Ebullioscopy

(also ebulliometry), a method of physicochemical analysis based on measuring the increase in the boiling point of a solution in comparison with the boiling point of a pure solvent.

According to Raoult’s laws (seeRAOULTS LAWS), for an infinitely diluted solution of a nonvolatile substance and in the absence of electrolytic dissociation, this increase, Δt_b, is proportional to the molal concentration m of the solution; Δt_b, = E_em, where E_e is the coefficient of proportionality (ebullioscopic constant), which is characteristic of each solvent and does not depend on the nature of the solute. Thus, E_e for water is equal to 0.526; for benzene, 2.57; for dioxane, 3.27; for camphor, 6.02; and for dibromoethane, 6.43; all quantities are expressed in °C. Along with cryoscopy, ebullioscopy is used to determine the molecular mass of a solute, the activity of the solvent and the solute, or the degree of dissociation of the weak electrolyte. The molecular mass M of the solute is computed according to the equation

where P₁, and P₂ are the masses of the solute and the solvent, respectively, expressed in grams. The temperature difference Δt_b is measured by means of a Beckmann thermometer or sensitive thermocouples.

REFERENCE

Kurs fizicheskoi khimii, 2nd ed., vol. 1. Edited by Ia. I. Gerasimov. Moscow, 1969.

S. A. POGODIN

单词	ebullioscopy
释义	ebullioscopy ebullioscopy (ɪˌbʌlɪˈɒskəpɪ; ɪˌbʊl-) n (Chemistry) chem a technique for finding molecular weights of substances by measuring the extent to which they change the boiling point of a solvent[C19: from ebullioscope, from Latin ebullire to boil over + -scope] ebullioscopic adj eˌbullioˈscopically adv Ebullioscopy Ebullioscopy (also ebulliometry), a method of physicochemical analysis based on measuring the increase in the boiling point of a solution in comparison with the boiling point of a pure solvent. According to Raoult’s laws (seeRAOULTS LAWS), for an infinitely diluted solution of a nonvolatile substance and in the absence of electrolytic dissociation, this increase, Δt_b, is proportional to the molal concentration m of the solution; Δt_b, = E_em, where E_e is the coefficient of proportionality (ebullioscopic constant), which is characteristic of each solvent and does not depend on the nature of the solute. Thus, E_e for water is equal to 0.526; for benzene, 2.57; for dioxane, 3.27; for camphor, 6.02; and for dibromoethane, 6.43; all quantities are expressed in °C. Along with cryoscopy, ebullioscopy is used to determine the molecular mass of a solute, the activity of the solvent and the solute, or the degree of dissociation of the weak electrolyte. The molecular mass M of the solute is computed according to the equation where P₁, and P₂ are the masses of the solute and the solvent, respectively, expressed in grams. The temperature difference Δt_b is measured by means of a Beckmann thermometer or sensitive thermocouples. REFERENCE Kurs fizicheskoi khimii, 2nd ed., vol. 1. Edited by Ia. I. Gerasimov. Moscow, 1969. S. A. POGODIN ebullioscopy ebullioscopy The calculation of the molar mass of a solution (degree of dissociation) based on multiplying Kb, the ebullioscopic constant, by the molality of the solution.
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