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Author: Subject: Zinc chloride from tinning flux
tryptic
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[*] posted on 2-8-2004 at 08:19
Zinc chloride from tinning flux


Hi

I may need zinc chloride for an organic synthesis, but I'm not sure if I can buy it from anywhere, because it has some illegal uses..Apparently zinc chloride is present in many brands of tinning flux, see for example:

http://www.oatey.com/apps/catalog/instance_assets/assets/MSD...

I am a neophyte chemist, so the following could contain some silly errors, but could you extract zinc chloride from the Oatey tinning flux as follows:

1. Pour some tinning flux into water, stir it for a while, now some zinc chloride should be dissolved in the water, along with some ammonium chloride. Petrolatum, tin and the other impurities are insoluble in water.

2. To get rid of the ammonium chloride, wash the solution from part 1 with DCM. Because zinc chloride is more soluble in DCM than water, DCM should now contain much of the zinc chloride. Ammonium chloride is almost insoluble in DCM so very little of it will be present.

3. Evaporate the DCM to obtain moderately pure ZnCl2 though some ammonium chloride may be present.

Is this even remotely correct..?

Or should I instead first dissolve tinning flux in DCM then extract with water? Also drying the DCM with MgSO4 etc could be useful for reducing the amount of ammonium chloride dissolved in water..?

Or could you use some neat acid extraction technique here..First dissolve tinning flux in water, add some hydrochloric acid to make the water solution even more acidic (Will the hydrochloric acid do any damage to the ZnCl2..?) Now will the excess acidity push the ZnCl2 from the water phase into the DCM phase? (Assuming stirring, and of course assuming that HCl isn't soluble in DCM, or is it?)

[Edited on 3-8-2004 by vulture]

[Edited on 3-8-2004 by vulture]
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[*] posted on 2-8-2004 at 09:47


Why not just dissolve zinc in HCl?

You can get zinc from Canadian pennies. The ones made in 97-99 are copper plated zinc. I think some American pennies are zinc and copper too, but Im not sure about the time periods.




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[*] posted on 2-8-2004 at 10:30


Of course..Thanks! I wonder why I didn't think of that before..Many coins over here have a mixture of zinc, copper and nickel..But even better, I found some neat gift plates that are apparently made of pure zinc. Great!
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[*] posted on 2-8-2004 at 10:51


Instead of using zinc, why not use the (vastly cheaper) zinc oxide, which is readily available from pottery suppliers.



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[*] posted on 2-8-2004 at 14:16


zinc oxide, hmm..Didn't find any from pottery suppliers, but apparently it's used in veterinary medicine, given to pigs for diarrhea or something like that.

I just noticed that there was an older thread about this in the general chemistry forum..Apparently with a water solution of hydrochloric acid and zinc you get hydrated zinc chloride, unless you add some potassium chlorate (and use reasonably pure hydrochloric acid???)

Of course I'd have the same problem with that extraction from tinning flux..(doh!)
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[*] posted on 2-8-2004 at 14:20


Why not just heat it until it loses its water of crystallization?



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[*] posted on 2-8-2004 at 14:23


Quote from Hjalmar Poelzig:

>>
ZnCl2 and basic salts

When hydrated ZnCl2 is heated, one is left chiefly with Zn(OH)Cl and HCl.

If you want anhydrous ZnCl2, dissolve raw zinc metal in HCl, add a bit of KClO3 and evaporate the HCl.

The product will still contain a small amount of basic salts, but is usable for most purposes
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[*] posted on 2-8-2004 at 14:35


Oh :o



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[*] posted on 2-8-2004 at 14:43


Ammonium chloride and petroleum agents will evaporate if the mix is heated enough. Zinc chloride anhydrous will not break down at high temp and has a boiling point of 732 C so unless you get the extraction mass fairly hot you should not loose considerable ZnCl2. Some of the additional additives may still be there though resulting in additional purification methods, e.g., extraction of the mass with ether, or alcohol and evaporating, both of which ZnCl2 is soluble in. Be sure to keep your solvents anhydrous from here on out as you should avoid hydrating your chloride and ruining your hard work ;)

More madscientist-esque methods would involve igniting a mix of CCl4 or C2Cl6 with Zn powder and collecting the 'smoke'. Or just reacting Zn with Cl2 gas, but I bet this would be hard to get to complete reaction without some sort of molten metal atomizer unless it is already powdered

[Edited on 8/2/2004 by BromicAcid]




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[*] posted on 2-8-2004 at 14:57


Whoa, neat idea! Ammonium chloride boils at 520 degrees celcius so maybe I'll need to invest in a Bunsen burner and some stuff like that..Yeah. On the other hand the leftover ammonium chloride maybe wouldn't even be a problem because I'll be using DCM from now on..

Thanks

I wonder how likely it is that the petrolatum fumes will be ignited by the heating flame..Probably not very likely, the fumes will cool off before hitting the flame and probably petrolatum won't burn very energetically anyway, and the amount will be pretty small..

But I imagine that the fumes could condense pretty quickly and leave an annoying sticky film to things..But I guess that's a price you have to pay

[Edited on 3-8-2004 by vulture]
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[*] posted on 24-8-2004 at 08:04


Quote:


If you want anhydrous ZnCl2, dissolve raw zinc metal in HCl, add a bit of KClO3 and evaporate the HCl.



Could someone explain to me how KClO3 works in here? - Thanks a lot...
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[*] posted on 30-12-2005 at 14:13


Sorry to bring up an old thread (i think?)
But is there anything other then chlorate that will work to dry it or any other way to dry it?

Could i mix somthing such as MgSO4 with the hydrated ZnCl2, this may dry it and then perhaps extract that with alcohol leaving the hydrated MgSO4 or would the alcohol disolve it also?




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[*] posted on 30-12-2005 at 15:35


Buy the way I routineley see zinc oixde on ebay for making dental cements.

FYI I remember reading in a chemical history text about how a prominent 18th or 19th century chemist isolated zinc chloride by heating zinc oxide with dry ammonium chloride. Zinc Oxide is a VERY weak base or more correctly, amphoteric. But at the 500 or so degree boiling point for ammonium chloride there would be free HCL to react with the zinc oxide. Maybe the resulting water is carried away with the ammonia? Better yet make a zinc ammonium chloride double salt and heat that and continously add conc HCl while it dries. Heck i might try this myself:)




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