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Author: Subject: Safe preparation of lead oxides
Arcaeca
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[*] posted on 25-8-2019 at 17:54
Safe preparation of lead oxides


So I've been toying with the idea of making red pigment from lead - either lead tetroxide, aka "red lead" aka minium, or lead(II) oxide in its "letharge" form. They can apparently be formed by burning lead metal in air at certain temperatures.

I can easily get my hands on lead metal, and I can also fairly easily, uh, catch things on fire, but given the toxicity of lead I'm assuming just burning lead metal out in the open is probably not a great idea. And even if I did prepare them, I would need to grind the crystals formed up in a mortar and pestle, a process that would release lead oxide dust into the air that you'd definitely not want to breathe in and that my dust masks are probably not sufficient to block.

Can lead oxides still be prepared relatively safely, given certain precautions, or should I just not bother?
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TheMrbunGee
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[*] posted on 25-8-2019 at 20:06


You can make them at lower temperatures by melting lead with K/Na nitrate (not sure about other nitrates, guess the corresponding nitrite should not be explosive.) Doing this in well ventilated area with some PP (oxide dust flies around) should be safe.

I have done this but I have never got the nice pure red oxide, it is just ugly orange, and purifying gets quite messy. That is why I did not try a lot.



[Edited on 26-8-2019 by TheMrbunGee]

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Arcaeca
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[*] posted on 26-8-2019 at 16:52


So the one on the left is your own attempt and the one on the right was purchased, or what?
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S.C. Wack
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[*] posted on 26-8-2019 at 18:09


It looks like PbO on the left and my Pb3O4 is uglier...it's not easy, the dry way...IIRC all my PbO came from heating the precipitated carbonate...the CO2 may have kicked up dust...I can't remember for some reason.

There is (Blanchard says) a mostly wet and probably better way to make Pb3O4, from PbO and PbO2 in aq. NaOH.

[Edited on 27-8-2019 by S.C. Wack]




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TheMrbunGee
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[*] posted on 26-8-2019 at 21:47


On the right is purchased, yes and on the left is my attempt of melting lead metal and NaNO3, but I was after NaNO2 so I just collected all of the lead oxides as they were, so - impure. Not the process If purity and color is important.



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Antiswat
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[*] posted on 27-8-2019 at 23:28


i would suggest using some kind of a high temperature filter like melamine sponge when decomposing toxic compounds
ive had my fun with nickel poisoning just from a steel pot where i evaporated a liquid containing insoluble nickel oxalate, at the very least consider supplements that inhibits uptake of the specific heavymetal, for mercury that would be selenium




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[*] posted on 28-8-2019 at 07:01


Quote: Originally posted by Antiswat
||
|| i would suggest using some kind of a high temperature filter like melamine sponge when decomposing toxic compounds
|| ive had my fun with nickel poisoning just from a steel pot where i evaporated a liquid containing insoluble nickel oxalate, at the very least consider supplements that inhibits uptake of the specific heavymetal, for mercury that would be selenium

maybe just do it in a fumehood or in the open, not in the kitchen





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Arcaeca
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[*] posted on 6-9-2019 at 18:35


Okay, so I've ordered some graphite crucibles and I have a propane blowtorch (for a number of projects - not specifically lead). IF I decide to go through with trying to make lead oxides, based on the answers in this thread, am I correct in concluding that no safety precautions are necessary besides wearing a dusk mask/respirator and optional lead uptake inhibitor supplements?
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wg48temp9
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[*] posted on 7-9-2019 at 02:35


Potentially a graphite crucible will react with lead oxide, nitrates, nitrites and most oxidizing salts. That may be a minor problem to the clay/graphite crucibles if they are mostly clay.

I suggest you use a seamless steel can or a stainless steel dish.

From memory the type of lead oxide produced when heating lead is dependent on the temperature. I suggest you find a procedure and follow that.

From wiki: Lead(II,IV) oxide is prepared by calcination of lead(II) oxide (PbO; also called litharge) in air at about 450-480 °C:[4]

6 PbO + O2 → 2 Pb3O4
The resulting material is contaminated with PbO. If a pure compound is desired, PbO can be removed by a potassium hydroxide solution:

There is an elaborate prodedure for it in prepchem:
http://www.prepchem.com/synthesis-of-lead-tetroxide/




[Edited on 9/7/2019 by wg48temp9]




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Pumukli
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[*] posted on 7-9-2019 at 09:51


If we are in the Responsible practices thread anyway then it may not seem too odd when I say: why not draw the line and simply stop playing with Pb, Cd and Hg?

I mean collecting the elements is OK (in reasonably small ammounts), maybe some electrochemistry on Pb and Hg anodes may slip through as well, but deliberately making more or less soluble compounds of these metals is irresponsible I think.

We are pursuing a hobby and our lives or survival of our families are not dependent on it. So we can say that no, I don't do this or that. :) E.g. I don't mess with amalgam reductions. If a synthesis depends on it then I don't do that synth or try to find an alternative. If a recipe calls for Pb-nitrate or -acetate to coagulate proteins then I try to achieve the same effect by using zinc- or copper-salts. (Although copper is just slightly better than the mentioned three.) I refused to take a kilo CdSO4, though it was literally for pennies. But why would I stockpile such a compound?

Why would I take the risk of accidental slow poisoning myself via inhalation of dusts, vapours, or via skin contact of these compounds? These pretty much "one way" compounds: they enter the body, then they don't want to leave.

For each of his own, but in the Responsible practices thread this opinion may find some open ears.
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wg48temp9
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[*] posted on 7-9-2019 at 14:13


When you consider that its not so long again every time you used 50l of gasoline in your car you had spread up to 7.5g lead a round or the red lead and white lead at one time used in paint and the leaded solder in old electronics. Lead is still used in lead acid batteries , roofing, bullets, pellets, fishing weights and even hair dye. Then it is probably no more irresponsible than all that and a lot less irresponsible than the previous use of Arsenic and hexavalent chromium to preserve wood used in children's play parks.

I am not advocating irresponsible use of lead. Any usage will inevitably increase human exposure above background levels but I am suggesting its important to have a sense of proportion about it.




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[*] posted on 8-9-2019 at 23:39


While working on lead dioxide electrodeposition topics I noticed that reacting sodium plumbite solutions with a moderate concentration H2O2 tends to to give the "red lead oxide"percipitate. Plumbite can be made by dissolving lead(II)oxide PbO in alkali solutions. Lead metal also tends to form plumbite in strong alkali solutions, but the reaction is veeeeery slow.
If one needs only a small amount then perhaps this method might be useful as it can be conducted without heating (if one starts with PbO) and the release of lead fumes that accompany that process.
Either way, working with coupious amounts of lead compounds is not a healthy undertaking by any means.




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Arcaeca
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[*] posted on 13-9-2019 at 21:14


Well, I got my graphite crucibles, so I chucked a couple lead drywall anchors in one and heated the bajeezus out of it (to what temperature I don't know - it was hot enough to be completely liquid but not hot enough to glow). At first it was a pale yellow-gold color, and I swished the crucible around a couple times to mix it moltem metal up and allow the lead not at the surface to be exposed to oxygen so it could form oxides. And at some point, after some swooshing and at a very high temperature, it turned not yellow or red or orange, but... blue?

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[*] posted on 14-9-2019 at 01:23


Quote: Originally posted by TheMrbunGee
||
|| You can make them at lower temperatures by melting lead with K/Na nitrate (not sure about other nitrates, guess the corresponding nitrite should not be explosive.) Doing this in well ventilated area with some PP (oxide dust flies around) should be safe.
||
|| I have done this but I have never got the nice pure red oxide, it is just ugly orange, and purifying gets quite messy. That is why I did not try a lot. | [Edited on 26-8-2019 by TheMrbunGee]

The blue color was probably caused by a thin oxide layer similar to the blue color on heated steel.

From wiki: "Steel turns blue because of a thin oxide layer that forms on the surface of the metal. The thin film interferes with light waves, which enhances some wavelengths while reducing others"







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