YSI 9300 Photometer - Manual (Page 79)

PHOTOMETER TEST INSTRUCTIONS
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MOLYBDATE HR
Formulations containing Molybdate are used as corrosion inhibitors in industrial
water treatment. In particular, molybdate finds application in closed recirculating
systems such as hot water heating systems and chilled water systems. Molybdate-
based formulations have replaced older forms of corrosion inhibitor such as
chromate.
When using molybdate treatment it is necessary to control the Molybdate
concentration within specified levels depending on the application involved.
Moreover since molybdates are widely used in water treatment and in industrial
processes, molybdate is an increasingly important test for effluents and industrial
discharges.
The YSI Molybdate HR test provides a simple means of measuring high levels of
molybdate in industrial waters and effluents and covers the range 0 - 100 mg/l
MoO4.
Method
Molybdates react with thioglycollate under acid conditions to give a yellow
colored complex. Slightly oxidising conditions are maintained during the
acidification stage in order to keep the molybdate in a fully oxidised state. Under
the conditions of the test, iron does not interfere and there is no significant
interference from other metals at levels likely to be found in industrial water
systems. The reagents are provided in the form of two tablets for maximum
convenience. The test is simply carried out by adding one of each tablet to a
sample of water.
The intensity of the color produced in the test is proportional to the molybdate
concentration, and is measured using a YSI Photometer.
PHOTOMETER METHOD
AUTOMATIC
WAVELENGTH
SELECTION
0 – 100 mg/l MoO
4
PHOT.22.AUTO