39. The Viscosity of Fluids

After learning the present address, you will be able to

Define viscosity and viscosity coefficient

Format the method to measure viscosity using Ostwald viscometer Identify the average molecular weight of a polymer

Determine the surface focus of 1-butanol in aqueous solution

Gauge the distribution agent of a solute betweenn two solvents

39. 1 Introduction

Viscosity, among the transport properties, arises because of intermolecular attractive and comparatively long-range causes. Viscosity agent ([pic]), a particular constant feature of a liquefied could be stated by the following equation of Poiseuille.

[pic] (39. 1)

where Versus is the volume of liquid sent in time to, through a capillary of radius r and length M, with a hydrostatic pressure G.

In an equipment designed in order that equal quantities of fluids can movement through the same capillary of length M and radius r, ( may be crafted as

[pic] (39. 2)

If g remains regular in any provided location and h, the height through which the liquid falls is stored constant, over equation turns into,

[pic] (39. 3)

wherever k may be the dimensional continuous of the device.

If two liquids are compared making use of the same equipment, it follows that

[pic] (39. 4)

If [pic], the coefficient of viscosity of just one of the element, is known from a previous measurements, then[pic], the viscosity of the other the liquid, can be worked out from the measured quantities, d1, d2, t1 and t2.

30. a couple of Viscosity way of measuring of a liquefied:

The viscosity of two liquids may be compared by using an Ostwald Viscometer which in turn consists of two bulbs, one attached with a capillary pipe and U-tube below the capillary tube when other light bulb is attached to the additional arm of u-tube for a level lower than the various other bulb. The liquids of known densities are allowed to flow through the capillary maintaining precisely the same differences of levels in the limbs plus the time formula which affects the circulation lead to the relation:

[pic] (39. 5) exactly where (1 and (2 are viscosity coefficients of the water and water, respectively. d1 and d2 are the densities of the liquid and normal water, respectively. Knowing the value of viscosity of just one liquid, one can calculate the viscosity of other the liquid.

The procedure pertaining to measurement of viscosity is just as follows. The viscometer is fixed vertically on the stand and 10 mL or perhaps 20mL of water is definitely pipetted in to the lower light bulb. The volume of water (10 mL or 20 mL) is selected so that the liquid can be conveniently sucked in to the upper light bulb leaving some in the lower light bulb. It is sucked up in the other light bulb to a level about the mark above the bulb. It is now released and stop clock is started when the meniscus passes across the tag. The clock is usually stopped if the mark under the bulb is definitely passed. The time is recorded at the moment. A similar procedure is definitely repeated two or three times and their typical is used in calculations.

Likewise, the research is repeated with the given liquid. Using the specific gravity bottle, anybody can determine the actual gravity of the liquid and calculate the viscosity. The viscosity of water in room temperature is used through the tables.

39. 3 Try things out: to determine the normal molecular weight of the plastic

Viscosity of a polymer answer could be examined to determine typical molecular weight of the plastic. An average molecular weight can be calculated for the reason that polymer molecules do not every have the same mass.

Empirically it has been found which the intrinsic viscosity is very sensitive both to the shape and molecular weight of the macromolecular...


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