YSI 9300 Photometer - Manual (Page 91)

PHOTOMETER TEST INSTRUCTIONS
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Phosphates are extensively used for treating water in boilers and steam raising
plant. Phosphates are added to control the deposition of sediment and deposits
within the boiler. It is an essential part of the treatment programme to monitor the
phosphate level to ensure this is within the correct range of deposition control.
The YSI Phosphate HR test provides a simple method of measuring phosphate
levels in boiler waters over the range 0 - 100 mg/l PO
4
.
Method
The YSI Phosphate HR test is based on the vanadomolybdate method. The
distinct advantage of the YSI method is that all reagents required are provided
in the form of a test tablet. The test is carried out simply by adding a single
tablet to a sample of the boiler water. A supplementary tablet may be optionally
used for the removal of Silica interference.
In the test, phosphates react with ammonium molybdate, in the presence of
ammonium vanadate, to form the yellow phosphovanadomolybdate. The
intensity of the color produced in the test is proportional to the phosphate
concentration and is measured using a YSI Photometer.
Sample Collection
Samples drawn from boiler sampling points may be hot and contain particulate
matter. Prior to analysis samples should be cooled to below 25°C and filtered
through a Whatman No 42 filter paper.
Reagents and Equipment
YSI Phosphate HR Tablets
YSI Phosphate SR Tablets
YSI 9300 or 9500 Photometer
Round Test Tubes, 10 ml glass (PT 595)
Photometer Method
AUTOMATIC
WAVELENGTH
SELECTION
0 – 100 mg/l
PHOT.29.AUTO