February 22, 2020, 03:10:15 AM
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Topic: How to break down calcium carbonate at home  (Read 280 times)

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Offline Village_Troy

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How to break down calcium carbonate at home
« on: January 10, 2020, 03:20:39 PM »
Hello, everyone.

I need to make several neat holes in seashell (basically the main component is calcium carbonate CaCO3).

First idea was to simply drill, but it turned out to be too tough - two bits were broken with a very little progress.

The internet readily suggests thermal decomposition. But relatively high temperature is needed (circa 850°C) and also heat moves slowly in all directions, which isn't controllable.

Then was en Eureka-moment - simply burn through with electric current! But of course excitement lived short - in solid state it doesn't conduct electricity.

Therefore all my hopes rest upon chemical means only.

1. They say acids will do. But the only acids I can easily get hold of are acetic (ethanoic, CH3COOH) in form of a vinegar and citric C6H8O7. Both are weak and diluted. It seems, vinegar can be boiled for a while to increase acid's concentration. This may work, but again liquids react in all directions, so it's also not very well controllable.

2. Also I have an acetone ((CH3)2CO), and this may somehow work too. Not sure though.

3. Then for some reason I've thought about potassium permanganate (KMnO4), which is also readily available. It also should react, it seems. But of course I don't know for sure and how intensive reaction will be if any. In form of powder it's more controllable, which is great.

So, basically the question is: could you provide some insights, useful suggestions or perhaps some other ideas?

Thanks in advance.

Offline Borek

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Re: How to break down calcium carbonate at home
« Reply #1 on: January 10, 2020, 03:31:37 PM »
What was the rpm? In my experience (not with shells though, laminated PCB) drilling hard materials with a low speed ruins bits quite fast without any effect, but with Dremel (or something similar) at several thousands rpm it works nicely. With acid you will face the same problem as with heating - no way to precisely control where the acid goes, so you will dissolve the shell not only where you want, but also around.
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Offline Village_Troy

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Re: How to break down calcium carbonate at home
« Reply #2 on: January 11, 2020, 05:14:08 AM »
My drill is not that fast (only 3000 rpm), but I don't think it is a great idea to buy new tool simply to make sure it will not work anyway (which may be the case).

At this point I'm inclined to try KMnO4 first, if no other ideas will arise.

Offline Borek

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Re: How to break down calcium carbonate at home
« Reply #3 on: January 11, 2020, 10:34:03 AM »
At this point I'm inclined to try KMnO4 first, if no other ideas will arise.

Only thing I expect is stains, there is nothing that can easily react here.

To be more precise: there are some possible reactions, but they will be very slow and definitely not of the type you expect. No dissolution, no oxidation, just some metathesis, plus permanganate decomposition, yielding brown MnO2 (stains), oxygen (running away) and some potassium compound (most likely carbonate with CO2 absorbed from the air).
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Offline Borek

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Re: How to break down calcium carbonate at home
« Reply #4 on: January 11, 2020, 01:50:22 PM »
One more thing: have you tried googling fro "drilling sea shells"? I see there are some videos and DIY pages.
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Offline Enthalpy

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Re: How to break down calcium carbonate at home
« Reply #5 on: January 13, 2020, 12:01:16 PM »
I drilled through a Champagne bottle, and I don't expect a seashell to he harder. Sapiens Sapiens drilled through shells as they arrived in Europe. It can't be that difficult.

Did you try a drill bit for concrete? The ones with a carbide insert at the tip. I had expected high-speed steel to suffice easily. Maybe the speed was too high and liquid cooling insufficient, so the steel overheated.

By chemical means (but I would drill), a good acid would be the way to go. Battery electrolyte, rust remover, and so on.

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