User manual HANNA INSTRUMENTS HI 3810

[. . . ] In man's environment, water must contain at least 2 mg/L of oxygen to protect water pipes from corrosion. However, boiler system water, in many cases, cannot contain greater than 10 mg/L oxygen. The Hanna Dissolved Oxygen Test Kit can determine the oxygen concentration in water quickly and easily. [. . . ] An azide is present to prevent any nitrite ions from interfering with the test. On addition of acid, manganese oxide hydroxide oxidizes the iodide to iodine (Step 2). Since the amount of iodine generated is equivalent to the oxygen in the sample, the concentration of iodine is calculated by titration of thiosulfate ions that reduce the iodine back to iodide ions. ­ Step 1: 2Mn2+ + O2 + 4OH 2MnO(OH)2 ­ Step 2: MnO(OH)2 + 2I + 4H+Mn2+ + I2 + 3H2O 2­ 2­ ­ Step 3: I2 + 2S2O3 2I + S4O6 INSTRUCTIONS READ ALL THE INSTRUCTIONS BEFORE USING THE TEST KIT LOOK AT THE BACK PAGE FOR THE ILLUSTRATED PROCEDURE · Rinse the glass bottle 3 times with water sample and fill to overflow. Insert stopper and ensure that a small part of the sample spills over. SPECIFICATIONS Range 0 to 10 mg/L (ppm) O2 Smallest Increment 0. 1 mg/L (ppm) O2 Analysis Method Azide Modification Titration Sample Size 5 mL Number of Tests 110 (average) Case Dimensions 260x120x60 mm (10. 2x4. 7x2. 4") Shipping Weight 910 g (34. 0 oz. ) · Add some more sample to fill the bottle completely. Carefully stopper the bottle again and ensure that a part of the sample spills over. This is to make sure that no air bubbles have been trapped inside, which would corrupt the reading. · Invert several times the bottle. The sample becomes orange-yellow and a flocculent precipitate will form if oxygen is present. · Let the sample stand and the flocculent precipitate will start to settle. · After approximately 2 minutes, when the upper half of the bottle becomes limpid, add 10 drops of Sulphuric Acid Solution. · Again stopper the bottle and invert it until all particulate material is dissolved. The sample is ready for measurement when it is yellow and completely limpid. · Remove the cap from the plastic vessel. [. . . ] Add an amount of unused sample in the glass bottle to the 10 mL mark of the plastic vessel. · Proceed with the test as described before and multiply the values on the syringe scale by 5 to obtain mg/L oxygen x 5 = mg/L O2 in the sample. REFERENCES 1987 Annual Book of ASTM Standard, Volume 11. 01 Water (1), pages 629-638. Official Methods of Analysis, A. O. A. C. , 14th Edition, 1984, pages 620-621. [. . . ]