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The fine powdered silica containing small amounts of calcium salts, synthesized from acid clay, is suitable as a reinforcing filler for rubber. The properties of this powder was compared with those of various fine powdered silica synthesized by the ordinary soldium silicate method.(1) The fine powdered silica synthesized from active silica hydrogel and others by the ordinary sodium silicate method were added to rubber in various amounts. The effects of this addition to rubber was compared. It was found that there is little difference in character except that the flexure resistance and abrasion resistance of the former is very good. (In actual practice, those properties are suitable as a filler for rubber sole compounds.) (2) When the comparison of (1) is made for the same hardness, the same tendency becomes more remarkable.(3) It is known from the data of (2), obtained for the same hardness, that the modulus is almost proportional to abrasion.(4) The mixed system of thiazol and thiurum compounds gives satisfactory effects on rubber in general when it is used as a accelerator of rubber to which fine powdered silica synthesized from active silica hydrogel is added.

Thermal analysis of superconducting YBa2Cu3Ox ceramics was studied by TG-DTA between 25•‹ and 900•Ž. The weight loss due to release of structural oxygen was 1.5%, 1.3% and 2.0% in air, oxygen and nitrogen, respectively. The YBa2Cu3Ox ceramics absorbed oxygen rapidly around 330•Ž. Change of oxygen content of this compound was reversible under the cycle of heat treatment in oxygen containing atmospheres. The phase transition from orthorhombic to tetragonal structure occurred at 570•Ž in nitrogen, 620•Ž in air and 680•Ž in oxygen atmospheres.

The influences of kind and methed of additien of activater, and accelerator have been investigated on compounds containing fine powdered calcium silicate synthesized from acid clay. As a result, the following informations have been obtained:-(1) Method of addition of activator: The comparison was made with fine powdered silica which had been obtained from acid clay. It was found more effective to add at preparation of the powder than mix to rubber; this tendency was more pronounced with fine powdered calcium silicate.(2) As activator, an amine (Acting B) and a polyalcohol (diethylene glycol) indicated a good activating effect on silica and calcium silicate, respectively.(3) The mixed system of thiazol and thiuram compounds was excellent as accelerator; it was characteristically found that sulfenamide (CM) had shown no delayed effect.

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