APRIL, 1934 251 COOLING EFFECT of EVAPORATION. A LECTURE DEMONSTRATION ALTON L. MARKLEY Skidmore College, Saratop Springs, New York T HE FOLLOWING experiment for producing a water is completely immersed in ether the water will lowering of temperature by the evaporation of freeze solid in about 30 minutes. If the test-tube is ether has been found convenient because of the removed and held in a stream of water for a few seconds simple method of disposing of the ether vapor. the ice will be loosened and may then be withdrawn as An ordinary gas-collecting bottle (260 cc., wide- a chunk on the end of the thermometer. mouthed) is filled almost half full of ether and fitted A record of the drop in temperature may be put on with a stopper bored to bold a test-tube, an inlet tube, the board, readings being taken every few minutes. and an outlet tube. The test-tube extends into the The temperature usually drops several degrees below ether as far as possible, the inlet tube extends almost to the freezing point before ice forms, and consequently the bottom of the bottle, and the outlet tube extends the phenomena of undercooling and the liberation of just through the bottom of the stopper. The inlet heat during crystallization can also be demonstrated. tube is connected to the gas jet, and the ether caused to The effect of different solutes on the freezing point evaporate by bubbling gas through it. The outlet may also be shown by this experiment, as suggested tube is connected to a Bunsen burner where the mix- by Hauben.' ture of gas and ether vapor is burned. A thermometer, and 5 to 10 CC. of water are Put into I HAUBEN, Sna s., "A demonstration of cooling by evapora- the test-tube. If the part of the test-tube filled with tion," J. CHEM. EDUC., 9, 1115 (~une, 1932).

Cooling effect of evaporation. A lecture demonstration

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APRIL, 1934 251

COOLING EFFECT of EVAPORATION. A LECTURE DEMONSTRATION

ALTON L. MARKLEY

Skidmore College, Saratop Springs, New York

T HE FOLLOWING experiment for producing a water is completely immersed in ether the water will lowering of temperature by the evaporation of freeze solid in about 30 minutes. If the test-tube is ether has been found convenient because of the removed and held in a stream of water for a few seconds

simple method of disposing of the ether vapor. the ice will be loosened and may then be withdrawn as An ordinary gas-collecting bottle (260 cc., wide- a chunk on the end of the thermometer.

mouthed) is filled almost half full of ether and fitted A record of the drop in temperature may be put on with a stopper bored to bold a test-tube, an inlet tube, the board, readings being taken every few minutes. and an outlet tube. The test-tube extends into the The temperature usually drops several degrees below ether as far as possible, the inlet tube extends almost to the freezing point before ice forms, and consequently the bottom of the bottle, and the outlet tube extends the phenomena of undercooling and the liberation of just through the bottom of the stopper. The inlet heat during crystallization can also be demonstrated. tube is connected to the gas jet, and the ether caused to The effect of different solutes on the freezing point evaporate by bubbling gas through it. The outlet may also be shown by this experiment, as suggested tube is connected to a Bunsen burner where the mix- by Hauben.' ture of gas and ether vapor is burned.

A thermometer, and 5 to 10 CC. of water are Put into I HAUBEN, S n a s., "A demonstration of cooling by evapora- the test-tube. If the part of the test-tube filled with tion," J. CHEM. EDUC., 9, 1115 (~une , 1932).