Sciencemadness Discussion Board

Preparation of Mercuric Sulphide Question

Theophilus - 9-12-2005 at 08:19

I'm a member of a living history organization and I'm trying to recreate medieval techniques for making pigments. I've got a nice batch of white lead and another nice batch of vitiriol growing, now I want to try somthing else.

I found this description in a book called "On Divers Arts" by a guy named Theophilus, written in the 12th century. It seems easy enough, but I'm wondering how dangerous this is?

(I don't have the book with me right now, I'm typing this from memory.)

Theophilus says to take two parts finely powdered sulfur and one part mercury, and put them into a glass vessel. Then seal it tightly with clay, and put a layer of clay all over it. Heat it next to the fire until the clay is hard. Then put it into a very hot fire. He says you will hear a loud crackling sound. When the sound stops, remove it from the fire and let it cool. On opening it you will find a bright red powder.

So if I try this am I going to turn my back yard into a Superfund site, or what?

IrC - 9-12-2005 at 09:05

Can you scan the book and include it in the books section? This is the type of book I spend years looking for and I have never seen this one.

Fleaker - 9-12-2005 at 10:01

I shouldn't worry too much about it, although the method itself seems counterproductive since mercury sulfide decomposes at high temperatures. Since mercury sulfide will form at standard conditions (room temp and one atmosphere) and as such, is often used as the preferred spill absorber along with zinc powder you can just add metallic mercury to powdered sulfur and you will get cinnabar.

Theophilus - 9-12-2005 at 11:11

Quote:
Originally posted by IrC
Can you scan the book and include it in the books section? This is the type of book I spend years looking for and I have never seen this one.


While the copyright is expired on the original, the translation is a copyrighted work. It's still available on Amazon, which is where I got my copy. It's only $10.

Here's a link: http://www.amazon.com/gp/product/0486237842/002-9077570-9043...

Theophilus - 9-12-2005 at 11:15

Quote:
Originally posted by Fleaker
I shouldn't worry too much about it, although the method itself seems counterproductive since mercury sulfide decomposes at high temperatures. Since mercury sulfide will form at standard conditions (room temp and one atmosphere) and as such, is often used as the preferred spill absorber along with zinc powder you can just add metallic mercury to powdered sulfur and you will get cinnabar.


I'll try that and see what happens. But I've read about cleaning up mercury spills with sulfur and what I've read says that it turns brown (and to keep adding sulphur until it doesn't turn brown any more). The vermillion (cinnabar) pigment isn't brown, it's bright red. I was thinking the heat (and maybe the pressure from heating the sealed vessel) caused it to form a different crystalline structure or something.

garage chemist - 9-12-2005 at 11:32

I have tried the preparation of mercuric sulphide before and written about it in this thread:
Preparation of Vermillion(forget the processes with NaOH or K2CO3, they are dangerous due to formation of soluble Hg compounds).

I was eventually successful, the trick lies in sublimating the HgS (prepared with excess of sulfur) in a test tube with powerful heat, collecting the hard black sublimate (the "aethiops mineralis", as the alchemists called it), grinding it in a mortar until it becomes bright red (takes long), and then extracting the excess of sulfur with hot toluene.
The crude black HgS can also be ground as a slurry with water in the mortar, this eliminates dust formation.

Never experiment with or store mercury in the house, I've got my tightly capped mercury bottle inside a jam-jar with some sulfur in it and the sulfur slowly becomes black from escaping mercury vapors. It is creepy!

[Edited on 9-12-2005 by garage chemist]

Dr. Beaker - 10-12-2005 at 09:27

just remember that Newton's greatest acheivments were before his experiments with mercury.

Mr. Wizard - 10-12-2005 at 10:55

I too store my Hg containers in a plastic sealed container with some sulfur. The black sulfide is visible on top of the sulfur. The silver labeled bottle next to the top cork has a lot of the black sulfide dust stuck to the bag by static electricity. Everyone should be very aware of the vapor problems with Hg stored or spilled in living areas.

DarkHgS.jpg - 39kB

garage chemist - 16-12-2005 at 08:35

I want to add that sulfur and liquid mercury at room temperature react very slow.

In one of my early attempts at HgS preparation I put a drop of Hg into a mortar, added a spatula of flowers of sulphur and began grinding at it. The sulfur rapidly became black and the mercury became split into numerous small droplets inside the black powder. I continued grinding until no more droplets were visible.
But on examination of the powder (dissolution of the HgS with Na2S solution) lots of small Hg droplets became visible and united to form a larger droplet.

Grinding sulfur with Hg does not reliably convert the entire Hg into the sulfide. It should only be used as a means of pre-mixing before heat (enough to melt the sulfur and boil the Hg: only Hg vapors react with sulfur) is applied to effect their complete combination.
And use an excess of sulfur, of course.

Most important, never rely on putting sulfur on Hg spills!
It will not react! Only Hg vapors react with solid sulfur.
Zinc dust is a much better adsorbent for spilled mercury.
Very handy for collecting small droplets is also an amalgamated piece of copper wire, the Hg immediately clings to it on contact.