Molecular weight determination ebulliometry

Determination of Number-Average Molecular Weights by Ebulliometry... 

Some kf values so obtained are water 1.8, acetic acid 3.8, benzene 5.1, succi-nonitrile 20.3, camphor 40. The large kf oi camphor makes it especially useful in molecular weight determinations. Like ebulliometry, the cryoscopic method is also limited to relatively low-molecular-weight polymers with M up to 50,000. 

M. Ezrin, Determination of molecular weight by ebulliometry, in Characterization of Macro-molecular Structure, Natl. Acad. Sci. U.S. Publ. 1573, Washington, D.C., 1968. 

The molecular size of polymers is commonly expressed by the molecular weight, radius of gyration, intrinsic viscosity or inherent viscosity. The molecular weight is commonly determined by gel permeation chromatography (GPC) or light scattering. For relatively low molecular weight polymers, ebulliometry... 

Methods for the determination of Molecular weight based on colligative property are vapour-pressure lowering, boiling point elevation (ebulliometry), freezing-point depression (cryoscopy), and the Osmotic pressure (osmometry). 

Ebulliometry. Ebulliometry (34,42-47) is another technique for determining the depression of the solvent activity by the solute. In this case the elevation of the boiling point is determined. The boiling-point elevation ATb is measured with sensitive thermocouples or matched thermistors in a Wheatstone bridge. The molecular weight Mn is calculated from... 

The other methods for determining M, by using the colligative nature of the polymer solutions are ebulliometry and cryoscopy, by both of which the maximum molecular weight obtainable is about 2 x 10. The detailed principles and practical techniques for determination of by these methods are described in refs 12 and 13. Note that these two methods are available only at specific (boiling or melting) temperatures for given solutions and are limited in applications. 

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