COMPARISON OF VARIOUS METHODS FOR THE DETERMINATION OF SPECIFIC SURFACES OF SUBSOILS

Retention of ethylene glycol monoethylether (EGME) and ethylene glycol (EG), and sorption of nitrogen and water vapour, were studied on a wide range of soils from New Zealand and Fiji. EGME retention was mainly affected by the amount of EGME liquid present in the desiccator, the interaction with the desiccant (CaCl2), the amount of residual water in the samples, and the time taken to establish end-points. The extent to which each of these factors influences the weight of EGME retained was different for each sample. Surface areas from nitrogen sorption (BET) were not related to those derived from EGME retention in the same way for all soils; EGME retentions did not vary systematically with clay mineralogy. A constant conversion factor cannot be used to convert retentions of polar liquids (EGME, water and EG) to specific surface values, and retention data by itself cannot be used to measure the absolute surface areas of soils.