Viscosity of Propylene Glycol Solutions

1. Preparing the Viscometer

1. Prepare seven solutions with varying concentrations of propylene glycol in water (between 0 - 100 mole % polypropylene glycol). Label all solutions. These will be used for calibration. Obtain a sample of the unknown concentration and set it aside
2. Check the samples for lint, dust, or other solid material. If needed, filter the sample through a sintered glass filter or fine mesh screen.
3. Clean the appropriate viscometer using water, and dry with filtered air to remove the final traces of solvents. Lower viscosity solutions will use size 50 capillary glassware, size 100 will be used for the unknown solution, and higher viscosity solutions will use size 150 capillary glassware.

2. Charging the viscometer

1. Pour the sample into the viscometer until it fills at least half of the bigger bulb. Then, wipe the arm clean.
2. Place the viscometer into the holder and insert it into the constant temperature bath. Align it vertically with a small plumb bob in the large tube or use a self-aligning holder.
3. Allow the sample to equilibrate to the water bath temperature. Allow approximately 10 min for the sample to come to the bath temperature at 40 °C and 15 min at 100 °C.
4. Apply suction to the arm and draw the liquid into the tube.

3. Measuring the Efflux

1. Use a stopwatch and measure the time required for the meniscus of the sample to flow between the indicated markings. This is the efflux time
2. Repeat steps 6 and 7 for duplicate runs. And repeat the entire procedure for each sample.