Sciencemadness Discussion Board

Safe preparation of lead oxides

Arcaeca - 25-8-2019 at 17:54

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?

TheMrbunGee - 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]

WhatsApp Image 2019-08-26 at 07.29.10.jpeg - 190kB

Arcaeca - 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?

S.C. Wack - 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]

TheMrbunGee - 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.

Antiswat - 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

Ubya - 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

Arcaeca - 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?

wg48temp9 - 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]

Pumukli - 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.

wg48temp9 - 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.

markx - 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.

Arcaeca - 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?

IMG_4699.JPG - 2.6MBIMG_4698.JPG - 2.1MB

wg48temp9 - 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"




Arcaeca - 21-10-2019 at 19:33

Welp, I tried making lead tetroxide by putting some lead carbonate I made earlier (from lead acetate (from lead metal + vinegar + hydrogen peroxide) + calcium carbonate) in a crucible and heating to try to anneal it to lead tetroxide, since according to Wikipedia that's a thing. Just got an ugly pale orangish (#e4bb87 is a good approximation) - certainly not scarlet, as the picture on Wikipedia would suggest.

So... another path is apparently lead acetate + potassium plumbate, for which I assume sodium plumbate is an acceptable substitute. And sodium plumbate can apparently be made from lead dioxide in an NaOH solution, and lead dioxide can apparently be made by oxidizing lead acetate with NaClO. So... dissolve lead in vinegar, add bleach, add NaOH, then add more lead acetate? Can anyone confirm this works?

Ubya - 22-10-2019 at 02:59

oxides color can vary a lot, just because it is an ugly orange it doesn't necessarily mean low quality

teodor - 22-10-2019 at 05:00

Did somebody try to prepare Pb3O4 by the wet method as described in Brauer - K2Pb(OH)4 + K2Pb(OH)6 ? If you did, could you please share experience also with the plumbites/plumbates preparation.

@Pumukli I think it is good to proof the information by citing some sources. Your phrase "they enter the body, then they don't want to leave" needs some clarification. I found, that "adults typically absorb up to 20% of ingested inorganic lead after a meal and up to 60-80% on an empty stomach " . 95% of absorbed lead is stored in bones. "In times of stress (particularly pregnancy and lactation), the body can mobilize lead stores, thereby increasing the level of lead in the blood" . "The body accumulates lead over a lifetime and normally releases it very slowly" - https://www.atsdr.cdc.gov/csem/csem.asp?csem=34&po=9 . Thank you for make us aware about the lead toxicity but let me ask: could it be done in some scientific way to make us able to get usefulness from it?
You didn't mention a special medicine which as far as I know is used in cases of lead poisoning to speed up the discharge of lead reserves in the body - and it is a very interesting topic.
Also, how you propose to sort these metals - Hg, Cd, Pb in the order of increasing danger? So, if I plan to do experiments with them during my short life which of them should I hold to the last days? (But I personally would prefer to discuss life and health issues in separate threads, it is annoying to read it in threads dedicated to specific topics also because our friends who die from some diseases people mention here - like cancer or poisoning - in 99.999% got them not from chemistry hobby).

[Edited on 22-10-2019 by teodor]

Arcaeca - 22-10-2019 at 08:45

Quote: Originally posted by Ubya  
oxides color can vary a lot, just because it is an ugly orange it doesn't necessarily mean low quality


It does if you intend to use it as a pigment, i.e specifically for its color.

S.C. Wack - 22-10-2019 at 13:30

Vorobyova suggests repeatedly boiling the product made from PbCO3 with a soluble Pb salt such as the acetate, before washing and drying.

Arcaeca - 22-10-2019 at 21:24

Okay, so I've have lead(II) acetate (concentration unknown; made from letting lead metal decompose in a jug of vinegar and hydrogen peroxide) and I added bleach (5% - 10% NaClO according to the MSDS) expecting it to turn black or something given the typical color of PbO2. Instead it turned a darkish orange once I added enough; it's not really the scarlet color I was expecting of Pb3O4, but apparently NaClO can decompose into NaOH, so if the NaClO reduced the PbAc2 to PbO2, then some excess NaClO decomposed to NaOH which reacted with the PbO2 to yield Na2PbO4, which then reacted with some other PbAc2 in solution... I guess Pb3O4 is a possible side product? Or is the orangeish color from the hexahydroxyplumbate ion or what? Keep in mind this is all BEFORE adding NaOH.

I don't have a good handle on the reaction conditiona required to make PbO2 from PbAc2 (which I really want to get right, since PbO2 is an intermediate for both lead tetraoxide and ammonium hexachloroplumbate, which I want to make). At such low concentrations, how much bleach would be required? At what temperature? How long should I wait before adding NaOH to turn it into sodium plumbate, or do I add both the bleach and NaOH at the same time?

teodor - 23-10-2019 at 02:32

Did you try to follow Brauer procedure for PbO2 from PbAc2 , KOH and Ca(OCl)2, Arcaeca?

Pumukli - 23-10-2019 at 07:23

"I think it is good to proof the information by citing some sources."

What if I did not want to proof anything? I merely gave a hint of the possibility of chronic lead poisoning. Then anyone who want to play with these compounds can look up the relevant facts. I did not bothered because I'm not interested in them.

I didn't mention any special medicine, yes. Because it is the "responsible practices" thread and if someone had been so reckless as to got poisoned by these compounds - while played "responsibly" with them, then the proper treatment had been the responsibility of his/her doctors!

I don't propose to sort them either. For me they are practically in the same league: the stay-away league. If you asked me Hg is probably the worst due to its highest vapour pressure at room temp and its ability to form toxic substances with various organic compounds. As I'm mostly into org. chem. it is something to be worth taking into account.

teodor - 23-10-2019 at 07:44

I totally agree with you about the importance of making people aware of the danger, the difference is only I think to make them listening we should provide some accurate information.

For example : how is it safe to mix lead salts with organic solvents. Based only on my poor chemical background I can imagine that it is not possible to create lead-organic compound just by mixing, we should prepare at least grignard reagent to do the job. Experience of people who understand the topic could help.
Also: volatility of salts, especially nitrates. It is in the range 100-150 C according to some sources. How is safe to do some reaction, for example decomposing carbonate.

To make people aware we can only supply the information. We cannot say: do not do that. We can say: if you do that - you will get that etc.

Arcaeca - 23-10-2019 at 11:51

Quote: Originally posted by teodor  
Did you try to follow Brauer procedure for PbO2 from PbAc2 , KOH and Ca(OCl)2, Arcaeca?


Sort of? I don't actually own the book but the procedure in the pdf hosted by this site uses CaOCl and KOH, neither of which I thought I could get my hands on easily, so I was substituting in NaOCl (liquid bleach) and NaOH. However looking through an older thread (tid: 1932) apparently using bleach is discouraged since it has NaOH and NaCl impurities that form side products. And it's come to my attention that CaOCl is sold as a pool chlorinator; this is what they have at my local hardware store, but it's certainly far from pure; based on the MSDS could I expect a significant amount of side product, or would it be better to just stick with the bleach?

IMG_5075.JPG - 2.1MB IMG_5074.PNG.jpg - 192kB

EDIT: Wait, apparently they did get it to work with bleach, but at 75 C for an hour, so I'll try doing it with a hot water bath instead of ambient temperature later today.

[Edited on 10-23-2019 by Arcaeca]

teodor - 23-10-2019 at 13:05

The book is in the SM library. http://library.sciencemadness.org/library/books/brauer_ocr.p...

Page 757.

For most reactions KOH/NaOH is not relevant, and I was wrong - according to the procedure - NaOH. Also, most of receipts that mention bleach or Ca(OCl)2 work with a technical grade staff - it is so common that purification usually mentioned separately together with the procedure how to purify it. Also, according to Brauer "technical grade Ca(OCl)2 (70-80% Cl) or from double this amount of technical grade bleacing powder". It says "boiled for a few minutes".

teodor - 25-10-2019 at 14:29

Today I've made a bit of PbO and PbO2.

1) Pb(NO3)2 + 2HCl = PbCl2 + 2HNO3

PbCl2 is almost insoluble. I think lead acetate could also be used instead of nitrate.

2) PbCl2 + 2KOH + H2O = PbO * nH2O + KCl

After addition of 6M KOH the white lead chloride turns its colour to orange.

3) PbO * nH2O + H2O2 = PbO2 + (n+1) H2O

I just added enough 12% H2O2, the orange lead (II) oxide immediately turned to black-brown lead (IV) oxide. Excess of H2O2 starting to decompose with evolution of O2 .

No heating was required. To convert all PbCl2 to PbO * nH2O some mixing is required (because the mass becomes dense upon KOH addition).


[Edited on 25-10-2019 by teodor]

fusso - 25-10-2019 at 14:50

Why make PbCl2 when ur gonna convert it to the oxide anyways?

Arcaeca - 25-10-2019 at 22:29

I just filled a mason jar with 1 part lead(II) acetate (concentration unknown, made from lead drywall anchors and unknown quantity of 3% hydrogen peroxide dumped into some 5% vinegar) and 1 part bleach (5-10% NClO according to the MSDS), and a couple lead anchors and put the mason jar in a boiling hot water bath until it cooled off. This resulted in a fair amount (by my standards, anyway) of brown precipitate I assume is PbO2.

I could then try to turn this into sodium plumbate with a large excess of NaOH and then combine that with more lead(II) acetate to make the lead(II,IV) oxide, but frankly it seems easier to make by direct reduction in air at 400 C.

Aaaanyway, since this is the Responsible Practices board, I guess I should ask what to do with the waste products of this reaction. It still smells faintly of bleach and probably still has at least some lead ions left in solution, but beyond that I have no idea what's in it. I've been collecting it in a half-gallon mason jar to evenually take to the county hazmat disposal since I don't know what else to do with it.

IMG_5086.JPG - 1.7MB

teodor - 26-10-2019 at 05:49

Quote: Originally posted by fusso  
Why make PbCl2 when ur gonna convert it to the oxide anyways?


This is a good question. Select any answer you like:

1. To separate lead from other metals which compose the lead alloy which is used in the lead-acid gel battery.
2. To recover nitric acid without distillation, because it is a very good chemical for lead extracting.
3. Because I have no idea how to get PbO from Pb(NO3)2 by water chemistry methods. Pb(NO3)2 + KOH gives a white precipitate (basic nitrate?) which is just dissolves again in excess of KOH without forming orange PbO.

[Edited on 26-10-2019 by teodor]

teodor - 26-10-2019 at 08:13

Quote: Originally posted by Arcaeca  
This resulted in a fair amount (by my standards, anyway) of brown precipitate I assume is PbO2.


So, you have a lot to improve.

Quote: Originally posted by Arcaeca  

Aaaanyway, since this is the Responsible Practices board, I guess I should ask what to do with the waste products of this reaction. It still smells faintly of bleach and probably still has at least some lead ions left in solution, but beyond that I have no idea what's in it. I've been collecting it in a half-gallon mason jar to evenually take to the county hazmat disposal since I don't know what else to do with it.


First, and it is most important, also not evident from your photo - all your products must be inside some containers (not outside). You should think literally about every drop when you work with such compounds.

Second, and that is what I do, for products which have basic pH - I collect them in a container with enough Na2CO3 to convert lead salts to insoluble lead carbonate (for acidic products H2SO4 could be possible better, to avoid gas formation). I put also filter papers and the first portion of water when I wash glassware into that container also. Generally, you can find information about disposal methods using google search in this forum.

[Edited on 26-10-2019 by teodor]

Arcaeca - 26-10-2019 at 18:07

So I put all the still wet PbO2 precipitate I had in a metal baking pan and put it over my makeshift kiln as a lid - the thinking being that allegedly in oxygen PbO2 decomposes to Pb3O4 around 400 C or so, so the hot gases in the kiln could heat the bottom of the pan, which would transfer the heat to the PbO2 which could be oxygenated from above. This would be easier with better temperature control with a hotplate or furnace and borosilicate glassware, but as I have none of those, I have to work with what I have.

After the remaining liquid boiled off, I was left with this residue, which certainly doesn't look like Pb3O4, and I'm not really sure what it is. It's likely the kiln simply didn't get hot enough so the black stuff could be some other lead oxide that PbO2 decomposes to at a lower temperature, or maybe it's the product of decomposed lead acetate that was unreacted in solution, or some side product with residual NaClO at high temperatures? I have no idea what this but it's certainly not the reddish-orange I was going for.

IMG_5119.JPG - 2.2MB

S.C. Wack - 27-10-2019 at 11:07

Quote: Originally posted by Arcaeca  
PbO2 decomposes to Pb3O4 around 400 C or so


...after treatment with PbO and NaOH...a black char may have something to do with using vinegar, unless the acetate was recrystallized or something (although nice crystals are possible from vinegar IME).

Arcaeca - 28-10-2019 at 15:25

Quote: Originally posted by S.C. Wack  
Quote: Originally posted by Arcaeca  
PbO2 decomposes to Pb3O4 around 400 C or so


...after treatment with PbO and NaOH...

Okay, I've never heard of this in any procedure for making Pb3O4. I thought PbO2 could be reduced in air directly to Pb3O4.

So to be clear: once I've made brown PbO2, I know dissolving it in a strongly alkaline solution yields some light-colored slightly yellowish precipitate, and then I do what to make reddish-orange? Just heat it to 400 C or am I missing something?

S.C. Wack - 28-10-2019 at 15:44

It's #2 from the link on the first page, taken from my scan of Blanchard. No doubt both the oxide and tetroxide can be formed by heating the dioxide, but there is usually a good reason for processes more than a sentence long.

teodor - 29-10-2019 at 03:15

Oh, indeed, I found it, Blanchard N 48/2 . It is much simpler wet method than in Brauer, which depends on Na2[Pb(OH)6] which is rather complex to get. Thank you for the information.