Physical properties are those porpertiese of a substance which do not change irrespective of hte size of hte sample that is examined. From hte instrument point of view, the physical properties of materials are often involved in the design of instrument comoponents. They are also an important factor in calibraion of some meters and in the sizing of devices such as flowmeters, control valve and saftey valves.

VISCOSITY is the property of fluid which affects its behavior. If a fluid is defined as being a substance undergoing continuous deformation when subjected to shear stress, then the consistencey can be termed as the resistance offered by hte fluid to such deformation. If static pressure and temperature are fixed, the consistency is constant for gases and Newtonian liquids and is called absolute viscosity. The consistency of non-nwwtonian fluids varies even though the static pressure and temperature are fixed, a function of the applied shear stress.

In the Principia published in 1687, Sir Isaac Newton postulated that the resistance which arises from the lach of slipperiness of the parts of the liquid, other things being equal, is proportional ot hte velocity with which parts of hte liquid are separated from one another. This lack of slipperiness is what we now call viscosity.

Various Viscosity measuring instruments

• Capillary viscometer.
• Efflux Cup Viscometer.
• Rotational Viscometer.