Water-soluble Sulfur Research Articles

Gas hydrates in aqueous-organic systems: III. Hydrate formation in polyacrylamide gel

Summary The formation of gas hydrates in polyacrylamide gels was attempted using hydrate formers with different solubilities in water. Hydrate crystals of highly water-insoluble trichlorofluoromethane formed only at the gel-hydrate former interface. Hydrate crystals of highly water-soluble ethylene oxide formed abundantly within the gel, and the depth of penetration depended on the equilibration time prior to initiation of crystallization. Equilibration for 166 hrs resulted in the formation of ethylene oxide hydrate throughout a 5-cm column of gel. All ethylene oxide samples were observed to recrystallize following the initial crystallization process. Hydrate crystals of highly watersoluble sulfur dioxide and slightly soluble dichlorofluoromethane also formed within the gel. The sulfur dioxide hydrate crystals were present in quantities similar to those obtained with ethylene oxide, whereas the dichlorofluoromethane hydrate crystals were far less abundant. Several of the experiments were successfully repeated using an agar substrate. In the case of dichlorofluoromethane, the quantity of hydrate crystals in the gel was influenced by the method of formation. This was not true of ethylene oxide hydrate.

Soil properties in relation to the sulphur and phosphorus status of some basaltic soils

Twenty-three basaltic soils from elevated areas in northern New South Wales were examined for sulphur and phosphorus status by growing Phalaris tuberosa L. in pots in a glasshouse. Sulphur deficiency was more common and more severe than was phosphorus deficiency. To determine whether there may be some topographic control of sulphur or phosphorus status, soil colour was examined, as in general the reddest soils were found in the highest positions in the landscape. The soils were first considered as one group and then as subgroups of sedentary, colluvial, and alluvial soils. Using redness to rank the soils, there was no overall relationship to sulphur or phosphorus status. However, colour of the sedentary soils was significantly correlated with sulphur status (r = 0.92***), the reddest soils being the most deficient. The sulphur status of the brown colluvial and greyish brown alluvial soils showed no relationship to colour; they were uniformly severely deficient. Phosphorus deficiency was not associated with soil colour. Neither soil pH nor redox potential was related to the sulphur and phosphorus status of the soils. There was only a weak correlation (r = 0.60**) between the water-soluble sulphur content of all soils, but a stronger correlation (r = 0.81**) when only the sedentary soils were considered. Several soil phosphorus fractions could be satisfactorily used to distinguish between phosphorus-deficient and phosphorus-sufficient soils.

Soil sulphur fractions as chemical indices of available sulphur in some Australian soils

A range of soils from eastern Australia hare been examined for a number of fractions of soil sulphur. These have been compared with plant sulphur uptake and yield of oats grown in pot culture in order to assess their possible values as indices of available sulphur. In all of the soils examined, most of the sulphur was present in organic forms and in most cases at least 50 per cent. could be extracted by 0.1N sodium hydroxide. Similar amounts were released as sulphate by ignition of the soil and similar amounts were also estimated by a reduction method. These three fractions were highly correlated with one another and with the total sulphur, but each was poorly correlated with the sulphur uptake and yield of oats in pot culture experiments. The results indicated that an appreciable proportion of the soil sulphur may consist of organic sulphates. The amounts of free water-soluble sulphate were small and were unsatisfactory as indices of yield. In addition to free sulphate, aqueous extracts also contained some organic sulphur which was easily oxidized to free sulphate by dilute hydrogen peroxide. The amount of water-soluble sulphur could be substantially increased by heating the soil prior to extraction. The fraction of the soil sulphur which was extracted after heating with water on a boiling water-bath, followed by heating for 1 hr in a hot-air oven (heat-soluble sulphur), was found to be highly correlated with both sulphur uptake and yield of oats grown in pot culture. It seems likely that this heat-soluble fraction ma3 provide a satisfactory index of available sulphur.