Silver tarnishes because...

TerryC · Sep 8, 2012

Here is a bit of trivia that I have some doubt about. I will check further. According to the Web page "Wikipedia", silver tarnishes because of the sulfer that is introduced into the atmosphere by human pollutants. That means that, before humans "discovered" and isolated the element sulfer, about 500BC, silver did not tarnish. Hmmm. More reading is required. Interesting, though. TTC

TreasureWriter · Sep 8, 2012

This is a good question since it is very relevant to preserving out metal detecting finds.

Wikipedia most often it is simply an opinion on a subject as posted by a layman.

Here's the deal with silver tarnishing. Anything that gives off Hydrogen Sulfide (not Sulfur per Se') will cause silver to tarnish. Things like oil from your hands, ammonia, fossil fuels, wool, rubber as well as foods like eggs, salad dressing, table salt and onions. Humidity also plays a roll in how fast the silver tarnishes. There are literally thousands of things that will react with silver and cause it to tarnish that have always existed in nature. Hydrogen Sulfide is released as a natural breakdown occurs in these items.

Chisos · Sep 8, 2012

Ag+O2 > AGO2 Silver plus a diatomic molecule of oxygen yields or produces Silver Oxide(tarnish). Since the stuff first formed on earth to today.

Gunrunner61 · Sep 8, 2012

Interesting ? I kinda want to go with TreasureWriter on this one. Like he say's It occurs in nature If you've ever drank the water in South Ga. that smell of rotten eggs, It's Hydrogen Sulfide.

CoinFetcher · Sep 8, 2012

Wikipedia generally has a anti-human tone

U.K. Brian · Sep 9, 2012

Take two identical silver coins with patina (if you like it) or tarnish if you don't. Clean one but leave the other untouched and see how your detector reacts "depth" wise, especially in discrim. mode.

Chisos · Sep 9, 2012

Gunrunner61 said:
Interesting ? I kinda want to go with TreasureWriter on this one. Like he say's It occurs in nature If you've ever drank the water in South Ga. that smell of rotten eggs, It's Hydrogen Sulfide.

I stand corrected. Thanks.

gleaner1 · Sep 9, 2012

Silver is stable in oxygen and water, but tarnishes when exposed to sulfur compounds. Black is not the only color result of sulpher. Nice old silver coins in collections for decades take on the greens and blues and gold colors from sulfur compounds found in the paper of the holders. There has been discussion that a light dusting of powdered sulfur within the coin holders or folders will rather rapidly (years, not decades) force these colors.

Bum Luck · Sep 9, 2012

Sulfur is a frequent component of volcanoes and enters the earth's atmosphere upon eruption. Geologists tell us that volcanoes have been erupting since the earth was formed, billions of years ago. In fact, more of this occurred then than now.

Of course, one has to believe in volcanoes, geologic time, and atmospheres. For those that don't, it probably is a source of confusion and denial.

TerryC · Sep 9, 2012

U.K. Brian said:
Take two identical silver coins with patina (if you like it) or tarnish if you don't. Clean one but leave the other untouched and see how your detector reacts "depth" wise, especially in discrim. mode.

Brian, You should have a "first row seat" on this subject. Roman coins (silver) that have been buried (hence, not subjected to pollution) for centuries come out of the ground UNTARNISHED. Right? That fact could be verification of this fact. Right, Brian? Tnx. TTC

Jason in Enid · Sep 9, 2012

Complete garbage! Sulfer has been present since the dawn of the earth. The article you read was pure BS.

Bum Luck · Sep 9, 2012

None of this subject is simple.

Sulfur is the seventh to eighth most present chemical in the human body by weight.

Silver tarnishes primarily with sulfur compounds, but also with nitrogen and oxygen.

Sulfur is present in large quantities in the earth, and it cycles through the atmosphere like many other chemicals, associated with water which I mention here so you have a foundation for the variability.

The vectors for this happening are volcanoes, biological processes, geologic erosion, and human combustion of sulfur-bearing materials; coal and oil are the major ones.

It's called the Sulfur cycle. Google it up; I did and learned a lot. I hung out with a chemical genius in grade school, took chemistry in high school and college, and I kept with it to a degree, not the least of reasons which is my love of fireworks. That helped to understand it.

So, Terry, if the article said that, it was incorrect. Sulfur has been present in the atmosphere for about 3 ga, easily older than minted coins - har! Actually, it can only happen if oxygen is present since sulfur needs it to oxidize into sulfuric and sulfurous acids. That's also when oxygen was produced by photosynthesis in significant amounts.

Anthropogenic perturbation to the natural atmospheric sulfur cycle, or the impact from human activity, has accounted for a significant increase, and that increase is unevenly distributed, mostly in latitudes 35 to 50 North - hardly surprising.

Here's a paper on it, done by real scientists, not Wiki authors:
Bates et al -- Sulfur Emissions to the Atmosphere from Natural Sources

Quiz on Tuesday.

TerryC · Sep 10, 2012

Bum Luck said:
None of this subject is simple.

Sulfur is the seventh to eighth most present chemical in the human body by weight.

Silver tarnishes primarily with sulfur compounds, but also with nitrogen and oxygen.

Sulfur is present in large quantities in the earth, and it cycles through the atmosphere like many other chemicals, associated with water which I mention here so you have a foundation for the variability.

The vectors for this happening are volcanoes, biological processes, geologic erosion, and human combustion of sulfur-bearing materials; coal and oil are the major ones.

It's called the Sulfur cycle. Google it up; I did and learned a lot. I hung out with a chemical genius in grade school, took chemistry in high school and college, and I kept with it to a degree, not the least of reasons which is my love of fireworks. That helped to understand it.

So, Terry, if the article said that, it was incorrect. Sulfur has been present in the atmosphere for about 3 ga, easily older than minted coins - har! Actually, it can only happen if oxygen is present since sulfur needs it to oxidize into sulfuric and sulfurous acids. That's also when oxygen was produced by photosynthesis in significant amounts.

Anthropogenic perturbation to the natural atmospheric sulfur cycle, or the impact from human activity, has accounted for a significant increase, and that increase is unevenly distributed, mostly in latitudes 35 to 50 North - hardly surprising.

Here's a paper on it, done by real scientists, not Wiki authors:
Bates et al -- Sulfur Emissions to the Atmosphere from Natural Sources

Quiz on Tuesday.

Tnx, Bum Luck... and others. I tried to re-find the statements in Wikipedia. Couldn't find it. I'm sure it's still there, just got to find it. I'm sure it's a slanted view anyway. Thanks for the replies. Good to see others are interested. TTC

Bum Luck · Sep 10, 2012

TerryC said:
Tnx, Bum Luck... and others. I tried to re-find the statements in Wikipedia. Couldn't find it. I'm sure it's still there, just got to find it. I'm sure it's a slanted view anyway. Thanks for the replies. Good to see others are interested. TTC

Thank you Terry, for bringing it up - I learned a lot. Always like that.

To get to your original post, I think that some silver coins don't corrode because those chemical processes aren't present - first, it needs water, and then the sulfur and the pH is also a factor.