Boiling, freezing and melting points

When a non-volatile solute is dissolved in a solvent, the vapour pressure of the solvent is lowered. Consequently, at any given pressure, the boiling point of a solution is higher and the freezing point lower than those of the pure solvent. For dilute ideal solutions, i.e. such as obey Raoult s law, the boiling point elevation and freezing point depression can be calculated by an equation of the form 

Solvent Freezing point, °C Boiling point, °C Kt KkgmoE Kkg moE  

The cryoscopic and ebullioscopic constants can be calculated from values of the enthalpies of fusion and vaporization, respectively, by the equation 

Boiling points and freezing points are both frequently used as criteria for the estimation of the purity of near-pure liquids. Detailed specifications of standard methods for their determination are given, for example, in the British Pharmacopoeia (2000). 

The boiling point elevation (BPE) of some 40 saturated aqueous solutions of inorganic salts have been reported by Meranda and Furter (1977) who proposed the correlating relationship 

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