Ammonical Nitrogen Measurement Calculator IS 3025

---

Principle

Ammonia after distillation is dissolved in boric acid and mixed indicator and can be titrated with H₂SO₄. Boric acid is so weak acid that it does not interfere with acidimetric titration.

---

Apparatus

• Distillation apparatus (All borsillicate glass appratus)
• Pipette
• Heating Mantle
• Volumetric Flask
• Burets borosilicate glass

---

Interferences

Residual chlorine reacts with ammonia; remove by sample pretreatment.

---

Range

Minimum Detection limit of Ammonical Nitrogen is 0.05 mg/L.

Reagent

• Ammonia Free Water
• Borate Bufffer Solution
• Sodium Hydroxide, 6N
• Decholorinating reagent
• Neutralization agent: NaOH 1N, H₂SO₄ 1N
• Mix indicator Solution
• Boric acid
• Sulphuric Acid
• Methyl red and methyl blue indicator

---

Reagent Preparation

• Ammonia Free Water
  Distillation –Eliminate traces of Ammonia in distilled water by adding 0.1 mL of Conc. H₂SO₄ in 1L distilled water and redistillation, Discard the first 100 ml distilled.
• Borate Buffer solution
  Add 88 mL 0.1 N NaOH solution to 500 mL approximately 0.025 M Sodium tetra borate solution or 9.5 g sodium tetra borate and dilute to 1000 mL with distilled water.
• Sodium Hydroxide, 6N
  Dissolve 24 g NaOH in distilled water and dilute up to 100 mL.
• Mix Indicator Solution
  (A) Dissolved 0.200 g Methyl red indicator in 100 mL 95% Ethyl or Isopropyl alcohol. (B) Dissolve 0.100 g Methyl Blue in 50 mL 95% ethyl or Isopropyl alcohol. Combine two solutions. Prepare Monthly.
• Boric Acid
  Dissolve 20 g Boric acid (H₃BO₃) in distilled water, add 10 mL mixed indicator solution and dilute to 1000 mL.
• Standard Sulphuric Acid
  Dissolve 10 mL 1N H₂SO₄ dilute to 500 mL with distilled water.

Ammonical Nitrogen (mg/L) = $\frac{\left(A-B\right)\times 280}{mL of sample}$

If Normality of H₂SO₄ is other than 0.02 N, use following formula.

Ammonical Nitrogen (mg/L) = $\frac{\left(A-B\right)\times N\times 14\times 1000}{mL of sample}$

Where,

• A = Sample reading
• B = Blank reading