2.7 Determination of phosphate phosphorous in water (po43-)

A level of phosphorous in water directly affects on the absorption of the water. The higher concentration of phosphorous is, the higher absorption. Every 0,01 mg/l of phosphorous absorbance increases on 0.024. It causes negative impact on ecology of lakes. It causes eutrophication.

During this lab we used the following reagents and equipment: Working solution of phosphorous (1 mg/l), Sulphuric acid, 4 mol/l, Ascorbic acid, 5 g/100 ml, Acidic molybdate solution, different kind of bakers and flasks, spectrophotometer

We had to preparing blank, preparing standards and preparing sample. At first, we filled flask with 50 ml of distilled water and added 0,5 ml of 4 mol/l sulphuric acid into the flask. Then we prepared different standard solutions containing 0.05, 0.10, 0.25 and 0.50 mg/l of phosphorous. They was made by diluting phosphorus solution by water

Standard (mg/l)	Volume of working solution (ml)
0,05	5
0.10	10
0.25	25
0.50	50

They was prepared by dilution 1 mg/l phosphorous solution by water. We added the calculated volume of working solution into the 100 ml flask and filled it by distilled water until the mark. Also, we measured 25 ml of each standard into flasks and added 25 ml of water and 0,5 ml of 4 mol/l sulphuric acid into every flask. Then, we started to making sample. For this aim we measured 25 ml of sample in a flask with measuring cylinder and added 25 ml of distilled water and 4mol/l sulphuric acid. After this we added 2 ml of ascorbic acid and molybdate ­reagent into each flask and mixed solutions after each adding. We waited for a 10 minutes and started measuring the absorption of solutions at 880 nm wavelength . We collected the following results.

Solution	Absorbance
0,05 mg/l	0,016
0,10 mg/l	0,052
0,25 mg/l	0,161
0,50 mg/l	0,345

ЛИНИЯ И КОНКЛЮЖН