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IQI.-P-SOOOOA <br /> 4.5.4.2 Determination of nickel factor. Weigh exactly 0.05 g. of pure • r . <br /> mets.l'ic ole dissolve in a 250 . flask with a mixture of 5 ml. of <br /> concer.trated sulfuric acid, 5 ml, of concentrated nitric acid and 5 ml. of <br /> distilled water. Evaporate the solution until dense white fumes of sulfur <br /> trioxide are evolved and then cool it. Add a slight excess of ammonium <br /> hydroxide and bring to a boil. Cool the solution to room temperature and <br /> add ',s ml. of the chloride pyrophosphate mixture (4.5.4.1.2). Titrate with <br /> the ztundard sodium cyanide solution (4.5.4.1.3) until the precipitate which <br /> formed has redissolved. Calculate the nickel factor as follows: <br /> Nickel factor (K) = gra of nickel <br /> ml. of NaCN solution used <br /> 4.5.4.3 Test procedure. Weigh approximately 5 grams of the sample as <br /> recei•:ed into a 250 mi. beaker. Add 15 to 20 drops each of concentrated <br /> hydrez-hloric acid and the sodium nitrate solution (4.5.4.1.1) and stir for <br /> 2 minutes. Add 100 ml. of the chloride pyrophosphate mixture (4.5.4.1.2). <br /> Add aj- onium hydroxide dropwise until the solution turns red litmus paper <br /> blue. At this point the solution should be clear. Titrate the solution <br /> with the standard sodium cyanide solution (4.5.4.1.3) as follows: <br /> Add 1/2 ml. of the sodium cyanide solution and stir for 2 minutes. <br /> A precipitate should form. Continue adding the sodium cyanide solution drop- <br /> wise until the precipitate dissolves and the solution is clear. The point <br /> at which the solution clears is the end point. Calculate the percent nickel <br /> as follows: <br /> Percent nickel = (A-B)(K)(100) <br /> W <br /> Where: A = ml. of N&CY <br /> B = ml. of NaCN for blank <br /> K = nickel factor (see 4.5.4.2) <br /> W = weight of sample in grams <br /> 4.5.5 Nitrate determination. The nitrate content shall be determined <br /> using the following reagents and procedure. <br /> 4.5.5.1 Preparation of nitron rea eat. A 10 percent nitron solution is <br /> prepared by dissolving 10 g• of nitron diphenylenedianilohydrotriazole) in <br /> 100 ml. of 50 percent glacial acetic acid and then filtering. Keep in a <br /> dark colored bottle. <br /> 4.5.5.2 TestProcedure- Withdraw sufficient volume of dilute test solu- <br /> tion (see 4. to contain 0.05 to 0.10 gram of nitrates and weigh into a <br /> 250 ml. beaker. Add 100 m1. of distilled water and 2.0 ml. of 6N sulfuric <br /> acid. H"t to boiling and add 10 ml. of nitron reagent. Cool and place in <br /> d glass <br /> an ice bath for 1-1/2 hours. Filter through a weighed, fritte <br /> 8 <br />