Experiment:3
Title of the Experiment: determination of viscosity of a liquid using a viscometer
Introduction:
Ostwald viscometer is used to determine the viscosity of the Newtonian fluid.
When the liquid flow by gravity time required for the liquid to pass between
two mark A and B through the capillary tube is determined. The time of flow of
liquid under test is compared with the time required for the liquid of known
viscosity, the viscosity of unknown liquid.1-3
η1 can be determined using the following equation.
η1=ʆ1t1/ ʆ2t2 X η2
ʆ1=Density of unknown liquid
t1 =Time of flow of unknown liquid
ʆ2 =Density of standard liquid
t2 =Time of flow of standard liquid
η2=Viscosity of standard liquid
Viscosity measurements are used in the food industry to maximize production
efficiency and cost-effectiveness. It affects the rate at which a product travels
through a pipe, how long it takes to set or dry, and the time it takes to dispense
the fluid into packaging.
Apparatus and Chemicals:
o Viscometer
o Flask
o Beakers
o Stopwatch
o Pipette
o Weighing balance
o Volumetric flasks
o Unknown liquid
o Water
o glycerin
Safety Information
Glycerin needs to be kept away from other chemicals, acids, and combustible
materials in a cold, dry place with good ventilation.
Avoid direct skin contact when handling glycerin, and wash your hands well
afterward.
Glycerin can be combined with other compounds, although caution should be
taken to prevent combining it with incompatible substances.
Leaks and spills: To avoid slipping hazards, mop up any glycerin that has
leaked or spilled right away.
Glycerin can be securely disposed of in a sewer system or with regular home
waste because it is biodegradable. However, it is always advised to abide by
local laws while disposing of any chemicals.
Experimental Setup:
The viscometer was mounted vertically position on a suitable stand.
Water was filled into the viscometer up to mark A.
The time was counted for water to flow from mark A to mark B.
The same procedure was repeated for the test liquid by using the above formula
viscosity of the test liquid could be determined
5. Experiment Findings:
Weight of empty bottle= 13.57g
Weight of bottle + sample= 41.03
Weight of sample = 27.46
Time of flow of water= 38.33s
Time of flow of glycerin = 62s or 1 mint 2s
The viscosity of unknown = (density of unknown * time of flow of unknown/
density of water * time of flow of water)* viscosity of water
(1.020 * 62) / (0.997* 38.33)* 0.8931 = 1.4779
Conclusion:
The viscosity of an unknown can be easily calculated using an Ostwald viscometer
and these results indicate that the unknown liquid we were using was glycerin with
a viscosity of 1.4779
7. Possible errors and their mitigation:
The error associated with misalignment towards the unbounded sides of the
capillary (left to right) can be quite severe if the surface tension of the fluid (or
lack thereof due to surface contaminates on the capillary cell walls) allows the
sample to "leak" out of the flow cell
% error in V=2(Δd/d)+(Δh/h)(i) using scale ΔV/V=(2×0.1/2.4)+(0.1/10−5)=9.28%
(ii) Using calipers ΔV/V=(2×0.01/4)+(0.01/10.5)=0.9%.
o 8. Application of this activity to real-world problem
o In the industrial sector, the viscometer has a broad range of applications and
is an important instrument for the verification of quality products.
o In glass manufacturing, viscosity control is carried out throughout the
manufacturing process, since this parameter has a significant effect on other
physical properties, such as melting, softening, and crystallization.
o The calculation of viscosity oil refining is important because it is a key
element in determining the amount of liquid that can be transported in a
pipeline during a specific period. Fluid properties can be dramatically
affected by small changes in viscosity.
o Printing inks – water-based lacquers, inks, printing inks.
o Paper industry – Pigment dispersion, Paper additives, emulsions.
o Food industry – honey, milk, jelly sugar solution, beer, fruit juice.
o Chemical industry – Solvents, resin solutions, adhesives solutions, polymer
solutions.
