Sodilim aluminate

Sodilim aluminate is manufactured from bauxite, which is roughly powdered, calcined, and introduced into sodium hydroxide solution of specific gravity 1.45. The mixture is heated under high-pressure steam (80 lbs. per sq. inch), when the alumina passes into solution. The liquid is passed through a filter-press, and then through wood-pulp to free it from ferric hydroxide, etc. Aluminium hydroxide is prepared from this solution by stirring into it a quantity of the hydroxide previously prepared. On standing, the greater part of the aluminium separates out from the solution as aluminium hydroxide. The precipitate is washed in a filter-press, and the mother liquor concentrated and used again for attacking more bauxite. This process, due to Bayer, has largely superseded the older method of decomposing the sodium aluminate by passing carbon dioxide through the solution.