Analytical Method: Silicon (total) in drinking water

Photometric determination using the Silicon molybdenum blue method subsequent to fusion melting

Instruments and Reagents:

Cat.No. 173016  Spectroquant® VIS Spectrophotometer Prove 100 or

Cat.No. 173017  Spectroquant® UV/VIS Spectrophotometer Prove 300 or

Cat.No. 173018  Spectroquant® UV/VIS Spectrophotometer Prove 600 or

Cat.No. 109748  Spectroquant® Photometer NOVA 30 or

Cat.No. 109751  Spectroquant® Photometer NOVA 60 or

Cat.No. 173632  Spectroquant® Colorimeter Move 100

Cat.No. 114946  Rectangular cells 10 mm and/or

Cat.No. 114947  Rectangular cells 20 mm and/or

Cat.No. 114944  Rectangular cells 50 mm
Cat.No. 114794  Spectroquant® Silicate (Silicic Acid) Test
Cat.No. 100857  Spectroquant® Silicate (Silicic Acid) Test
Cat.No. 106392  Sodium carbonate anhydrous for analysis
Cat.No. 100716  Sulfuric acid 25 % for analysis
Cat.No. 116754  Water for analysis
Silicon occurs in waters and neutral solutions in the form of water-soluble, monomeric orthosilicic acid (H4SiO4) and in the form of diverse, mostly colloidal polysilicic acids. The reactive forms comprise monomeric silicic acid together with that Portion of the polymeric acids which is converted to the monomeric form during the reaction itself. The non-reactive polymeric Portion tan be converted to the monomeric form by alkaline mineralisation. In this way it is possible to differentiate between "soluble" and "total" silicic acid.
Sample preparation -Depolymerisation of non-reactive silicic acid (colloidal silicic acid)
Evaporate 50 ml of water for analysis sample with 0.5 g sodium carbonate in a Pt or PTFE dish and boil gently to about half the original volume, add 1.6 ml sulfuric acid 25 % and fill up to 50 ml with water for analysis.
Determine with the above mentioned test kit.
Silicon (total) content in mg/l  =  analysis value in mg/l Si


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