Spectrophotometric analysis with ammonium molybdate

1 Spectrophotometric analysis with ammonium molybdate General remarks 

The cooled water sample is decomposed using hydrofluoric acid/per chloric acid, thereby depolymerizing the entire silicic acid and converting it into a form capable of reaction with ammonium molybdate (W. Fresenius and W. Schneider). After adding boric acid to complex the hydrofluoric acid, 

Experience has shown that after a short familiarization period the method described below is simple to carry out and provides rapid, reliable 

The method is suitable for determination of between 0.5 and 250 mg of Si02/1 in natural waters. If the content of silicic acid is above 25 mg/1, silicic-acid-free distilled water must be used for dilution. 

All solutions used must be stored in plastic flasks so as to ensure that no silicic acid is dissolved out from glass. 

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