Here's the thing about it I researched it and followed Doug's lead. as a scientist there is nothing mysterious about it. Touchstones were used BUT we now use acids which they did not before I like the ring But acids we did not have
Since they probably did not have the acids that we use now, they may have had some kind of reactant, or just went by color comparisons to reference streaks that were of known purity ??
They do compare the streak to reference streaks. See the Wikipedia article on Touchstones. Whether "they" had acids depends on who "they" were. The alchemists of the Middle Ages deserve a lot of credit. Nitric acid and hydrochloric acid both date to the 13th century; and the Geber processes are the ones sometimes still used for them today. However, sulfuric acid (vitriol) was known to the Sumerians. They catalogued several kinds by color - something we still do. Short of those mineral acids, the only available oxidizers were urine (usually horse urine) and vinegar. But, again, credit the alchemists. By distilling vinegar, you can get glacial ascetic acid.
Yeah, I thought so too, until I looked it up. http://www.britannica.com/EBchecked/topic/600649/touchstone But if you really want to research it, try this book to start -Studies In Ancient Technology - http://books.google.com/books?id=sT...v=onepage&q=touchstone silver ancient&f=false The very first paragraph of this one will tell you that touchstones were not just used on gold - http://www.scribd.com/doc/32031595/The-History-Of-Touchstone-Testing-For-Gold The gold or silver to be tested was rubbed on the surface of the touchstone ............ http://books.google.com/books?id=PD...e&q=touchstone ancient silver testing&f=false http://download.springer.com/static...528_af8f63f9f07991716f68d5a0684c96b5&ext=.pdf There's lots out there, so it appears that touchstones were indeed used to quickly test silver.
GREAT references there, Thanks a lot! I just didn't think to google those search terms, but you nailed it perfectly. I read up on and now feel much more knowledgeable about the ancient methods.