The Viscosity of Liquids
39. The Viscosity of Liquids
After studying the present lecture, you will be able to
Define viscosity and viscosity coefficient
Outline the method to measure viscosity using Ostwald viscometer
Determine the average molecular weight of a polymer
Determine the surface concentration of 1-butanol in aqueous solution
Measure the distribution coefficient of a solute betweenn two solvents
39.1 Introduction
Viscosity, one of the transport properties, arises because of intermolecular attractive and relatively long-range forces. Viscosity coefficient ([pic]), a specific constant characteristic of a liquid could be expressed by the following equation of Poiseuille.
[pic] (39.1)
where V is the volume of liquid delivered in time t, through a capillary of radius r and length L, with a hydrostatic pressure P.
In an apparatus designed so that equal volumes of liquids can flow through the same capillary of length L and radius r, ( may be written as
[pic] (39.2)
If g remains constant in any given location and h, the height through which the liquid falls is kept constant, above equation becomes,
[pic] (39.3)
where k is the dimensional constant of the apparatus.
If two liquids are compared using the same apparatus, it follows that
[pic] (39.4)
If [pic], the coefficient of viscosity of one of the substance, is known from a previous measurements, then[pic], the viscosity of the other liquid, can be calculated from the measured quantities, d1, d2, t1 and t2.
30.2 Viscosity measurement of a liquid:
The viscosity of two liquids can be compared by making use of an Ostwald Viscometer which consists of two bulbs, one attached with a capillary tube and U-tube below the capillary tube
After studying the present lecture, you will be able to
Define viscosity and viscosity coefficient
Outline the method to measure viscosity using Ostwald viscometer
Determine the average molecular weight of a polymer
Determine the surface concentration of 1-butanol in aqueous solution
Measure the distribution coefficient of a solute betweenn two solvents
39.1 Introduction
Viscosity, one of the transport properties, arises because of intermolecular attractive and relatively long-range forces. Viscosity coefficient ([pic]), a specific constant characteristic of a liquid could be expressed by the following equation of Poiseuille.
[pic] (39.1)
where V is the volume of liquid delivered in time t, through a capillary of radius r and length L, with a hydrostatic pressure P.
In an apparatus designed so that equal volumes of liquids can flow through the same capillary of length L and radius r, ( may be written as
[pic] (39.2)
If g remains constant in any given location and h, the height through which the liquid falls is kept constant, above equation becomes,
[pic] (39.3)
where k is the dimensional constant of the apparatus.
If two liquids are compared using the same apparatus, it follows that
[pic] (39.4)
If [pic], the coefficient of viscosity of one of the substance, is known from a previous measurements, then[pic], the viscosity of the other liquid, can be calculated from the measured quantities, d1, d2, t1 and t2.
30.2 Viscosity measurement of a liquid:
The viscosity of two liquids can be compared by making use of an Ostwald Viscometer which consists of two bulbs, one attached with a capillary tube and U-tube below the capillary tube