What concentration of H2S is needed to tarnish silver?

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A. There is no precise answer to your question as the amount of tarnishing you see will be a function of the Relative Humidity, gas concentration and time of exposure. Silver will react with extremely low levels of hydrogen sulfide.

However, the gas is so pungent that it is difficult to withstand more than 5-10 ppm of the gas - if this gets exceeded you can become desensitised and not smell it at all; this is when it kills you!

You will be aware that silver will go black in an atmosphere where you cannot smell hydrogen sulfide, so the minimum level will be in the ppb or even ppt range; however, the detection of the reaction will be dependent on how long the silver is exposed to the gas. The rate of reaction will also be dependent on the relative humidity of the air, as the water is needed to dissolve the gas. Hydrogen sulfide and silver react to form black silver sulfide, one of the most insoluble salts of silver and this is what causes the tarnish. However, it can be very easily reduced by putting it in a dilute solution of sodium carbonate ⇦this on eBay or Amazon] and attaching a piece of aluminium foil to the article. Fluorescent lights do produce some UV light, depending on the filler gas, but commercially available domestic or general purpose industrial lights do not constitute a UV health hazard.

A. Hi, David. Unfortunately, I can't figure out where you're going. If you are trying to tarnish silver, it is certainly dead easy to do it instantly with liver of sulfur ⇦this on eBay or Amazon [affil links] -- you certainly don't need to design a controlled air environment to make silver tarnish :-)

... or are you trying to explain why silver tarnished quickly in some situation? ... or are you trying to develop a tarnish resisting treatment for silver and you want to test it in the worst realistic ambient environment? ... or ...

Please help me by starting with: "Here is my situation . . ." rather than an abstract question, and maybe we can help. Thanks!

A. Hi Justine.

A. I don't know the actual ppb sulfide concentration, but we've been told by our helpful contributor James Watts that sealing a silver item into a plastic baggie with a crushed hard boiled egg will expose it to sufficient sulfide to tarnish it in a day. Good luck.

Regards,

A. Hi, James. Liver of sulfur is very available ⇦this on eBay or Amazon [affil links] and far less corrosive that sulfuric acid, but I can't guarantee that it won't affect the paper or polymer; you'd need to try it. Crushed hard boiled eggs, sealed in some way to keep their gasses on the silver might work too.

Regards,

Q. Thank you. Would a powdered form of Liver of Sulfur tarnish silver? Or does it need to be liquid? What about other dry chemicals containing sulfur, such as gypsum or pure sulfur? JW

A. Hello again James. Liver of sulfur is available as a dilute liquid or as a solid to be mixed with water to make a liquid --

Whether solid liver of sulfur powder would work in dry condition, sorry, I don't know. Gas from the eggs yolks should work without any solid or liquid involved though.

Regards,

A. Hi, James. Sulfur dioxide or hydrogen sulfide gas will do it, but they are very hazardous. I think crushed hard boiled eggs will give off a small amount but can accomplish the task.

Regards,

A. Virtually any concentration of sulfide, no matter how small, will tarnish silver. The rate will be lower at low concentrations, but the reaction with silver will still occur.

Hydrogen Sulfide

Hi Don. Per Wikipedia .47 ppb is the odor threshold whereas 10 ppm (20 thousand times as high) is the OSHA limit for 8-hour exposure. If you and your customers cannot smell it, I think you'll be very hard pressed to convince the landlord that he must spend money or ask other tenants to change their ways.

I think more use of silver protection strips, designed to absorb sulfides, might help though. Good luck.

Regards,