High-temperature phase equilibria in the system 2CaO,Si0,-3Ca0,P20, have been investigated by high-temperature microscopy and X-ray analysis. The system presents a continuous series of solid solutions with a meltingpoint maximum at 2240", contradicting earlier findings. A new high-temperature form of 3Ca0,P20, has been discovered which does not survive quenching to room temperature, but is completely miscible with the a form of ZCaO,SiO,.A t lower temperatures two compounds are formed by solidstate reactions, the known silicocarnotite stable below 1450" and a new phase, denoted as " A," stable below 1125", having the approximate composition 7Ca0,P20,,2Si0,. Powder X-ray measurements are given for each phase in the system, either as obtained in a specially designed high-temperature X-ray camera or, where appropriate, as recorded at room temperature in a focusing camera.THE section 2Ca0,Si0,-3Ca0,P,05 in the ternary system Ca0-Si02-P205, which is relevant to processes in the steel, cement, and fertiliser industries, has been examined la with widely differing conclusions. This divergency can be attributed to the experimental Tromel, Stahl und Eisen, 1943, 63, 21.

Summary: The various methods of steam curing are briefly described and preliminary laboratory data on the effect of low pressure curing are given. An approximate method for assessing the effect of a stated cycle of operations is described. The effects of time and temperature, type of aggregate, type of cement and size of specimen are discussed.

The effect of phosphorus pentoxide on the burning of Portland‐cement clinker and the setting and hardening of the resultant cement has been investigated, using both synthetic mixtures and the raw materials which it is proposed to use for cement manufacture in Uganda. It is shown that the P2O5 forms a solid solution with the 2CaO,SiO2 of the cement clinker and reduces the content of 3CaO,SiO2. Consequently the early strength falls as the P2O5 increases until, when the P2O5 reaches 2·25% of the clinker, the cement fails to meet British Standard requirements. Formulae are given from which the percentage of compounds present in the clinker can be calculated, and the procedure for determining the proportion of clay in the raw mix is described.Test data on concrete are given; cement high in P2O5 is affected more markedly than normal cement by an increase in water: cement ratio.

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may be increased by the suction induced by the rapidly flowing water at the tip.Mayne 1 has shown that rapid oxidation of ferrous hy~roxide at a_pH_value greater than 5 gives goethite while slow oxidation leads to the formation of an intermediate between magnetite and ferric oxide (yFe 20 3 ). Thus the formation of goethite in the present case is readily explained. The formation of magnetite, the second constituent, is not likely to occur in the same area at the same time as goethite since slow oxidation would appear to be necessary. Therefore, the oxidation to form this compound must occur in some areas sheltered from the direct action of the water. This may occur in pockets of ferrous ion-containing water trapped in the goethite crystals or by slow oxidation of the ferrous ion during its passage through the whisker either by a small amount of oxygen contained in the water or by oxygen diffusing through the wall of the .tubule.