Sciencemadness Discussion Board

The lead salts preparation thread!

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kazaa81 - 12-3-2006 at 11:40

Hello,

I decided to create a thread about lead salts preparation, with the hope that everyone will help posting synthesis and preparations, so that we will make a pdf for the prepublications thread.

Here is a link of a zip containing tables extracted from Handbook of Chemistry and Physics, with lead salts properties:
Lead Salts properties.by.kazaa81
(thanks to my friend for hosting the file!)

So, lets start! :D

[Edited on 12-3-2006 by kazaa81]

garage chemist - 12-3-2006 at 12:55

A few weeks ago I made a good sized quantity of lead acetate.
It was created by dissolving lead in a mixture of acetic acid (ca. 25% concentration) and H2O2.
The acetic acid must be present in considerable excess, since the mixture must never be allowed to become basic (the H2O2 would decompose violently and splash around the solution).

Lead sheet is added to an excess of 25% acetic acid, heated to nearly boiling and 30% H2O2 slowly dripped in, under constant stirring. The lead is dissolved rapidly, without gas evolution (only a very small amount of oxygen is generated).
The solution is then decanted, while still hot, from a small amount of undissolved lead and carefully evaporated in a warm place (don't boil the solution!), like on the heater in your room. A pleasant fragrance of acetic acid will fill the house during the process.

BTW, there is already a thread on this. Could someone merge this thread with it?

chochu3 - 12-3-2006 at 22:50

a month or so ago after making litharge (lead oxide) as by product from sodium nitrate reduction, I added aqueous hydrochloric acid and the long needle white crystals formed were lead chloride.

The_Davster - 12-3-2006 at 23:12

A while back I dissolved some shot in acetic acid and H2O2, filtered insolubles, and then added HCl. I wanted to make a lots of crystals of PbCl2, but I did not have the patience/balls to make large volumes of hot concentrated lead chloride solution(indoors). That and I used too much HCl so it was vaporizing while I was heating the solution.

12AX7 - 13-3-2006 at 01:47

Lead hydroxide

Dissolve sodium or potassium nitrate, sodium chlorate or sodium perchlorate in water sufficient to make a conductive solution. (Potassium chlorate and sodium chloride also work, but KClO3 has low solubility and NaCl must be hot for this process to work; sodium acetate isn't a strong electrolyte.) Attach a bar of lead to a +5V supply and use any conductive material for the cathode (steel sheet, copper, graphite, titanium, etc.). Anode reaction: Pb = Pb(2+) + 2e- (lead dissolves into anolyte). Cathode reaction: 2H+ + 2e- = H2 (hydrogen ions are removed, causing a basic (excess of hydroxyl ions) catholyte). When solution mixes, hydroxide precipitates lead ions, forming white Pb(OH)2.

Some carbonate (as CO2 bubbled into the solution) can be added to produce lead carbonate (basic, I believe).

The process using chloride ions must be performed warm, else the lead ions will precipitate with chloride ions at the electrode, causing passivation and oxidation to brown PbO2.

Lead can also be heated in air and stirred (use ventilation!), but it does not produce much oxide; the product is essentially sand-sized lead droplets with a layer of suboxide (Pb2O) on the surface.

Tim

woelen - 13-3-2006 at 05:30

Lead nitrate
I added 7 grams of lead shot to appr. 25 ml of 52% HNO3. The lead at first dissolves vigorously, but at the end, the reaction becomes very slow. Heating was needed to dissolve all of the lead in the acid. During the reaction, a white very fine crystalline precipitate of Pb(NO3)2 was formed. Be very careful at this stage. Lots of brown fumes of NO2 are formed and also fine droplets, containing lead (II) ions may be thrown into the air. Do this initial step outside or in a good fume hood.

I heated the solution carefully, until it almost was dry, with constant stirring to assure that no local hot spots are formed, where the lead nitrate decomposes.

The final drying was done by spreading the solid on a piece of glass and letting it dry in contact with warm air (e.g. a radiator will do). In summer, a hot dry place, also is suitable. After a few hours, a white crust and powder was obtained. The powder I have still is quite acidic, but I did not recrystallize it again. The acidity is advantageous with aqueous experiments (lead (II) tends to hydrolyse very easily), but for pyro-applications it certainly is not good at all.

kazaa81 - 13-3-2006 at 05:33

Thanks all for replying, any preparation welcomed!

I was thinking about electrolytical production of PbCl2...can one use lead as anode of a NaCl or HCl solution? The Cl- ions would combine with lead and form white PbCl2?

Also...from wikipedia:
"PbCl2 is used in synthesis of lead(IV) chloride (PbCl4): Cl2 is bubbled through a saturated solution of PbCl2 in aqueous NH4 forming [NH4]2[PbCl6]. The latter is reacted with cold concentrated sulfuric acid (H2SO4) forming PbCl4 as an oil."

If you don't know from what lead salt preparation start to post, just check the tables...there are plenty of lead salts and even more reactions to make them!


[Edited on 13-3-2006 by kazaa81]

garage chemist - 13-3-2006 at 07:46

PbCl2 is easily prepared by dissolving lead in HCl of moderate strength, the reaction taking some time (few weeks). The reaction is faster when the HCl is heated.

When NaCl solution is electrolysed with two lead electrodes, mainly Pb(OH)2 is formed due to the OH- ions being formed at the cathode reacting with the initially produced PbCl2.
However, by stirring this Pb(OH)2 with HCl, PbCl2 is formed.

PbO2, lead dioxide, is very easily made by electrolyzing 20% H2SO4 with two lead electrodes. At the cathode hydrogen is evolved, at the anode PbO2 is formed as a dark brown powder.
The electrolysis can be continued until the entire anode is converted into PbO2. The PbO2 is isolated by filtering the solution, washing and drying the PbO2.

PbO2 is a powerful oxidiser, capable of forming very energetic pyrotechnic mixes, especially with powdered metals.

12AX7 - 13-3-2006 at 10:07

Quote:
Originally posted by garage chemist
PbCl2 is easily prepared by dissolving lead in HCl of moderate strength, the reaction taking some time (few weeks). The reaction is faster when the HCl is heated.

When NaCl solution is electrolysed with two lead electrodes, mainly Pb(OH)2 is formed due to the OH- ions being formed at the cathode reacting with the initially produced PbCl2.
However, by stirring this Pb(OH)2 with HCl, PbCl2 is formed.

PbO2, lead dioxide, is very easily made by electrolyzing 20% H2SO4 with two lead electrodes. At the cathode hydrogen is evolved, at the anode PbO2 is formed as a dark brown powder.


As I mentioned, anodic corrosion of lead in NaCl leads to Pb(OH)2 when sufficiently hot, or a soft crust of PbCl2 and PbO2 when cooler. This is not a satisfactory method to produce PbCl2 or PbO2.

Anodization of lead in sulfuric acid leads to PbO2, as a crust. Some flakes off, but not much. This method does not produce useful amounts of PbO2, unfortunately.

The best method for PbCl2 is to oxidize the metal and then react with HCl. Direct reaction with HCl is slow (weeks) and/or painfully annoying (boiling HCl, my nose rejoices), or else wasteful of oxidizer (H2O2, etc.), though the latter depends if it's a concern of yours...

Tim

kazaa81 - 13-3-2006 at 13:01

What if one try to use lead anode and/or cathode in a strong HCl solution? Would be the production of PbCl2 better?

garage chemist - 13-3-2006 at 14:03

Yes, lead anode in HCl should make PbCl2 in good amounts.

Although I don't know why you'd want PbCl2... its solubility is too low for it to be of real value.

12AX7 - 13-3-2006 at 21:32

Well, you can't use acid because the metal plates across...

Even in concentrated HCl, hot enough to dissolve a reasonable amount of PbCl2, I doubt it'll hold too much before lead metal plates out. It's just not very reactive.

For synthesis you want Pb(NO3)2, true, but I like PbCl2 for its hot solubility and furry crystal texture. 8)

Tim

BromicAcid - 14-3-2006 at 00:14

The metal will plate across but if you preform the electrolysis in a manner completely unconducive towards electroplating you can dissolve the anode much faster then it will plate on the cathode. For instance I did electrolysis with nickel electrodes in HCl with 14 amps and 12 volts. The solution heated to boiling within a few mintues but before it could go any further what was left of the anode had broke off at the surface and the cathode only had some strange spires on it. I let it cool and repeated a few times and before I knew it I had a saturated solution of nickel chloride.

To get over the low rate of solvoylsis of Pb in HCl couldn't you just get an aquarium bubbler and bubble air into it? This would prove useful to make the acetate. One of the older methods involved hanging lead plates above a bath of acetic acid, the combination of the fumes and the air attacking the plates and the sugar of lead being scraped off periodically.

kazaa81 - 16-3-2006 at 05:41

Actually, I am leaving some pieces of Pb in 30% HCl, but as expected, the reaction is very slow, so slow that it can't be even imagined to be posted in the pdf we will make... :o
I am thinking about dissolving the "sponge" Pb made from NaCl electrolysis...
I will soon try electrolysis of Pb in HCl (maybe using only one Pb electrode) and reaction of Pb with Cl2...If someone can try something too, we will appreciate this!

[Edited on 16-3-2006 by kazaa81]

Axt - 16-3-2006 at 07:24

Extract from "The Preparation of Pure Inorganic Substances", E. H. Archibald, Wiley, New York, 1932.

Its only 3 pdf pages, but such is my scanning skillz that its ~1Mb. Contains the preparation of <i>pure</i> lead, lead nitrate, lead chloride and lead bromide. If one, for whatever reason needed it "pure".

http://xfiles.ft100.net/images/pure_inorganic_substances-lea...

kazaa81 - 16-3-2006 at 10:34

Thank you Axt...I've searched some about this on Brauer "handbook of inorganic preps" but if you read in the lines...
"LEAD, PUREST FORM
Commercial electrolytic lead (about 99.995%) is sufficiently pure
for most laboratory purposes. However, it contains, depending on
the method used in its production, varying concentrations of minute
amounts of Cu, Bi, Fe, Zn, Cd, As, Sb, Sn, Se, Te and rare metals,
totaling about 5-50 • 10^-6 g. of impurities/g"

:o of course here we are claiming that 99.995% isn't enough pure for we!
I think you can understand these aren't really the preparations needed by an amateur chemist, and so, for our pdf.
I've an idea about how to structurate it (the pdf):
- A general part talking about lead and a table with lead salts properties
- A part concerning about how to change metallic Pb in soluble-salts Pb
- A last part concerning about methasynthesis of soluble-Pb-salts, because some of these are otherwise difficult to obtain without a methasynthesis.

Lead Acetate

12AX7 - 22-5-2006 at 06:21

Am finally crystallizing some lead acetate today.

The solution is brown with, I presume, iron acetate, and probably some amount of copper acetate as well. This was obtained by reacting vinegar with my lead oxide, which has been produced variously by reacting lead with HCl and neutralizing the PbCl2; electrolyzing lead in a neutral chlorate or acetate solution; etc. The iron impurity is probably from the metal sheet I calcined the product on.

There is also some (probably basic) lead acetate now in solution, from the first product I made (which didn't crystallize very well).

The solution has gone from a gallon down to er.. maybe 16 ounces in a jar. Funny story, I stuck the syruppy liquid in the freezer to attempt to crystallize it. When it was cool, I came back and it was completely solid, even with the round crystallization fronts like when supersaturated sodium acetate is seeded into growth.

I have since melted the mess and it seems to be better behaved now. It is currently cooling to room temperature and forming mats of variably brown crystals, which I will filter, wash and recrystallize to, hopefully, a much happier white product...

Tim

12AX7 - 27-5-2006 at 16:24

Question: does your lead acetate trihydrate typically clump?

My product is currently a crystalline/prismatic, free flowing powder with some clumps not broken up, but when left to sit in free air for a day or two it gets sticky and needs to be shaken to get it free again. It also smells of acetic acid.

Tim

Lead Acetate

MadHatter - 27-5-2006 at 16:56

The credit for this procedure belongs to many people but I thought it worth mentioning.

Some copper carbonate(cheap from the pottery shop) is added slowly to hot vinegar and
stirred until no more CO2 is produced. Number 9 bird shot or any other suitable small lead
pieces is put into the solution. After a few days the lead will displace the copper ions and
the blue-green colour will disappear. Filter out the remaining lead and copper formed.

I prefer to keep the lead acetate in solution to plate PbO2 onto gouging rods.

12AX7 - 30-5-2006 at 20:24



Recrystallized (once) lead acetate, still a yellowish tinge. Still caking up and smells. Haven't weighed it but probably around a pound. Still more to recrystallize and add to the pile.

Tim

Magpie - 10-12-2006 at 11:08

I had recently prepared some crystals of lead (II) acetate*3H20 using assay grade PbO, of which I have a supply good enough for several lifetimes. Then I got to making FeS (or attempting to) and needed to test my products to verify the synthesis. My method was to treat a few mg in a small test tube with 6N HCl then carefully waft a few vapors in my direction to check for H2S. I had heard of lead acetate papers being used in some of the old lab manuals for detecting H2S and was wishing I had some. So yesterday I made up a 5% aqueous solution of lead acetate*3H2O in an evaporating dish and soaked some 7cm filter papers in it. These were then hung up to dry overnight. Today I cut the papers into strips and tried them out on some H2S. They worked as you can see in the photo below:

lead acetate paper.jpg - 86kB

SAM4CH - 10-12-2006 at 12:02

I prepared lead acetate from Pb3O4 "was used in paint" and let it react with acetic acid over night at room temp. and I got very clear and colorless solution, then I recrystalized very nice crystals with no yellow or red color.

guy - 10-12-2006 at 12:43

Hey, did anyone get an insoluble salt while recrystallizing Lead acetate? I think it could be lead subacetate, but it wont dissolve in excess acetic acid either.

12AX7 - 10-12-2006 at 13:46

Did you use tap water? Hell, even the "distilled" vinegar I have makes white junk (most likely sulfate or chloride) when lead ions are added. :(

Tim

guy - 10-12-2006 at 15:12

Quote:
Originally posted by 12AX7
Did you use tap water? Hell, even the "distilled" vinegar I have makes white junk (most likely sulfate or chloride) when lead ions are added. :(

Tim


I used Distilled Vinegar only. So its not the carbonate? Thats cool then, I can just filter it off then.

12AX7 - 10-12-2006 at 19:00

I have a solution of mildly acidic (about equal to that from hydrolysis, it's not too stinky) lead acetate drying as we speak. It has little scum in it, last I checked.

Tim

SAM4CH - 11-12-2006 at 06:48

what about your PbO? is it pure or technical? I think the problems always in lead raw like PbO, Pb3O4, and lead alloy? you can prepare pure Lead acetate in simple method:

1) purification your lead alloy (more the 90%Pb) by electrolysis solution, I tried with diluted HCl and it give good results, you will get fine powder with high current "I think there are better bath for purification of lead".
2) wash your powder with distilled water and then put it in acetic acid for 24 hours, you will get clear solution with some ppt filter it and recrystalize your salt by heat at 80-100 to prevent any oxidation of acetate, cool and collect your crystals.

12AX7 - 11-1-2007 at 18:35

The most beautiful lead acetate crystals yet.

Chem_PbAc22.jpg - 43kB

tnhrbtnhb - 13-1-2007 at 22:07

AAAAUUG! I think this should be said.....For a pro chemist I don't suppose this is a problem, but for beginners at home.....

The toxicity of lead is greatly underestimated by the general public! And greatly understated in chemistry books. I had lead poisoning when I was 8 or so from lead dust from battery terminals, and lead paint, and my dad *is a chemist*. IT IS BAAAAAADDDDDDDD!!!! He still doesn't believe it's seriously poisonous, inexcusably stupid..... But just because it's LD50 is high, doesn't mean it can't cause devastation at very low doses. You don't even notice you're getting poisoned, it's kind of like being sleep deprived all the time (but much worse), instead....

Check it out, the max. intake per day is only a few *micro*grams.
And for young-uns it should absolutely be banished from their environment. There's no way you can practicaly handle it in a safe fashion.
These pages are mostly about lead paint, but obviously it applies to other lead sources too.....

http://www.nsc.org/library/facts/lead.htm
http://www.niehs.nih.gov/oc/factsheets/lyh/govtdo.htm

guy - 20-1-2007 at 14:57

I have some Lead and vinegar in a beaker, its turned orange. Same thing happened when I heated a sodium acetate solution. What happened?

[Edited on 1/20/2007 by guy]

UnintentionalChaos - 20-1-2007 at 15:43

Sorry to be slightly off topic, but does anyone have ANY info on lead oxalate? I can find absolutely nothing on the internet. I'm looking mostly for its bp/decomp temp.

Instant white precipatate(Lead Acetate)

atomicproject - 11-3-2007 at 16:16

While setting up the necessities to make lead acetate, I decided to pour the acetic acid on while still boiling. Immediately, a large amount of white precipitate formed and settled all over the lead like the aftermath of a snow storm.

Any ideas what this stuff is ?

not_important - 11-3-2007 at 16:29

Quote:
Originally posted by UnintentionalChaos
Sorry to be slightly off topic, but does anyone have ANY info on lead oxalate? I can find absolutely nothing on the internet. I'm looking mostly for its bp/decomp temp.


Sol. 0,15 mg/100ml @ 18 C
sp. gr. 5,28
decomposes circa 300 C

Pyridinium - 19-3-2007 at 13:39

Quote:
Originally posted by guy
I have some Lead and vinegar in a beaker, its turned orange. Same thing happened when I heated a sodium acetate solution. What happened?

[Edited on 1/20/2007 by guy]


Was your NaOAc made using vinegar?

Lead acetate can form colored complexes with some of the flavonoids & other impurities of natural products (presumably, this includes vinegar). Even though vinegar is said to be distilled, some impurities will have come over if it wasn't done via sub-boiling distillation.

Now, if you didn't have transition metal impurities in your NaOAc and it still turned orange, not sure what it could be. The pure ones shouldn't turn color though.

What kind of container are you storing your vinegar in?

guy - 19-3-2007 at 13:58

Quote:
Originally posted by Pyridinium
Quote:
Originally posted by guy
I have some Lead and vinegar in a beaker, its turned orange. Same thing happened when I heated a sodium acetate solution. What happened?

[Edited on 1/20/2007 by guy]


Was your NaOAc made using vinegar?

Lead acetate can form colored complexes with some of the flavonoids & other impurities of natural products (presumably, this includes vinegar). Even though vinegar is said to be distilled, some impurities will have come over if it wasn't done via sub-boiling distillation.

Now, if you didn't have transition metal impurities in your NaOAc and it still turned orange, not sure what it could be. The pure ones shouldn't turn color though.

What kind of container are you storing your vinegar in?


I bought it in the plastic container. I think it may have "carmelized" or something like that. It only turns to brown when it becomes really concentrated. Maybe as it evaporates NaOH accumulates an may cause some carmelizing.

PbO from Alkali metal nitrate and Lead metal

dann2 - 9-5-2007 at 10:23

Hello,

Can PbO be made in a straight forward manner from Sodium Nitrate + Lead Metal.
Sodium Nitrite being the biproduct.

Dann2

Magpie - 9-5-2007 at 10:40

Yes, I believe it can.

When I used to make NaNO2 using raw lead and NaNO3 there was always a lot of orange precipitate formed as byproduct. I'm sure this was PbO as it looked just like the PbO that I had bought.

Eclectic - 9-5-2007 at 10:55

Also, electrolyzing lead electrodes in ammonium nitrate solution is supposed to to work...

[Edited on 5-9-2007 by Eclectic]

dann2 - 9-5-2007 at 11:10

I tried the Ammonium Nitrate + Lead anodes and Cathodes.
There was alot of Spongy Lead forming.

With the Lead Metal + Nitrate what do I do?
Dissolve the (Na) Nitrate in water and add Lead and Heat?

Would Ammonium Nitrate do.

TIA.

Dann2

Eclectic - 9-5-2007 at 11:36

You have to use molten NaNO3.

You didn't get lead hydroxide/oxide as the electrolysis proceded? I thought H2 was evolved and lead hydroxide/oxide precipitated.

12AX7 says NaNO3, NaClO3, or NaClO4 work as electrolytes.

Ah Ha! I bet the ammonium nitrate solution solubilizes the lead hydroxide, just like it does lead chloride.

[Edited on 5-9-2007 by Eclectic]

dann2 - 9-5-2007 at 12:05

Quote:
Originally posted by Eclectic
You have to use molten NaNO3.

You didn't get lead hydroxide/oxide as the electrolysis proceded? I thought H2 was evolved and lead hydroxide/oxide precipitated.

12AX7 says NaNO3, NaClO3, or NaClO4 work as electrolytes.

Ah Ha! I bet the ammonium nitrate solution solubilizes the lead hydroxide, just like it does lead chloride.

[Edited on 5-9-2007 by Eclectic]


I did get a white precipitate coming on the anode. The anode needed cleaning every half hour or so. If it was not cleaned Lead Dioxide started to form on it. (Thats what it looked like). Spongy lead was forming on the Cathode. The whole thing was rather messy.
Would a diaphram help?

Will try the Na Nitrate + Lead for litharge.#

Cheers,

DANN2

Eclectic - 9-5-2007 at 12:21

Alkaline conditions at the cathode precipitate PbOH2, acidic conditions at the anode dissolve Pb, so I think a diaphragm might hurt rather than help. Na salt electrolytes would probably work better. Maybe fiddle with cell conditions so lead does not plate out, use AC, stirring?

Stirred molten lead and NaNO3 melt is a mess too...

dann2 - 9-5-2007 at 17:55

Quote:
Originally posted by Eclectic
Alkaline conditions at the cathode precipitate PbOH2, acidic conditions at the anode dissolve Pb, so I think a diaphragm might hurt rather than help. Na salt electrolytes would probably work better. Maybe fiddle with cell conditions so lead does not plate out, use AC, stirring?

Stirred molten lead and NaNO3 melt is a mess too...


Thanks for reply,

Will the lead ions and the OH ions not meet at the diaphram and react there (precipitate Lead Hydroxide) and therefor keep the anode free from hydroxide ppt.

I have been doing some reading from here:

http://www.sciencemadness.org/library/books/the_manufacture_...

Alkali conditions at the cathode due to formation of some ammonia cause Plumbites to form. The plumbites then cause spongy lead to deposit. page 45 (I am not up to speed on the chemistry myself).


Will persevere.

Dann2

Eclectic - 9-5-2007 at 18:14

Sounds like it's best to avoid ammonium and nitrate altogether and use bicarb and sodium chlorate. See page 42-43.
Thanks for the reference, as I couldn't recall where I had seen ammonium nitrate used. :(

I think the PbOH2 might clog up the pores in a diaphragm.

[Edited on 5-10-2007 by Eclectic]

dann2 - 10-5-2007 at 17:44

Hello,


I obtained another patent US563,555 Manufacture of White Lead.

__________________
A cell with two diaphrams is used.
Alkali Metal Nitrate is used. So can acetate.
Concentration not stated.
Anode in one compartment is Lead.
Cathode in another compartement is copper.
Third compartement is in the middle.
As the cell is operated liquid is drawn from Anode
compartement and the middle compartement and mixed outside the cell.
Lead Hydroxide precipitates and the liquid is returned to cell.
Current density on anode is 15.5mA per square cm.

(The hydroxide is then converted to Basic carbonate by air.)
____________________________________________-

Tim Williams suggested that Perchlorate would be better
than Nitrate or Chlorate as it is harder to reduce (at cathode) and therefor you will get less Lead Metal forming on the Cathode.

To work a cell with no diaphram you would need a mechanical moving brush set up to keep the hydroxide off of the Anode. (or sit there yourself wipeing (and weeping!))
IMHO.

I attempted to make Litharge from Sodium Nitrate + Lead.
First attempt I used Stiochiometric amounts and got lots of Lead Metal.:D
Next time I kept adding the Nitrate to the molten Lead untill I reckoned all metal was gone.
It seems easy enough.

What will happen if I heat too much.

Dann2

Filemon - 11-5-2007 at 13:02

Quote:
Originally posted by dann2
Hello,

Can PbO be made in a straight forward manner from Sodium Nitrate + Lead Metal.
Sodium Nitrite being the biproduct.

Dann2


Can one make the reaction with tin?

NaNO3 + Sn => NaNO3 + SnO

12AX7 - 11-5-2007 at 13:55

It probably goes to SnO2. I don't know if NO2- would be reduced further, or if transient species like nitrogen atoms would be oxidized to nitrite by the SnO2.

Tim

dann2 - 13-5-2007 at 05:49

Hello,

Finished my second attempt at making PbO using
Lead Metal and Na Nitrate. I stirred and stirred adding
Na Nitate untill I was sure that all the Lead was gone.
I washed but there was still quite alot of Lead Metal
still not reacted.
I presume that alot of the Oxygen is escaping.

It least the ingredients are cheap and the products easy to seperate.

PS: It's a bit messier than I originally thought :-|

Is there anything I could add to catalize the reaction??

DANN2

not_important - 13-5-2007 at 06:18

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.

12AX7 - 13-5-2007 at 11:51

I never got good results, hell any results, from stirring hot lead. The process makes a green granular substance that turns out to be lead spheroids with little oxide on top. Also little weight gain.

Tim

dann2 - 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]

Eclectic - 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]

not_important - 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.

Lead Carbonate

dann2 - 14-5-2007 at 16:31

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

Eclectic - 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.

Rosco Bodine - 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]

Eclectic - 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.

Rosco Bodine - 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 !

Eclectic - 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.

Basic Lead Carbonate from Lead Sulfate

Rosco Bodine - 6-6-2007 at 00:54

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)
This file has been downloaded 1136 times


Various Pure Lead Monoxides

Rosco Bodine - 6-6-2007 at 00:58

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)
This file has been downloaded 1131 times


Basic Lead Hydroxide

Rosco Bodine - 6-6-2007 at 01:01

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

Attachment: US3230043 LEAD_OXIDE_HYDROXIDE.pdf (146kB)
This file has been downloaded 2157 times


Purifying lead for the making of lead compounds

alancj - 6-6-2007 at 03:10

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

not_important - 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.

Eclectic - 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.

Rosco Bodine - 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]

Chemophiliac - 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.

more lead salts patents

Rosco Bodine - 6-6-2007 at 23:48

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)
This file has been downloaded 1077 times


and the second

Rosco Bodine - 6-6-2007 at 23:51

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)
This file has been downloaded 1344 times


IPN - 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]

Polverone - 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.

Rosco Bodine - 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)
This file has been downloaded 1352 times


hashashan - 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?

Lead Oxide

12AX7 - 19-12-2007 at 21:22

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

chemoleo - 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...

12AX7 - 19-12-2007 at 23:43

Hehe, I'm not one for microscale. The crucible only had 1/2" of stuff in it, which is on the small side for me. :D

The fun thing about scientific descriptions like that is they attempt to hide excitement. It's like one of Faraday's lectures, when he was "heating a piece of potassium metal ... [it exploded] oh, sometimes it does that... [gets another]". What could be more nonchalant than mentioning in passing that the fume hood was levelled? :D

I'll be dissolving the salt matrix and, hmm I should've poured off the lead metal while it was molten- ah well, I can do that later just as well. Lead in anything over (II) will give off Cl2 in HCl, so yes, it should be easy to tell which it is. :)

If any PbO2 was formed, it certainly isn't as acidic as I'd expect it; Cr2O3 readily forms dichromate in a chlorate melt, displacing Cl2 gas. No Cl2 was formed in this reaction. Sodium plumbate(IV) is reasonably stable, innit?

Tim

some lead complex oxides of possible interest

Rosco Bodine - 20-12-2007 at 00:36

http://dx.doi.org/10.1016/0167-2738(92)90245-K

http://dx.doi.org/10.1016/0167-2738(96)00161-0

http://dx.doi.org/10.1016/j.solidstatesciences.2007.07.004

I have requested these articles :D
so hopefully they are soon available
and we can see them to learn more .

After reviewing these articles it is not encouraging that these materials would be of experimental interest outside
of a semiconductor manufacturing facility because of the
methods of grinding and pelleting , sintering and high temperatures required . So I am not attaching these references . Sorry folks , my reference digging has turned
up no gold nuggets today although the proportional formulas
do look so interesting .

[Edited on 20-12-2007 by Rosco Bodine]

Lead Nitrate

Xenoid - 25-1-2008 at 12:07

Lead nitrate is the most soluble lead salt (55g/100g water), and is a popular choice for a plating bath when making PbO2 anodes. The following procedure was described briefly by "tentacles" in one of the anode making threads. The method is very useful as it does not require nitric acid. The procedure is essentially the "nitrate" version of the copper carbonate / acetic acid method described by "MadHatter" earlier in this thread for producing lead acetate (I have also used this very successfully) in that Pb is brought into solution by electrochemical replacement by Cu.
After a few initial hiccups, I found this nitrate method to be both cheap, safe, elegant and relatively simple.

The method is based on making copper nitrate from two cheap and easily obtained agricultural chemicals (calcium nitrate and copper sulphate) and then reacting the copper nitrate with Pb metal, to form lead nitrate.

1) Ca(NO3)2 (164.2g) + CuSO4 (159.6g) ---> Cu(NO3)2 (187.6g) + CaSO4

2) Cu(NO3)2 (187.6g) + Pb (207.2g) ---> Pb(NO3)2 (331.2g) + Cu

Equation 1 is a metathesis reaction in which CaSO4 is precipitated, and is a useful procedure for producing many different nitrates. Unfortunately it can be difficult for the amateur as the CaSO4 precipitate is particularly thick and it can be difficult to separate from the desired nitrate solution. In this situation, a vacuum or pressure filtration system is needed if one wants to work at reasonable concentrations. If you do not have adequate filtration, it may be possible to do this in a stepwise fashion at lower concentrations. Ensure that you have the correct starting material, do not use calcium ammonium nitrate (CAN) as this is an ammonium nitrate - calcium carbonate mix.

Remember blue copper sulphate is in the form of the pentahydrate, so you will require 1.56 times the stoichiometric amount in equation 1. Use a slight excess of Ca(NO3)2 and remember that CaSO4 has slight but appreciable solubility (.21g/100g) some of this can be removed by concentrating the Cu(NO3)2 solution and cooling to 0 oC. The CaSO4 will crystallise out as very fine short aciculate crystals. If it is not removed it will react with the Pb++ to form insoluble PbSO4.

Once you have obtained your blue Cu(NO3)2 solution, place it in a beaker and hang excess strips of brushed and cleaned lead sheet in the solution. Shot or other forms of Pb could be used, but may need stirring from time to time. Immediately, any shiny Pb surfaces will turn brown, after a minute or so, when a strip is removed, shiny specks of Cu will be seen, these may turn brown within a few seconds of being removed from the solution. After several minutes, a distinct plating of Cu will be observed on the Pb sheet, and it will become corroded as it goes into solution.

Leave the reaction to proceed for 24 hours in a ventilated place (some nitrogen oxides are produced). After this time all reactions should have ceased and the solution will be a very pale green colour. Filter out all the debris and insoluble material, add a few drops of nitric acid, concentrate by boiling and allow to cool slowly to 0 oC. The Pb(NO3)2 crystallises out as snow white, well formed, octahedral crystals.

Image shows 88g of Pb(NO3)2 (beautiful but deadly).

Pb(NO3)2xtals.jpg - 27kB

12AX7 - 25-1-2008 at 13:41

Ooh, octahedral! I love octahedra! :)

Sweet! (And probably literally, like lead acetate!)

Tim

Aqua_Fortis_100% - 25-1-2008 at 15:35

Really NICE!

I will surely try that in a later momment..

Quote:
Originally posted by Xenoid:

Ensure that you have the correct starting material, do not use calcium ammonium nitrate (CAN) as this is an ammonium nitrate - calcium carbonate mix.



Why dont use this?
Assuming that in some places its the only avaliable OTC gardening and most next of the desired pure Ca(NO3)2.

I'm assume that one will have some work to use this , but seems to be easy , just mixing this CAN with hardware lime and bring to boil in an open ventilated area (because of the ammonia) and let it boiling for a long time and/or when ammonia smell stops.
Even the SMDB library has an article regarding this:
http://www.sciencemadness.org/library/cano3.html

Quote:
Leave the reaction to proceed for 24 hours in a ventilated place (some nitrogen oxides are produced). After this time all reactions should have ceased and the solution will be a very pale green colour. Filter out all the debris and insoluble material, add a few drops of nitric acid, concentrate by boiling and allow to cool slowly to 0 oC. The Pb(NO3)2 crystallises out as snow white, well formed, octahedral crystals.



Why nitrogen oxides are evolved ? It just seems to be a little weird , not (?)


It can seems like a little off-topic and I'm missing something but ,
Why lead nitrate seems to be *always* preferred over lead acetate in PbO2 anode plating?

[Edited on 25-1-2008 by Aqua_Fortis_100%]

Xenoid - 25-1-2008 at 16:22

Quote:
Originally posted by Aqua_Fortis_100%

Why dont use this?
Assuming that in some places its the only avaliable OTC gardening and most next of the desired pure Ca(NO3)2.


Why nitrogen oxides are evolved ? It just seems to be a little weird , not (?)




What I really mean't was, don't confuse the two. There are a bewildering array of mixtures of calcium nitrate / ammonium nitrate / calcium carbonate. These come under such names as CAN, Nitrochalk, etc. I used pure calcium nitrate from a hydroponics supplier, it was only NZ$12 for 5Kgs. If you have to make calcium nitrate, this is a large extra step, and defeats the simplicity of the procedure somewhat!

Some nitric acid is produced as a side reaction, the pH of the solution drops to about 4 and bubbles occur around the lead. I assume with both Cu and Pb metal in close proximity a complex electrochemical cell is formed. Perhaps someone else may be able to explain this more authoritatively.

Aqua_Fortis_100% - 25-1-2008 at 16:52

Oh sorry Xenoid, I really missed what you have said ..

And really, using pure materials will be much cleaner and better!

Thank you by the practical info about this NOx generation.. Looking at first , theoretical , seems to be a "inofensive" (no poisonous gas generation , although poisonous liquid ).. Only seems to occur a displacement between Pb an Cu+2..So this can be dangerous since one could even consider safe to do this indoors..
And as you said, is probably some kind of side reaction, although I have no idea how this reaction occurs..

[Edited on 25-1-2008 by Aqua_Fortis_100%]

chloric1 - 25-1-2008 at 18:35

Xenoid-It is quite notable that you obtain such white crystals from a dirty green solution still containing copper ions. I am glad this worked out for you.

12AX7 - 25-1-2008 at 19:47

I often get clear, colorless, well-formed crystals from colored solutions -- yeah, after forgetting about the solution for about a month! I am suprised your crystals are white, why would that be? Could also be the white stuff is obscuring any green.

Tim

Xenoid - 25-1-2008 at 20:08

@ chloric1

Actually the solution was not really "dirty green". I only filtered the solution using paper towel in a sieve. I have done this procedure twice now, the first time the solution was almost colourless, just a slight greeny blue, the second time was slightly more strongly coloured. But hey, we are not talking grass-green here, just very pale. Given the difference in ionic radii, it's unlikely any Cu is incorporated into the Pb(NO3)2 crystalline structure.

@ 12AX7

Lead nitrate IS white, it's not colourless. White crystals look quite wierd, actually!

[Edited on 25-1-2008 by Xenoid]

Xenoid - 28-1-2008 at 17:54

Quote:
Originally posted by Xenoid

Lead nitrate IS white, it's not colourless. White crystals look quite wierd, actually!



Hmmm..! I might just have to comment on my own post here!

My description of lead nitrate being white does not appear to be correct! It was based on my own observations of lead nitrate crystals which I had made previously from Pb and nitric acid, they also formed white (not colourless) crystals in the bottom of the beaker, they had been sitting in the fridge for several weeks. Today I decided to extract all the lead nitrate from this preparation to add to my new supply. I redissolved the crystals in water with a few drops of nitric acid added, and slowly cooled the saturated solution, some beautiful crystals formed. The overall appearance is white, but many of the crystals appear perfectly clear, some have whitish cores, and some are zoned.

My chemical data book refers to lead nitrate as white, but it also says NaCl, NaClO3 and KNO3 etc. are white. In fact it doesn't differentiate between white and colourless, so it is not much help.

I realise colourless crystals can look white due to inclusions of liquids and gases as well as fractures, etc. But the white lead nitrate crystals previously described, are very well formed, they almost look as though they are molded from white PVC. Perhaps the presence of a little nitric acid in the solution causes the white crystals.

I was just wondering what other people's experiences with lead nitrate have been, I wonder if I purify further will I get wholly colourless crystals.

Edit: Just recrystallising another batch and they look just whitish/colourless, nothing unusual. Wonder what caused the intense, snow white appearance of the first crystallisation.

[Edited on 28-1-2008 by Xenoid]

chloric1 - 28-1-2008 at 18:36

I second the white claim. When I prepare lead nitrate from lead and nitric acid, I always far exceed the saturation point of lead nitrate. I get a fine granular rocksalt like white substance. I never tried to get larger crystals.

JohnWW - 28-1-2008 at 18:55

Lead nitrate? That is Pb(II) nitrate, and has to undergo electrolytic oxidation and hydrolysis for PbO2. Pb(NO3)4 probably cannot be isolated, but the basic nitrate PbO(NO3)2 would probably exist as a soluble intermediate salt.

kilowatt - 16-7-2008 at 17:48

Here is my latest setup for preparing lead sulfate from scrap lead, actually for the separation of the scrap alloy into lead, tin, and antimony. I am using a water cooled battery of 8 cells filled with 33% sulfuric acid and scrap lead electrodes in series running on about 18V AC (2.25V AC per cell), which is somewhat equivalent to charging and discharging a lead acid cell 60 times per second. The lead sulfate rapidly falls away and collects at the bottom of the cells, while tin sulfate remains dissolved. Higher cell voltages make it go faster but there is more loss to fuming and spatter. As I understand it, antimony sulfate could be separated by washing the precipitates in sulfuric acid.

Larger pic here.

HPIM1435.JPG - 77kB

tumadre - 17-7-2008 at 08:23

How much current is that? or do you prefer not to know:D

kilowatt - 17-7-2008 at 09:41

I couldn't find my current meter until after I posted this. I did later though, and it's about 15A.

tumadre - 17-7-2008 at 12:08

well the transformer is about the right size:D

kilowatt - 17-7-2008 at 14:45

That's actually a pole transformer wired for 2400:480. I'm using it at less than 1/20th its rated voltage and 1/3rd its rated current for this. I've done some fun high voltage stuff with that transformer too.

Picric-A - 20-7-2008 at 03:54

this is a tiny bit of the topic.
Until now i have made my lead dioxide from a 3 way process.
First i heat lead (of wich i have lots of) in a steel cruicible at around 600 degrees C. This makes Lead monoxide PbO (litharge).
Then calcination of PbO at aroung 460 degrees C produces Lead tetroxide Pb2O3.
Finally dissolve the lead tetroxide in nitric acid wich produces Lead dioxide- usefull Lead Nitrate- usefull
Pb3O4 + 4 HNO3 → PbO2 + 2 Pb(NO3)2 + 2 H2O

im now going to try the electrolosis of sulphuric acid dil using lead electrodes.
can someone tell me how i go about electroplating lead dioxide on carbon arc electrodes?
Picric-A

DJF90 - 20-7-2008 at 04:18

Lead tetroxide is Pb3O4, which can be written as 2PbO.PbO2 (as it has lead in a mixed valence, II and IV).

dann2 - 20-7-2008 at 05:55

Quote:
Originally posted by Picric-A
this is a tiny bit of the topic.
Until now i have made my lead dioxide from a 3 way process.
First i heat lead (of wich i have lots of) in a steel cruicible at around 600 degrees C. This makes Lead monoxide PbO (litharge).
..................

..............can someone tell me how i go about electroplating lead dioxide on carbon arc electrodes?
Picric-A


How long do you have to heat the Lead metal to get it to convert to Lead Monoxide?
What are the dimensions of the crucible that you use to heat it (area exposed to air).
Do you keep scooping off the Monoxide as it is formed or just leave the crucible there for long enough to convert a large amount of metal?

See the 'More on PbO2 anodes' thread for some info on coating Graphite with Lead Dioxide.

Dann2

Picric-A - 20-7-2008 at 07:20

It doesnt take long to convert to PbO however the lead forms a oxide layer wich you have to scape off occasionly. the oxide forms quickest at 600 degrees c wich is why i reccomend that however you need to scrape it off every minute or so.
My cruicible is 6cm wide by 9cm tall. becuase i have a small cruicible i have to make it in small batches:(
what i am aiming for next is to get a low form cruicible, say 15cm wide and 3cm high. this will avoid the need for continuous scooping of oxide layer. hope this helps,
Picric-A

Picric-A - 20-7-2008 at 08:10

the picrtue shows the products of roasting lead at around 600 degrees C. I didnt do it for long enough so not all the lead managed to react.
on the left is a yellowish black pile of lead oxide, Pb2O3 + PbO and on the right is puddle of unreacted lead. In front is the cruicible i used.

EDIT by Davster:
Don't rape the board formatting. I edited it for you



[Edited on 20-7-2008 by The_Davster]

picric a image.JPG - 17kB

Picric-A - 20-7-2008 at 08:13

woops i think its a bit big :P soz admin!

12AX7 - 20-7-2008 at 09:13

Yeah, way too fucking big, and horribly out of focus to boot.
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