Test Lead at Home: How to Identify Unknown Metals

[DaveC426913]

(I think I might have asked this a few years ago...)

Looking for a home test for lead. I've got this lump off metal that I'd like to test.

I bought a lead test strip but it's inconclusive - it says there's low concentrations of lead even if I follow all directions and test twice using two methods (direct application and solution of flakes).

The lump is very much like lead. It is:
- dark grey when oxidized, shiny silver-grey when cut clean
- very heavy for its size
- ductile. I can mark it with a knife.

(Since I'm not sure what it is, I guess I should see if it's radioactive eh? Where's that roll of film?)

 

[pzona]

What kinds of chemicals do you have access to? I've got some ideas using precipitation reactions involving an acid and two compounds (one with the metal directly above lead on the activity series, and one with the metal below). You can probably see where I'm going with this, but I'll figure out details and post them when I get a chance.

 

[turbo]

I bought a couple of these kits, Dave, and ended up giving away (for decorative use only) or throwing out quite a number of items that my wife had bought over the years - most of them originating in China and bought at discount places like TJMaxx. The most common offenders were colorful pottery and ceramic items. The tests are sensitive enough to pick up lead in glazes, so I'm pretty sure that a surface-wipe on that metal would give you a good indication if it's lead or a lead alloy like solder or type-casting material containing lead and antimony.

http://www.leadinspector.com/

 

[DaveC426913]

What kinds of chemicals do you have access to?

Normal household. I could buy certain things if they're readily available. Not sure about special chemical compounds.

I bought a couple of these kits, Dave, and ended up giving away (for decorative use only) or throwing out quite a number of items that my wife had bought over the years - most of them originating in China and bought at discount places like TJMaxx. The most common offenders were colorful pottery and ceramic items.

This is a solid chunk of amorphous metal, outwardly textured like a rock, but homogenously metal.

The tests are sensitive enough to pick up lead in glazes, so I'm pretty sure that a surface-wipe on that metal would give you a good indication if it's lead or a lead alloy like solder or type-casting material containing lead and antimony.

http://www.leadinspector.com/

Test 1: I scraped the lump to get a shiny new surface. Applied the test strip (soaked with vinegar) directly to the surface for 15 seconds.
Test 2: Scarepd off a tiny pile of shavings into a cup. Soaked shavings in vinegar for several hours. Applied test strip to solution for 15 seconds.

Both showed 'low'.

So I consider the tests inconclusive. If it had registered 'zero' or 'high' I would have accepted it, but a 'low' rating is the last thing I expect.

 

[mrjeffy321]

Lead does not react with most acids very quickly (save for nitric acid), due to low solubility of the lead salts and the low position of lead in the reactivity series of metals.
But it will, slowly, react with acetic acid (vinegar) producing a solution of Pb+2 ions. Higher surface area on the lead in the acid, and higher temperatures increase the rate of reaction, but it is fairly slow.

One can precipitate Pb+2 ions out of solution with iodide (I-) ions, such as those found in an tincture iodine solution (like what you might use on a cut). The resulting precipitate of lead(II) iodide is a bright yellow color.
You might try this. But it assumes that you have enough lead ions in solution for you to actually see any precipitate you might form.

 

[mrjeffy321]

If you are successful in dissolving lead into solution, make sure and dispose of it properly and do not just pour it down the drain. Be very careful around soluble lead salts, not to mention the potential lead shavings you already made.

 

[Dadface]

Measure its density.The volume can be measured by water displacement.

 

[chemisttree]

You might try dissolving it in some HCl (muriatic acid). If you have access to some FeCl3(electronics store) add a little bit to your HCl solution to hasten the lead/acid reaction. When substantially all of your sample is dissolved (it should bubble during dissolution), withdraw a sample and dilute it with some water. Test using the lead test kit for water analysis. Adjust pH of the dilute solution with a solution of bicarb if necessary.

 

[Borek]

If it is lead you should be able to melt it in a can over gas stove. I was casting lead weights as a kid.

Just remember about ventillation and stuff.

--

 

[alxm]

If it is lead you should be able to melt it in a can over gas stove. I was casting lead weights as a kid.

Just remember about ventillation and stuff.

Actually, in terms of metals you can melt on a stove, zinc is more dangerous from a hazardous-fumes standpoint. The boiling point of lead is 1749 C, relatively high, versus 907 C for zinc.

 

[pzona]

Lead does not react with most acids very quickly (save for nitric acid), due to low solubility of the lead salts and the low position of lead in the reactivity series of metals.
But it will, slowly, react with acetic acid (vinegar) producing a solution of Pb+2 ions. Higher surface area on the lead in the acid, and higher temperatures increase the rate of reaction, but it is fairly slow.

One can precipitate Pb+2 ions out of solution with iodide (I-) ions, such as those found in an tincture iodine solution (like what you might use on a cut). The resulting precipitate of lead(II) iodide is a bright yellow color.
You might try this. But it assumes that you have enough lead ions in solution for you to actually see any precipitate you might form.

This is similar to what I was thinking. Lead (II) iodide is one of the most easily identifiable precipitates, but as DaveC said he mainly has household chemicals only, I don't know whether this will be feasible. Most iodine solutions sold for first aid anymore contain potassium iodide instead of just iodine, at least from my experience, and I don't know off the top of my head whether the lead would replace the potassium (I'm guessing not, since potassium is pretty high up on the activity series).

Maybe let the KI dissociate in a polar solvent and then add some filings from the unknown sample (don't know whether or not filing pieces off is feasible) to maximize the surface area. This is the best way I can think of to get lead (II) iodide, and detect the lead if it's there.

 

[mrjeffy321]

This is similar to what I was thinking. Lead (II) iodide is one of the most easily identifiable precipitates, but as DaveC said he mainly has household chemicals only, I don't know whether this will be feasible. Most iodine solutions sold for first aid anymore contain potassium iodide instead of just iodine, at least from my experience, and I don't know off the top of my head whether the lead would replace the potassium (I'm guessing not, since potassium is pretty high up on the activity series).

Maybe let the KI dissociate in a polar solvent and then add some filings from the unknown sample (don't know whether or not filing pieces off is feasible) to maximize the surface area. This is the best way I can think of to get lead (II) iodide, and detect the lead if it's there.

The iodide salt (which I guess, as you say, is KI) in the tincture iodine does contain iodide ions in solution. When mixed with lead ions, a precipitate will form. The lead does not need to replace potassium (as in a single replacement reaction) since the lead is already oxidized. It is a double replacement reaction where the PbI2 precipitate out and leaves KC2H3O2 still in solution.

Both acetic acid and iodide ions are readily available in household chemicals, namely vinegar and tincture iodine.

 

[Borek]

Iodine is very weakly soluble in water and due to its volatility is easily lost from the solution. Howerever, in the presence of excess iodides it reacts creating I₃^- anion

I₂ + I^- <-> I₃^-

and that makes iodine solution stable. This is fast and reversible reaction. So the solution still contanis excess iodides.

Whether it can be used for lead iodide precipitation is another question - iodine solutions are colored and I am not sure if the precipitate (assuming there are minute amounts of it) will be visible.

--
methods

 

[DaveC426913]

Measure its density.The volume can be measured by water displacement.

Yeah. I tried to do that. My equipment led to a ... very wide error margin in the data.

 

[DaveC426913]

Be very careful around soluble lead salts, not to mention the potential lead shavings you already made.

Crap. Really?

I just wiped them off the kitchen counter into the sink.

 

[alxm]

Crap. Really?

I just wiped them off the kitchen counter into the sink.

Ohfercryingoutloud!

Take some environmental responsibility.. wastewater treatment plants don't remove heavy metals.
That's going into my drinking water! (or well, someone's drinking water)

 

[DaveC426913]

Ohfercryingoutloud!

Take some environmental responsibility.. wastewater treatment plants don't remove heavy metals.
That's going into my drinking water! (or well, someone's drinking water)

This was very naive of me.

This rock has been sitting on a shelf in my office for a year or more. I at least had the sense to have my son give it up when he showed it to me (He's 23). He said he'd had it in his pocket.

Waitaminnit. I've got 20 pounds of lead sitting in my trunk for scuba diving. It can't be that bad.

 

[Bohrok]

Ohfercryingoutloud!

Take some environmental responsibility.. wastewater treatment plants don't remove heavy metals.
That's going into my drinking water! (or well, someone's drinking water)

Reminds me of a lab in chemistry where we were supposed to put our solutions with metals (small chunks of them!) in a container and we were told not to put them down the sink. Since the teacher didn't put out a container till I asked him where to put the stuff at the end of the lab (and I was the last one), everyone else had forgotten or didn't bother, and put them down the sink... :yuck:

 

[mrjeffy321]

Lead in its solid, elemental, form can be slowly absorbed into your body by touch. Minor contact with it here and there is generally no big deal by itself. But it accumulates in your body over time and might eventually reach dangerous levels from chronic exposure.

Although absorption of solid lead into the body is relatively slow, water-soluble lead salts on the other hand are much more readily absorbed and pose a much greater danger. It is best to only generate and use lead salts in moderation and it dispose of them through the proper channels. Many cities have an environmental-waster disposal facilities where people can bring them their waste (such as lead paint, motor oil, …., other nasty stuff that should not end up in landfills or down the drain) and they will dispose of it for you for free. This would be the preferred way for an individual to dispose of lead waste.

Lead shavings also pose a greater risk compared with just a large solid lump of lead metal since there exists the possibility of breathing in some of the smaller flakes or accidentally ingesting them. So one might be wise to wear a mask and wash one’s hands thoroughly while / after handling fine flakes of lead.

 

[chemisttree]

He still hasn't determined if his lump of metal fogs unexposed film...

It could be worse, y'know.

 

[Dadface]

I think it's kryptonite.

 

[Borek]

Nah, IIRC kryptonite was green.

 

[DaveC426913]

Nah, IIRC kryptonite was green.

That depends. What colour are the Frogstar Fighters in your universe?

 

[DaveC426913]

OK, radioactivity: zero.

I would not have been amused to find out that I've been storing a lump of Plutonium on my office shelf...

 

[pzona]

Well the good news is since it's not radioactive, it has to be one of the first 82 elements, so lead is still a possibility. Also, you don't have to worry about pesky radiation messing with your cells :)

 

[Borek]

Well the good news is since it's not radioactive, it has to be one of the first 82 elements

Unfounded speculation.

--

 

[DaveC426913]

Unfounded speculation.

How so? It could be a higher element yet not be radioactive?



Why is your sig part of the body of your message?

--
buffer calculator, concentration calculator
pH calculator, stoichiometry calculator

 

[chemisttree]

Perhaps he is referring to Bismuth (atomic # 83).

 

[turbo]

How so? It could be a higher element yet not be radioactive?

Thorium 232 has a half-life of over 14Gy, so you might not be able to detect much radioactivity. Chances of you having a decent-sized chunk of it hanging around your house are pretty slim, though.

 

[chemisttree]

Same is true for Bismuth 209. Half life something like 2 X 10¹⁹ years.

 

[pzona]

Let me rephrase. Since it's not radioactive, it is most likely one of the first 82 elements. I understand that some higher elements could fall into this category (for example, bismuth-209, as was said), but how often do these elements present themselves in such large quantities in everyday life?

 

[Borek]

Let me rephrase. Since it's not radioactive, it is most likely one of the first 82 elements.

Unless it is technetium :tongue2:

 

[pzona]

Geez Borek, you and your exceptions :p

 

[Borek]

They are not mine, they are around

--

 

[DaveC426913]

OK, I took my sample into my brother's lab to test its density.


We measured its volume by dropping it in a full beaker of water and measuring the weight (and thus volume) of the water that was displaced on a microgram scale. By far the biggest problems we had were:
- eliminating the meniscus so we cold get an accurate water level, and
- ensuring that we drained all drops from the exteroir of the beaker onto the weight scale.

We used combinations of alcohol and/or hand soap to minimize the meniscus and used a microlitre pipette to recover any drops that lingered on the beaker. My brother, having spent decades in the lab, was able to estimate the few microlitre drops remaining and added them to the test sample. We figure we got our volume measurements to within +/-20 microlitres. We did the experiment 3 times.

Results:
The sample weighs 116.06g.
The volume is 10.13, 10.56 and 10.64 cm^3 for an average of 10.44 cm^3.

This results in a density of 11.12g/cm^3 +/- 0.02.

The published density of common lead is 11.34g/cm^3.

My measurement of the sample is within 2% of the density of lead.

I'm callin' it lead.