Preparation of a Carbonate-Free Complex Calcium Aluminate

Compounds found in portland cement are difficult to prepare completely free of carbon dioxide. The difficulty is further intensified in the case of calcium aluminate monosulfate by the instability of the compound in the course of its precipitation from solution and the consequent need for preparing it within a limited time. The compound has been prepared in a large quantity, free of carbon dioxide, by using a closed-system precipitation and filtration assembly, in which rapid movement of the reagent solutions and mother liquor is achieved by the manipulation of trapped pockets of previously prepared CO₂-free air. The precipitate is conditioned and packaged in a glove box in which a CO₂-free atmosphere is maintained. Techniques are described in detail.