Phosphate Testing Procedure

• Fill three test tubes to mark with sample water. (Remember to read at the bottom of the meniscus.)

• Treat one of the test tubes according to test procedures. (The other two will be used as blanks)

• Procedure:

• Use 1.0 mL pipet to add 1.0 mL of Phosphate Acid Reagent.

• Cap and mix. (Note: The cap will pop off if you do not hold it on while mixing. Shake gently to mix and make sure you are wearing gloves.)

• Use 0.1 g spoon to add one level measure of Phosphate Reducing Reagent.

• Cap and mix until dissolved.

• Wait 5 minutes.

• Remove Stopper from Test tube.

• Insert test tube with treated sample into slot in Axial Reader directly behind distilled water ampoule.

• Insert two test tubes with untreated sample into slots in Axial Reader on either side of treated sample.

• Slide Octect Comparator down until top is even with top of Axial Reader. (Hold comparator so natural light shines down through test tubes.) Compare color in center test tube to colors in top left corner of Octet Comparator.

• How to read:

• If the color of the test sample is less than the color of the lowest value, the result is recorded as “less than” the lowest value.

• If the color of the test sample matches one of the color standards in the upper left-hand quadrant, the result is taken as the value of that color standard.

• If the color of the test sample falls between these two values, the result is the average of these two values.

• If the color of the test sample is darker than the color of the second color standard, move the comparator to a position where the bottom of the Axial Reader and the bottom of the comparator are even.

• If a color match is not reached with the standards on the left-hand side of the comparator, the test sample and blank tubes are transferred to the right-hand side of the Axial Reading device. The ampoule of distilled water is transferred to the hole on the right-hand side of the comparator.