CTRL + Z by Cookie
January 18th, 2009 4:00 AMAlas. More chalk.
After discovering that I cannot make plaster from my local clumps of stone I set out to find out what I can do with chalk (CaCO3). This praxis is a bit science heavy and it is well over ten years since I did anything in a science room, so I hope the veritable scientists excuse me if I get the lingo wrong.
1. CaCO3. Is Chalk or Calcite. It means it has one particle of Calsium (the stuff our bones are made of), One part of Carbon (coal or diamonds) and 3 parts of oxygen. Chalk is happy the way he is set and is called "stable".
2. Subject Chalk to over 825 C. And chalk will burn (called calcination or lime burning). When anything burns it releases the C (Carbon) and combines it with the oxygen creating C02 (Carbon Dioxide, the stuff that Climate Change is partially about). So:
CaCO3 (Chalk) minus CO2 (Carbon Dioxide) leaves us with CaO (Calcium Oxide).
3. Now my former chalk (Calcium Oxide) is NOT happy how he is, he is unstable and has a tendency of returning back to when he was happy. It will grap CO2 from the air and combine back to being CaCO3 (Chalk). Gradually the air will in other words UNDO what I did to the Calcium oxide when I burned it.
4. To my former Chalks detrement I am not yet through with him. I give him a bath, or in other words add water to him. Remember that he is not stable where he is so he will indeed react with the Hydrogen and Oxygen in the water, causing heat and a strange sizzling sound. The heat of my test batch wasn't enough to cook an egg. I tried.
Here is the chemistry of the next transformation:
CaO added with H2O (water) creates Ca(OH)2 (Slaked lime, Hydrated lime, Portlandite as a mineral).
NOW LETS UNDO
5. My former Chalk is now called quick lime (used by the steel industry, glass makers and builders amongst others). He is also a bit dangerous now. If we take the water off him he will return to be the unstable Calsium Oxide (CaO). That we do by putting him back in the Kiln and heating him up. The exact reverse of part 4.
6. Remember how my former Chalk is not happy with how he is with only one Oxygen and no Carbon? Well leave him be for a time and he will CTRL+ALT+Z himself back to being good old (CaCO3).
Isle of Wight Chalk
Hot enough?
I don't have a thermometer on my kiln so I needed to find out what 825 C "looks like". The glowing bar is silver and it melts at little over 900 C. I know that if I leave the silver in for a while longer it will melt and so that the temperature is high enough for the calcination
Calcination
I had to do this several times. This is a picture of the first go. In the later ones I put the Chalk right under the flame to get it hot enough, but the pictures don't look as cool as this. Oh. And unless you know what you are doing... don't do this at home.
Calcium oxide
I need to let it cool down well. I noticed that the chalk appeared whiter than it did before the clacination.
Making quicklime
Download FLV
Here we go. Its not the bext quality footage, but notice the steam rising from the pot and that I am not wearing gloves (I probably should..) whilst holding it. They use chemical reactions like the one here in those single use finger and toewarmer packs you can buy at camping shops.
Not hot enough to cook an egg.
Slaked lime, or quicklime
This is the stuff that gets put on walls when limewashing. Its also been used to cover plague victims corpses in the middle ages (very well done for people who where not aware of the practise desinfecting) and in naval warfare according to wikipedia.
UNDO
the wet mixture goes back into the furnace to get rid of the water. Note, start with a low temperature and then gradually lift it up, otherwise it can spark and explode as the steam escapes from under the already dried top.
Back to calcium oxide
Dry. Even as the picture was taken the top layers of the chemical where grapping carbon dioxide of the air and reverting back to the chalk I started with.
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Thanks love. I thought you where impressed with me by default, because you like hangin around with me. The little alchemist in me is pleased. I thought you might appreciate this one.
WOW.
My inner Chemistry bunny is very very impressed!
Cool!
Now turn L's sword back into bog iron... :-)
Aww. Thats too easy. You just put it into a bog. And it wouldn't be the first sword disposed of in such a manner.
Gah! This is truly impressive.
I'm impressed!