Calcium Carbonate to Quicklime ERNEST B. WILSON Forest Hills High School, Forest Hills, Long Island
pOWDER ten or fifteen grams of marble chips in an iron mortar. Place half of the powdered limestone in an iron crucible. Cover the crucible with a lid in which a hole two or three millimeters in diameter has been punched or drilled. Heat the crucible strongly with a large burner. /
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ApPARATUS USED FOR CONVERSION OF CALCIUM CARBONATE TO QUICKLIME
Prepare a siphon by connecting a short rubber tube to a right-angle glass bend. The siphon may be constructed of metal or entirely of glass. However,
the rubber tubing makes the device more flexible and the glass bend does not heat as rapidly as metal. Lead carbon dioxide (see accompanying sketch) into one of two four-ounce gas bottles containing two or three centimeters of limewater until the 1imewater begins to turn cloudy. A precipitate becomes visible after two or three minutes. Shake the bottle to dissolve more of the carbon dioxide collected above the limewater. Present both bottles to the class for comparison. The bottle in which carbon dioxide was collected will be milky while the one exposed only to the air will be unchanged. Some surprise may be expressed because the carbon dioxide can be collected from an unsealed crucible in the above procedure. It may be explained on the premise that hot carbon dioxide rises up the short side of the siphon as it does in a hot chimney and that it cools and drops down the long side because of density greater than air. Collection of gas will cease if the end of the rubber tube is permitted to dip into the limewater. Fill two five-hundred-milliliter beakers with water and add five to ten milliliters of litmus solution that has been made distinctly acid with a drop or two of acetic acid. Pour the unheated half of limestone powder into one beaker. The litmus remains unchanged. After heating has continued for about five minutes, pour the contents of the crucible into the second beaker. The litmus immediately turns blue. The concentration of the litmus solution used should be adjusted so that an appreciable contrast is evident in the two beakers. This demonstration of the decomposition of calcium carbonate is unusual because tests are made for both products. The simplicity of the apparatus and the short time required, less than ten minutes, will appeal to high-school teachers. Also, the demonstration may be used as a student experiment when enough large burners are available.
Did You Know Your Periodic Table? Here is the answer to the ".test" given in last month's issue on page 222.
Group: Series I
2 3 4
I F P S I
II L T H
III D Z R
IV U
N G
V
M C y
VI A
Q K
VII VIII X V B E 0 W
Element: At. No.: Element: At. No.:
302
A B C D E F GH
I K LM
8 10 15 5 18 1 22 20 19 24 4 7 N 0 P Q R S T U VWXY Z 14 17 3 16 21 11 12 6 9 25 2 23 13
