The principle of the method specified is conditioning the extract solution to be analyzed, developing the blue silicomolybdate complex using ammonium molybdate and a reducing solution, measuring the optical density of the resulting colour complex by means of a molecular absorption spectrometer at 800 nm using 10 mm optical cells. Measures the concentrations of silicon, expressed as its oxide SiO₂. Applies to the analysis of extract solutions obtained from any kind of glass or glassware including laboratory and pharmaceutical ware, food and drink packaging ware, tableware and kitchenware.