The method of analysis

Nitrogen, Nitrate, High range 0-30 mg/l/

TM-5-6630-215-12 Alarm-Monitor Group (AMG) OA-9431/F88-9(V) CAGEC 97403 Manual
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TM 5-6630-215-12 (b) The method of analysis used in the high range test is a modification of the cadmium reduction method using gentistic acid in place of 1-naphthyl amine. The test registers both nitrates and nitrites present in the water sample and eliminates the need for dilutions by operating in the most usefull range. All the necessary reagents have been combined into a single stable powder called the nitrate reagent. (2) Nitrogen, Nitrate, Range 0-30 mg/l (figs. 2-11 and 2-12, and para 2-18). NOTE The Nitrate reagent is slightly temperature sensitive. For best results, the test should be performed with a sample temperature of 20° - 25°C (68° - 75°F). A deposit of unoxidized metal will remain after the Nitrate reagent powder has dissolved. This will have no effect on test results. The extent of color development in the nitrate nitrogen test using Nitrate reagent powder is partially affected by the shaking time and technique of the analyst. For most accurate results, the analyst should make successive tests on a solution containing a known amount of nitrate and adjust shaking time to obtain the most accurate results. (a) Take a water sample by filling a clean sample cell to the 25 ml mark. (b) Add the contents of one nitrate reagent powder pillow to the sample cell, stopper, and shake vigorously for exactly one minute. An amber color will develop if nitrate nitrogen is present. Allow at least 5 minutes for proper color development but do not wait more than 15 minutes before completing steps (c) and (d). (c) Fill another sample cell to the 25 mark with original water sample and place it into the cell holder. Insert the Nitrogen, Nitrate meter scale into the meter and adjust the wavelength dial to 500 nm. Adjust the light control for a meter reading of zero mg/l. (d) Replace the blank sample, step (c) with the prepared sample in the cell holder and read the mg/l nitrate nitrogen (N). (e) The results can be expressed as mg/l nitrate (NO₃) by multiplying the mg/l nitrate nitrogen (N) by 4.4. 2-47

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