EXPERIMENTAL
Instruments
The spectral measurements were made using ultraviolet
visible spectrophotometer, model WPAS 104 UK with 1
cm matched quartz cells. An electronic balance, model
GT 210 V, OHAUS and a muffle furnace – WCR- muff
– Nabertherm were used.
Preparation of Standard Solutions
All the chemicals used were of analytical reagent grade
and the solutions were prepared in distilled water.
Phosphate stock solution: 0.717 g of potassium
dihydrogenphosphate (KH2PO4) was dissolved in
distilled water and the volume was made 500 mL in a
volumetric flask. The working phosphate solutions were
prepared by its further dilution.
Preparation of working solution of ammonium
molybdate (2.5%)
50 mL of 5% ammonium molybdate reagent was diluted
and made up to the mark in a 100 mL of volumetric flask.
Preparation of sulphuric acid solution (10N)
28 mL of concentrated sulphuric acid solution was
diluted and made up to mark in a 100 mL of volumetric
flask.
Preparation of hydrazine hydrate (0.5M)
2.44 ml of concentrated hydrazine hydrate was diluted
and made up to mark in a 100 mL of volumetric flask.
Preparation of Samples
Water sample preparation
The water samples collected from various places of
Kathmandu were used for the phosphate analysis. The
samples were filtered through Whatmann-41 filter paper
in order to remove the insoluble particles. The filtrate
contains orthophosphate, condensed phosphate (pyro,
meta and poly forms) and organically bound phosphorus.
All these forms of phosphate may be present in soluble
form and in suspension. Since only ortho phosphate can
be determined by molybdenum blue method so pyro,
tripoly and polyphosphate were completely hydrolyzed