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what is the reason for capillary rise.???????????

Capillary rise is due to adhesive forces between the walls of the capillary tube and the fluid. adhesive forces pull the edges of the fluid upwards. the surface tension in the fluid constantly pulls molecules from the surface inward (due to higher molecular energy levels at the surface), but also holds the molecules at the surface together (cohesive forces). this causes all of the fluid to rise rather than just the fluid at the edges. the surface tension is fighting against the adhesive forces as well as the forces due to the weight of the fluid column being lifted. at a certain point, the weight of the fluid column being lifted will cause a net force greater than what the surface tension forces can withstand, and the fluid will stop rising. I suppose a change in the adhesive forces could cause a change in the capillary action (maybe a coating of something on the surface of the capillary tube, like a surfactant). the temperature of the fluid would also change things due to the higher energy levels of the molecules in the fluid and lowered attraction between them.

This is a close view of two narrow tubes, one containing water and the other containing mercury. The tube containing water exhibits positive capillary rise, where the water adheres to the sides of the tube causing the fluid to rise slightly. The tube containing mercury exhibits negative capillary rise. The fluid is drawn away from the walls of the tube, causing the fluid to sink slightly.