YSI 9300 Photometer - Manual (Page 102)

PHOTOMETER TEST INSTRUCTIONS
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Zinc compounds are used as corrosion inhibitors in industrial cooling water
systems and similar applications. Control of the zinc level is an important aspect
of corrosion control in such systems. Zinc and zinc containing alloys are widely
used in industry and zinc salts are commonly found in industrial effluents.
The YSI Zinc test provides a simple means of testing zinc levels over the range
0 - 4 mg/l and is suitable for testing cooling waters and industrial effluents, and
for the monitoring of natural and drinking waters.
Method
Zinc reacts with 5-(o-carboxyphenyl)-1-(2-hydroxy-5-sulphophenyl)-3-phenyl-
formazan (Zincon) in alkaline solution to give an intense blue color. The reagent
itself is orange in solution. At different zinc levels a distinctive color range from
orange through purple to blue is produced. In the YSI Zinc test a tablet reagent
containing both Zincon and an alkaline buffer is used for maximum convenience.
The test is simply carried out by adding a tablet to a sample of the water.
Samples containing high chlorine residuals are pre-treated with a special
dechlorinating tablet to prevent bleaching of the test colors.
The color produced in the test is indicative of the zinc concentration and is
measured using a YSI Photometer.
Copper reacts in a similar manner to zinc and a correction procedure using
EDTA is applied to those samples which contain both zinc and copper. EDTA
destroys the color complex formed with zinc.
Reagents and Equipment
YSI Zinc Tablets
YSI Zinc-Dechlor Tablets
YSI EDTA Tablets
YSI 9300 or 9500 Photometer
Round Test Tubes, 10 ml glass (PT 595)
Photometer Method
AUTOMATIC
WAVELENGTH
SELECTION
0 – 4.0 mg/l
PHOT.35.AUTO