CapillaryViscometry

Capillary viscometry is a technique used to measure the dynamic viscosity of a fluid. It relies on Poiseuille's Law, which describes the flow of a viscous fluid through a cylindrical tube. In this method, a known volume of fluid is allowed to flow under gravity through a capillary tube of known dimensions. The time it takes for the fluid to pass between two calibrated marks on the viscometer is measured. This efflux time is directly proportional to the viscosity of the fluid. The viscometer is typically a glass U-shaped tube with a capillary section and bulbs. The fluid is introduced into one arm of the U-tube and drawn up past the upper calibration mark, then allowed to flow back down through the capillary by gravity. The time taken for the fluid level to fall from the upper mark to the lower mark is recorded. To obtain an absolute viscosity value, the viscometer must be calibrated using a fluid of known viscosity. The relationship between the measured efflux time and viscosity depends on the viscometer's geometry and the acceleration due to gravity. Capillary viscometry is a relatively simple and inexpensive technique, making it suitable for routine analysis in various fields, including chemistry, materials science, and food processing. It is particularly useful for measuring the viscosity of Newtonian fluids.