Analysis of P2O5 by spectrophotometric method

Principle Analysis
Ortho phosphate reacts with Ammonim Vanado Molybdate that form a yellow complex compound of Ammonium Molybdate Phospho Vanado photo set at 420 nm absorbance.

Reaction
   (NH4) 2 P2O7 + HNO3 + HCl  2H3PO4
   2H3PO4 + (NH4) 6Mo7O24.4H2O¬ + NH4VO3 + 42 H + 
   {(NH 4) 3 PO 4} 2. 12MoO3.12 VO3.24H2O (yellow) + 42 (NH4) +

Reagents and Equipment
    a. Reagent
        1) concentrated HCl.
        2) Solution Molybdat-vanadate.
        3) Aquadest.
    b. Tool
        1) Spectrophotometer
        2) Analytical Balance
        3) Pumpkin Measure 100 mL and 500 mL
        4) Pipette 5 ml volume.
        5) Heating Plate.
        6) Whatman Filter Paper 40.
        7) Funnel.
        8) Stirer.

Work Procedures
    a. Example weighed 1 g, was added to glass beaker and added a little distilled water.
    b. Pipette 5 mL of concentrated HCl, put in a glass beaker and heated on a heating plate until               white smoke arise.
    c. Cooled, and added to 200 mL of distilled water. Then diluted in 500 mL volumetric flask                     and distirer until homogeneous.
    d. The solution was filtered with Whatman filter paper 40 and 5 mL pipetted into a 100 mL                 volumetric flask previously given molybdat-vanadate reagent, add distilled water to the mark.
    e. Flask shaken until homogeneous and read with a spectrophotometer at a wavelength of 420 nm.