Yeah, yeah, I know. Harriet Myers, Harriet Myers.
Whatever. We’ll see what the Bushtroll does next.
In the meanwhile, we made hydrogen sulfide!!! And it smelled real bad. Bad enough that it chased H.o.p. from our little science lab (kitchen). “Eeeeeew, yuck! That stinks!” and he ran. It’s tough doing science when your seven-year-old flees the room.
Kids like stuff that fizzes. In this case, the stink won out over the fizz and H.o.p. fled after a brief while. Did we learn anything? I dunno.
The idea is that silver tarnishes, combining with sulphur in the air, and forms silver sulfide, the black stuff on my jewelry.
2 Ag + S becomes Ag2S
When you remove the silver sulfide with a polish compound then you are also removing some of the silver. But there is a way to reverse the chemical reaction and turn the silver sulfide back into silver. Which is one reason we were doing this. Easily available ingredients and a desire to get some tarnish off of some jewelry.
Our science experiment didn’t explain the whys of its materials so I looked them up.
Put aluminum foil in a pan. Pour in steaming water. Toss in some baking soda and salt. Place your silver in it and watch the black go. We were told to do all this but the experiment didn’t tell us what’s happening in the process.
Why do you need the aluminum foil? Because the sulphur atoms are being transferred from the silver to the aluminum in the process and this forms aluminum sulfide, which is yellow.
3 Ag2S + 2 Al becomes 6 Ag + Al2S3
The baking soda solution is the catalyst, carrying the sulphur from the silver to the aluinum. And the aluminum and silver must be in contact with each other (our science experiment material didn’t say this) because this causes a small electric current to flow between them, an electrochemical reaction.
“What’s that stench?”
“It’s from our little electrolysis lab.”
The stench was hydrogen sulfide gas formed from the reaction of aluminum and the sodium carbonate (Sodium hydrogen carbonate, NaHCO3). The aluminum sulfide formed hydrolyzed to form the gases aluminum hydroxide and hydrogen sulfide.
We heated the water to boiling. We lined a pan with aluminum. We poured in water, added baking soda (fizzzzzzzzzzz!) and salt and dumped in some of my badly tarnished jewelry. Then it began to stink and H.o.p. fled.
Why the salt (sodium chloride, NaCl)? That wasn’t told us so I looked it up and found salt raises the ionic conductivity of the water thus facillitating electron transfer. It’s a salt bridge.
If we’d had an electric volt meter we could’ve connected one end to a piece of jewelry and aother to the foil and when the jewelry was in contact with the foil we would’ve seen a small small reading on the voltage meter.
So everyone’s all ready to use electrochemical reduction to clean their silver. Except that many silversmiths don’t recommend it. They say the surface of objects cleaned in this manner will act like a sponge and more readily absorb moisture and tarnish-producing gases. If someone happens by who can tell me why this is so, I’d appreciate it.
Now, did H.o.p. appreciate any of this. He liked the fizz. He didn’t like the stink. He looked dutifully at the little yellowish particles left in the pan and said, “Wow!” because he wanted to run off and do something else, like draw. I asked him if he might remember that Silver is Ag. He said no. I said maybe he could remember Sulphur is S. He said maybe so but he wasn’t sure. He ran off and signed into Brainpop to watch a flash video. I love Brainpop. They have a flash on the Periodic Table. I encouraged H.o.p. to watch it. He said it would be boring. I said no it wouldn’t be. The flash started with Moby looking at the Table and falling over. H.o.p. laughed. He will watch that flash now repeatedly and eventually learn a little something from it. As in that it exists. Or maybe not. He says it made his brain explode and wants to watch instead the flash on “Vertebrates”. He knows what a vertebrate is but he loves their explanation.
I tell you, we’re lousy scientists and chemists. But at least I didn’t follow the experiment we were given and toss the ingredients together and go voila! and not tell him what had happened. At least I dug up all the explanations I could find to be able to tell him about the chemical reaction.
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