Melting Point

Topics: Temperature, Liquid, Celsius Pages: 3 (998 words) Published: September 27, 2012
To identify an organic compound and check it’s purity using the capillary method (Melting Point) Procedure:
Purse Substances (Benzoic Acid Crystals/Urea)
1. Pure silicone oil in a clean and dry Thiele tube to a level just above the upper side arm of the tube. Pure 3mm of the pure substance (Benzoic Acid/Urea) into a clean watch glass, and using a metal spatula crush the substance into a small pile of powder. Insert the crushed powder into the open end of the capillary. Drop the capillary tube with the close end downward onto a bench through a glass tube to tighten the powder at the base of the tube. Repeat the process until all 3mm of the pure substance is inserted into the capillary. 2. Tie the open end of the sample capillary to a 260 Celsius thermometer with a rubber band while powder end is beside the mercury bulb. Clamp the thermometer into the Thiele tube, so that the rubber band is leveled above the silicone oil to avoid high temperature that can cause the rubber band to dissolve. Using a Bunsen burner, moderately heat the sidearm tip of the Thiele tube by moving the flame back and forth across about a 1 inch range, until it reaches 15-20 Celsius below the pure substance melting point (Benzoic Acid/Urea). Than adjust the heating rate at 1’C rise per minute. Record the temperature at which the substances starts to melt (T1), and the temperature in which the substance completely melts (T2). 3. For The mix substance of Benzoic Acid and Urea (Mixture), and equal amount of each substance must be crushed together in a clean and dry watch glass. Than follow similar steps that of a pure substance procedure, after the Silicon oil cools down. Unknown Mixture

1. Are group did not have enough time to start the unknown substance procedure.

When a substances reaches the equilibrium (constant) temperature between the sold phase and liquid phase, it is considered as the melting point. To melt a substance, the attraction...
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