Bulma And Vegeta Daughter

phosphorous pentoxide

phosphorus in the soil is conventionally expressed as phosphorus pentoxide (P 2 O 5) in the form assimilated IOE available for plants.

The total phosphorus pentoxide is of little importance because the localities are not comparable as insoluble calcium phosphate or ferric or aluminum (depending on the pH) or bound in organic form.

Precisely because of poor mobility of phosphorus fertilizer as it is administered prior to planting or seeding (preferably at the end of winter in February and March).

The allocation of sufficient phosphorus pentoxide is 0.1 ¸ 0.3 ‰.

Method Olsen-Watanabe

The method is applicable to land in water with pH greater than 6.5

Principle:

The method is based on capacity of sodium bicarbonate to lower the activity of calcium ions, allowing the extraction of phosphorus in the rate of football-related or co-precipitated with calcium carbonate.

The phosphorus content is determined photometrically by the development of the phosphomolybdate complex colored blue.

Material:

• spectrophotometer
  
• 2 flasks of 250 ml
  
• two pipettes of 5 ml


• 2 pipettes from 20 ml


• 3 pipettes of 50 ml
  
• 3 flasks from 100 ml


• flask 1000 ml
  
• magnetic stirrer
  

Reagents:

• extracting solution of 0.5 M sodium carbonate-bicarbonate, pH 8.5 (prepared by dissolving 42 g of sodium bicarbonate in 1 liter of water and adding 4.5 ml of sodium hydroxide up to 20% pH 8.5)
  
• activated charcoal (from wash to purify presence of phosphates: Shake the coal mining solution; gather coal on a Büchner funnel and washed several times with distilled water, dried in an oven at 110 ° C, as may still remain traces of phosphates is necessary to determine the phosphate content of 1 g of washed coal, and then subtract this figure from set in the ground)
  
• ammonium molybdate solution: Dissolve in a 100 ml flask 7.2 g of powdered ammonium molybdate in 250 ml of water and cool, in another flask and pour 250 ml of water, carefully , 107 ml (ie 196.8 g) of concentrated sulfuric acid (d = 1.84), cool and pour into a 1000 ml flask, cool and dilute to volume with deionized water (keep the solution in the bottle dark)


• reducing solution: aqueous solution of ascorbic acid 2.5% (prepared daily)
  
• phosphate solution: dissolve in a little 'water 0.1917 g of potassium phosphate biacido ( _{KH 2 PO} 4) and make up to 1 l with deionized water, shake well, take 200 ml and dilute to 1 liter with distilled water, 1 ml of this solution contains 0.02 mg P 2 _{O 5}


• concentrated sulfuric acid.
  

Construction of the calibration curve

In 6 flasks of 100 ml pour 50 ml of extracting solution. He added cautiously and stirring 1.5 ml of concentrated sulfuric acid, stirring until the effervescence ceases. Then add, respectively, from 0 to 5 - 10 - 15 - 20 - 25 ml of phosphate solution (containing 0.02 mg / ml _{P 2 O} 5).

tests contain 0, 1,2,3,4 and 5 mg / L of P 2 O 5 Shake and slowly add 20 ml of ammonium molybdate and 2 ml of ascorbic acid. Shake and place the flask on a boiling water bath for 30 minutes. Cool and up to the mark with distilled water.

is measured then the extinction of each solution at 650 nm against the blank (ie without the _{P 2 O} 5). It traces the straight line calibration setting on the abscissa the concentration of colored solutions in blue (expressed in mg P 2 O 5 / ml) and ordered extinction.

Procedure:

• Place in flask 5 g of fine soil and then air dried in an oven at 110 ° C.
  
• Add 1 g of activated charcoal (washed and dried) and 100 ml of extracting solution.
  
• Stir with magnetic stirrer for 30 min. and filter through dry filter. If the filtrate is colored, repeat the operation by increasing the dose of charcoal.
  
• In parallel, repeat the process in the flask without soil (blank).
  
• put in three flasks: 50 ml of extraction solution, 50 ml of coal alone, 50 ml of the soil.
  
• add, cautiously, 1.5 ml of concentrated sulfuric acid and stir carefully until the end of the effervescence.
  
• Add 20 ml of distilled water, 20 ml of ammonium molybdate solution and 2 ml of reducing solution.
  
• Place the flask on a boiling water bath for 0 min.
  
• Cool.


• volume with deionized water.


• Measure the extinction at 650 nm against the test with only one solution mining.


• To calculate the amount of phosphates similar use of the calibration curve .
  

Comments:

• This method is most suitable for calcareous soils as lo ione bicarbonato agisce abbassando l'attività degli ioni Ca ²⁺ (precipitazione di CaCO ₃ ) e provocando la solubilizzazione di una parte del fosfato di calcio.
  
• Nei terreni neutri e acidi, il pH tamponato a 8,5 evita la solubilizzazione di eccessive dosi di fosfato legato al ferro o all'alluminio e le precipitazioni secondarie che si avrebbero a pH più elevati.


• L'acido ascorbico riduce l'acido fosfomolibdico.

CONCENTRAZIONE P ₂ O ₅ campione = 8,339 mg/L

CONCENTRATION _{P 2 O} sol.estraente 5 = 0.68 mg / L

VALUE OBTAINED _{P 2 O} 5 = 7.66 mg / L 0 about 8 ppm