ldanielrosa
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determining alloy elements in lead, and more
I'm sure it won't be easy, but I'm not afraid to expand my supply list.
At the moment I'm melting down old wheel weights for milling balls, but I may use some of it to mix up bronzes too. The weights have some antimony in
them, but is there a fairly straightforward way to determine how much?
I'm also trying to figure how clean the slag from the cutting table is. The stuff is mostly magnetite, but when I put some in a jar with HCl, I got
what looks like iron powder on the bottom of the brown liquid I expected. Did some of it reduce? Is there another test I should try?
Last item. The school gets some aluminum millings from a boat business, but we can't really control the impurities that come with it. I'm already
trying to get a ratio of junk vs. aluminum/alumina with HCl, but beyond that I'd like to have a good guess to the metallic content and the oxidized
content of these shavings.
This really has legitimate purposes- every year one of the instructors demonstrates the Goldschmidt reaction for casting and welding applications.
This runs pretty dirty because of the unknowns in the materials, and I'd like to help fine tune the demonstration.
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blogfast25
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Quote: Originally posted by ldanielrosa  |
I'm also trying to figure how clean the slag from the cutting table is. The stuff is mostly magnetite, but when I put some in a jar with HCl, I got
what looks like iron powder on the bottom of the brown liquid I expected. Did some of it reduce? Is there another test I should try?
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Assuming the slag is a mixture of magnetite and iron, only prolonged boiling in strong HCl or H2SO4 would cause it to dissolve, especially of the
magnetite was annealed. Basic chemtexts tell you most metal oxides are soluble in acids but don't tell you the conditions in which the dissolution
takes place: many calcined d-block metal oxides are pretty impervious even to the hottest/strongest mineral acids...
| Quote: Originally posted by ldanielrosa | Last item. The school gets some aluminum millings from a boat business, but we can't really control the impurities that come with it. I'm already
trying to get a ratio of junk vs. aluminum/alumina with HCl, but beyond that I'd like to have a good guess to the metallic content and the oxidized
content of these shavings.
This really has legitimate purposes- every year one of the instructors demonstrates the Goldschmidt reaction for casting and welding applications.
This runs pretty dirty because of the unknowns in the materials, and I'd like to help fine tune the demonstration. |
For thermite (Goldschmidt) reactions for welding purposes the presence of some alumina in the aluminium shouldn't be a great problem. It will make the
reaction run a littler slower and a little cooler but for welding applications you don't want a mix that just goes 'pooooooffff!' in a couple
of seconds. Most welding mixes will have been formulated specially to run a bit slower. The alumina ends up in the slag anyway.
To separate the alumina from the aluminium in millings/cuttings will depend on the state of the alumina. Relatively weak solutions of mineral acids
should be able to dissolve the metal (it's very reactive), leaving behind the oxide. If some of the oxide goes into solution you'll get false
readings. How are you planning to finish the assay anyway?
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not_important
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Got a decent balance/scales? A crude method would be to weigh a sample of lead, preferably as turnings, filings, small shot, &ct.
Treat the sample with dilute nitric acid (concentrated HNO3 diluted with 1 to 2 volumes of water). As the reaction slows down, warm the mixture until
all reaction appears to cease. Dilute with an equal volume of water, filter, wash any precipitate twice with water with a drop or two of HNO3 in it,
add the wash water to the original filtrate.
Use ammonia to adjust the pH of the filtrate to around 5-6. Add a solution of ammonium sulfate to precipitate PbSO4. Filter, wash the ppt with some
cold very rather ammonium sulfate solution.
Any solids left from the nitric acid dissolution of the sample are oxides or antimony, as yellowish Sb2O4, and tin. Assuming there is no tin the
Sb2O4 can be dried at a low temperature and weight. The lead sulfate can be weight and dried as well, simple math will give you the proportions of Pb
to Sb.
The filtrate from the precipitation of PbSO4 will contain ammonium nitrate and sulfate, and any other metals that were in the lead.
I'd suggest doing a test run or two to get a feel for how much acid and sulfate are needed - you can calculate the amounts and use some in excess,
particularly with the acid, but a test run in nice to confirm.
As for the slag from the cutting table, yup - long heating with HCl is needed. After it's been chewed on awhile, addition of small amounts of HNO3 may
help things along. There well may be silicon in there, silicon containing alloys tend to be acid resistant, as well as alumina and refractory
carbides.
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