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Author: Subject: The lead salts preparation thread!
dann2
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[*] posted on 13-5-2007 at 15:13


Quote:
Originally posted by not_important
The reactions going on are

2 NaNO3 => 2NaNO2 + O2
Pb + NaNO3 => NaNo2 + PbO
2Pb + 4NaNO3 => Pb3O4 + 4NaNO2

The reactions with lead are exothermic and run fast, not catalysis is needed, nor do I know of any. As lead is much denser that the sodium compounds, it is better to add the lead in a somewhat divided or thin sheet form to the molten sodium nitrate. Your stirring needs to kick up any lead at the bottom of the container, an inverted T shape that sweeps across the bottom should work OK.

If you're not after the NaNO2, it might be better to just heat the lead in air at slightly above its melting point, skimming off the PbO whenever it gets thick enough.

And if it's lead salts you're after, the lead-acetic acid-air route works OK, just keep it running until everything has dissolved.


I did notice that at the very bottom of the (stainless steel soup bowl) container where things were very hot the product was turning a VERY bright red which I guessed to be Pb3O4 (Red Lead). But it seemed to turn to PbO when mixed in with the rest of the mess. (PbO is what I want.)

I stirred, or it could me more accurately put, mashed and mashed adding in more and more Nitrate.
I would guess about half of the Lead is left. I started with 400 grams.
If I add the Lead to the molten Nitrate it melts immediately but mostly fall to the bottom. I have to stir anyways. Perhaps if you had very finly powdered Lead that might help.

I am not sure of the purity of the Lead. It is roofing Lead from local hardware store. It would hardly have Antimony added as Antimony is for hardening and this is not wanted in roofing Lead IMHO.

Is the Lead, acetic acid, air method where you simply hang sheets of Lead in the vapours of Acetic acid and let the Acid + CO2 from the air convert the Lead to Basic Lead Carbonate??

Edit:

Would Propionic acid do instead of Acetic. I have loads of Propionic acid. (Corn preservative)



Cheers,
Dann2

[Edited on 13-5-2007 by dann2]
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[*] posted on 13-5-2007 at 15:29


I think roofing lead has a bit of copper.

If you wanted to make a lot, you could use a cast iron pot with a drill and metal paint stirrer set up as an overhead stirrer.

NaOH as flux with a bit of NaNO3 as oxidizer worked very well to burn out most of the impurities in 300 lbs of weathered scrap roofing lead I reclaimed once. There was plenty of dross left over for conversion to lead salts.

(Molten lead and NaOH on your skin really HURTS.)

[Edited on 5-13-2007 by Eclectic]
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[*] posted on 13-5-2007 at 23:37


Actually, lead for steep roofs was (is?) hardened with antimony, which is likely to form insoluble compounds in mildly acid to mildly alkaline solutions and so shouldn't be too hard to separate from the lead salts.

As for the acetic acid rout, there's the low tech method http://www.crscientific.com/leadacetate.html and a slightly higher tech one where you use an aquarium air pump and bubble stone to aerate the acidic solution with bits of lead in it. You could use propionic acid instead of acetic, but check the solubility of the lead salt. Cover mossy or bit of sheet lead with water and add a bit of acid, bubble air through the mix. Add water to keep the volume up, and some acid ever so often to keep the reaction going. After the lead metal is gone add acid to give a definite excess and warm for awhile to dissolve basic salts.

So, but avoids messing with higher temperatures or using up nitrate, which might not be a problem for you.

You could also make HNO3 from the nitrate and use that to dissolve the lead, the HNO3 doesn't need to be very concentrated.
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[*] posted on 14-5-2007 at 16:31
Lead Carbonate


Thanks for replys.

The roofing Lead around my neck of the woods has no Copper in it as I make Lead Nitrate with it (from Nitric acid) long time ago and I got no blue colour.

I have a large quantity of Nitric + Sulfamic acid mixture (liquid)
It is used for washing milking machines once per month (I guess they must get pretty dirty :o)
I tried to make Lead Nitrate with this from Lead Metal and got a hugh amount of grey precipitate.
What do you thing the Grey PPT was?

I don't know the %'s of acids in the mixture.
I have read on this board that Lead Sulfamate is very soluble. I thought at the time (guessing) that the grey stuff was Lead Sulphate from the sulfamate.
If I boil/distill the solution of acids willl the sulfamic acid be left behind with the Nitric acid going over into the receiver?




I pulled the following from a conversation I had with a guy a few years ago.

________________________________
You can make (pretty) pure PbCO3.

From that, you can easily make some lead acetate with vinegar (or cleaning quality (=more concentratic) acetic acid). I have not tried this exact procedure, but I use a similar procedure to purify my lead foil.
I start with nitric acid instead, and the rest is the same as what I do to purify the lead.
I eventually convert the carbonate to nitrate with nitric acid but if you have no nitric acid I suppose you can use acetic acid.
If the dissolving part works, the rest will be a piece of cake. It only takes some time, but I am sure it will work just fine.

You will need:-::
muriatic acid
NaNO3
lead/tin mix
sodium carbonate

First, take some muriatic acid, and dilute this to make a 10% hydrochloric acid solution.
In a liter of this solution, dissolve 244.7 grams of NaNO3 by heating the solution.
Watch out for HCl fumes! They can ruin your lungs. At least for a while.
When the NaNO3 has dissolved, don't stop heating.
Add 298 grams of your Pb/Sn mixture which you previously cut into as many small pieces as possible.
Brown gas will evolve.
This is NO2, and it's something to watch out for. It attacks the lungs (like HCl).
Stir every once in a while and keep the solution hot.
The lead/tin will dissolve and pretty soon the solution will be saturated with PbCl2.
It will crystallise. Keep heating and stirring the solution as long as the NO2 evolves.
Dissolving lead foil in nitric acid takes me half an hour.
It will take you somewhat longer, since the solution is less concentrated.
Add some water every once in a while to make up for what has evaporated.
When the reaction has ended, let the solution cool to room temperature.
Then cool the solution further to about 0 deg. C. Filter to obtain raw PbCl2. Recrystallise this PbCl2 from a boiling saturated solution (cool it to 0 deg C to increase the yield). This should produce pretty pure PbCl2. Now, weigh the PbCl2 (You do not have to dry it first).
Place the PbCl2 in a container and to every 100 grams of PbCl2 add 50 grams of sodium carbonate.
Add 300 ml's of water (or more if it doesn't seem enough) and boil the mixture for about 15 minutes. Stir well.
Then, let the PbCO3 that has formed settle and decant the liquid. Add 300 ml's of fresh water and boil again. Let settle, decant and repeat one more time.
This should remove any Na2CO3 that is left in the PbCO3.(lead carbonate)
The bicarbonate will work fine instead of carbonate. So will NaOH (but then you must make sure you don't add too much NaOH. If you do it will redisolve the lead hydroxide/oxide formed). Potasium salts can also be used if they are easier to find.
If NaCl ppt's you can always add a little extra water to redissolve it.
That will only slow down the reaction between the lead/tin alloy and the NaNO3 in HCl solution a little.
The Sn dissolves. I don't know what that grey silt is exactly. That depends on so many factors (concentrations, temperature, pH). I guess you can filter it and use it. The lead will be extracted if there is any in there.
The tin dissolves, but won't precipitate.
SnCl2 is quite soluble. PbCl2 is not , and this is what seperates the tin from the lead. The tin stays in solution and the PbCl2 crystallises.
The additional recrystallisation of the obtained PbCl2 below will purify the lead further removing almost all the tin that may be left Will NaCl ppt? 39g/100ml @100C or 300 ml will hold 117g NaCl.
I guess there isn't that much there.
Indeed.
There is 11.6 g NaCl per 100 ml of solution.
But even if the NaCl does precipitate it will be removed in the next step: the repeat wasing of the precepitated PbCO3 with boiling water.
That is supposed to remove any Na2CO3 left, but it will also remove the NaCl that may be left.
You now have pure PbCO3. Make this into any lead salt you need by adding the corresponding acid.
For instance, use acetic acid to make lead acetate, use nitric acid to make lead nitrate, sulfuric-->sulfate.
__________________________________

Do Ya thing it would work OK??

Cheers,

Dann2
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[*] posted on 14-5-2007 at 18:24


Sounds like a lot of work. Can you get or make nitric acid or acetic acid? Nitric dissolves lead and precipitates insoluble Sn and Sb oxides. Acetic acid with stirring and hydrogen peroxide added dropwize should dissolve lead rapidly, but it would make a lot of heat, and you don't want to let potentially explosive peroxyacetic acid to build up. Also too much H2O2 and you get lead tetracetate along with the lead diacetate.
I have wondered if dissolving lead chloride with the aid of ammonium nitrate to increase solubility and precipitating carbonate with sodium carbonate would be a speedier conversion of chloride to carbonate.
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[*] posted on 14-5-2007 at 19:51


Use of sodium carbonate for neutralizing solutions of soluble Pb++ salts precipitates the *basic* carbonate
Pb3(OH)2(CO3)2 which is the old lead paint pigment called "white lead" .

Use of sodium bicarbonate is required if you want to
precipitate the *normal* carbonate of lead PbCO3 .

I haven't checked the solubility profiles or ratios which
would seem right for the sodium nitrate plus HCl reaction described above , but did note one point which seemed
strange concerning the preparation . It would seem that if the HCl is going to be diluted from the usual 31.45% muriatic to 10% HCl , then it would make more sense to
use the required amount of dilution water to predissolve
the nitrate and simply pour the two liquids together .

Use of ammonium nitrate instead of sodium nitrate could possibly work as well or better .

Instead of working in the neutralization stage with a boiling digestion of solids .....
I would favor decanting a nearly boiling hot saturated solution of PbCl2 into an also already dissolved warm sodium carbonate solution , with agitation . Then add
more water to the original digestion flask and heat to dissolve more PbCl2 and repeat this process until
all of the PbCl2 has been converted to the basic carbonate .

At 100C the solubility of PbCl2 in plain water is about
33 grams per liter , but at 20C only about 10 grams per liter . With dissolved sodium chloride present as the byproduct in the original reaction mixture , the solubility of
the PbCl2 would likely be much lower . However in the
presence of an ammonium byproduct salt the solubility of PbCl2 possibly could be much greater . Experiments may confirm that ammonium nitrate is therefore superior ,
but I have no data on this .


It will probably require something in excess of 4 moles of nascent nitric acid per gram mole of lead (207.19 g. ) to accomplish the reaction if it follows the reaction

Pb + 4HNO3 ----> Pb(NO3)2 + 2HOH + 2NO2

But half of the nitric acid is regenerated by excess HCl
then reacting with the intermediate Pb(NO3)2

Pb(NO3)2 + 2HCl ---> PbCl2 + 2HNO3

So the net reaction would probably then be

Pb + 4HCl + 2NaNO3 -----> PbCl2 + 2NaCl + 2HOH + 2NO2

This reaction would probably be pushed by having maybe 5% excess of NaNO3 with respect to Pb and maybe 10%
excess of HCl with respect to NaNO3 .


The nitrogen oxides which evolve from this reaction are
a thousand times more toxic and dangerous than any
fumes from HCl ....no exaggeration , have the same respect for them as if they were cyanide . Think of them
as the "sleeper cell" agent which lurks about any laboratory awaiting their opportunity to make you a statistic .

[Edited on 15-5-2007 by Rosco Bodine]
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[*] posted on 15-5-2007 at 02:52


Ammonium nitrate and HCl is nasty. You get fumes of NCl3 along with NOCl.

With NaNO3 and HCl, you get NaCl in aqua regia.
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[*] posted on 15-5-2007 at 08:52


Working at hot temperatures the formation of the NCl3 would be unlikely , and the formation of some NOCl in
hot aqua regia will occur in either case .....but it should scarcely be noticed as a toxin since the NO2 would have already killed a person a hundred times over before those
other agents became any significant factor . Another
thing almost certain to be present is PbCl4 .

On this procedure should be stamped in boldface warning ,

INHALATION WARNING ! Caution !
DEADLY FUME HAZARD !
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[*] posted on 15-5-2007 at 09:40


I have used ammonium nitrate in HCl to dissolve the cobalt matrix out of old tungsten carbide inserts. It sure seemed more acrid, chokeing, and lacrimentory than normal aqua regia to me! :o

I have since discovered that the dissolution is quite rapid in plain HCl with the application of electricity.
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[*] posted on 6-6-2007 at 00:54
Basic Lead Carbonate from Lead Sulfate


I haven't really checked much further concerning
the reactions for lead chloride specifically ,
but I have turned up some other interesting
lead salts preparations in patents which have
value . Some of the described reactions may apply to
whatever scrap lead source or other methods have
already been described in this thread . Anyway
for whatever value these reactions may be , it
seems pertinent to add these references .

[Edited on 6-6-2007 by Rosco Bodine]

Attachment: US2152242 Basic Lead Carbonate from Lead Sulfate.pdf (274kB)
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[*] posted on 6-6-2007 at 00:58
Various Pure Lead Monoxides


This is the traffic light lead monoxides patent ....

green
yellow
red

:D

Just pick the color you like

Attachment: US3497382 Methods for green, yellow, red, PURE_LEAD_MONOXIDES.pdf (64kB)
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[*] posted on 6-6-2007 at 01:01
Basic Lead Hydroxide


This would be a good one for neutralizing
the acidity which rises during PbO2
plating operations

Attachment: US3230043 LEAD_OXIDE_HYDROXIDE.pdf (146kB)
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[*] posted on 6-6-2007 at 03:10
Purifying lead for the making of lead compounds


Quote:
Originally posted by Eclectic
NaOH as flux with a bit of NaNO3 as oxidizer worked very well to burn out most of the impurities in 300 lbs of weathered scrap roofing lead I reclaimed once. There was plenty of dross left over for conversion to lead salts.
[Edited on 5-13-2007 by Eclectic]


Does this reaction preferentially oxidize the alloying elements first? I have bullet lead, (bird shot) that I want to purify. What were the proportions used?

I tried the nitrate + Pb procedure the other day. I used KNO3 and a stoichiometric amount of lead shot. There was a lot of lead left over, and I noticed it seemed to be softer than my shot. I did not add any NaOH.

I think that there is probably arsenic* alloyed with my lead, and I'm assuming there is antimony in it for hardness. There may be tin, bismuth, copper… and a whole host of other minor impurities; all of which I want out!

Thus far, I have made lead nitrate by reacting the metal with nitric acid, which was made by reacting calcium nitrate fertilizer with drain cleaner grade sulfuric acid and filtering calcium sulfate from the resulting paste. It works reasonably well with suction filtering (normal filter paper works fine if you do it cool), and the best I estimate you can get from this method in terms of concentration is about 30% by volume HNO3. I don’t know how pure the nitrate can be reasonably expected to be even after a couple recrystallizations. Does arsenic stay behind in the insoluble crap left undissolved?

I have also tried electrolytic purification of my lead. The shot is cast into plates, and using them as anodes, electrolyzed in a hot solution of lead chloride, plating a spongy lead on a stainless steel cathode. The problem with this is:

1.) The electrolyte isn’t very conductive, necessitating high voltage (though this could serve to keep the solution hot)
2.) The anodes form a black, very fine coating of the alloying elements that have been left behind, which tends to float off and implant itself in the lead deposit on the cathode. This necessitates wide electrode spacing or a diaphragm to keep the solutions separate.
3.) Since the solution isn’t very conductive, and the electrodes can’t be very close for the reasons given in 2, the process is pretty slow. So you have to sit there for hours scraping the cathode as the lead deposit builds up, all just to collect a few tens of grams of purified lead. My attempts at an automatic scrapper have failed do to a lack of a plastic that doesn’t deform in the hot electrolyte.

The resulting lead is, however, very soft, meaning that some purification is certainly resulting. I have been contemplating doing the electrolysis process on a larger scale, using something like a 5 gallon container, and a rotating stainless steel cathode with a fixed spiral scraper that continuously pushes the lead into a compartment, or even completely out of the electrolyte, as well as giving the anodes “jackets” to keep the alloying particles away from the cathode.
One big advantage with doing this is you get finely divided lead, which also oxidizes in air easily, making it easy to react with acids. Reacting PbO with nitric acid is a lot more pleasant, as well as efficient, than using the metal directly.

It would be interesting to compare the softness of the lead (the softer the purer) treated by the above various methods. IE… the electrolytic lead, lead produced form recrystallized PbCl2, and lead treated with NaNO3 and NaOH in the molten state.

*I read that arsenic is added to lead shot when it is cast from a tower, because it improves the roundness; and the sack of shot I have advertises that it is dropped from a tower like in the good ol' days.

-Alan
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[*] posted on 6-6-2007 at 04:12


Your NaNO3 will have some Ca and sulfate left in it. so you may get some PbSO4 left behind. I don't know where the arsenic would end up in this case, I suspect it goes into solution.

A discussion of sources of lead metal and what's likely to be in the alloys. Check the fluxing bullet metal section - a flux of borax, boric acid, and Na or K nitrate is one clean-up method, another I've heard of is using NaOH with the chlorate based plant killer, which is sodium metaborate plus sodium chlorate. The metaborate is the 'alkaline' form of borates, and so doesn't consume the NaOH.

http://www.lasc.us/CastBulletNotes.htm


Antimony compounds in solution will plate out onto lead, if I'm remembering correctly, I'd expect it to be left behind on the anodes. Arsenic may end up in solution.

Sounds like you do need to get a diaphragm in there, so that you can reduce the electrode spacing.
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[*] posted on 6-6-2007 at 04:25


My thinking was that most of the impurities would oxidize in preference to lead, and had read somewhere of a lead purification process that involves blowing oxygen through the molten lead, much like the Bessimer process for steel, but much less spectacular. NaOH melts at about the same temp as lead and makes a very fluid reactive flux. I just added NaNO3 a bit at a time with stirring and heated until the dross on top became a solid stiff paste, then skimmed it off and repeated several times. The resulting lead is very soft and seemed to solidify with a very coarse crystal structure when cast into 3 x 5 x 1.5 inch ingots.
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[*] posted on 6-6-2007 at 09:53


From what I have been reading on this , although it has not been specifically described that it can be done this way , it would seem that battery scrap containing lead plates , PbO2 and PbSO4 could be processed by digestion
with HCl and NH4NO3 to convert the metal and oxides to
PbCl2 > filter out the undissolved PbSO4 for separate treatment with Na2CO3 and NaOH to convert to Basic Lead Carbonate . Also treat the PbCl2 with the Na2CO3 plus NaOH to form Basic Lead Carbonate . Possibly the
process for both reactions could be done in one pot without even filtering the unreacted PbSO4 from the first step . Anyway , once you have converted the three principal lead values in the battery scrap to basic lead carbonate and filtered it out from the ammonium chloride / sodium chloride
supernatant , rinsed it with water , it can be dissolved
in acetic or nitric acid , filtered again , and converted
to whatever other salt desired , or refined electrolytically
back to the metal . For electrolysis back to the metal , it would probably first be plated out as PbO2 from the acetate or nitrate , and then the cell polarity reversed to redissolve the PbO2 and plate it out as the pure Pb .

By manipulation of pH and current densities , the Pb should be very much purified through such a process .
But really , just by stepwise chemical purifications ,
the lead can be purified beyond 99% before any
electrolytic methods are employed .

I don't have the charting of the various pH and concentration / temperature values which have been worked out by industrial recyclers .....but lead can be gotten to a form of high purity for some of its compounds
purely by chemical refinement , without resorting to
electrolysis , except where the most demanding sorts
of need for absolute purity is applicable , as for
semiconductor applications .

[Edited on 6-6-2007 by Rosco Bodine]
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[*] posted on 6-6-2007 at 14:43


I would like to make some Lead Acetate so I can make other Pb compounds fairly easily but I don't know whereto get high strength Acetic Acid or Hydrogen Peroxide. What are my best bets for getting these 2 compounds in high strength solutions?

Additionally, what's a high-yield method for preparing PbO and PbO2, these oxides are perfect for making then making the chloride by dissolving them in warm HCl. How could I make PbCl4 though? That would be exotic.

Has anyone ever made Na2PbO3 or CaPbO3? I thing plumbates would be pretty cool to synthesize, CaPbO3 would be like the Lead analogue of the mineral calcite, which is CaCO3.

I have only synthesized one lead compound before and my yield was VERY low, I placed Pb strips in cold HCl and I got tiny, very lustrous crystals after about a month but the yield was so low I couldn't use any of the product. The crystals coated the lead strips and they were pretty attractive, so I cut off piece of a strip the size of a postage stamp covered in crystals and saved it.
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[*] posted on 6-6-2007 at 23:48
more lead salts patents


Here are a couple more patents which show some interesting reactions via a combination of electrolytic and chemical methods .

Attachment: US414935 Electrolytic MANUFACTURE_OF_WHITE_LEAD.pdf (95kB)
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[*] posted on 6-6-2007 at 23:51
and the second


This one is similar but uses the free acids
and accellerates the reaction via electrolysis .

Attachment: US459946 Electrolytic refining of metallic Lead , via lead hydroxide , and lead salts.pdf (172kB)
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[*] posted on 15-6-2007 at 08:18


I recently found some old PbO made from lead nitrate by first converting it into Pb(OH)2 with NaOH and then to PbO by addition of H2O2. The resulting PbO was orange/yellow.

I decided to make some lead carbonate from it and started to dissolve it in nitric acid. I thought it would just form a clear solution after each addition of PbO and heat up a little but instead the solution turned brown with some suspended particles and the oxide didn't dissolve fully but there remained some blackish residue.
Also large amounts of gas formed. Could be CO2 or O2. I'll take few pics while I test the gas.

Does anyone have any idea what happened?

Here are the pics:

http://koti.mbnet.fi/otto2000/pic/before_addition.jpg
http://koti.mbnet.fi/otto2000/pic/after_addition.jpg

The change in color is not that strong now as I added more nitric acid. Also the gas that forms doesn't put out a burning piece of wood but it doesn't light it either when it's just glowing.

EDIT:

After adding all of the oxide the solution was brown/black. I guess it is just PbO2 formed with the PbO when I prepared it by adding H2O2 to the Pb(OH)2.
[Edited on 15.6.2007 by IPN]

[Edited on 15.6.2007 by IPN]
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[*] posted on 15-6-2007 at 08:47


Quote:
Originally posted by Rosco Bodine
Here are a couple more patents which show some interesting reactions via a combination of electrolytic and chemical methods .

I have done something similar before. If one takes dilute acetic acid (distilled white vinegar) and adds a few percent of sulfuric acid to it, then immerses lead electrodes in the liquid and applies current, the anode start to dissolve with the immediate formation of a white lead sulfate precipitate streaming down from the anode. The sulfuric acid needs to be occasionally replenished as it is captured by the dissolving lead, and the anode may need periodic shaking or scraping to dislodge a growing lead sulfate shell. Doing this with lead sheet gave some slightly impure material since small pieces of unconsumed lead would sometimes break off and fall to the bottom.

The lead sulfate, once filtered and given a cursory water wash, can be heated with an excess of sodium carbonate solution to produce lead carbonate, as demonstrated by the effervescence and dissolution of the white material in sulfamic acid solution.

Or, if you are willing to be patient and sacrifice more vinegar, it's possible to use straight vinegar until lead begins depositing on the cathode (as described in the second patent). This dilute lead acetate solution can be used as-is for (say) preparing H2S test strips, or it can be combined with other acids giving less soluble lead salts to produce precipitates, or it can be allowed to evaporate over a long period to eventually give crystals of lead acetate. It's inefficient, but it is convenient if you only need small quantities and/or low concentrations of soluble lead.




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[*] posted on 15-6-2007 at 12:00


I think if your source of acid is strictly as an added material from outside the cell , you can actually use
AC across two lead sheet electrodes at a low potential ,
or a series of plates so that the divided potential is
something around 0.6 volt ....and you will get a surface
oxide - hydroxide formation which then should go into solution as the basic lead salt or normal lead salt of the acid . The voltage must be limited however , because at
higher potential the relatively inert higher oxides of Pb will
form and passivate the electrodes ....so this is one place where low voltage will absolutely be required . And if AC is used , both plates should be consumed at an equal rate in neutralizing the acidity as well as nullifying any tendency towards polarization .

In a polarized cell using a lead anode in a hot ammonium nitrate solution .....I believe that lead nitrate would form
via a low level DC voltage and free ammonia would be evolved , although this might go no further than the basic lead nitrate ....that would be halfway there , and still useful if it works , avoiding the usual loss of nitrogen from nitric acid ,
and losing it as ammonia instead :D

Attached is a pertinent reference concerning the reactivity of fused ammonium nitrate , however I would expect that a similar reactivity though slower would also be observed for aqueous solutions , and even moreso for such reactions being accellerated by electrolysis .

Attachment: Fused Ammonium Salts as Acids Reactions in Fused Ammonium Nitrate.pdf (540kB)
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hashashan
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[*] posted on 20-6-2007 at 00:14


I decided i want to purify my lead nitrate solution.
i dissolved some lead weights with nitric acid. Decanted the acid and dissolved all i could with water' filtered off the undisolved crap.

can i call this solution pure enough or should i recristalize it in some way?
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[*] posted on 19-12-2007 at 21:22
Lead Oxide


Again curious about oxidizing molten lead. Air never worked well for me, but what about that stuff I have a lot of...

Experiment

A two pound lead ingot was melted in a thin steel crucible with a propane torch and some sodium chlorate was added with stirring. The salt melted, forming a molten salt flux on top of the lead metal, which solidified due to the cold salt (NaClO3 melts cooler than Pb). Some bubbling (decomposition to O2) and brown precipitate was noted. The reaction appears to be relatively slow and steady at this temperature, around 300-400°C. More NaClO3 was added, in total an estimated 100 g. After further heating (over 400°C), the reaction rate increased noticably and the solution became thicker. The heat was removed. Within one minute, the surface started burning and, a second later, a column of yellowish smoke issued from the crucible. Simultaneously, the bottom half inch of the crucible became bright red hot (approximately 900°C). In one second, the reaction had ceased and molten lead metal remained, with molten sodium chloride floating on top. In the sodium chloride, and coated on the walls of the crucible, was a yellow to brown substance, likely PbO given the temperature. In about half a minute, the material cooled sufficiently that the salt layer froze solid. The laboratory was vacated to allow the smoke to settle.

Discussion

Sodium chlorate is a strong oxidizer, and at elevated temperatures, a vigorous one, prone to runaway. In this small reaction, a substantial amount of material was probably lost due to the exotherm. If the temperature were held at a moderate temperature (perhaps 400-500°C), through controlled cooling and using a large excess of lead for thermal mass, I think this reaction could produce a substantial amount of lead oxide.

The oxide produced is unknown. I don't know exactly what color fused or wetted PbO is, and the reaction temperature, even at coolest (300°C), is quite hot for PbO2. Further experiments and analysis should reveal clues.

Tim




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chemoleo
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[*] posted on 19-12-2007 at 21:57


12AX, thumbs up for a nice scientific description of the experiment.
The same should be tried for the perchlorate, or permanganate, or dichromate (although it will be harder to discern what's going on from the reaction products)
I'm delighted you call a two pound ingot a 'small experiment'. That's the spirit. Just don't get harmed.
I guess I don't need to point out how to determine what the nature of the oxide is? The colour for one is quite telling...
YOu might be out of luck in making the peroxide there...




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