Page 90 - Analytical Chemistry I E-book

Determination of ammonium salts

Two methods can be used for analysis of NH + salts:

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1- Ammonium salts are conveniently determined by conversion to ammonia with
strong base followed by distillation. The ammonia is collected and titrated as in
Kjeldahl method (Simplified Kjeldahl method).

2- Formol titration:

This is the pharmacopial method for determination of ammonium chloride

(NH4Cl). Formaldehyde (HCHO) is added to ammonium salt sample. They react

together giving hexamine and equivalent amount of acid. The produced acid is

titrated with standard NaOH using phenolphthalein as indicator.

4 NH + + 6 HCHO ⎯→ 4 H+ + (CH ) N + 6 H O
4 26 4 2

Hexamine