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.