A Rapid Method for Determination of Silica in Iron Ore and a Spectrophotometric Method for Phosphorus

DETERMINATION OF SILICA OXIDE iron ores usually are found in intimate association with sllica and phosphorus compounds. heir quantitative separation and purification sometimes present difficult problems to the chemist. Silicic acids may represent various degrees of dehydration. They are exceedingly weak, but combine with metallic oxides and form some of the most stable , oxides in nature, the silicates. When iron ores are treated with hydrochloric acid, they yield practically all their iron. However, apart from rare exceptions, varying amounts of insoluble residues of silica, alumina, lime, magnesia and compounds of phosphorus, sulphur, titanium, chromium and others will be left. If the oxides of silicon, aluminum and titanium are present in small quantities, the insoluble residue is generally very been recommended, such as a number of lead and boron salts. The introduction of these salts, which offers certain advantages, requires, however, their removal before the other constituents can be analyzed, and this elimination is sometimes difficult. Usually in quantitative analysis silicates are dissociated by fusing them in a platinum crucible with sodium carbonate, thereby forming sodium silicate, NasSiOa, sodium aluminate, NazM204, sodium titanate, NazTiOa, and carbonates of other elements. All the carbonates are soluble in hydrochloric acid, but also some silicic acid is formed that must be rendered insoluble. To this end the solution is evaporated several times, as the first evaporation still leaves as much as 5 per cent of the silica soluble. Even after a number of evaporations, minute quantities of silica may be found with the iron and alumina present. small, but the presence of these oxides is more usual in larger quantities. TherePerchlmic Acid as an Agent for Dehydrating fore, only a special treatment can break SiliGic Acid