Sciencemadness Discussion Board

Lead nitrate from Pb(OH)2 and Mg(NO3)2 - feasibility

Zandins - 18-6-2016 at 07:25

Greetings sciencemadness community,

In order to electroplate a lead dioxide anode, a soluble lead salt, such as lead nitrate, is required. However, I currently do not have access to it. Instead, I have theorized an alternate method of its synthesis, which goes as follows:

First, lead plate is recovered from an old, scrapped car battery. The plate is washed in NaHCO3 solution and cleaned of any battery-paste. It is then used as an anode for electrolysis of an indifferent electrolyte at circa 5A current. The plate quickly evolves and forms white flakes and precipitate in the solution.
1) Am I correct in assuming the precipitate is lead (II) hydroxide?

The white powder would then be washed with distilled water and dissolved in 1L of H20 until saturated ( Wikipedia gives solubility as 15.5 g/L) and magnesium nitrate would then be added.
Pb(OH)2 + Mg(NO3)2 --> Pb(NO3)2 + Mg(OH)(s)
Magnesium hydroxide is extremely insoluble in water and is expected to precipitate out. Then, the precipitate would be filtered off and a fresh dose of Pb(OH)2 added, et cetera.

2)What are your thoughts? Is it feasible to actually carry this out?

Zandins

blogfast25 - 18-6-2016 at 07:46

Quote: Originally posted by Zandins  


The white powder would then be washed with distilled water and dissolved in 1L of H20 until saturated ( Wikipedia gives solubility as 15.5 g/L) and magnesium nitrate would then be added.
Pb(OH)2 + Mg(NO3)2 --> Pb(NO3)2 + Mg(OH)2(s)
Magnesium hydroxide is extremely insoluble in water and is expected to precipitate out. Then, the precipitate would be filtered off and a fresh dose of Pb(OH)2 added, et cetera.



What matters here are the Solubility products or Ksp values, not the solubility limits.

For Mg(OH)2: Ksp = 1.5 x 10-11 (Wiki)
For Pb(OH)2: Ksp = 1.4 x 10-20 (Wiki)

That means the displacement reaction you propose is simply not possible, because the lead (II) hydroxide is in fact less soluble than the magnesium hydroxide.

Edit:

This source gives slightly different values for the Ksp values but the lead hydroxide is still about 10000 times less soluble than the magnesium hydroxide.

[Edited on 18-6-2016 by blogfast25]

DraconicAcid - 18-6-2016 at 08:22

If you want a soluble lead salt, then I think your best bet would be to dissolve the hydroxide in nitric or acetic acids.

PHILOU Zrealone - 18-6-2016 at 08:53

Or pechloric acid!

DraconicAcid - 18-6-2016 at 09:00

Quote: Originally posted by PHILOU Zrealone  
Or pechloric acid!


I'm assuming the OP has more easy access to acetic acid than perchloric.....

Point taken

Zandins - 18-6-2016 at 09:36

Quote: Originally posted by DraconicAcid  
If you want a soluble lead salt, then I think your best bet would be to dissolve the hydroxide in nitric or acetic acids.


In this case, I think I will heat the Mg(NO3)2 to 330C in a steel crucible to decompose it, and bubble the NO2 through water to make the required nitric. Anyway, thanks to Blogfast25 for pointing out my misconception.
Quote: Originally posted by PHILOU Zrealone  
Or pechloric acid!



As for the perchloric, it is one of the principal chemicals for which I require the PbO2 anode in the first place.Although according to my Solubility Megatable(attached), I can also use chloric, bromic, hexafluorosilicic, formic and acetic acids. Plenty of options.

TabR2.jpg - 791kB

gsd - 19-6-2016 at 08:57

If you have an access to acetic acid and hydrogen peroxide then you can directly form lead acetate from lead metal without going thru' hydroxide route.

There is a plenty of discussion of this on this forum.

gsd

Jstuyfzand - 19-6-2016 at 11:34

I wonder, if you use Copper and lead acetate, would electroplating in alcohol work? Copper acetate doesnt dissolve in water.

EDIT: Nevermind

[Edited on 19-6-2016 by Jstuyfzand]

j_sum1 - 19-6-2016 at 16:32

I have a strip of lead with a nice stable coating of lead dioxide on it that I use for electrolysis. Granted, I have not been using it for chlorates or perchlorates so in that sense it is untested. But it could not have been easier to make.

I simply used the strip of lead to electrolyse copper sulfate to make sulfuric acid. After a number of runs the electrode is looking pretty good. If your target was the electrode rather than the acid you could forget about the copper sulfate solution and simply use H2SO4. The process is certainly a lot simpler than my attempts to deposit PbO2 on a graphite substrate or to make something from lead dioxide directly.

PHILOU Zrealone - 20-6-2016 at 07:08

Quote: Originally posted by DraconicAcid  
Quote: Originally posted by PHILOU Zrealone  
Or pechloric acid!


I'm assuming the OP has more easy access to acetic acid than perchloric.....

Or formic... :P

PHILOU Zrealone - 20-6-2016 at 07:21

Quote: Originally posted by Zandins  

Quote: Originally posted by PHILOU Zrealone  
Or pechloric acid!



As for the perchloric, it is one of the principal chemicals for which I require the PbO2 anode in the first place.Although according to my Solubility Megatable(attached), I can also use chloric, bromic, hexafluorosilicic, formic and acetic acids. Plenty of options.


Nice table...
What does the P, H, M, - stands for?
I guess...
P --> soluble
H --> unsoluble/precipitate
M --> moderately soluble
"-" --> unstable

HClO4 is M while it should be P...

Zandins - 20-6-2016 at 08:25

Yes, although I do not know the specific limits separating soluble/moderate/insoluble.
The HClO4 puzzles me too, probably a misprint...

As for the original topic, I think I will melt the meshes down into a solid plate and try the sulfuric acid approach. Some sources state the coating becomes porous and unreliable, but I guess there is only one way to find out.

P.s. Everyone is more than welcome to use the Supertable for their own purposes, if need be.

[Edited on 20-6-2016 by Zandins]

AJKOER - 21-6-2016 at 06:38

An interesting experiment would be to treat aqueous Lead acetate with CO2. Collect the fresh precipitate of PbCO3 and rinse. Then, treat with more aqueous CO2 with added Copper(ll) nitrate (and not Mg(NO3)2 as Magnesium forms a soluble hydrogen carbonate, but not Copper which appears to form only a basic copper carbonate).

Logic: Lead(II) carbonate, PbCO3 is prepared industrially from the action of CO2 on a cold dilute lead(II) acetate (warm solutions will form the basic carbonate per Wikipedia at https://en.m.wikipedia.org/wiki/Lead_carbonate ).

There is a limited increase of the solubility of PbCO3 in aqueous CO2 (see table at http://lead.atomistry.com/lead_carbonate.html ) and the presence of an acidic Cu(NO3)2 may foster the formation of the PbHCO3(+) and with an excess of CO2 other carbonate complexes (see reference below, Table 3.1). As such, the solubility product hurdle associated with PbCO3 may be obviated.

I am not expecting a significant effect by CO2 on the copper salts (see, for example, page 15 at https://books.google.com/books?id=ZR8ZAQAAIAAJ&pg=RA2-PA... ).

The role of pH and dissolved inorganic carbon (DIC includes CO2) has been a topic of research in promoting soluble Pb concentration in drinking water. See, for example, Table 3.1, page 27 available at https://www.google.com/url?sa=t&source=web&rct=j&... .

I can envision three possible results, no Pb(NO3)2, a very limited amount associated with only a small amount of soluble Pb complex formations, or an acceptable yield.
-----------------------------

One may be able to prepare Cu(NO3)2 by mixing aqueous CuSO4 and 2 KNO3, and freezing out the K2SO4.

[Edited on 21-6-2016 by AJKOER]

DraconicAcid - 21-6-2016 at 08:04

Quote: Originally posted by PHILOU Zrealone  

Nice table...
What does the P, H, M, - stands for?
I guess...
P --> soluble
H --> unsoluble/precipitate
M --> moderately soluble
"-" --> unstable

HClO4 is M while it should be P...



It's Russian, soluble = растворимый
insoluble = нерастворимый (the prefix "ne-" is the same as "non-" or "in-").

fusso - 28-4-2018 at 14:58

Quote: Originally posted by Zandins  
Yes, although I do not know the specific limits separating soluble/moderate/insoluble.
The HClO4 puzzles me too, probably a misprint...

As for the original topic, I think I will melt the meshes down into a solid plate and try the sulfuric acid approach. Some sources state the coating becomes porous and unreliable, but I guess there is only one way to find out.

P.s. Everyone is more than welcome to use the Supertable for their own purposes, if need be.

[Edited on 20-6-2016 by Zandins]


Can you plz also provide the xls(x) file? I'd like the xls(x) format rather than a jpg thx

VSEPR_VOID - 28-4-2018 at 16:42

Whatever you make remember to add it to the List of Chemicals and Materials Made by Sciencemadness.org Users

https://docs.google.com/document/d/1AoI2VA5L4bmFw2HwXS2OVYTV...

yobbo II - 29-4-2018 at 13:29

http://www.sciencemadness.org/talk/viewthread.php?tid=5490#p...

Lead salts preparation thread