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A piece of natural chalk, SASO3 moisten with a drop of hydrochloric acid Hcl (you can take pharmacy acid). Where fell the drop noticeably vigorous boil. Make a piece of chalk with "boiling" drop in a candle flame or dry alcohol. The flame will turn a beautiful red color.

This phenomenon is known: calcium, part of the chalk, makes the flame red. But why acid? It reacts with chalk, forms soluble calcium chloride CaCl2 , its spray drift gases and flows directly into the flame from this experience becomes more effective.

Unfortunately, this experience with the extruded school chalk fails - it has a mixture of baking soda (sodium salt), and the flame is colored in orange. The best experience is obtained with a piece of white marble, moistened with the same acid. And to make sure that the salts of sodium paint flames in intense yellow color, you will be able, with flame grain of salt NaCl (or just "salted" the fire).

For the next experiment with chalk will need a candle. Tie it on a noncombustible base and make the flame a piece of chalk (marble, shells, egg shells). Chalk is covered with soot, the temperature of the flame is small. We're going to burn chalk, and this requires a temperature of 700-800°C. How can that be? It is necessary to increase the temperature, blowing through the flames the air.

With pharmacy pipette, remove the rubber cap and instead wear rubber or plastic tube. Blow into the tube so that drawn through the end of the pipette, air enters the flame on the wick. The flame will be deflected to the side, its temperature will rise. Aim the tongue on the sharp part of the chalk. This site will incandesce white, chalk will become here in burnt (burnt) lime Cao, and at the same time stand out carbon dioxide.

Do this several times with pieces of chalk, marble, egg-shell. Burnt pieces put into a clean tin can. While they cool, the big slice, place in a saucer and add a drop of water on the place, which was volatile. You hear a hiss, all the water is absorbed, and calcined plot will crumble into powder. This powder - slaked lime CA(Oh)2.

Add more water and add a drop of a solution of phenolphthalein. The water in the saucer will become red; hence, slaked lime forms an alkaline solution.

When baked the pieces have cooled, place them in a glass jar or bottle, fill with water, close the lid and shake the water will become cloudy. You already know that we now get lime water. Let the liquid settle and pour the clear solution into a clean flask. Pour a little lime water in a test tube and can be put with it the previously described experiments with gases. But you tricks, like turning "water" in the "milk" or "water" in the blood".

O. Holguín. "Experiments without explosions"
M., "Chemistry", 1986


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