Page 32 - PC 101 Interactive practical book

MANSOURA NATIONAL UNIVERSIY
PHARM D- CLINICAL PHARMACY LEVEL I PHARM. ANAL. CHEM. I (PC 101)

Exp.: Determination of NH 4Cl & HCl mixture

Our target is to determine the concentration of each component of the mixture

P Pr ri in nc ci ip pl le e : :

a) For HCl only: (E.P HCl)

HCl only is determined by direct titration of the mixture against

standard NaOH using M.O. indicator.
(NH 4Cl does not interfere because it needs boiling to react with NaOH).

b) For the total mixture [NH 4Cl & HCl]: (E.P total)

The determination of the total depends on the addition of neutral

formalin (HCHO) to the mixture where it reacts with NH 4Cl leading to

the production of an equivalent amount of HCl {Formol method}.

4 NH 4Cl + 6 HCHO  (CH 2) 6N 4 + 4 HCl + 6 H 20
(sample) neutral Hexamine
formalin or Equivalent
Hexamethylene to NH4Cl
tetramine sample

Then both (HCl) produced from NH 4Cl and (HCl) originally present in the

mixture are directly titrated ≠ standard NaOH using ph.ph. indicator.

NH 4Cl & HCl

HCl both are titrated ≠ standard NaOH

 NH 4Cl only ≡ (E.P total - E.P HCl)

P Pr ro oc ce ed du ur re e : :

a) For HCl only: (E.P HCl)

1) Transfer 10 ml of the mixture into a clean conical flask.

2) Add 2 drops M.O. indicator.

3) Titrate ≠ 0.1 N NaOH.

{ Color change at E.P.: from Red to Orange }

32 | P a g e