Before the viscometer is used, it must be carefully and thoroughly cleansed. Table of equivalentsġ pound-force second per square inch (reyn)ĭistilled water, methanol, ethanol, and propanolġ. One poiseuille is 10 poise or 1000 cP, while 1 cP = 1 mPa It is sometimes referred to as the poiseuille (symbol Pl). This is the SI unit of viscosity, equivalent to newton-second per square metre (N Many everyday fluids have viscosities between 0. It is the viscosity of a fluid in which a tangential force of 1 dyne per square centimetre maintains a difference in velocity of 1 centimetre per second between two parallel planes 1 centimetre apart.Įven in relation to high-viscosity fluids, this unit is most usually encountered as the centipoise (cP), which is 0.01 poise. Named after the French physician Jean Louis Marie Poiseuille (1799 – 1869), this is the cgs unit of viscosity, equivalent to dyne-second per square centimetre.

Instruments for measuring flow properties of highly viscous fluids and molten polymers are more often called plastometers or rheometers (J.M, C. Of the many types, some employ rising bubbles, falling or rolling balls, and cups with orifices through which the fluid flows by gravity. A commonly used type (Brookfield) measures the force required to rotate a disc or hollow cup immersed in the specimen fluid at a predetermined speed. 2006).Īn instrument used for measuring the viscosity and flow properties of fluids. The other quantity called kinematic viscosity (represented by the symbol ν “nu”) is the ratio of the viscosity of a fluid to its density (Mott, R. The quantity defined above is sometimes called dynamic viscosity, absolute viscosity, or simple viscosity to distinguish it from the other quantity, but is usually just called viscosity. There are actually two quantities that are called viscosity. Viscosity describes a fluid’s internal resistance to flow and may be thought of as a measure of fluid friction. It is commonly perceived as “thickness”, or resistance to flow. Viscosity is a measure of the resistance of a fluid to being deformed by either shear stress or extensional stress. It appears that there is a property that represents the internal resistance of a fluid to motion or the “fluidity”, and that property is viscosity. The situation is similar when a fluid moves relative to a solid or when two fluids move relative to each other. The magnitude of the fore needed to move the table depends on the friction of coefficient between the table and the floor. To move a table on the floor, for example, we have to apply a force to the table in the horizontal direction large enough to overcome the friction force. When two solid bodies in contact move relative to each other, a friction force develops at the contact surface in the direction opposite to motion.

Through the data we had gathered, relative viscosity can be computed using the formula (μ 1 /μ 2 ) = (ρ 1/ ρ 2) * (t 1/t 2) and found out that as the temperature of a liquid increases, its relative viscosity decreases… A pycnometer was then used to measure the density of the samples at 40, 50, 60 ˚C through ascertaining the volume of the apparatus and mass of the liquid. The group recorded the time required for the upper meniscus of the liquid samples to subsequently pass the two calibration marks of the viscometer at a specified temperatures (40, 50 and 60˚C ) and observed that as the temperature of the sample increases, the time necessary from one point to another decreases. To measure the relative and absolute viscosities of distilled water, methanol, ethanol and propanol, Ostwald – Cannon- Fenske viscometer was standardized and used.

Absolute water viscosity at 15 c