Sciencemadness Discussion Board

Lead Sulfide

Baphomet - 16-4-2007 at 02:21

How hard is it to make PbS?

I have lead sheet and flowers of sulphur. Would powdering the lead, then mixing and heating work?

Thanks

joeflsts - 16-4-2007 at 06:03

This is kind of interesting.

Joe

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Baphomet - 21-4-2007 at 19:30

Cool thanks for the info

What I was wondering was, is it possible to produce PbS in a reaction similar to the exothermic combination of Zn or Fe with Sulphur?

When iron dust is mixed with sulphur and a hot wire inserted the reaction is very fast. However it's not happening for the lead / sulphur combo :(

Jome - 22-4-2007 at 14:50

Pb is very close to being a noble-metal on the EC scale, hence no reaction.

Bubbling H2S through a solution of lead nitrate or acetate will likely give you free PbS, although the reactions are both based on equilibriums. Pusting this to the right could probably be done by PbCO3 in the solution. You could even start PbCO3 + NA/HOAc and then bubble H2S through that.

Makes me curious, whats the PbS for?

not_important - 22-4-2007 at 20:59

A short skim of references only turned up one reference to a dry method of making PbS - heating lead in sulfur vapour. This doesn't sound like a very energetic reaction.

UnintentionalChaos - 22-4-2007 at 21:53

PbS is commonly mined as the mineral galena, which is entirely insoluble. It has a melting point of around 1100C, so any layers formed on the outside of lead particles or any experimentation with molten lead are likely to give you nothing. Bubbling H2S (which you can make by dripping a strong acid onto the easily produced FeS) through a soluble lead salt like Pb(NO3)2 should precipitate PbS powder. Don't do anything with H2S outside of a good fume hood or with extremely good ventilation since its nastier stuff than hydrogen cyanide gas

garage chemist - 22-4-2007 at 23:51

Currently I precipitate a lot of metals with H2S in the university lab, and PbS precipitates already at pH 1. So bubbling H2So through a lead nitrate or better acetate solution will give you PbS as a deep black precipitate.
Lead acetate s made from the metal by dissolving it in a mixture of H2O2 and 25% acetic acid ("spirit of vinegar", or even better pure acetic acid from the pharmacy, ordinary vinegar is useless).
We always prepare H2S by heating "sulfidogen", which is a mixture of paraffin (wax) with sulfur. This works well but the test tube is useless afterwards because it cant be cleaned (byproduct is carbon in the form of a coke deposit).

[Edited on 23-4-2007 by garage chemist]

Magpie - 23-4-2007 at 09:29

I remember H2S being available in the hood of a chemistry class I took in the '60s. There was a valve on the wall with a spigot. Attached to the spigot was a rubber hose which you could place in your test tube. I imagine that this was coming from a tank with a regulator. I wouldn't have wanted to be the instructor responsible for making sure that all the clueless freshman had turned off the valve and that the hood fan was always on. :o

I have made H2S by heating paraffin and sulfur and sort of made it from some homemade FeS and acid. GC is right that the paraffin/S method ruins your test tube. Recently I made it by dropping H2SO4 on Na2S, which is cheaply available. I liked this method by far the best.

As others have warned, H2S is deadly. When using it in any significant quantity adequate ventilation is essential.

Zinc - 23-4-2007 at 09:48

I once mixed powdered lead with sulfur powder and put it in a test tube. I then heated it with a torch. I plugged the test tube with my finger. Suddenly the mixture started glowing read/orange and the teast tube burstead. I never analysed the black scattered powder so I don't know if it was lead sulfide.

UnintentionalChaos - 23-4-2007 at 10:21

Stupid question, but have you ever tried using Conc. Sulfuric and 30% peroxide (piranha etch, Caro's acid, etc.) to dissolve the carbon residue out of the test tubes? For those of us who have trouble getting glassware, spending a small amount of reagents seems trivial if it will work. I only have 15% peroxide on hand, but have used it to eat some stubborn residues out of glasware. The dilution by the water in the peroxide, though keeps it from attacking he carbon it reduces the residues to (though they usually wipe off very easily afterward). I've used really awful cheap sulfuric acid for this too, the mixture becoming glass clear and ceasing to smell (other than like acid) as the contamination gets oxidized.

Zinc.....you plugged a test tube full of hot metal and sulfur with your finger....There may have been some lead sulfide there, but the fact that it scattered probably kept most of it from reacting. If there was a decent reaction the powders must have been extremely fine.

Zinc - 23-4-2007 at 10:29

Quote:
Originally posted by UnintentionalChaos
you plugged a test tube full of hot metal and sulfur with your finger....


Not the brightest idea I agree but I didn't have any plugs...

not_important - 23-4-2007 at 20:03

Quote:
Originally posted by UnintentionalChaos
Stupid question, but have you ever tried using Conc. Sulfuric and 30% peroxide (piranha etch, Caro's acid, etc.) to dissolve the carbon residue out of the test tubes? For those of us who have trouble getting glassware, spending a small amount of reagents seems trivial if it will work. I only have 15% peroxide on hand, but have used it to eat some stubborn residues out of glasware. The dilution by the water in the peroxide, though keeps it from attacking he carbon it reduces the residues to (though they usually wipe off very easily afterward). I've used really awful cheap sulfuric acid for this too, the mixture becoming glass clear and ceasing to smell (other than like acid) as the contamination gets oxidized.


I've used it, but with somewhat stronger H2O2. Nitric acid works in many cases.

Another trick I picked up from a 1930 lab manual is magnesium nitrate, which I made from calcium nitrate fertiliser and Epsom salts. Put just a little into the glassware, maybe a half gram. Heat the glassware over a flame until the nitrate 'melts', dissolving in its own water of crystallisation Slowly rotate the glassware so as to expose all of the crabon or what ever to the nitrate. If it stops working and another small amount of magnesium nitrate and continue. Cool, rinse with warm water, then a little dilute hydrochloric acid, and wash up the glassware as normal. It's worked well for getting partially carbonised resin out of flasks.

UnintentionalChaos - 23-4-2007 at 20:39

I like the Mg(NO3)2 idea very much. Less chance of killing yourself and no heavy metal ion contamination either (reason to avoid chromic acid).