Silicic acid can be found in all natural waters in small quantities (usually up to 20 mg/l), partially in a fully dissolved form, partly in a colloidal state.
Boiler feed water for medium- and high-pressure boilers should be free of silicic acid to the greatest extent possible, since there is a risk that silica scale will form in the boiler.
The method describes how to determine the silica content of water photometrically with a cuvette test.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
In an acidic solution, in the presence of ammonium molybdate, dissolved silicic acid or silicates produce silicomolybdic acid which exhibits a yellow color. After the addition of a reducing agent, a blue color emerges which is proportional to the quantity of the silicic acid present in a certain concentration range.