Sciencemadness Discussion Board

Growing pyrite (iron sulfide) crystals

angeltxilon - 8-10-2017 at 13:07

Recently I obtained iron sulfide by react iron with sulfur.

I was wondering if it is possible to grow iron sulfide crystals via dissolving this sulfide in some acid or substance and then leaving it volatilise, in a similar way to grow crystals in water.

DraconicAcid - 8-10-2017 at 14:39

Not very likely. If you dissolve it in some acid, the most likely thing to volatilize is H2S.

Additionally, pyrite is FeS2, not a simple sulphide. Which is too bad- it forms lovely crystals.

Harristotle - 9-10-2017 at 05:55

I have no idea if this will work, so please accept this as wild speculation.

Suppose you took your iron sulfide, placed it in one of chironex's autoclaves, that he used for making quantum dots. ie, one of these http://www.ebay.com/itm/Hydrothermal-Autoclave-Reactor-Teflo...


Place some of your iron sulfide, and then some water and heat to a couple of hundred degrees in an oven. Slowly cool and see if you get any crystalisation.

Open carefully, in a well ventilated area.
Keep your dog handy so you can blame him, if any of your friends walk by and sniff ! :)

I am thinking this is probably a bit like the geochemical processes, and you might be able to get some solubility at high temp.

your mileage may vary, and I have no real clue on this - only an experiment will tell!

Cheers,
H.

DraconicAcid - 9-10-2017 at 09:00

If we're going into wild speculation, a hydrothermal process with some ionic solvent (such as a hydrated metal salt such as calcium nitrate tetrahydrate) might work better.

Sir M - 9-10-2017 at 09:24

Couldn't the iron sulfide be dissolved in warm solution made by dissolving sulfur in NaOH to form soluble polysulfides?
Got the idea from dissolving of HgS, which works that way.

wg48 - 9-10-2017 at 13:06

Zinc sulphide crystals are grown from molten sodium chloride using a two zone quartz reactor with a temperature difference between the zones. In the hotter zone is placed the source zinc sulphide, which dissolves and diffuses to the cooler zone where it crystallises.

Perhaps it would work with iron pyrites perhaps with a different salt. If I remember correctly it was in a patent. It would be a challenge building a 800C + reactor with two temperature controlled zones.

I found the patent https://www.google.com/patents/US3374067

It was KCl not NaCl.


[Edited on 9-10-2017 by wg48]

DraconicAcid - 9-10-2017 at 13:30

Quote: Originally posted by wg48  
Zinc sulphide crystals are grown from molten sodium chloride using a two zone quartz reactor with a temperature difference between the zones. In the hotter zone is placed the source zinc sulphide, which dissolves and diffuses to the cooler zone where it crystallises.

Perhaps it would work with iron pyrites perhaps with a different salt. If I remember correctly it was in a patent. It would be a challenge building a 800C + reactor with two temperature controlled zones.

I found the patent https://www.google.com/patents/US3374067

It was KCl not NaCl.


[Edited on 9-10-2017 by wg48]


That's interesting to know. There are a number of different chloride salts and mixtures that one could try that would melt at a lower temperature, which may or may not dissolve the sulphide at a given temperature. It might be possible to dissolve the pyrite at a high temperature, and slowly decrease the temperature to one at which the pyrite isn't soluble, but the salt is still liquid.

ETA: http://www.sciencedirect.com/science/article/pii/S1876610215...

There's a eutectic mixture of the chlorides of potassium, sodium, calcium, and magnesium that melts at 385oC, and is very stable up to 500oC. If the pyrite will dissolve appreciably at 500 oC, then crystallize as the temperature is reduced to, say 400 oC, then crystals may form. Then you let it cool to room temperature and separate the crystals from the matrix with water.

[Edited on 9-10-2017 by DraconicAcid]

wg48 - 9-10-2017 at 14:15

Quote: Originally posted by DraconicAcid  


ETA: http://www.sciencedirect.com/science/article/pii/S1876610215...

There's a eutectic mixture of the chlorides of potassium, sodium, calcium, and magnesium that melts at 385oC, and is very stable up to 500oC. If the pyrite will dissolve appreciably at 500 oC, then crystallize as the temperature is reduced to, say 400 oC, then crystals may form. Then you let it cool to room temperature and separate the crystals from the matrix with water.

[Edited on 9-10-2017 by DraconicAcid]


I thought about a eutectic too but I would expect they would have thought about that too.

Heat up to dissolve and then cool down to form the crystals is achievable with just a crucible so that is much simpler. I suspect that if the amount dissolved is small you will only get small crystals where as the two zone diffusion method would just need more time. But the heat up and cool method would be a good starting point to get the right mixture of salts and temperature. Apparently various crystals can be grown this way if a suitable molten salt or combination is available.

There is also the possibility of using a deep eutectic ionic liquid apparently some dissolve metal oxides perhaps one dissolves sulphides

crystal grower - 10-10-2017 at 08:29

If you go to the nearest iron mine and pick up any rock with little pyrite vein, it will be probably much prettier than what you would ever manage artificially.
Not saying it's not worth it if you're interrested in the "science part". Just wanted to let you know it isn't the easiest thing really.



[Edited on 10-10-2017 by crystal grower]