Arsenic tanning question

Submitted by Tiffany on 12/1/04 at 2:15 PM. ( tnthomas@udel.edu ) 128.175.230.96

I'm hoping one of you might be able to answer my question, so here goes. I'm a geochemist doing reseach on soils contaminated by arsenic surrounding old leather tanning facilities. I'm trying to find out EXACTLY how the arsenic is used and what form (is it pure arsenic, arsenic oxide, arsenic sulfide, liquid or powder etc.). SO far I have only found vague references to arsenic in tanning, but nothing specific. Can one of you please help me? Feel free to reply to my e-mail address if you have information. Thanks!

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This response submitted by George on 12/1/04 at 2:20 PM. ( georoof@aol.com ) 205.188.117.7

Then type in "arsenic soap". It wasn't use in TANNING, it was used as a bugproofer. Then came DDT, then Endolan U, and now.....nothing.


Arsenic

This response submitted by cur on 12/1/04 at 4:47 PM. ( ) 4.227.116.11

This may be a WAG of the first order, but here goes:

Like George said, Arsenic was once widely used as a preservative and insect repellant in the taxidermy industry. Arsenic powders were used in industry too to reduce bacterial action or to prevent putrification of animal waste by-products.

I don't know how old the tannery sites reference are, but if they existed prior to 1880, then arsenic presence might be the result of adding the element to float to reduce bacterial development in the vegetable tanning processes used up to the 1880's. Or to treat shaving and other animal waste piles.

After the early 1880's until present, chrome tanning was used more and more extensively. Arsenic, as you probably know, is rarely found in natural deposits. Most Arsenic exists in combination with other metal elements or compounds. Silver, gold, iron, bauxite and chromite ores all contain trace amounts of arsenic. Chrome ores were mined in the US beginning around 1820, or so, or at least that is when chrome oxides became plentiful and began to replace Turner's Yellow on artist palettes.

Early chromite processing plants did not have the refining capabilities that were developed during the late nineteenth and early twentieth centuries. Some chrome ore deposits have just trace amounts of Arsenic, while others contain subtantial amounts. Since chromium salts were used in the tanning vats, and up to 75 percent of tanning waste product is effluent from the float, I would surmise that the early chrome oxides contained arsenic and that might be the source of concentrations at your found sites.

Oak bark and other vegetable tan processes would not contain a concentration of mineral salts, sulphides and oxides. If the arsenic concentration is equal at both vegetable tan process and chrome tan process sites, then my theory is out the proverbial window. If similar levels exist at both plants, then treatment of putrid residue and use as a preservative on salted hides and in solution as a bactericide may be the souce of your found arsenics.

Years ago, slow transport methods may have forced use of arsenic to preserve skins en route to tanneries. Rehydrating the hides would produce high concentrations in the soaking vats which would in all liklihood be emptied on site.

There are some tanneries such as the 200 year old Holmes-Hall group in the United Kingdom that may be able to shed light on the direct use of arsenic in the tanning process. Holmes-Hall can probably be found on the internet, or by searching through one of the tanning consortiums or organizations.

WAG, or not, hope this helps.


Sodium arsenate powder

This response submitted by duckfeathers on 12/1/04 at 5:19 PM. ( ) 68.236.47.232

Used only as a permanent bug or whatever killer, sodium arsenate powder was mixed with water as the final soak in the process. There are most likely other recipes but this is what I remember.


You know, Cur, I'd forgotten that (No surprise there)

This response submitted by George on 12/1/04 at 7:00 PM. ( ) 205.188.117.7

You know arsenic was originally used as embalming fluid and I'm told that the reason Abraham Lincoln's body looked so good when unearthed a few years back was because of that single fact. I'm not quite that old. I just used it as a bug proofer.


Sodium arsenic soak

This response submitted by cur on 12/1/04 at 7:58 PM. ( ) 4.227.116.11

Was done before mounting a hide. Dunno about commercial leather processing with dying and fat-lacquering and all the other processes to make final product leather, I would imagine that soaking in arsenic would not be done for most leathers after finishing. Could be, maybe that is why my daddy told me to never chew on shoes.


Oops

This response submitted by cur on 12/1/04 at 9:25 PM. ( ) 4.227.116.11

That was Sodium Arsenate soak....not arsenic. Arsenic is an element, As, Arsenates are metal oxides.


Oops

This response submitted by cur on 12/1/04 at 9:25 PM. ( ) 4.227.116.11

That was Sodium Arsenate soak....not arsenic. Arsenic is an element, As, Arsenates are metal oxides.


THANK YOU ALL!

This response submitted by Tiffany on 12/2/04 at 12:47 PM. ( tnthomas@udel.edu ) 128.175.230.96

Thank you all so much, this was particularly helpful. My problem was that all the websites only referred to "arsenic", which, as you pointed out cur, is an element and I was suspicious that elemental arsenic was actually being used for tanning. I am unsure of the type of tanning done at this particular site, but I will try to find out. If any of you has any more info or can point me in a good direction that would be great. I'll check into the Holmes-Hall group and see if I can find anything else. Again, I really appreciate all the input!


Buggy

This response submitted by Buggy on 12/15/04 at 10:12 PM. ( ) 69.14.195.217

ARE YOU A LAWYER?


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