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Author: Subject: PbO2
Quince
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[*] posted on 12-6-2005 at 02:17


Quote:
Originally posted by chemoleo
Well here it goes... the dissolution of lead metal with cheap OTC materials. I copied parts over of what I posted at E&W already:

Can the last step be speeded up with electrolysis or peroxide?

Copper acetate can itself be made by electrolysing a copper anode in vinegar (graphite cathode).

[Edited on 12-6-2005 by Quince]
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[*] posted on 12-6-2005 at 12:54


Nah, I don't think you need to speed it up.

With stirring a few times a day to knock Cu off of the lead, and a HUGE excess of lead (lots of surface area too, lead turnings are easy to make) it only took 2-3 days for the solution to become colorless.




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Quince
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[*] posted on 12-6-2005 at 23:49


So I made copper carbonate and added a slight excess of vinegar, but it was going too slow so I started adding the lead filings while it was stirring.

The solution became darker blue as more copper left the carbonate form, and copper dust was settling to the bottom. But then -- WTF!

Instead of the solution becoming clear, as I was adding more excess of lead, it became milky grey, and the copper color of the dust also changed to grey! After filtering through a coffee filter, there's still a lot of fine grey dust in the filtrate. To test the solids, I put them in a bit of HCL with H2O2, and a milky green liquid with white-grey precipitate formed. I'm guessing the green indicates copper, but what the hell is the precipitate, lead oxide?

So I don't know, do I have lead acetate in the filtrate or not? Is the grey stuff probably just the excess lead? Rubbing the solids between my fingers, I don't see any of the copper color that was there at all.




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neutrino
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[*] posted on 13-6-2005 at 02:31


It sounds to me like either your lead was impure or the reaction stopped prematurely (as a result of too much lead), leaving undissolved lead particles floating around. The white precipitate would be PbCl<sub>2</sub>.
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[*] posted on 13-6-2005 at 03:20


Lead + carbon dioxide = PbCO3.

It was probably entering solution as normal, then combining with carbonic acid that hadn't had time to leave solution.

Tim




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Quince
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[*] posted on 13-6-2005 at 04:03


Wouldn't the vinegar dissolve the carbonate? The solution is still acidic. Can I assume that there is some lead acetate in the solution, as that was my goal, and that all the copper would have been be precipitated?

[Edited on 13-6-2005 by Quince]




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[*] posted on 13-6-2005 at 05:02


Hm true, it ought to dissolve carbonate. The acid may be too weak though, seems to me a double excess (or more) is needed to dissolve some things. If there was an excess of lead metal, yes it should be only lead in solution.

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[*] posted on 13-6-2005 at 08:58


Quote:
Originally posted by Quince
...Rubbing the solids between my fingers...


Hmm. You might want to be (more) careful w/ lead compounds, even if they are in a solid form. I don't need to start listing off the various MSDS sheets and all that stuff, do I?;)




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Quince
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[*] posted on 13-6-2005 at 12:03


Bah, the ancient Romans used lead pipes for drinking water, and they did fine...oh, wait... :D

[Edited on 13-6-2005 by Quince]




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[*] posted on 13-6-2005 at 14:35


Actually my Mom's Aunt's house in Leven, Scotland still aparently has lead pipes. She's in the high nineties, so no obvious ill effects! Very little lead evidently is dissolved, especially once the pipes have been used for a while.



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Quince
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[*] posted on 13-6-2005 at 14:41


I'd be worried about her fertility.



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[*] posted on 13-6-2005 at 16:20


Probably the scale in the water has built up a protective layer on the inside of the pipes. That's one of the reasons Romans didn't all suffer from lead poisoning.
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[*] posted on 13-6-2005 at 18:31


I don't know about that. Quoting from http://www.reevesjournal.com/CDA/ArticleInformation/Retrospe...
Quote:
Still more alarming was the conspicuous pattern of mental incompetence that came to be synonymous with the Roman elite. This creeping cretinism manifested itself most frighteningly in such clearly degenerate emperors as Caligula, Nero, and Commodus. It is said that Nero wore a breastplate of lead, ostensibly to strengthen his voice, as he fiddled and sang while Rome burned. Domitian, the last of the Flavian emperors, actually had a fountain installed in his palace from which he could drink a never-ending stream of leaded wine.




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[*] posted on 13-6-2005 at 22:29


I don't understand this. After I filtered the solution, it was still very light blue, so I threw in a chunk of lead. The lead didn't turn coppery, it turned dark grey-brown. Now, I had previously used a steel file to file down the lead, could contamination from the file be doing this? The color looks similar to lead sulfide, but I don't see how that can be.

[Edited on 14-6-2005 by Quince]




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[*] posted on 14-6-2005 at 02:21


Sorry for straying off topic here, but the reason the rich had lead poisoning was different. They used to boil sour wine (vinegar) in lead pots and sell the lead acetate thus obtained to the rich (it was said to taste like sugar.)
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[*] posted on 14-6-2005 at 03:59


Well, lead acetate WAS called "sugar of lead" in the olden days, at least before the deleterious effects of using this sweetener became evident.

It is said that the mechanism of its taste is similar to that of sugar in that they interact with almost the same set of receptors.

sparky (°_°)




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[*] posted on 14-6-2005 at 08:37


Quote:
Originally posted by Quince
I don't understand this. After I filtered the solution, it was still very light blue, so I threw in a chunk of lead. The lead didn't turn coppery, it turned dark grey-brown. Now, I had previously used a steel file to file down the lead, could contamination from the file be doing this? The color looks similar to lead sulfide, but I don't see how that can be.

[Edited on 14-6-2005 by Quince]


Try taking a sample of the solution and diluting it about 1:10. Try plating some copper out on a piece of lead using this solution. See if the habit of the plated metal is different this time. It may be that you are getting copper, but oftentimes the metals that plate out rapidly from concentrated solutions don't look at all like their normal selves.

Other than that possibility, we'd have to go over the species in solution (including possible contaminants) and see what else could be forming.
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[*] posted on 14-6-2005 at 09:50


That sounds like copper to me. The copper sludge that forms really doesn't look at all like shiny copper. Try putting an iron nail in copper sulfate or copper acetate- the copper formed will probably closely resemble the stuff you're wondering about.

The light blue color of the solution dissapearing would be another indication that it is copper.

Be careful with lead dust/filings! I think turnings are better because there's no dust involved, they have plenty of surface area, and they probably can be easily removed from the copper sludge.

Cyrus




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[*] posted on 14-6-2005 at 11:22


I've made a new batch of copper acetate, and as I don't want to ruin this one with the possibility of contaminated lead I was using, I'm wondering where to get pure lead.



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[*] posted on 14-6-2005 at 13:34


Pure lead was (and to a small extent still is) used for sealing cast iron drain pipe joints. Matter of fact, there's a 5 pound ingot on the shelf down at Ace Hardware.

Tim




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[*] posted on 15-6-2005 at 06:19
The Chain


Look for metals higher up on the chain as a possible source of contamination. There won't
be too many: Silver, Mercury, Platinum, Gold. Lead can displace any of these.

Lead "sugar" Acetate ? No wonder Rome fell !


[Edited on 15-6-2005 by MadHatter]




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[*] posted on 15-6-2005 at 06:41


My second batch worked OK -- that is, until I accidentally knocked off the beaker with a couple of grams dissolved lead acetate off the radiator it was on for evaporation. I spilled it all over me and broke the beaker...



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[*] posted on 15-6-2005 at 07:44


Quince, here's a link for you

http://www.chelationtherapyonline.com/articles/p113.htm

Pb(OAc)2 can be absorbed through skin. I do not know the rate of absorption without looking it up.

You were wearing gloves and a lab apron, I hope?

Edit: Bromic it looks like you're right... did some further reading:

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&a...

In that study, Lead acetate is only slightly more absorbed than lead oxide, which itself is basically not absorbed at all.

The calcium supplements (and magnesium) will help anyway. Calcium disodium EDTA is even better.

[Edited on 15-6-2005 by Pyridinium]
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[*] posted on 15-6-2005 at 11:32


Lead acetate isn't too readily absorbed, I would hardly worry about it, just take a bunch of calcium supplement tablets and don't give it a second thought.
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[*] posted on 15-6-2005 at 19:37


Well, I have to do it a third time now, that's what I was pissed off, besides the fact that I've only one beaker left. I have no place left in my room to keep all my labware, so I've basically piled it all on an armchair...



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