Viscosity of Pure Liquids and Solutions

4591 Words Mar 27th, 2014 19 Pages
Viscosity, η, is the resistance of a fluid to flow. The units of viscosity could be poise, dyne-seccm2, gcm-s, N-sm2 or Pa-s. Determination of the viscosity of a fluid is done by measuring the time of flow of a given volume of (V) of the liquid through a capillary tube under the influence of gravity. There are generally 3 types of viscometers for this capillary flow method–the Ostwald Cannon-Fenske, and the Ubbelohde viscometers. The flow is governed by the Hagen-Poiseulle Equation:
V=r4tπ∆P8ηl (eq. 8.1) where r is the tube radius, l is the tube length, t is time, ∆P is the pressure difference at the tube ends, and η is viscosity.
Since the tubes of the viscometer are open at both ends and with the assumption that the
…show more content…
Many trials in each run were employed until there’s an obtained three flow time with differences of 0.1 sec or less. For viscosity of pure liquids and solutions, the viscometer was calibrated using the general procedure. It was done with the use of water, acetone and ethyl acetate as the calibrating liquids.
For the temperature dependence of viscosity using the pure test liquids which were methanol and 2-propanol, flow time runs were made at 20, 25, 30, 35, 40, 45 and 50 °C.
For the effect of concentration, binary solution of the test liquids and water of concentrations 0.10, 0.20, 0.40, 0.60, 0.80, and 0.95 mole fraction of solute were prepared. Each solution was subjected to the general procedure. Bath temperature was maintained at 300C. The density of each solution was determined using a pycnometer.
For viscosity of polymer solution, a stock solution of sodium carboxymethylcellulose (NaCMC) was prepared by dissolving 5.00 grams NaCMC in 0.100M NaCl, and diluting it in a 250-mL volumetric flask using the same solvent. The solution was then transferred to a 500-mL volumetric flask and then diluted to volume using the same solvent. The solution was mixed gently while avoiding the formation of foam.
Solutions of 0.05, 0.10, 0.25, 0.50, 0.75 and 1.00 g/mL were prepared in 50-mL volumetric flasks using 0.100M NaCl for dilution. The general procedure was done for each solution using the Ubbelohde viscometer.
The same procedure is done using 0.001M
Open Document