Determination of Silica and Phosphate

 

Ø  Apparatus:-

·         10 ml cylinder

·         Silica Crucible

·         Platinum Crucible

 

Ø  Reagents:-

·         Sulphuric Acid (AR Grade)

·         Nitric Acid (AR Grade)

·         Ammonium Molybdate 10% (w/v) Solution

·         Ammonium Nitrate (AR Grade)

 

Ø  Procedure:-

Take approximately accurately 2 g sample in an accurately pre-weighted Silica Crucible. Then add sufficient amount Sulphuric Acid to wet the solution for digestion. Then digest very carefully in a fume hood. After complete digestion burn the crucible with sample at about 400°C in Muffle Furnace for about 2 hours. Then cool to room temperature. Then wash the residue through a Whatman 42 filter paper again and again until the filter paper becomes free of acid and store the filtrate for Phosphate test. Then after complete filtration take the filter paper with residue in a pre-weighted (C) Platinum crucible. Then burn that at about 800°C for approximately 2 hours. Then cool to room temperature. Then take the weight of Platinum crucible with sample (A). Then add sufficient amount of Hydrofluric Acid for reaction with Silica and heat the crucible for required time of complete smoke reduction. Then take the final weight (B).

Then take the filtrate in a 250 ml beaker and add 5 ml Nitric Acid (AR Grade) and boil for 5 minutes. Then cool to room temperature. Then add 15 ml Ammonium Molybdate 10% (w/v) Solution. Then heat using water bath. Weight for complete sedimentation. Then filter through a pre-weighted Whatman 42 filter Paper (F). Wash that precipitate with 2% (w/v) Ammonium Nitrate Solution for several times. Dry that filter paper in the Hot Air Oven at approximately 110°C. Then take the final weight accurately of filter paper with precipitate (F₁) after cooling.

 

Ø  Calculation:-