Phosphates (PO₄^-3)

    Phosphates act as water softeners. They promote the growth of plants, particularly algae. Too much phosphate will choke the waterways of oxygen and cause odors in the water. Phosphates reduce the ability of waterways to support aquatic life. They enter waterways from fertilizers, pesticides, industries, and cleaning compounds. The phosphate is absorbed into the ground and then runoff carries it into the water. Excess phosphates in waterways are the result of human activity.

Procedures:

1. Rinse out cuvettes with test water.

2. Fill cuvettes with test water.

3. Pour in contents of PhosVer3 packet and shake for one minute.

4. Let it set for two minutes.

5. Using the Explorer, set the screen to view green absorbance. The Explorer will take all colors of absorbance and transmition, the display allows for paper and pencil recording of the green absorbance.

6. Calibrate the probe by placing a cuvette of distilled water in the colorimeter. Press the small green button on the probe. When the light goes off, the probe is ready to use.

7. If phosphates are present, a blue color will form. Place the cuvette in the colorimeter free of smudges and finger prints. Read the value off of the Explorer, then push the play button to store the data on the Explorer. Press the play button again to stop the data collection

8. Repeat steps 1-7 for three more trials

9. The calibration curve constructed in May 2005 provided an equation of y=.285x + .035 with an r=.993. y is the green absorbance and x is the concentration of phosphates in parts per million

10. Use absorbance (y) to calculate the ppm