Download Surface Area Measurement by Ethylene Glycol Monoethyl Ether EGME Sorption | SSC 220 and more Lab Reports Agricultural engineering in PDF only on Docsity! UCDavis SSC 220 Pedology Surface Area Measurement by Ethylene Glycol Monoethyl Ether (EGME) Sorption Read this procedure. Read Chapter 7 in Jackson. Read: Carter et al. 1986. Specific surface. p. 413-423. In A. Klute (ed.) Methods of soil analysis. Part 1. Physical and mineralogical methods. 2nd ed. Agronomy No. 9. SSSA, Madison, WI. 1. If you have limited clay or fine silt, keep the clay from the CEC measurement. Scrape the clay from the centrifuge tubes and weigh duplicates into clean, pre-weighed aluminum dishes (weigh everything to 0.0001 g). Sample mass is best in the 200 mg range, but work with what you have. If you have plenty of clay and fine silt, weigh duplicate 200 mg (500 mg if dominantly kaolinite) samples (0.0001 g) of each into pre-weighed aluminum dishes. Pre-weigh one aluminum dish as a blank. Be careful when carrying dry clay samples around in the lab due to air currents and the risk of sample loss. 2. Oven-dry samples and blank at 105 °C overnight. Cool samples in a CaCl2 desiccator. Weigh samples to a constant weight (± 0.5 mg between successive weighings) and WEIGH RAPIDLY. 3. After samples have come to constant weight, add 2 ml EGME to each sample and to the blank pan. Place samples in the desiccators labeled "CaCl2 for EGME" only(!). Let stand for 30 min. Evacuate with the house vacuum for 30 min, close stopcock, turn off the house vacuum, and let stand under vacuum for 2 h. 4. After 2 h, allow air to enter the desiccator SLOWLY by opening the stopcock slightly. WEIGH RAPIDLY and record weights. Do not allow samples to stand outside the desiccators prior to weighing. 5. Return samples to the desiccators, repeat the 30-min evacuation and 2-h stand under vacuum, and weigh rapidly. Repeat the process until the samples reach a constant weight. This generally occurs by allowing the samples to stand in the evacuated desiccator overnight (stopcock closed, but house vacuum off). That is, evacuate and weigh the samples 2 or 3 times on the first day, then 2 or 3 times the second day or until weights are constant. 6. Determine the mass of EGME sorbed. The assumptions here are that there is a monolayer of EGME over the entire clay surface and that the area of the sample surface covered by a molecule of EGME is known. Subtract the blank weight to account for impurities in the EGME. 7. Calculate specific surface = mass EGME X 3496.5 m2 g-1 mass sample 8. If there are uncertainties concerning the measurement, add 2 ml EGME to each sample and repeat the whole process. 9. If you have limited sample material, keep the samples. They can be washed, dried, and used for other analyses.
