Melting Point

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* Introduction

The melting point is defined as the temperature at which the solid is in equilibrium with its liquid, and this characteristic is very unique, so a substance can be determined by the melting point. Determination of the melting point is very important technique in many areas of chemistry especially, in organic chemistry area because the melting point is really significant in order to identify the purity and the identity of a substance. Measuring the melting point is a fast and cost-effective technique which remains a strong link to the vast pre-instrumental chemistry literature, so the technique is still used for measuring purity of organic and pharmaceutical compounds. For that reason, determination of the melting point is more than just a classroom exercise in the organic chemistry lab. * Objective

1- In this experiment we will familiarize ourselves with the technique of melting point determination and its relevance to determining the purity of the crystalline solid.

2- We will determine the melting points of two different pure solids, urea and trans-cinamic acid, two compounds with similar melting points.

3- We will then determine the melting point ranges of onemixtures of these two substances, and plot the eutectic point diagram to generate a melting point pattern for the two solids.

* Experimental procedure

a) Equipments:

1- Melting point apparatus
2- Glass tubing
3- Capillary melting point tube
4- Very small, finely powdered pure urea, pure cinnamic acid and three mixtures .

b) Procedure:

1- Take about 50-100 mg of thin, finely powdered sample and fill a capillary melting point tube with the sample by thrusting the open end of the tube into the powder several time .

2- Vigorously tap the seal end of the tube on the table or drop the melting tube, closed end down, through the length of a glass tubing onto the bench top .

3- Insert the tube into the melting point...
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