Calcium Carbonate -> Calcium Oxide, but only getting Hydroxide. Ideas?

[Voltux]

I was trying to calcine some CaCO3 (Calcium Carbonate), but ended up with Calcium Hydroxide.

To test if I had Calcium Carbonate I added it to some vinegar, no gas was produced. I then mixed in a small amount of the powder with a large amount of water and passed CO2 through it, and it became a milky white which led me to believe I have Calcium Hydroxide. I also tried added the final powder to water, which did not heat up.

I heated up my CaCO3 in a laboratory furnace (Electric) at roughly 920°C for 30 minutes which left me with my current product.

Do I need to have a nitrogen/argon gas purge of some sort??

Any ideas are appreciated! Thanks!

 

[Borek]

You are doing strange tests and drawing strange conclusions.

To test if I had Calcium Carbonate I added it to some vinegar, no gas was produced.

Some gas should be produced, so this test - if anything - shows you didn't have a calcium carbonate. I wonder if you didn't mean you were testing for oxide?

I then mixed in a small amount of the powder with a large amount of water and passed CO2 through it, and it became a milky white which led me to believe I have Calcium Hydroxide.

Sorry, no idea what you are trying to test for. Assuming the powder was CaO, after mixing it with water it became Ca(OH)₂. It doesn't mean your powder WAS calcium hydroxide.

I also tried added the final powder to water, which did not heat up.

How much powder, how much water?

 

[Voltux]

You are doing strange tests and drawing strange conclusions.



Some gas should be produced, so this test - if anything - shows you didn't have a calcium carbonate. I wonder if you didn't mean you were testing for oxide?

I was testing with vinegar to verify a change had taken place, and that it was heated long enough. This would only show that I did not have a carbonate.

Sorry, no idea what you are trying to test for. Assuming the powder was CaO, after mixing it with water it became Ca(OH)₂. It doesn't mean your powder WAS calcium hydroxide.

I suppose you're right that both CaO, and Ca(OH)2 would form a milky white mixture, but when I added the powder to water (just enough water to cover the powder ~20-50ml) there was absolutely no change in temperature as measured with an IR thermometer and by touch.

How much powder, how much water?

20-50ml, just enough to cover the powder.

 

[Borek]

I was testing with vinegar to verify a change had taken place, and that it was heated long enough. This would only show that I did not have a carbonate.

Have you checked that the carbonate before roasting was reacting with the acid?

20-50ml, just enough to cover the powder.

How much powder? A pinch, or so much that the water was only a thin layer on the surface?

 

[AlephZero]

I wonder if you got the CaCO3 hot enough. Wikipedia gives the minimum temperature as 825C.

You certainly don't need a gas purge. Cement making isn't "high tech" chemistry! Heating a 10mm diameter limestone chip directly with a roaring bunsen burner flame for a couple of minutes should work. But a bunsen flame is about 1500C, not 920C.