Titration as the Silicomolybdic Acid

Sample. Up to 10 ml volume containing up to 10 mg SiOj, in the pH range of about 1-7. 

Procedure. Place 40 ml reagent G in the thermostat at 20 C and adjust the sample to the same temperature before mixing. After the desired reaction time stop the reaction by adding 25 ml of acid solution A. After 15 sec add 25 ml of solution B from a burette. Cool the mixture to 10-15 C and filter in a fritted glass crucible of porosity G4 wash free of HCl. Disperse the precipitate in water dissolve the residue from the filter with 10 ml 1 Af NaOH, and wash it into the precipitate suspension, which dissolves. Back-titrate with solution D using 5 drops of reagent C. 

One milliliter of 1 N NaOH consumed by the precipitate corresponds to 2.504 mg Si02. 

Colloid Chemistry of Silica and Silicates, Cornell University Press. Ithaca. N.Y.. 1955. 

Fournier, Silica in Thermal Waters. Laboratory and Field Investigations, Proc. 

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