Bio-Rad AG® MP-50 Cation Exchange Resins - Manual (Page 10)

6.2 Materials
AG 50W-X8 resin, 50-100 mesh, hydrogen form–10 grams
Econo-Column ® chromatography column, 1.0 x 0.79 cm
Methyl orange indicator solution (0.1%)
20 mM NaOH standard solution
3 M HCl
Flask–250 ml
6.3 Protocol
1. Pass approximately 150 ml of tap water through the
resin column.
2. Discard the first 20 ml of effluent.
3. Collect a 100 ml aliquot of effluent in a 250 ml flask.
4. Titrate with 20 mM NaOH to methyl orange end
point (yellow).
5. Calculate the salt content from the equivalents of
base used.
6.4 Calculation
Meq dissolved salts = ml of base x normality of base.
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Section 6
Sample Protocol for Cation
Exchange Resins
6.1 Determination of Total Salts in Tap
Water
Approximately 85% of the Continental United States
is afflicted with hard water (3 grains or greater/gal). The
following is a rapid method of determining the total ionic
content of tap water as well as a good illustration of the
potential of ion exchange techniques. If the water
containing dissolved ions is allowed to flow over a
cation exchange resin, the metal ions will be
quantitatively exchanged for the hydrogen ions of the
resin. These hydrogen ions will appear in the eluant and
may then be titrated with standardized NaOH. Because
of the electroneutrality of the dissolved salts, the
milliequivalents of cations also represent the
milliequivalents of salts.
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LIT203B 6/17/98 12:00 PM Page 14