Problems with tarnished silver? I have the solution for you. A mix you can make with kitchen items and that will remove said tarnish in 30 seconds flat.
Let’s talk silver chemistry, shall we? Don’t go running away yet. I promise it’s not as painful as it sounds. (and if you really want to, you can scroll down and skip to, how to do this at home)
First of all, we need to talk about reduction-oxidation (redox) chemistry. You’ve all heard about electrons. You probably know they are a very small part of the atom and they orbit around the nucleus, which is in turn made of neutrons and protons. Changing anything in the nucleus of the atom requires, of course, nuclear chemistry. In other words, a lot of energy. That’s because protons and neutrons are highly compacted at the nucleus and they have several forces keeping them together. Electrons however, really like to mingle.
When an atom gains an electron, we say it was reduced because we reduced the oxidation state. In other words, we increased the negative charge of the atom. When an atom loses an electron, we say oxidation occurred because the atom is now less negatively charged. Let’s look at a common example.
The most common example of oxidation is iron oxide or rust. Iron metal has an oxidation state of 0. This means it has the number of electrons it should have. However, when iron metal comes in contact with atmospheric oxygen, it likes to oxidize. This means iron now has an oxidation state of 2+, while oxygen is now more negatively charged. Importantly, we can’t have reduction without oxidation and viceversa. This is a game of pairs in which someone gives someone else its precious electrons.
So what about silver? Unlike iron, when silver oxidizes it is not reacting with oxygen, but with hydrogen sulfide (a compound of sulfur).
2 Ag(s) + H2S(g) → Ag2S(s) + H2(g)s
Above is the chemical equation for the reaction. Silver reacts with hydrogen sulfide, generating hydrogen gas and silver sulfide. This has a characteristic black color and we commonly call it tarnish.
So how do we remove it? with household items!
Tarnished silver jewelry
Step 1. Grab a (beaker) regular glass or glass bowl (DO NOT USE METAL!!!) and place aluminum foil at the bottom, covering the whole surface as shown below.
Step 2. Bring 2 cups of water to a boil (you can increase the volume if you are planning on treating a large piece of jewelry)
Step 3. Pour the boiling water in the glass which has the aluminum foil. Add to it about 2 tablespoons of baking soda. You should see bubbles appear as the baking soda dissolves and carbon dioxide is released.
Step 4. Immediately add the piece of jewelry to clean. Make sure it touches the aluminum foil as we require contact between the two metals for a faster and more efficient reaction.
HERE’S A VIDEO TO SHOW YOU WHAT WILL HAPPEN!
As you can see, there are tiny bubbles forming right where the earrings come in contact with the foil. Why? because this is what’s happening…
OXIDATION: 2 Al(s) + 6 OH– (aq) –––> Al2O3(s) + 3 H2O (l) + 6 e–
REDUCTION: Ag2S(s) + 2 H2O (l) + 2 e– –––> 2 Ag(s) + H2S (aq) + 2 OH– (aq)
OVERALL: 3 Ag2S(s) + 2 Al(s) + 3 H2O (l) –––> 6 Ag(s) + 3 H2S (aq) + Al2O3(s)
If you look at the first reaction, you can see that aluminum metal is now being converted into aluminum oxide (this will turn the foil brownish). Silver sulfide (Ag2S) is being converted into silver metal (Ag) and hydrogen sulfide (H2S).
Hydrogen sulfide is a gas. A pretty nasty one which can be toxic at high levels. Which is why we need the baking soda!
3 NaHCO3(aq) + 3 H2S(aq) => 3 NaHS(aq)+3 H2O(l)+ 3 CO2(g)
Sodium bicarbonate (NaHCO3) reacts with hydrogen sulfide (H2S), generating carbon dioxide (CO2 )and sodium hydrosulfide (NaHS) . This way, the sulfur is contained in the water and you can safely dispose of it down the sink .
So here you go, you HAVE DONE KITCHEN CHEMISTRY!!!
Now for the questions…
Do I need boiling water? yes! because a lot of chemical reactions, like this one, require energy. Boiling water has lots of energy acquired through heating and it helps drive the reaction forward so it takes very little time.
Would it work with cold water? I’m afraid the process can’t happen that way because we are not providing the system the oomph it needs to react.
Am I losing silver? No! this method is great because you get rid of the tarnish without losing a single silver atom!
Can I repeat the process with other pieces of jewelry? you can, but you’ll need more foil, water and bicarbonate. Doing the reaction once consumes the reactants and thus more reactant is needed to repeat it.
I hope you enjoyed the short kitchen chemistry experiment. Because we can, all, achieve better living through chemistry.