This chemical is used to etch copper foil.It makes the copper go
black.Once dry it can be polished up leaving a residue behind where
needed.It comes in the form of a stone like substance.A small piece
dissolved in water,Turns into a yellow colour and has a smell like
rotten eggs.
I require suppliers for this chemical in South Africa,U K or the
States but firstly South Africa.

There'd be no problem in the UK or US, but SA seems tricky.
Best I can find - and its not too good- is
http://www.daytona.co.za/products.htm
They don't have K2S that you want, but they have sodium sulphide,
which, if my chemistry hasn't completely left me, will have similar
properties.

I have someone coming over from the States, Philadelphia next month as
well as family in the UK. Can you tell me where I can obtain this
chemical at both places please.
I have contacted daytona,as it is weekend ,I expect to hear from then
during next week.
Many thanks,
Mitch Webber

I may have spoken too soon - sorry - I figured I'd just wander over to
Sigma-Aldrich, and there it would be.  Not so.

I don't like your chances of getting it on a plane:  this stuff
"explosively decomposes on shock".
http://www.itcilo.it/english/actrav/telearn/osh/ic/1312738.htm

and is highly toxic:
http://www.ci.tucson.az.us/arthazards/metal2.html

I looked high and low and turned up little, except this:
http://www.silverprint.co.uk/chem24.html
I hope it helps.

Also consider that local supplier of Na2S - some of the links
suggested it was an alternative.  If all else fails - rub rotten eggs
on your copper and use H2S!

Oh BTW, K2S is also called "Liver of sulfur".  I didn't try to track
it through this name.

Regards
xarqi

FeS + 2 NaOH -> Fe(OH)2 + Na2S ?   

I don't know if it is that simple; but FeS (Ferrous Sulfide) is at
least not poisonous or explosive, and can be taken onboard a plane.
NaOH (lye) is avaliable everywhere.

FeS + 2 NaOH -> Fe(OH)2 + Na2S?
Yup - under pressure at 400 degrees Celsius
http://www.oretest.com.au/news_letter_pdfs/nletters_9.htm

And if there's O2 around, you get Na2SO4.

What about in aquatic solution? Will the FeS dissolve in a strong solution of lye?

I'm only an "accidental chemist", but I don't think the reaction will
go too well unless you push it.  Something about activation energy
perhaps.

I'm a bit frustrated by this.  There seem to be plenty of references
to people using K2S for this purpose (curiously, mostly in Arizona),
but nobody is saying where they get it from!

Found it! (At least how you can make it your self:)

"Mix 50% solution Caustic (NaOH/KOH) 1 to 1 with water 
Bring to a low boil 
Add 1/2 to 3/4 lbs sulfur per 1 gallon of solution and continue to
boil until sulfur is dissolved.
(Sulfur is readily availabe over-the-counter at most pharmacies)"
Source: http://www.finishing.com/79/57.html


Liver of sulfur will work exactly like Potassium Sulfide, it is a
mixture of various alkali polysulfides.


This page suggests another source:
"If you wish to use "liver of sulfur" you can purchase at gardening
supplies nurseries as "lime sulfur", calcium polysulphide. If you wish
to antique then dilute to 1-10 ml/litre. If you wish to strip copper
use 50% strength."
Source: http://www.finishing.com/128/71.html