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This recipe for home-made handwash (liquid soap) consists of bar soap, water, Epsom salts, and coconut oil.

The author specifically warns against using 'artificial' Epsom salts, preferring the naturally occurring type, because the 'artificial' type is supposedly contaminated by heavy metals incl. arsenic.

Note – Be sure to get natural salts as some are man made and a full of unwanted chemicals. A lot of Epsom salts are made from synthetic materials, they are manufactured in factories from neutralized Sulfuric Acid, which is very high in heavy metals and arsenic. The REAL Epsom salt is naturally occurring mineral deposit in spring.

According to Wikipedia, Epsom salts are made by reacting sulfuric acid with magnesium oxide or magnesium carbonate.

I find it difficult to believe that 'artificial' Epsom salts would have appreciable amounts of heavy metal contamination, as neither sulfuric acid nor magnesium oxide are known to be frequently contaminated with heavy metals. A quick search on Google Scholar gives no results on the topic of heavy metal contamination in Epsom salts.

The only way I am aware that heavy metals might enter the process is if the sulfuric acid was produced from smelter stack gases, which do have appreciable heavy metal content. This is done at Mount Isa Mines, where $\ce{SO2}$ from the copper smelter stack gas is scrubbed out to make sulfuric acid, but the entire output of this plant goes straight to fertilizer production.

Is the above claim about heavy metal contamination of Epsom salts credible, or just an urban myth?

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    $\begingroup$ I've never heard about these claims before and I had too look it up too. It seems that the "arsenic" contamination is mostly discussed on sites with little to no scientific background. I think that your analysis is reasonable and agree that the contamination story is just an urban myth. $\endgroup$ – Klaus-Dieter Warzecha Jan 26 '14 at 15:41
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    $\begingroup$ I wouldn't be surprised to find that "natural" salts had higher levels of contamination. $\endgroup$ – matt_black Jan 26 '14 at 19:38
  • $\begingroup$ There is a lot of tramp sulfuric acid which contains all sorts of impurities everywhere- its an easy way get rid of sulfur dioxide produced from smelting and other places. $\endgroup$ – user2617804 Jan 28 '14 at 0:22
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Here in the US, they sell different grades of Epsom salt, from USP down to plant food. I'd presume that depending upon what the product will ultimately be used for, the manufacturer may use MgO with different purity levels - the lower the purity, the cheaper the product. Even the "bath salts" grade contain trace amounts of arsenic and selenium (see the first link below). Among the "medicinal" offerings, some are labeled "for external use" and others are labeled "for external and internal use." I suspect that anything with the "for external and internal use" label would be more than safe enough to use in handwash.

Here are some links you might find helpful:

http://k.b5z.net/i/u/2182313/f/Tech%20Data%20Sheets/Tech_Data_Sheet-bath_salt-epsom_USP-3.pdf

http://www.drugs.com/otc/104235/pepsom-flying-p-epsom-salt.html

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As seen on a 25kg bag of Epsom Salts:

Epsom Salts bag

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    $\begingroup$ I did XRF for years. A mg/kg is a part per million (ppm). When you start looking at ppm levels of contaminants in salts you will find all sorts of impurities. Even ACS reagent grade chemicals are full of junk at the ppm level. It is really really hard to get 99.9999% pure of anything. // Not disputing label, just pointing out that these would be trace level impurities... $\endgroup$ – MaxW Mar 9 '17 at 2:09
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Chemicals from chemical makers have labels about hazards and any kind of minor components and well as the grade of purity. I don't know Epson salt specifically in your country, but most probably there is a cosmetic or food grade version, which must be safe for you. If a salt is pure enough for bath salt, it is pure enough for washing hands (you don't drink soap, so food grade is not necessary). UNLIKE many natural, organic or whatever shaman-branded products, the "artificial" chemicals has a strong quality and safety control and they actually make all those info public.

Just a note: Home-soap makers are notoriously bad in chemistry and bad in safety. I have seen many recipes that make no sense, extremely hazardous and you produce a mediocre-to-bad quality soap. From the wording of the inserted quote I would expect he/she is a nice, but uninformed amateur at best. Be careful with those recipes.

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home-made handwash (liquid soap) consists of bar soap, water, Epsom salts, and coconut oil.

Bar soap - OK. Might be sodium or potassium fatty acid carboxlates, or syndet. Epson salts - not OK. Bivalent cations turn literal soap into insoluble slime. Synets don't much like it either. Coconut oil - not OK. Why are you adding grease to soap?

Supermarket, soap aisle, find something nice. I once washed my hands with Dove bar soap. It took a day to get them clean again. Maybe that's what you want.

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  • $\begingroup$ The question is about heavy metal contamination of Epsom salts, not so much about the particular home-made soap recipe. (I buy mine from the supermarket, same as everyone else.) $\endgroup$ – Li-aung Yip Jan 29 '14 at 3:50
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    $\begingroup$ The question is about how to recognise nonsense writing. And Uncle Al's answer shows that the writer of that recipe sells snake oil. $\endgroup$ – Georg Mar 21 '15 at 20:38
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Well I'm no expert but I wanted to do a liver flush and bought some Epsom salts (magnesium sulfate heptahydrate), apparently safe for ingestion and after seeing this page further searching led to this: http://www.fao.org/fileadmin/templates/agns/pdf/jecfa/cta/68/Magnesium_Sulfate.pdf

Section 4.2 is relevant and the key phrase is "limited to those that originate from the starting material".

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    $\begingroup$ LOL - I'd agree. Anyone who wants to do a "liver flush" is no expert. $\endgroup$ – MaxW Mar 9 '17 at 2:02

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