Determination of viscosity

1. DETERMINATION OF
VISCOSITY OF A
LIQUID
Name : rohith
Roll No : 22H51A7349

2. AIM :
To determine the viscosity of a liquid using
Ostwald's viscometer.

3. APPARATUS :
Ostwald's
viscometer
Specific gravity
bottle
Stopwatch

4. Chemicals:-
Water Acetone

5. PRINCIPLE:
VISCOSITY IS ONE OF THE PROPERTIES OF LIQUID AND
DEPEND ON TEMPERATURE. IT IS THE RESISTANCE OF
THE LIQUID TO FLOW. HIGHER THE VISCOSITY, GREATER
WILL BE THE RESISTANCE TO ITS FLOW. IT OPPOSES THE
RELATIVE MOTION OF ADJACENT PORTION OF TWO
LIQUIDS AND IS REGARDED AS A KING OF INTERNAL
FRICTION WHEN A LIQUID IS FLOWING THROUGH A
NARROW TUBE.IT IS POSSIBLE THAT THIN LAYER OF
LIQUID IS IN CONTACT WITH WALLS IS STATIONARY AS A
RESULT OF VISCOSITY, THEREFORE, THE NEXT LAYER
WILL SLOW DOWN TO SOME EXTENT. THIS EFFECT WILL
CONTINUE TO DIMINISHING EXTENT UPTO THE CENTER
OF THE TUBE, WHICH IS MEASURED IN MILLIPOISE .

6. Formula is
𝜂𝑎
𝜂𝜔
=
𝑑𝑎 × 𝑡𝑎
𝑑𝑤 × 𝑡𝑤
Where
𝜂𝑎= viscosity of test liquid
𝜂𝜔= viscosity of water=8.9 millipoise
𝑑𝑎= density of test liquid
𝑡𝑎= time taken for test liquid
𝑑𝑤= density of water
𝑡𝑤= time taken for water

7. Procedure:
1. Clean the viscometer and set vertically in the thermostat.
2. Take measured volume of water into bulb 'B' at left hand side.
3. Then suck the liquid into the bulb on the right hand side through a rubber bulb till the level of liquid rises
above the mark 'X’.
4. Allow the liquid to flow through the capillary tube from 'X' to 'Y' and note the time 'T' in seconds.
5. Take atleast 3 readingfor each liquid.
TABULOUR FORM:
S.No Time taken for water Average(tw) Time taken for liquid Average(ta)
1.
2.
3.

8. STEP II:
Determining Density for WATER 𝑑𝑤& GIVEN LIQUID 𝑑𝑎.
Mass of empty specific gravity bottle 𝑚1= gms
Mass of specific gravity bottle containing 10ml water 𝑚2= gms
Mass of water M=𝑚2-𝑚1
gms
𝑑𝑤=M/V=
Similarly for GIVEN LIQUID da
Mass of empty specific gravity bottle 𝑚1= gms
Mass of specific gravity bottle containing 10ml test liquid 𝑚2= gms
Mass of test liquid M=𝑚2-𝑚1
gms
𝑑𝑎=M/V =

9. Calculation:
𝜂𝑎
𝜂𝜔
=
𝑑𝑎 × 𝑡𝑎
𝑑𝑤 × 𝑡𝑤
𝜂𝜔= viscosity of water=8.9 millipoise
𝑑𝑤= density of water= gm/ml
𝑡𝑤= time taken for water= sec
𝜂𝑎= viscosity of test liquid= millipoise
𝑑𝑎= density of test liquid= gm/ml
𝑡𝑎= time taken for test liquid= sec
𝜂𝑎 =
𝑑𝑎×𝑡𝑎
𝑑𝑤×𝑡𝑤
× 𝜂𝜔
=

10. Result:
The viscosity of given liquid was found to be millipoise.