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Method ID:

HI0001EN

0.1N Sodium Hydroxide Titrant Concentration

Titrator Application Methods:

General Methods - r. 2.3

Description

Method  for  the  standardization  (titer  determination)
of  0.1N  Sodium  Hydroxide  (NaOH)  titrant  solution
against  Potassium  Hydrogen  Phthalate  (KHP).  The
results are expressed in

N (eq/L)

Reference:

AOAC Official Methods of Analysis, Official Method
936.16

Electrode



HI 1131B

Combination pH Electrode



HI 7662-T Temperature Probe

Reagents



HI 70456

0.1N Sodium Hydroxide solution (1 L)



HI 70401

Potassium Hydrogen Phthalate (20 g)



HI 70436

Distilled Water (1 gal)

Accessories



HI 70300L Storage Solution (500 mL)



HI 7071

Electrode Fill Solution (4*30 mL)



HI 7004L

pH 4.01 Buffer Solution (500 mL)



HI 7007L

pH 7.01 Buffer Solution (500 mL)



HI 7010L

pH 10.01 Buffer Solution (500 mL)



HI 740036P 100-mL Plastic Beaker (10 pcs)



Analytical Balance with a minimum resolution of

0.0001g is recommended

NOTE:

A pH electrode calibration is not needed for

this method.

Procedure



Connect the pH electrode and temperature probe

to the titrator.



Press “

Select Method

” from the main screen. Use

the arrow keys to highl

ight „HI0001EN 0.1N NaOH

Titr. Conc.‟ and press “

Select

”.



Install a 25-mL burette filled with 0.1N sodium

hydroxide solution (HI 70456) on pump-one and
verify that no air bubbles are present in the burette
or tubing. If necessary prime until all air has been
removed completely.



Crush approximately 3 grams of potassium

hydrogen phthalate (HI 70401) and dry it for 2
hours at 120°C. Cool to room temperature in a
desiccator.



Place a clean 100-mL plastic beaker on the

analytical balance.



Zero the balance.



Carefully weigh approximately 0.20 grams of dried

potassium hydrogen phthalate into the beaker.

NOTE:

Ensure that all of the potassium hydrogen

phthalate is on the bottom of the beaker.



Record the exact weight of the sample once the

balance has stabilized with an accuracy of 0.0001
grams.



Remove the beaker from the balance and add

distilled water to the 50-mL mark on the beaker.



Place the beaker under the stirrer assembly and

immerse the pH electrode, temperature probe and
stirrer. Ensure that the reference junction of the
pH probe is 5-6 mm below the surface. If
necessary add extra distilled water.



Press “

Start

”. You will be prompted to enter the

analyte size (weight of KHP). Use the numeric
keypad to enter the exact weight and press
“

Enter

” to start the analysis.

NOTE:

Ensure that the KHP dissolves completely

during the pre-titration stir time. Erroneous results
may occur if the sample does not dissolve
completely prior to titration. If necessary the pre-
titration stir time can be increased.



At the end of the titration, after detection of the

equivalence point, 'titration completed‟ will appear
with the titrant concentration. The result is
expressed in

N (eq/L) of sodium hydroxide



Remove the electrodes and stirrer from the

sample and rinse them thoroughly with distilled
water.



Record the result (titer concentration).

NOTE:

For improved accuracy, repeat this

procedure a minimum of three times and calculate
the average value.