Page 94 - Pharmaceutical_Analytical_Chemistry_1_Theoretical_Notes_Level_1

Mansoura National University
Pharm D-Clinical Pharmacy Program Level 1 Pharm. Anal. Chem. 1 (PC 101)

Determination of Ammonium Chloride (NH Cl)
4
➢ NH Cl is acidic because it is a salt of strong acid (HCl) & weak base (NH OH).
4 4

➢ NH Cl can be determined by 2 methods:
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[A] Formol method [specific method for ammonium salts].

[B] Back (residual) titration method.

4 NH Cl + 6 HCHO → (CH ) N + 4 HCl + 6 H O
4 2 6 4 2
Sample Neutral Hexamine or Equivalent to NH Cl
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Formalin Hexamethylene tetramine sample


(A) Formol Titr. ≠ stand. NaOH using
ph.ph. ind.
Method:

It depends upon addition of HCHO (neutral formalin) to NH Cl sample
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resulting in the formation of an equivalent amount of HCl that can be

titrated against standard NaOH using ph.ph. indicator.

boiling
NH Cl + NaOH → NaCl + NH  + H O
4 3 2
Sample known excess
of stand. NaOH

B) Back
NaOH + HCl → NaCl + H O
(residual) 2
remaining titrant
titration unreacted part

method: It depends upon boiling NH Cl with a known excess of standard NaOH
4

producing ammonia which is removed by boiling.

Then the remaining unreacted part of NaOH is back titrated against standard

HCl using M.O. or ph.ph. indicator.

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