Читать книгу Industrial Poisoning from Fumes, Gases and Poisons of Manufacturing Processes - Josef Rambousek - Страница 22

Chrome ironstone, lime, and soda are ground and intimately mixed. They are next roasted in reverberatory furnaces, neutral sodium chromate being formed. This is lixiviated and converted into sodium bichromate (Na₂Cr₂O₇) by treatment with sulphuric acid. Concentration by evaporation follows; the concentrated liquor is crystallised in cast-iron tanks. The crystals are centrifugalised, dried, and packed. Potassium bichromate may be made in the same way, or, as is usually the case, out of sodium bichromate and potassium chloride.

The bichromates are used in the preparation and oxidation of chrome colours, but their principal use is in dyeing and calico printing, bleaching palm oil, purifying wood spirit and brandy, in the preparation of ‘Swedish’ matches, in the manufacture of glass, in photography, in dyeing, in tanning, and in oxidation of anthracene to anthraquinone.