Ask A Scientist Chemistry Archive

status       educator
age          40s

Question -   One of our students came to me and wanted to know if I
had any Copper Sulfide in my office to make a crystal.. I am the Health
Aide in our school.  What is Copper Sulfide and can you make crystals
with it?
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Copper sulfide occurs in a number of minerals. Its simplest formula is CuS 
but that belies the number of forms it can be found in nature. Check out 
the web site:
http://mineral.galleries.com/minerals/sulfides/covellit/covellit.htm
If you do a search on "mineral collectors" or a search term you can find 
any number of supplies if you want one for a paper weight.

Vince Calder
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A better source would be a science teacher.  It is a compound commonly found in science labs, 
and I think there are "recipes" for growing crystals with it.  A science teacher could also go 
over safe handling guidelines with a student.

Pat Rowe
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Katherine,

All sulfides of copper are hopelessly insoluble on water and therefore cannot be used for 
crystal growth experiments. It is likely that the student mis-read the name of the compound. 
Copper sulfate (not sulfide) is the water-soluble copper compound that is ordinarily used for 
crystal growth demonstrations. It is a beautiful blue color and can enable production of very 
pretty (although fragile) crystals.

Regards,
ProfHoff 806
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In general you can obtain material safety data sheets (MSDS) by searching on the Internet 
(just search on MSDS in yahoo, etc).  You will get a list of health hazards etc, and decide 
then decide things.

Steve Ross
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Hi Katherine!
Even copper sulfide I (Cu2S) or copper sulfide II (CuS) can be crystallized, i think that maybe 
your student was looking for copper sulfate from which one can grow  beautiful  crystals. 
Copper sulfate was used to kill algae and microrganisms in swimming pools
and water reservoirs and must be manipulated very carefully due to its toxicity.
Thanks for asking NEWTON!

Mabel
(Dr. Mabel Rodrigues)
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Copper sulfide (CuS, Cu2S) is not terribly dangerous in itself.
But a very notable hazard is that someone might mix it (as powder) with acid,
causing a strong release of hydrogen sulfide, H2S, which can clear a school out by stink.
Toxic too, if you wait around tolerating it in high concentrations, or it exudes in your face.
I guess it is not as hazardous as sodium sulfide, Na2S, in that regard.
We had some Na2S in high school, and someone did clear out the school with it.  Fond memories...
but not for you.

How does your student intend to liquify the Copper Sulfide powder and regrow it as a crystal?
Cu2S melts at 1100C, which seems pretty hot unless you are in a college lab.  I do not know 
offhand what can dissolve it nicely for regrowth.
Not most water solutions.  Nitric acid can dissolve it, but then it is not sulfide any more, 
but sulfate or sulfite.
Something with ammonia or cyanide or thiocynate, maybe.
It is likely that solutions to grow tiny CuS or Cu2S crystals from, would be made with Copper 
thio-Sulfate or other non-sulfide chemicals, and then be electroplated very slowly.
Copper sulfides are opaque black substances, academically interesting for mineralogy, or 
because they can be part of one layer of Copper-cadmium-sulfide solar cell thin films, which 
are made by electroplating.

Copper sulfATE  (CuSO4) is more a high-schooler's speed, if that is where you are.
The crystals are pretty, clear colored blue or green.
Crystals can be grown merely by evaporating its water solution.
Just maybe that is what was meant all along.
Furthermore, with a 500-ohm resistor, a D-cell,  a copper wire, and 2 months,
you can grow sturdy little copper metal crystals on the tip of a graphite battery core.
From a simple green CuSO4 solution with bits of dirt in it.  I did that at home when younger; 
thought it was kind of neat, if slow.

Ask your student what he/she hopes the crystal will look like.
If you proceed with sulfide, check the facts, get the whole scenario, warn about acids, 
monitor.

Jim Swenson
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