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Author: Subject: The lead salts preparation thread!
dann2
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[*] posted on 20-7-2008 at 11:58


Hello,

How long would it take to make (say) 50 grams Monoxide?
I tried this once and it appeared to be very slow BUT my molten Lead was less than 600C.

Sitting and scooping for hours seems very boring!
Wonder if you were to set up a cheap aquarium pump to bubble air through the molten Lead using a glass tube. You could leave the whole lot sitting for a few days.
Care of one's eyes (and other bits of one's anatomy) of the splatter etc would be essential.

Dann2
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[*] posted on 20-7-2008 at 13:36


Was your lead glowing red hot? maybe there wasnt enough oxygen.
I normally make less than 50g at a time but if you kept it hot enough it wouldnt take long, it takes me about 5mins to make 30g batches.
lol i have tried that, every time i tried it lead would always clog up the tube as the cold oxygen flowed through it. :( Maybe if you blow a fast stream of air at it from a pump or something that wold speed it up for you?
tommorow i think i will make a low lying but wide iron cruicible and see how well that works.
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[*] posted on 20-7-2008 at 20:45


Last time I tried that, I got what turned out to be a green granular substance (it was yellow to orange when hot) which, when treated with HCl, gave H2 and not much white stuff. It turns out the lead skin adheres quite nicely to the metal, so you get little beads coated in, I suppose, suboxide.

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[*] posted on 21-7-2008 at 01:30


yea, you didnt heat it strong enough so it didnt seperate fully, hence the granular form
cant explain the green, like u say probs some suboxide :P
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JohnWW
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[*] posted on 21-7-2008 at 04:55


Preparations of PbO ("litharge"), (once used as a pigment in paints, now disfavored because of the neuro-toxicity of Pb compounds, and because of the variability of its color), are often light yellow or lime-green, even without any impurities except possibly a trace of Pb3O4 ("red lead", also used as a paint pigment). Higher concentrations of Pb3O4 in PbO would be indicated by an orange color. PbO is also used as a component of yellow or orange pottery glazes, and (being colorless when pure in bulk in siliceous glasses) in concentrations of up to 30 or 40% in lead glass, used for paperweights and in French lead crystal because of its weight.

A quicker preparation, if HNO3 is available, may be to dissolve Pb in HNO3 to obtain Pb(NO3)2, then heating that to drive off nitrogen oxides (caution - use fume hood) to leave PbO.

If carbonate is added to such a solution of Pb(NO3)2, insoluble PbCO3 (cerussite, an important Pb ore), or the hydrous form, 2PbCO3.Pb(OH)2 (hydrocerussite) can be precipitated out, leaving nitrate in solution. These can be used as an alternative to PbO in many reactions, and converted to PbO by heating sufficiently, to about 315 to 400ºC, to drive off CO2. It was the precipitated hydrous form, hydrocerussite, 2PbCO3.Pb(OH)2, that was called "white lead", and formerly used as the white pigment in white and pastel paints, until superseded by TiO2 because of the neuro-toxicity of Pb compounds and the superior opacity of TiO2.

[Edited on 22-7-08 by JohnWW]
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[*] posted on 21-7-2008 at 12:14


yes then lead the NO2 fumes through water to regain the nitric used in the production of the Pb(NO3)2. been there done that lol :P
the one problem is if your desired product is Pb3O4 then you will need to reheat it to get it, so ultimatly its easier starting off with heating lead.
does anyone know of any other method of converting PbO to its higher oxide? eg, via a simple cost effective chemical reaction? thanks,
Picric-A
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[*] posted on 21-7-2008 at 12:30


Quote:
Originally posted by Picric-A
yea, you didnt heat it strong enough so it didnt seperate fully, hence the granular form
cant explain the green, like u say probs some suboxide :P


I don't think it was that. I got similar results ranging from the temperature where rapid oxidation starts (the metal surface appears iridescent) to red heat, all the way up to the melting point of PbO, which tends to dissolve (lead can dissolve a few percent of the oxide) and attack my crucible (steel can) where it isn't in solution.

Quote:
Originally posted by JohnWW
Some preparations of PbO ("litharge"), which is usually white (and once used as a white pigment in paints until TiO2 became standard)


No, lead carbonate (or subcarbonate) was used as pigment, because it was cheaper than TiO2, which is better. PbO is always colored.

Quote:
Originally posted by Picric-A
does anyone know of any other method of converting PbO to its higher oxide? eg, via a simple cost effective chemical reaction? thanks,
Picric-A


Oxidation only works for some modifications, so I'm told. Heat it too far and it recrystallizes into the other form, that won't oxidize.

Even from freshly prepared Pb(OH)2, I've never gotten anything darker than light orange.

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[*] posted on 21-7-2008 at 13:51


The Pb3O4 that I made IIRC by heating white PbCO3 to yellow PbO and heating further in air was only red when hot and is quite orange, but not in the same way as say dichromate. A duller, more ochre sort of dark orange. It did not take long convert at all. The color seems to be dependent on preparation as is told in books and can be seen in images from sellers of it. Methods of preparation chemical and otherwise can be found in some books that are available.
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[*] posted on 1-8-2008 at 15:42


I tried heating lead to make PbO last night. I used my casting furnace with a crucible holding about 10-15lbs of lead. At first the PbO was coming off granular and mixed with lead, even at moderate red heat, maybe 600-700°C. It was orange-red while even barely hot but turned yellow/black as it cooled down. Later on in the process the lead started smoking, so I turned the burner down to just a low idle, barely visible incandescence on the surface, and liquid oxide was now floating on top. When I scooped it out it hardened to a glassy dark grey appearance. According to every MSDS for PbO the melting point is over 800°C, and I was nowhere near that at that time. Presumably Pb3O4 which has a much lower melting point was forming, or some mixture which has a low melting point. I was getting very little of the oxide on the surface so I put a tube down into the crucible connected to my air compressor with a needle valve and left it bubbling for a few hours, still only getting a very small amount of the liquid oxide.

Should I turn the furnace up to a high heat over 800°C to get better PbO yield? Does Pb3O4 decompose to PbO at higher temperature? I don't like how it smokes and I lose so much oxide this way (not to mention the fumes!!). I may be able to rig some sort of a trap for the smoke if I use the forced air from the tube to oxidize the lead, since it doesn't depend on air getting to the top of the crucible.

Edit: Well I'm running it at higher temperature right now, and it is making stuff, just not quite sure what. Probably PbO and/or Pb3O4. It is going slowly, but a little faster at least. It doesn't smoke too much, but I am still not going near it much because of the fumes. The stuff wets my crucible which is annoying. I am afraid it might slightly dissolve the crucible which is made of silicon carbide, but there doesn't seem to be much damage so far. Here's a pic of the progress.

[Edited on 1-8-2008 by kilowatt]

HPIM1439.JPG - 127kB




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[*] posted on 2-8-2008 at 00:25


Silicon and PbO do not get along; molten PbO and lead oxidizes metals and reacts with Si cpds. including the carbides, and dissolves the product further. You do not have Pb3O4, 470-480C has been recommeded for its formation; higher is bad and it is completely decomposed below 650C.

In order for the lead to come into good contact with oxygen some sort of agitation is needed.
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[*] posted on 2-8-2008 at 01:51


My experience is the SiC crucible itself just slowly burns, even without lead. The glazing is about gone on mine. Without protection, the graphite bonding burns nicely in air at these temperatures.

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[*] posted on 2-8-2008 at 03:01


Pb3O4 is formed when PbO is heated in air at about 300-350 C, at red heat it decomposes back to PbO.

PbO formed at temperatures below bright red -too low to melt it - will be yellow when cool, if fused it will be more of a red colour; the yellow form is more reactive.

PbO is very easy to reduce. carbon monoxide will do so at a few hundred C. If you are using a fuel-fired furnace, as opposed to an electric one, do the best you can at keeping the flue gases away from the lead.

An iron container is likely the best to use, fused PbO wicks into pores in many ceramics that resist it's solvent action, and most silicate based ceramics are attacked to some extent by PbO.

Litharge usually does have some lead mixed in with it, unless care is taken when making it. You can collect the cold litharge and crush it, then heat in air with stirring at barely visible red heat to oxidise the unreacted lead.
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[*] posted on 2-8-2008 at 05:15


Quote:

In order for the lead to come into good contact with oxygen some sort of agitation is needed.

Well I was continually bubbling air through it, I dunno how much more contact/agitation you could get. I will try a lower temp later today with an iron crucible with a lid on it.

Thanks for the advice.

[Edited on 2-8-2008 by kilowatt]




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[*] posted on 3-8-2008 at 19:52
Lead Nitrate


A few minutes ago I set up a non-divided DC electrolysis cell with nearly saturated ammonium nitrate and lead electrodes to see if I could get lead nitrate (for nitric acid production) and ammonia. Immediately dark black material, which I would presume to be lead dioxide, started falling away from the anode, with the cathode quickly darkening as well. The cathode is definitely producing a lot of ammonia. Within just a couple minutes the anode was already noticeably worn down; this is a surprisingly fast process and I expect the electrode to be pretty much gone in just a few hours. I'm not sure about all the lead dioxide forming, is this going to want to react to lead nitrate on its own or am I going to have to decompose it and put it back in the electrolyte (which should be enriched with nitric acid)? Also does lead form any ammonia complexes?

Edit: The cathode is now surrounded by a spongy or gelatinous dark gray material. What is this? Some sort of ammonia complex? Or is spongy lead being electro-deposited around the cathode? When heated it converts quite readily to yellow PbO.

2nd Edit: After letting the cell rest for a few minutes the spongy material appears to have dissolved or settled out.

3rd Edit: I have unquestionably made lead nitrate with this setup; when a sample of the electrolyte was heated in a test tube beyond the decomposition of ammonium nitrate, copious amounts of N2O were liberated and yellow PbO was left behind. There is a lot of solid gray material at the bottom of the cell, presumably spongy lead. I will see if any dissolves after sitting overnight. It may need removed and recycled depending on how much or little the ammonium nitrate has been converted to nitric acid through loss of ammonia.

[Edited on 3-8-2008 by kilowatt]




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[*] posted on 3-8-2008 at 20:08


300-350C sounds crazy low for Pb3O4 from PbO. Nothing that I've read gives such a low temperature. Have a reference?
The temperatures that I gave above were from Mellor.
In this article, where

"not only the effect of temperature upon the rate of oxidation of different starting materials but also the physical and chemical properties of the red lead formed from the different substances under different conditions of temperature have been studied. We have studied red lead made from litharge, lead hydroxide, white lead, lead sponge, metallic lead and lead tartrate.",

after 15 hours heated to 400C in a rotating jar in a furnace swept with air, they say that the litharge was less than half converted.

"The temperature best suited for the formation of red lead varies with the starting material used. About 425-430° is best for white lead, 450-470° for litharge and lead sponge, and about 450°. for converting lead hydrate and metallic lead to red lead. In fact, 450° may be taken as the temperature at which red lead can be economically formed from any suitable starting material."

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[*] posted on 3-8-2008 at 22:01


@kilowatt

Why dont you simply fuse your lead with ammonium nitrate? Just heat the nitrate until it melts, then add the lead in small pieces. The mix will start bubbling vigourously and lots of ammonia is produced. When reaction is over, add hot water to dissolve the lead nitrate, filter and evaporate until crystals start to appear. Cool in the fridge to obtain your lead nitrate. Couldn't be easier.

Note that if your lead contains Sn, the ammonium nitrate will oxidize it to SnO2 appearing as a white precipate when water is added to the fused mass. Decant & filter the liquid to remove these impurities.
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[*] posted on 3-8-2008 at 22:17


That would be quite convenient, thanks for the idea. I'm surprised it reacts so quickly and in that manner and will have to try this out on a small scale tomorrow. However molten ammonium nitrate can be fairly dangerous/unstable and I'm not sure I'm so keen on doing 5kg batches of this like I intend to with the electrolysis. After all, there is just a fine line between ammonium nitrate's melting and decomposition temperatures. I'm also not sure that it would be any more energy efficient than the electrolysis, but perhaps. Definitely something to look into.

I already intended to use this process to separate the scrap lead alloy, and just started a new thread with more specifics.

[Edited on 3-8-2008 by kilowatt]




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[*] posted on 4-8-2008 at 05:13


S.C. Wack - from an older industrial chemistry tome, don't remember which. I'll try to find it again tomorrow. I do remember seeming to get lower yields of red lead at 450-500 then at 350-400 but this may have something to do with other factors.
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[*] posted on 15-8-2008 at 17:23


Quote:

Why dont you simply fuse your lead with ammonium nitrate? Just heat the nitrate until it melts, then add the lead in small pieces. The mix will start bubbling vigourously and lots of ammonia is produced.

Back regarding this method, as I stated before fusing a large quantity of ammonium nitrate and randomly dropping lead into it initiating a vigorous exothermic reaction seems extremely dangerous. It wouldn't take much overheating from the reaction to send the AN melt into thermal runaway. Another problem is that pure lead nitrate has no melting point and is solid at the temperature of fused ammonium nitrate. Thus when the lead nitrate concentration gets sufficiently high the reaction stops, and much AN is not consumed. In my test runs I had to decompose it off which always results in a considerable report (probably a serious explosion if scaled up) as it nears the end just before nitric fumes come out.

It would be preferable to carry out this reaction in a minimal amount of high boiling solvent for the nitrates. This should be done by adding the fused ammonium nitrate from a heated addition funnel into a RBF containing the solvent and enough lead pellets to complete the reaction with a stirrer, as opposed to adding lead to the full amount of ammonium nitrate. DMSO looked tempting but it is not compatible with strong oxidizers. Perhaps there is a eutectic mixture of sodium/potassium or lithium nitrates that would work (pure lithium nitrate melts at 255°C, still too hot) but I have not been able to find any information or phase diagrams for alkali nitrate mixtures. Perhaps fused alkali nitrates would be reactive with lead anyways, I am not sure. Can anyone think of another solvent that would work here (stable liquid from 160°C to 200°C, compatible and miscible with lead nitrate and ammonium nitrate, unreactive with lead)?




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[*] posted on 15-8-2008 at 17:52


Fused potassium and sodium nitrate react with metallic lead to form the alkali metal nitrite and lead oxides.
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[*] posted on 15-8-2008 at 18:28


What about a liquid lead amalgam? As long as excess lead is used, the mercury should not nitrate as lead would reduce mercury nitrate. With thorough mixing and/or ammonium nitrate added to the bottom of the bath with a dip tube solid lead nitrate should float to the top. I am not sure how well it could be assured that all the AN has been reacted.



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[*] posted on 16-8-2008 at 03:23


Quote:
Back regarding this method, as I stated before fusing a large quantity of ammonium nitrate and randomly dropping lead into it initiating a vigorous exothermic reaction seems extremely dangerous. It wouldn't take much overheating from the reaction to send the AN melt into thermal runaway. Another problem is that pure lead nitrate has no melting point and is solid at the temperature of fused ammonium nitrate. Thus when the lead nitrate concentration gets sufficiently high the reaction stops, and much AN is not consumed. In my test runs I had to decompose it off which always results in a considerable report (probably a serious explosion if scaled up) as it nears the end just before nitric fumes come out.


Yes the reaction IS exothermic. One just needs to melt the AN then remove the burner and put the lead in. If it is cut into sufficiently small pieces the reaction is selfsustaining i.e. the generated heat will keep the AN melted.

I never had problems with thermal runaway. I didnt try it on a large scale tough. From a theoretical standpoint it might happen tough - at high temperatures the NO3- might as well oxidize the NH4+ instead of the Pb.

There should be not nitric fumes tough! If you use stochiometric amounts then at least on a small scale the reaction will run smoothly, with the nitrate being reduced to nitrite which decomposes into N2 and H2O. The NH4+ reacts with the nitrate ion to ammonia and water. If you observe nitric fumes then they are from decomposing lead nitrate, not AN. Also the fact that you report a small explosion is quite worrying as there is nothing in this reaction which could explode! Lead metal does not form explosive ammines. You might have impurities of other metals present. AN also does not explode from heat, even when dropped onto a red hot heating plate all you get is a flame and a whoosh! sound.

Quote:
Can anyone think of another solvent that would work here (stable liquid from 160°C to 200°C, compatible and miscible with lead nitrate and ammonium nitrate, unreactive with lead)?


Yepp, its called water ;)

I never even thought about this but this reaction should work perfectly well in aequous solution too. Water surely does not interfere with the reaction, as it is constantly produced by the reaction itself. Also it is known that even a cold AN solution does oxidize metals like iron and copper altough very slowly. You can try this easily: Just put a nail into a beaker with AN solution. After a few days you will observe a yellow precipate of iron hydroxide. When you use copper the solution slowly turns blue.

Thus you should try this: Make a conc. AN solution, heat to boiling and put in small pieces of scrap lead metal. Equilibrium should be driven to the right by decomposing ammonium nitrite into N2 and H2O and boiling off of ammonia. Advantages are: No solidification of fused mass at the end of reaction and thus no risk of decomposing Pb(NO3)2 (nitric fumes). Also the reaction temperature will be way below decomp. point of AN. The only problem I see is that it might react very very slowly. So make sure you cut your lead into very small pieces. Lead powder certainly would be best.

Here's the reaction:

Pb ---> Pb+2 + 2e-
NH4N+5O3 + 2e- ---> NH4N+3O2 + O-2
2N-3H4 + O-2 ---> 2N-3H3 + H2O
NH4NO2 ---> N2 + 2H2O
NH4+ ---> N + 3e- + 4H+
NO2- + 3e- ---> N + 2O2-

Thus:

Pb + 3NH4NO3 ---> Pb(NO3)2 + 2NH3 + 3H2O + N2

You need 1.2g AN for every gram of lead metal.

Good luck :)
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[*] posted on 16-8-2008 at 14:50


Quote:

If you observe nitric fumes then they are from decomposing lead nitrate, not AN. Also the fact that you report a small explosion is quite worrying as there is nothing in this reaction which could explode!

Yes, that's what I was referring to. After the ammonium nitrate had been pretty much decomposed off I continued heating until the decomposition of lead nitrate, as a qualitative test for the presence of lead nitrate. In the test tube it always started with a considerable flash/pop followed by the controllable release of the nitric fumes. The decomposition of ammonium nitrate is quite capable of causing an explosion in such a situation where the temperature is quite high. It is quite possible the last amount of AN decomposes explosively especially given the rather rapid heating I used. I'm not sure about the nature of antimony nitrate or ammine complexes or if it would even form in the reaction, but there is certainly considerable antimony content in my mixed scrap lead alloy. Other metals capable of ammine complexing, such as copper, may be present in smaller amounts; the alloy comes from a mixture of random scrap lead articles.

I didn't realize the lead/AN reaction gave off nitrogen. The reaction can thus be considered a 1.5x waste of ammonium nitrate when compared to one that does not reduce nitrate, such as electrolysis. The electrolysis probably breaks down ammonia too, but it is obvious that a lot is still released from my test rigs; not sure what the yields are.

At this point I might be better off using magnesium oxide methods to break down the ammonium nitrate, later decomposing magnesium nitrate to release nitric vapors into a solution with lead filings. Perhaps there is no method for directly reacting the scrap lead and ammonium nitrate which has the characteristics I am seeking - a cyclic process or set of processes that produces nitric acid from ammonium nitrate without using up any additional acids/bases, and separates scrap lead into its constituent metals. The former goal should be achieved with magnesium nitrate. With that accomplished, the second goal should be achieved with the resultant nitric acid reacted directly with the scrap with no theoretical nitrate loss.

Thanks for all the info, and more ideas always welcome.

[Edited on 16-8-2008 by kilowatt]




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[*] posted on 23-9-2008 at 18:31


my experiance with lead acetate.


I have tried a few ways to make this salt.
the best I found which is already stated here is.

acetic acid + peroxide treatement on metallic lead.

some ideas here are wrong though.

if you have ample acetic acid covering the lead acetate then temperatures
slightly over 100 C are not a problem.

you can distill off the water/acid till half of the liquid is removed.

if let to cool in another flask. you get very very big shards of lead acetate.

then pour liquid back into distillation flask and continue.

I can process half a kilo of lead salt in a one liter flask per go this way.
all salt is very very clear and water soluble.

add 300 grams of lead too 400ml of 85% acetic acid in a 1 liter flask setup for
reflux with equalized addition.

start water in condensor and drip 50% peroxide into solution through condensor
at a rate of around 3 to 5 drops a second.
continue this till solution reflux's (around 25 min) then slow down addition rate
to keep slight reflux.

when all of lead has been disolved filter and cool.

you will instantly get 300g of lead acetate percipitate when flask reaches room temp

filter then distill 150 ml of liquid.

place mother liquid into a flask too cool.

when crystals form (around 100g) pour liquid into distillation flask and
distill half of its volume again.

continue like this till you have all of the lead acetate crystalls.

never let the crystalls dry completely in the air or they will turn into lead carbonate
or at least basic lead acetate.

never boil solution to complete dryness.

keep adding peroxide too solution untill lead has disolved.

any excess is just given off as oxygen and does not hurt reaction.

do not add peroxide after lead has disolved or else you get a percipitate

a great mixture for crashing lead acetate from solution
is 30% ethyl acetate 70% ethanol.


[Edited on 24-9-2008 by Ephoton]




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[*] posted on 1-11-2008 at 11:03
Pb(NO3)2 from Pb and N4NO3


kilowatt,

I'm interested in using your electrolysis method of making Pb(NO3)2 from NH4NO3 and Pb. I have difficulty finding PbO and could only obtain lead fishing sinkers. I have a steady supply of HNO3 from my arc furnace reactor. However, directly reacting lead with HNO3 is inefficient because 1/2 the acid decomposes into NO2.

My questions are:

1. What sized lead electrode did you use and how fast was the erosion?

2. How much current did you use?

3. How pure is the Pb(NO3)2 produced and what are the impurities?

Alternatively, if someone can tell me of a way to make Pb(NO3)2 with the chemicals at my disposal, or where to buy PbO, I'd like to hear it.

[Edited on 1-11-2008 by UncleJoe1985]
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