Tiffany:
Just to show you that our little forum can provide more answers than a truckload of enclopedae, here is what (I think) you are seeking.
Arsenic levels would be consistent in both pre 1880 vegetable tan plants and in post 1880 chrome tanning sites. In fact, it can still be found in the effluent from modern plants in many parts of the developing world.
I began a search to satisfy my own curiosity and began running through Interchem sites looking for various inorganic Arsenic compounds. I was amazed at how much Arsenic is still used in the 21st century, among other things, but I digress.
The magic bullet was Arsenic Sulphide, or Realgar (re-AL-gar), As2S2. Arsenic Sulphide was used in the old tanning plants as a de-hairing and organic waste (blood, etc) removal agent.
Typing Arsenic Sulphide into your browser will provide you with reams of data. One case history is cited regarding poisonings from effluent in Bengaldesh. The bones and other detritus from a tannery there were being used to produce chicken and fish feed. The feed was loaded with Arsenic. so were the chickens and the fish and the humans who ate the meat.
Another paper was produced by the United Nations' WHO (World Health Organization). The paper was produced by WHO's International Programme on chemical Safety (IPCS). IPCS Health and Safety Guide No. 70. IPCS can be found at http://inchem.org.
Hope this helps. We accept challenges and provide answers on this forum. Searching sure beat discussing the past election. I will email you this data and the URLs, just in case you don't come back to your posting.
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As others pointed out in the other post, arsenic soaks were used prior to doing a final mount but that was only after the tanning process was done. Arsenic compounds do not dissolve very well in water and the solution was actually warmed fairly high to dissolve as much as possible before the hide was repeatedly manipulated in the solution. However, this was for taxidermy purposes only.
My suggestion of the source of arsenic is quite different - and it is pure speculation in many ways. My dad worked in a Paper Mill as a chemist for 37 years, and told me once of an early method of getting bark off of trees before they were made into pulp. I beleive that they would slash a cut in standing trees and paint or rub in arsenic. A while later, all the tree bark would fall off and then the tree would be harvested.
My old home town of Ridgway, PA had a very large Tannery in the late 1890's through perhaps the 1940's or so, that primarily used bark tanning, the most common tanning method of the day. They would used various barks high in tannin, cut locally, which they would soak the hides in. My speculation, or say a reasonable guess, would be that some pulp mills sold the bark removed from the trees, to tanneries. Because arsenic was used to de-bark the living trees, that would be the possible source.
I have perhaps 20 old tanning books dating back many years in my Taxidermologist library at home, and I shall try to endeavor to look into the matter more fully when I get a chance.
That is a possibility, my research indicated that the two primary source trees for bark were hemlock and oak. Some of the old PA tnneries had to be re-located over time to be situated nearer the bark source. The bark was boiled on site to release the tannin liquors.
Arsenic is still used as a dipilatory agentin tanneries on the Indian Sub-continent. My guess was that if you are correct regarding the de-barking process, then the arsenic found at those sites could have been the result of:
1. Debarking, although I am not familiar with that process.
2. Effluent residue from discarded float.
3. Effluent residue from the depilitory and blood-out processing by use of Arsenic Sulphide.
4. Use of Arsenic to treat waste tissue piles.
5. Possible use of Arsenic as an anti-bacterial agent on slaughterhouse hides.
And, it is a good thing that Arsenic is not soluable, else the body absorbtion rate of 5% of ingested As would probably be a lot higher. Had it been higher, Bachman and the boys would have died younger than they did.
I wonder if there was any old lace found adjacent to those As saturated sites?
Steve, Tiffany, et al,
Several references regarding 19th Century bark harvesting refer to a practice of "tree skinning". Hemlock lumber is not of high quality and freshly cut hemlock trees do no float and could not be down stream transported. In the Parry sound region and elsewhere in Canada, Hemlock trees were felled in late spring, and gangs of workers called "tree skinners" stripped the bark from the logs. The bark was shipped to tanneries, and the logs allowed to lie until Fall, when they would be sufficiently dry to float out to mills.
The references located also referred to massive amounts of Oak, Chestnut and Hemlock bark being supplied tanneries by lumber mills. One source refered to early railroads hauling entire trains of bark to tannery sites. since it takes about two pounds of processed bark to tan one pound of hide stock, the demand was severe, and resulted in nearly wiping out the Eastern Hemlock (Tsuga canadensis).
Another possible source for trace Arsenic residue would possibly have been the result of using fermented grains for bating in the tanneries. Grain was treated with Arsenic to prevent rust and mildew until the middle of the twentieth century.
Tiffany, how does it feel to have your own private research team?
..in the Ridgway area. I have seen old photographs of huge piles of bark 10 feet high and dozens of feet long. I know that there was a manual method of using what was called a bark spud to get the bark off, but I am unsure if a chemical process supplanted the method, or aided it. The sheets of bark were huge, but then most trees were 3-4 feet DBH.
Here is a couple interesting links in regards to use of Arsenic - one on use in Natural History specimens, and the second a fascinating piece on the use of arsenic in history in a journal called the Chem educator. I located bothe by the new Google scholar search engine (http://scholar.google.com/)
http://www.spnhc.org/documents/CF16/sirois.pdf
http://chemeducator.org/sbibs/s0007002/spapers/720051rb.pdf
Taxidermacalophosus,
Since Tannin is water soluable, and will leach out of stipped bark that is wetted by rain or stray dogs, I should imagine that fresh bark would have been prefered over dried.
Hemlock produces one of the two types of tannin, and oaks and other trees and some shrubs were used to produce the other. Hides tanned with Hemlock alone are difficult to dye and will not accept iron and other mordants. The old tanners were able to balance out the bark mix to provide liquors that produced more utile leathers.
The old sawmills cut logs without stripping them, the bark edge being cut off the slabs. I guess that the cambrium and outer bark was then bundled and shipped off to the leather mongers. The old texts I read mentioned that the bark was either tarped or stored in covered sheds, I suppose that was to keep the rain away.
I haven't done a bark tan since I was a boy scout. We didn't strip any bark from a tree, and if my memory serves me correctly, the bark came from Herter's for the project. But then, most things came from Herter's back then. The worst thing we ever got from Herter's was an, "Early Minnesota Butter Churn". My grandmother got a hankering for home churned butter, so she ordered one. I was the churn mule. By the time we had butter, I was thinking about turning that churn into the front end of my next Jitney.
You all are better than a whole stack of journal articles!
OK, so here's a little more history on this particular site in Wilmington, DE. Aside from the incarnations as a tannery, ship yard, dry cleaners, gas station (?), and now a parking lot, it was also back filled with dirt from god-knows-where. SO, from the data I've gotten so far it looks like the main forms of arsenic originally introduced was realgar (As2S2) and sodium arsenate (Na2HAsO4). And it looks like the As2S2 has stuck around pretty much unchanged for quite a while. There are pieces of wood in the samples, but that could have been part of the orignal structure as there is also brick in the soils. At any rate, I now have more info than I know what to do with! Thank you all again for all your assistance!