The clay fraction of four soils derived from Pleistocene basalt in Victoria, under a Mediterranean type climate, have been studied by X-ray diffraction, differential thermal, infrared, and electron microscopic techniques. Their chemical dissolution with alkali has shown that they contain about 25 % of allophane having a SiO2/Al2O3 molar ratio of about 4. This ratio is higher than that reported for sesquioxidic allophane and halloysitic allophane, and the name 'siliceous allophane' is proposed.

A simple and rapid method for ultimate particle size analysis of soils has been developed which replaces the methods first introduced by Piper. The method relies on the removal of organic matter by sodium hypochlorite and a dispersion in an ultrasonic bath. This method has now been used nearly 2 years in our laboratories, and has resulted in a substantially greater throughput of samples with the same staffing component. The method is recommended for all service laboratories.

Clay mineralogical analyses were made of red soils and black soils developed from southern Victoria, Australia. The clays of the black soils are dominantly montmorillonite (39%) and vermiculite (16%) but have an average siliceous allophane content of 17%. The clays of the red soils are dominantly kaolinite and halloysite (26%) and chlorite (30%) but have an average halloysitic allophane content of 21%. Two to eight per cent of mica and quartz occur in both. A longer period of eolian dust accumulation and concurrent weathering and soil development have occurred in the red soils than in the black soils since the last cycle of geological erosion. A simple chemical method was used for the estimation of allophane (amorphous alumina, silica, and iron oxide with water) and kaolinite plus halloysite. After selective dissolution of allophane, free Al(OH)3, and amorphous SiO2 during 2.5 min of boiling in 0.5N KOH solution, the residue is subjected to heat treatment at 550°C to dehydroxylate the kaolinite and halloysite. This is followed by another 2.5 min dissolution treatment in 0.5N KOH and a further deferration with dithionite. Some iron‐rich montmorillonitesaponite (smectite) and vermiculite are also dehydroxylated on heating and subsequently are partially dissolved in the KOH. The kaolinite and halloysite constituents were then calculated.

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Appreciable increases in 'available' sulphur were noted for six soils from South Gippsland after oven drying at 40�C. Oven dried soils stored at room temperature or 3�C for periods of up to 12 months showed significant increases in sulphur extractable with calcium phosphate but not in sulphur levels extractable with charcoal plus calcium phosphate. Application of toluene as a bacteriostatic agent failed to stop increases in levels of sulphur extractable with calcium phosphate, although the magnitude of the increases was reduced. No significant increase of 'available' potassium due to oven drying was noted, and the period of storage had no noticeable effects on 'available' potassium levels. Therefore soil samples may be stored for periods of at least 12 months prior to analysis.