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State of Andhra Pradesh - Section
Section 04 in Andhra Pradesh Bio-fertilisers (Monitoring and Quality Control), Act, 2006
04.
Preparation of Reagents. - Sulphomolybdic acid.Take 20 g of Ammonium molybdate and dissolve in 300 ml of distilled waterAdd slowly 450 ml of 10 N2 S04.Cool the above mixture and add 100 ml of 0.5 percent solution of Antimonypotassium tartrate.Cool and make the volume to one litre. Store in glass bottle away from direct sunlight.Preparation of mixed Reagent. - Add 1.5 gm of L - ascorbic acid in 100 ml of the above stock solution and mix. Add 5 ml of this solution to develop colour. Mixed regent is to be prepared fresh as it does not keep for more than 24 h.Procedure. - Weigh the required material in a 100 ml conical flask.Add 50 ml of extractant and shake it for 30 min on rotary shaker.Filter the suspension through whatman filter paper No. 40. If the filterate is coloured than add a tea spoon of Darco-60 (activated phosphorus free carbon) reshake and filter.Take a known aliquot (5 to 25 ml) of the extract in a 50 ml volumetric flask.Add 5 drops of P-nitrophenol indicator (1.5 percent solution in Water) and adjust the pH of the extract between 2 and 3 with the help of NH2S04. The yellow colour will disappear when the pH of the solution becomes 3. Swirl gently to avoid loss of the solution along with the evolution of C04.When the C02 evolution has subsided. Wash down the neck of the flask and dilute the solution to about 40 ml.Add 5 ml of the sulphomolybdic acid mixed reagent containing ascorbic acid Swril the content and make up the volume.Measure the transmission after 30 min. at 880 nm using red filter. The blue colour developed remains stable up to 60 minutes.Record the concentration of Phosphorus (P) in the extract from the standard curve and calculate the concentration of soluble phosphorus as follows.Calculation. - (a) Weight of the substance taken = xg| Percent p =| ZX50X10 -6X5O X 100Y,X |