Question

explain the Barkley and Hartley method of determination of osmotic pressure

Answer 1

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Berkeley and Hartley’s method: The principle of the method is illustrated in Figure. The apparatus consists of two concentric cylindrical tubes, A and B. The porous tube, A, carries in it the semi-permeable membrane of copper ferrocyanide. The inner tube is surrounded in the outer tube, B. The outer tube has an opening at C through which pressure could be applied from outside. The porous tube A has two side tubes, D and E. The solvent is added to A through E. The side tube is a capillary tulle so that any small change in pressure in A could be easily detected by the movement of the liquid meniscus in the tube...



Due to osmosis the water from tube A flows to the solution in B and causes a movement in the liquid meniscus in D. Berkeley and Hartley prevented the inflow of water on tube B by applying an external pressure through C and maintained the liquid meniscus in at the a position until equilibrium. The excess pressure thus applied to the solution side to prevent water inflow gave the osmotic pressure at the temperature of the experiment. The apparatus is capable of giving good results in a relatively short time compared to other methods where the solvent is allowed to flow into the solution. In this method these is no change in concentration of the solution because no solvent is allowed to enter the solution tube. Pressure up to 150 atmospheres can be measured by this method. Some results of Berkeley and Hartley are given in Table....

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Answer 2

Explanation:

The Apparatus consists of a porous pot containing the semipermeable membrane of copper ferrocyanide .The porous pot is filled with water and is surrounded by a vessel containing the solution whose osmotic pressure is to be determined. The porous Pot is fitted with a capillary .Water from the porous pot will try to pass into the solution through the semipermeable membrane as a result of osmosis it is indicated by the fall in level of water in the capillary tube. Pressure is applied on the solution in order to maintain the water level in the capillary tube at the same level .This excess pressure increased by the pressure guage gives the osmotic pressure .