440 PRACTICAL ORGANIC CHEMISTRY Molecular Weight by Elevation of the Boiling-point. This method is strictly parallel in principle to that for the determination of molecular weight by depression of the freezing-point. When a substance is dissolved in a solvent, the boiling-point is raised, and the Molecular Eleva-tion Constant (K) of a solvent is the elevation of the boiling-point produced when i gram-molecule of a substance is dissolved in ioo grams of the solvent. This Constant again can be either calculated, or determined experimentally using a number of solutes of known molecular weight. The solvents most frequently employed are: MOLECULAR BOILING- ELEVATION SOLVENT POINT CONSTANT (K) Ether 35° 21-0 Acetone 56 17*0 Chloroform 61 36-6 Ethyl Acetate 77 27-5 Rectified Spirit* (95-6%) 78 11-5 Carbon Tetrachloride 78 48*0 Benzene 80 27*0 Cyclohexane 81 27*5 Water loo 5-2 i,2-Dibromoethanc 130 64/0 The method is used to determine the molecular weight primarily of those compounds which are too slightly soluble in the usual cold solvents
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.