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Definition of Distribution Law
The distribution law, also known as Nernst's distribution law, states that when a solute is distributed between two immiscible solvents at a constant temperature, the ratio of its concentrations in the two solvents is constant.
[Solute]A & [Solute]B are the concentrations of the solute in solvents A and B, respectively.
Kd is the distribution coefficient or partition coefficient.
Assumptions
The solute does not react chemically with any of the solvents.
The solute exists in the same molecular form in both solvents.
The system is at a constant temperature.
The solvents are immiscible.
Limitations of the Distribution Law
Chemical Changes: If the solute reacts chemically or changes state in one of the solvents, the law doesn't apply.
Solvent-Solvent Interaction: Even slight miscibility between solvents can affect the partition coefficient.
Temperature Variations: Changes in temperature can alter the partition coefficient, affecting distribution.
Concentration Dependence: High concentrations can lead to solute saturation or self-interaction, deviating from expected behaviors.
Physical Form Variations: Differences in solute ionization or physical state between solvents can impact distribution.
Applications of the Distribution Law
Drug Design and Pharmacokinetics: Essential for understanding drug distribution across body compartments, impacting dosing and delivery.
Environmental Science: Helps predict the movement of pollutants between phases like water and oil.
Extraction Processes: Guides the selection of solvents for efficient compound extraction in chemical and pharmaceutical industries.
Analytical Chemistry: Basis for solvent choice in liquid-liquid extraction, optimizing separation of analytes.
Food Industry: Influences the formulation by predicting how additives distribute between different phases.
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