2O3).
As for intermetallics, who knows; many of them are hard, but I don't know of any that are commonly made in a crystalline form like that. Large crystals implies purity, and master alloys (often mixtures of intermetallics) don't need to be that pure.
Oh yeah and speaking of grinders, if it's so hard, it's probably going to be really hot when struck by a nice fast grinding wheel -- if it makes a bright shower of white sparks it's probably something like Ti or Zr, if dull red sparks it's probably something relatively inert, and if nothing at all it's probably not as hard as it seems. (Failing a proper metallurgical hardness tester, you could do the good old Mohs test using assorted items around the house.)
Tim
-
Calcium oxidizes slowly in air. Magnesium? Neither is very heavy nor hard.
Suspecting something top-left transition metals, especially scandium, titanium, chromium, manganese, yttrium, zirconium. And of those, titanium should give a pink to purple Ti(3+) solution in sulfuric, chromium blue or green I think (but colored in any case), zirconium probably doesn't react at all, and scandium is very rare indeed. Manganese I think tarnishes more in air, but if not, may be a good candidate; it has a very pale pink color in solution, so it could be easy to mistake. Zinc, aluminum and other right-side transition and common metals aren't hard enough. Unless it's something really oddball like tellurium, which is also colorless in solution; but that's still not very hard, AFAIK.
We can certainly rule out iron, nickel and PGMs, which aren't colorless in solution, and besides iron, dissolve very slowly if at all in acid.
Once that metal stops bubbling much, if you can filter and neutralize it to get some hydroxide or carbonate (preferably use dilute NaOH, but baking soda will do), that may be informative. Also if the hydroxide dissolves in NaOH (amphoteric), or changes color over time (oxidation -- for example Mn(OH)2 is very pale, but quickly oxidizes to the brown Mn2O3).
As for intermetallics, who knows; many of them are hard, but I don't know of any that are commonly made in a crystalline form like that. Large crystals implies purity, and master alloys (often mixtures of intermetallics) don't need to be that pure.
Oh yeah and speaking of grinders, if it's so hard, it's probably going to be really hot when struck by a nice fast grinding wheel -- if it makes a bright shower of white sparks it's probably something like Ti or Zr, if dull red sparks it's probably something relatively inert, and if nothing at all it's probably not as hard as it seems. (Failing a proper metallurgical hardness tester, you could do the good old Mohs test using assorted items around the house.)
Tim
I hit it with the angle grinder and there were absolutely no sparks that i could see.
Also it might not be as hard as i made it seems but when you're going at it with a pair of snippers it does appear harder than say lead or tin.
For the acid test i did manage to get some good purchase on one corner and peel some metal off.
Yes i said peel, the crystals delaminated and peeled off the main chunk it's so weird.
It's not titanium for sure since titanium creates bright white sparks, and it's not magnesium that much i can tell because i have some pure magnesium ingots and they don't weigh nearly as much as this chunk does.
I wonder can i just pour some of the acid solution into some ethanol and watch the color as it burns?
-
I think it is pyrite. I also found a chunk when I was a kid, though the metal content was much less.
-
My guess would be cobalt.
-
Some news!
Went to try the ethanol experiment but before that i noticed the acid solution was a little thicker than expected.
Actually it was not thick, turns out some clear white crystals precipitated out of solution.
It's some kind of sulfate/ite right?
Next i'll try pouring the acid off and mixing some ethanol into the crystals, maybe i can get some colour when it burns
-
My guess would be cobalt.
Cobalt Sulfate solution has a red color.
-
Zinc? Do the flame test to see the color. Zinc would give blue-green color.
(https://upload.wikimedia.org/wikipedia/commons/thumb/f/f9/Zinc_fragment_sublimed_and_1cm3_cube.jpg/800px-Zinc_fragment_sublimed_and_1cm3_cube.jpg)
-
It is probably zinc or a zinc alloy from the look of the structure along the broken sides and reaction to sulfuric acid. Flame tests are often contaminated by sodium which tends to overpower the color of other elements unless they are quite pure.
-
I wonder can i just pour some of the acid solution into some ethanol and watch the color as it burns?
Maybe. The ethanol may burn with an orange flame (carbon) if you don't provide enough oxygen (like a yellow flame from a Bunsen burner with the vent closed vs. blue flame when open).
You could let some of the ethanol solution evaporate on a suitable utensil. If you cook with gas, just put some on the end of a stainless steel knife and place it in the blue flame.
-
Adding ethanol really made the crystals crash out.
Burning the ethanol solution did not reveal much, other than some orange licks of flame, but those might be just an incomplete burn of the ethanol.
After the ethanol burned off there was no residue but the spot did smell pretty strongly of sulphuric acid.
I agree that it could be zinc, as i remember zinc is pretty dense and makes some large crystals.
-
I would also try making a hydroxide of that metal (Me + H2SO4 -> MeSO4, MeSO4 + NaOH -> Me(OH)n). Many of them have distinct colors and physical properties, which may help to identify the metal.
-
I put a piece of the metal on an old blade, gave it a bunch of heat with my butane burner and only when it got super hot did i see the slightest lick greenish/lime/cyan colour.
So it's between zinc and antimony.
-
Salts have poor solubility in ethanol so that doesn't say much. Take a few grains and hold them in said flame; as they get orange hot, they should burst into green-blue flames. Only zinc does this, the temperature and color being diagnostic. (Cadmium is close, but has a different color, and its oxide is yellow. Zinc oxide is yellow when hot, quickly turning snow-white on cooling.)
Tim
-
I put a piece of the metal on an old blade, gave it a bunch of heat with my butane burner and only when it got super hot did i see the slightest lick greenish/lime/cyan colour.
So it's between zinc and antimony.
Make sure you run the control experiment with just the old blade :)
-
I put a piece of the metal on an old blade, gave it a bunch of heat with my butane burner and only when it got super hot did i see the slightest lick greenish/lime/cyan colour.
So it's between zinc and antimony.
Make sure you run the control experiment with just the old blade :)
Haha, I was just thinking the same thing. :)
The look and SG of antimony and zinc are pretty close (what, 6.75 vs. 7?), but my personal guess is zinc. :popcorn:
-
I put a piece of the metal on an old blade, gave it a bunch of heat with my butane burner and only when it got super hot did i see the slightest lick greenish/lime/cyan colour.
So it's between zinc and antimony.
Make sure you run the control experiment with just the old blade :)
I did after and the greenish flame is coming from the mystery metal.
I also torched the white crystals and they turned a quite ugly yellow, some barely green-ish flame could be seen when burning the stuff.
I found some sodium hydroxide so i mixed up some in a test tube and it seems to react with the metal, so it seems that the mystery metal might in fact be zinc.
-
I put a piece of the metal on an old blade, gave it a bunch of heat with my butane burner and only when it got super hot did i see the slightest lick greenish/lime/cyan colour.
So it's between zinc and antimony.
Make sure you run the control experiment with just the old blade :)
Haha, I was just thinking the same thing. :)
The look and SG of antimony and zinc are pretty close (what, 6.75 vs. 7?), but my personal guess is zinc. :popcorn:
Yeah internet said antimony does not react with dilute sulphuric acid so it has to be zinc.
Feels a bit unusual finding just a chunk like that laying around.
-
Suppose it could be a sheared/broken chunk of zinc anode. Think those usually have a bit of aluminum in them for strength or something, but maybe it happened to be pure. Solidification shouldn't be too directional or slow, they're just cast in steel molds I would guess. Maybe if it's a fragment of a much larger piece, it would do. *shrug*
Anyway, if zinc be the base then, have fun, you can melt that with a bit of aluminum and even less copper to make zamak I guess? :P Make a smaller anode? Do some electroplating? (Needs some additives besides just the salt and acid.)
Tim
-
Suppose it could be a sheared/broken chunk of zinc anode. Think those usually have a bit of aluminum in them for strength or something, but maybe it happened to be pure. Solidification shouldn't be too directional or slow, they're just cast in steel molds I would guess. Maybe if it's a fragment of a much larger piece, it would do. *shrug*
Anyway, if zinc be the base then, have fun, you can melt that with a bit of aluminum and even less copper to make zamak I guess? :P Make a smaller anode? Do some electroplating? (Needs some additives besides just the salt and acid.)
Tim
I remember taking old batteries apart for the zinc but i can't remember what i needed the zinc for.
Anyways i might eventually find a use for it i think electroplating might be interesting, also tin and zinc alloy can be used for aluminum soldering.
-
Find some unwanted copper, a can of Coke and make a battery :)
https://scitoys.com/scitoys/scitoys/echem/batteries/batteries.html
-
Find some unwanted copper, a can of Coke and make a battery :)
https://scitoys.com/scitoys/scitoys/echem/batteries/batteries.html
There's something in the back of my head telling me that zinc is important and i should keep any i can find.
Looks like i might be revisiting some old chemistry experiments. ;D
-
There's something in the back of my head telling me that zinc is important and i should keep any i can find.
https://www.youtube.com/watch?v=jWpPrWHBHcQ (https://www.youtube.com/watch?v=jWpPrWHBHcQ)
-
Try melting some of it into a thin enough piece to bend. Pure zinc makes a distinctive crying sound when bent.
-
Try melting some of it into a thin enough piece to bend. Pure zinc makes a distinctive crying sound when bent.
Yeah i know that, also hapens when you bend steel plates that have thick zinc plating.
-
Cool fact, the "tin cry" (also exhibited by zinc, and I've sometimes had mild steel maybe do it, but maybe that was due to oxides or other impurities Idunno?) is due to shockwaves as the crystals deform -- IIRC, something about, the crystals have relatively few slippage planes and relatively high binding force, but not so much that they fail instantly in brittle fracture; the effect is, when a plane does slip, it goes off explosively, faster than the speed of sound in the material. Hence the crystal slips all at once, and you hear a tic. A cacophony of these going off at once, and you get some angry hissing sound, a "cry".
Zinc is hexagonal, and tin tetragonal, while most other metals are fcc or bcc cubic.
So also, they tend to be less malleable or ductile -- though clearly, not so much that they can't be shaped about easily as any other metal or alloy. Not that zinc sheet or wire has much use, but tin foil and sheet were handy back in the day, and tin wire, well that's also known as solder. :)
(I forget what all the whole story about this is, or how much I might be leaving out -- things like induced twinning, or creep, which relieve stress, increasing plasticity despite the above facts. Although, I'm pretty sure it's not creep -- which however is very much a property of lead, which makes it very easy indeed to form into sheet/wire, and is part of why leaded solder is relatively soft, and well, creeps under load, which you've seen if you ever left some solder hanging partially off the bench.)
Tim
-
Zinc is hexagonal, and tin tetragonal, while most other metals are fcc or bcc cubic.
That's true for tin above about 13degC. Below that, it undergoes a change in crystal habit resulting in a much more brittle substance. Back in the days when tin cans were made of tin, they were used to store fuel for (ant)arctic expeditions. Needless to say, it wasn't a good choice.
(Just another strange fact taught 40+ years ago that finally gets an airing :) )
https://en.wikipedia.org/wiki/Tin_pest
-
...and there's also https://en.wikipedia.org/wiki/Zinc_pest , more closely related to OP's metal.
-
sit it in a little salt water and measure the voltage between it and a piece of copper in the same salt water. Knowing the electrode potential of copper and the voltage out of this crude battery should give a good pointer to what metal it is.
If it didn't melt under the butane torch then its probably not zinc. Or not pure zinc at least. MP 420C for zinc.