Viscosity

Protocol for measuring the viscosity coefficient

using Ostwald’s viscometer

Materials:

• Ostwald’s viscometer
• Distilled water: density = 10^3 kg/m^3; viscosity = 10^-3 Pa s
• Solutions of viscose: density 1 = 1,1 x 10^3 kg/m^3; density 2 = 1,2 10^3 kg/m^3
• Timer
• Berzelius beakers
• Filter paper

Procedure:

A. Measuring the time needed for a fixed volume of liquid to flow between two marks:

1. Place the viscometer vertically on the support

2. Select the upper and the lower mark (above and below of the glass bulb belonging to the capillary arm of the viscometer)

3. Add distilled water into the larger arm of the viscometer

4. Using the rubber bulb absorb the distilled water from the glass bulb until the meniscus reaches the upper mark

5. Let the distilled water flow and measure the time needed for the liquid to flow between two marks

6. Perform nine measurements

7. Repeat the measurements for the other two solutions of viscose

8. Write all of the values in a table:

9. Clean up and dry the viscometer; place it back in the support

10. Reorganize the working place.

B. Calculate the viscosity coefficients

1. calculate the mean, standard deviation and standard error mean for all investigated liquids
2. calculate the viscosity coefficients using the formula: η_x = η₀ (ρ_x t_x / ρ₀ t₀)

η_x = viscose coefficient for a solution of viscose

η₀ = viscose coefficient for solvent (distilled water)

ρ_x = density of the viscose solution

ρ₀ = density of the solvent (distilled water)

t_x = time for the viscose solution

t₀ = time for the solvent (distilled water)

3. state one-two conclusions related to your results