To determine partition coefficient of Naphthalene using shake flask method - Practical

 Aim: To determine partition coefficient of Naphthalene using shake flask method.

Requirements: Laboratory stand, separatory funnel (500 ml), calibrated cylinder (50 ml, 500 ml), funnel, beaker (500 ml, 100 ml), vial, mini-vial, automatic pipette, distilled water.

Theory: The octanol-water partition coefficient, K_ow, describes equilibrium partitioning of a chemical between octanol and water phases. It is an important parameter used in the assessment of environmental fate and transport of organic chemicals because the octanol phase is a surrogate for the lipid phase or organic carbon content of the environmental compartments. K_ow is one of the most important physico-chemical characteristics related to sorption on the soil or sediments, and bioaccumulation. K_ow is defined as an equilibrium ratio of the concentration in the octanol phase, C_o (µg ml^-1) and its concentration in the aqueous phase, C_w (µg mL^-1), by the equation: K_ow = C_o/C_w.

Procedure:

• Dissolve 0.011 g of naphthalene in 5 ml of octanol.
• Sonicate the naphthalene solution (5 min).
• Fill the naphthalene solution and 500 ml of distilled water in a separatory funnel.
• Shake the mixture for 10 min.
Note: Hold the funnel tightly at the stopper and the stopcock.
• Invert slowly and vent (open the stopcock) towards the back of the hood to release the pressure.
• Close the stopcock and shake the funnel gently, then vent again.
• Repeat this step until no more gas is released.
• Separate the octanol and water phases into the beakers.