Laserfiche WebLink
)[M-P-500M <br /> • crucible of medium porosity, having a nominal maximum pore diameter of 10-15 <br /> microns, and place a piece of ice in the crucible before filtering. The so- <br /> lution must be cooled to reduce the solubility of the nitron compound. Use <br /> the filtrate to effect transfer of all the precipitate. Wash the collected <br /> precipitate in the crucible with four 3 ml. portions of Ice water. Reboil <br /> the filtrate, and add a small quantity of nitron reagent to check the com- <br /> pleteness of the precipitation. Dry the crucible at 105 t 5'C (221 t 9'P). <br /> Cool in a desiccator and weigh. Repeat the weighing procedure until a con- <br /> stant weight is obtained. Calculate the percent nitrate as follows: <br /> Percent nitrate (NO3) _ (16.54)(W2)( <br /> Where: Wl = weight of sample represented by the aliquot, grams <br /> W2 = weight of precipitate after drying, grams <br /> 4.5.6 Zinc determination, (type Z only). The zinc content shall be deter- <br /> mined using the following reagents and procedure. <br /> 4.5.6.1 Preparation of reagents. <br /> 4.5.6.1.1 A buffer solution 5ha)1 be prepared by dissolving 350 al. of <br /> concentrated ammonium hydroxide and 54 grams of ammonium chloride in water <br /> and diluting to one liter. <br /> 4.5.6.1.2 An Eriochrome Black T indicator shall be prepared by dissolving <br /> 0.25 gram of Eriochrome Black T and 2.2 grams of hydroxylamine hydrochloride <br /> in 50 al. of methyl alcohol. <br /> 4.5.6.1.3 An ethylenediamine tetraacetate disodi.m solution shall be pre- <br /> pared by dissolving 37.2 grass of the dried salt in one liter of water. <br /> 4.5.6.2 Determination of zinc factor. Weigh accurately about 0.05 gram <br /> of ACS grade metallic zinc and dissolve in hydrochloric acid. Using red <br /> litmus as an indicator, add ammonium hydroxide wtil the last drop changea <br /> the litmus to blue. Add 30 al. of the buffer solution (4.5.6.1.1) and ti- <br /> trate with the ethylenediamine tetraacetate disodium solution (4.5.6.1.3) <br /> using 15 to 20 drops Eriochrome Black T indicator (4.5.6.1.2). The end point <br /> is reached when the color changes from red to blue. Calculate the zinc fac- <br /> tor as follows: <br /> Zinc factor (Z) = w <br /> A <br /> Where: W weight of zinc in grams <br /> A ml. ethylenediamine tetraacetate required for <br /> titration <br /> 1 <br /> 9 <br /> ��t1 <br />