Boiling-point ebullioscopic method

The molar weight of a substance in solution can also be determined from the elevation of the boiling-point whi di is produced, provided that the solute is not appreciably volatile at the temperature of the boiling solvent 

If w gm. of a substance when dissolved in W gm.-of a solvent raise the boiling-point of the latter by the molar weight of the dissolved substance is given by the expression— 

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The elevation of boiling point resulting from the addition to the solvent of a known weight of solute, enables the molality of the dissolved substance to be calculated, and hence the molecular weight of the solute if its weight concentration is known. This is the principle of the ebullioscopic method of determining molecular weights. 

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