A while ago I saw a cool video by the backyard scientist, and I decided to try it for myself.
It's a very old and relatively simple experiment,
but it's still quite interesting. When a piece of zinc is added to a solution of soluble lead salt,
crystals of lead metal will start to form.
Early chemists called this the tree of Saturn, because they believed there was a connection between
planets and metals, and they associated lead with Saturn.
To try this out for myself, I only needed two things: a soluble lead salt, and a source of zinc.
The lead salt I used was lead acetate, which I made a whole bunch of in my sugar of lead video.
The zinc comes from an even older video, where I melted down the shells of several batteries,
and casted it into a solid block. At the time,
There was no real reason to do this, and it was mostly just for fun, but I guess I finally found a use.
To get things started, I just need to make a solution of lead acetate.
I weighed out 10g, added it to 80mL of distilled water,
and then mixed it until everything dissolved.
It's important to use distilled water here, because minerals in tap water can sometimes react with the lead acetate, and make a cloudy
solution. It all dissolves after about a minute of stirring, and now I'm ready to add the zinc.
I wanted to keep the block suspended in the beaker,
so I wrapped it with some brass wire.
This way it floats about a centimeter or two above the bottom,
and it gives it space for the crystals to grow.
The moment the zinc's added, the lead immediately starts forming on it.
It's initially black because the particles are small, but very quickly some larger shiny lead crystals start to form.
What's going on here is a redox reaction between the zinc and lead, where the zinc is being oxidized and the lead is being reduced.
The zinc metal's giving up two electrons to form zinc ions, and the lead ions are picking them up to make lead metal.
The zinc ions dissolve into the water as they form, and the lead metal slowly grows as crystals.
In this case, the acetate is a spectator ion, and it doesn't take part in the reaction.
It just acts as a counter-ion for whatever is ionized, whether it's the zinc or the lead.
The two half reactions along with the acetate can then be added together to give an overall equation.
Anyway, I took a time lapse of the reaction over the following 12 hours.
After the time-lapse, I let it sit overnight, and this is what it looked like about 15 hours later.
I was really curious to see if it were possible to preserve this,
but the moment I took it out of the water, it all kind of collapsed on itself.
It still kind of looked cool though, so I figured that I might as well try.
The first thing I wanted to see was what would happen if I just let it sit out without doing anything.
Within just several minutes though, it already started to lose its shininess.
This is due to the formation of lead carbonate, as the lead metal reacts with moisture and air.
It deposits as a thin white layer on the surface, which dulls out its appearance.
I let it sit out for a little while longer, but it just got worse and worse.
I imagine if I just left it here, It would eventually turn completely white.
To try to make it shiny again, I added it back to the lead acetate solution, along with a bit of acetic acid.
The acid should remove the lead carbonate, and it seemed to kind of work.
At this point though, the thin and relatively delicate lead crystals, were already quite damaged.
However, I still wanted to see if it were possible to seal and protect it using something like a shellac.
Before spraying it though, I first need to wash it and dry it up.
The process I devised here was pretty simple; The middle beaker just had distilled water,
which was used to wash away the lead and zinc salts.
Then, in the third beaker it was rinsed with acetone to get rid of the water.
By now, the tree of Saturn was looking pretty miserable, but I decided to try the shellac anyway.
I really blasted it and gave it a complete coverage, and then I waited for it to dry.
For the first day or so, it actually seemed kind of okay,
but over the course of about a week, it became a miserable, white crusty mess.
Clearly my method doesn't really work, but besides this, I can't think of a super easy way to do it.
It seems like there's just problems the moment it's taken out of the water.
Not only does it start reacting with the air, but its nice tree structure is also destroyed, so it kind of defeats the purpose.
The solution to both these problems though, might be to just keep it in the water.
So I decided to repeat the experiment, and the first thing that I needed to do, was clean up the zinc.
It took me a couple weeks to finally get around to doing it, and by this time almost everything had turned white.
I scraped off as much as I could, and then I soaked it for a couple minutes in dilute nitric acid.
The nitric acid reacts with any oxides or carbonates that might be stuck to the surface, and renders them water-soluble.
This really helps to clean it up,
but it also attacks the zinc itself, so it's important to not let it soak for too long.
As it reacts with the zinc it generates a lot of heat,
and you can see that the water has warmed up quite a bit.
At this point I figured it was about done, so I took it out, washed it with a whole bunch of water,
and then polished it using a metal brush
I remade a lead acetate solution in the exact same way as the last time, and I dropped in the zinc.
I took another time-lapse, this time over the course of about nine hours, and then I let it sit overnight.
This is now 24 hours after I started,
and this is about 32.
I Covered the beaker with some plastic wrap, and now a week later it pretty much looks the same.
My original plan was to just leave it like this indefinitely and to see what would happen,
but unfortunately about a week later, I accidentally knocked it over.
I really did want to see how long this could last though, so I decided to do one final run.
But instead of just doing the same thing over again, I'm gonna do it on a slightly larger scale,
Seal it better, and do a complete time-lapse.
The others were cut short for the sake of time, but I'm gonna let this one run all the way to the end
So to set it up, I cleaned up the zinc again, wrapped it with some brass wire, and fed it through a stopper.
Then I used some hot glue to completely seal it and to fix it in place.
For this run I made twice the amount of lead solution, so about 20g in 160mL of water.
When I felt I was ready to get started, I just lowered in the zinc and pushed down the stopper.
It initially wasn't positioned very well though, so I quickly took it out and re-centered it.
I started a time-lapse, and then I waited for the crystals to reach the bottom, which took about 72 hours.
So three days later,
this is the final result.
It's definitely quite interesting looking, and I'm really curious to see how it'll change over time.
It is sealed decently well though, so I'm hoping it will last at least a year or more,
assuming I don't knock it over or something....
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