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Quick way to tell lead from low melting pt metal?

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  • Quick way to tell lead from low melting pt metal?

    I have lumps of metal from long ago projects, some are lead, some are low temp melting, 158 F according to the one virgin ingot. Probably back then I knew which was which. Short of putting them in a pot of boiling water, does anyone have a quick and easy way to tell them apart? And don't say lead test kit, they're pricey.

    Mcmaster has a 158 alloy listed as 50% Bismuth; 27% Lead; 13% Tin; 10% Cadmium. Did I really buy sh*t with cadmium? Those were the carefree days.
    Last edited by gellfex; 08-07-2016, 03:42 PM.

  • #2
    These metals are both so soft that you could cut a tiny bit off with a knife to test.

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    • #3
      Melting them is simple ?
      However, if you don't want to melt them, then do a desity test.
      Weigh a known sample of lead , and then drop it in a beaker full of water.
      The water that over flows can be measured in liquid volume, or weight and that will tell you the displacement of the sample.
      Then do the same for your mystery metals and it will tell you which is which.

      You have been listening to the PC Police. Cadmium is harmful IF IT IS HEATED TO VAPORIZATION.
      Using it in silver solder means reaching the hazourdous level if precautions are not taken.
      I bet that some of the nuts and bolts in your shop are "Cad Plated"

      Rich

      Lead is 6.555 ounces per cubic inch or .409 Lbs per cubic Inch
      versus
      .339 Lbs per cubic inch for Cerroloy 158
      Last edited by Rich Carlstedt; 08-07-2016, 05:01 PM.

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      • #4
        Rich, so what about all the cadmium paint warnings? Only for artists who lick their brushes? The boiling pt of pure cadmium is 765 oC, but the melting pt is listed as 321.1 oC. If I recall chemistry, the mixing of metals changes the melt of the alloy but not the vaporization of components, like distilling they will vaporize at their own temp. Or will they? IS alloying the same as a solution? I wouldn't be surprised if the answer was no.

        But your comment makes me feel much better about doing a tabletop special effect with molten 158 for a commercial way back when.

        So far dropping a small sample in boiling water sounds easier than the scientific way for measuring it's density. That had already occurred to me. Even just drilling it might work, for the sample, and I think I recall the 158 was far brittler than lead.

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        • #5
          Lead Check?
          http://leadcheck.com
          Sole proprietor of Acme Buggy Whips Ltd.
          Specialty products for beating dead horses.

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          • #6
            Look up the hardness of the alloys and scratch test.
            If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

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            • #7
              Surely, if you pour boiling water over a sliver of the low melting point alloy, it would melt and a sliver of lead would not, it's not rocket science!

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              • #8
                Originally posted by Beazld View Post
                That's a cunning plan but the instructions state it will indicate the presence of lead.
                The low melting point alloy contains lead and the leadcheck instructions don't say how to test for lead concentration in a sample or the difference in lead concentration between two samples ;-)
                If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

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                • #9
                  I'm starting to think waking up is bad for your health & dangerous for you.
                  "Let me recommend the best medicine in the
                  world: a long journey, at a mild season, through a pleasant
                  country, in easy stages."
                  ~ James Madison

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                  • #10
                    Originally posted by flylo View Post
                    I'm starting to think waking up is bad for your health & dangerous for you.
                    The only thing worse is going to sleep ;-)
                    If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

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                    • #11
                      Originally posted by flylo View Post
                      I'm starting to think waking up is bad for your health & dangerous for you.
                      I've always found that to be true. I usually put it off for as long as possible.

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                      • #12
                        Have a laugh now, smell it, yes that's right I've got lead poisoning I'm sure.
                        Oddly lead has a musty sickly smell, you notice it more if you leave it in a bag to sweat with some damp tissue, it's similar to antifreeze aka glycol.
                        Most metals have distinct smells with the exception of platinum, gold and silver, they do but I'm told dogs can smell them.
                        Ps manganese is the worst smell known, it's like stale piss, I never liked climbing into the manganese bunker (mainly because of the bloody big door at the bottom, and I didn't care if I had a harness on or not), it smelled rank in there.
                        Now everyone will be sniffing bits of metal, don't bother if you smoke your likely to be noseblind.
                        More sensibly do the Archimedean crown test, displacement to get volume as suggested, more scientific than sniffing!
                        ( I'm not joking about metals smelling but would not advocate it as an analytical method btw, just a bit of humour)
                        Mark

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                        • #13
                          When I scratched a piece of lead and piece of Cerrobend, the lead seemed softer. The Cerrobend is shinier, but that may just be because it is newer than the lead ingots I have laying around.

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                          • #14
                            The boiling water test is good.

                            The cadmium isn't going to jump out of the material and stab you. At any temp it has a vapor pressure, which as a solid, or in boiling water, is going to be a lot less than at its own boiling point.
                            1601

                            Keep eye on ball.
                            Hashim Khan

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                            • #15
                              It turns out all it takes is a scraper. The 158 is way more brittle as I recalled, and will flake off when scraped, while lead peels cleanly. But that does make me wonder about one of the advertized uses for the stuff, filling tubes for bending. Wouldn't the brittle metal crack in there? Or is it ductile "enough"?

                              BTW, here's the project that's got me breaking out my lead stash. Fluke fishing bucktails, 3/4 oz to 2 oz. Machined the mold with ball end mills.

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