MIL --- DTL --- 150E
C = Milliliters of potassium permanganate solution required for titration of the
excess ferrous iron,
D = Percent moisture calculated in 4.4.2, and
W = Weight in grams of specimen.
4.4.4 Water --- insoluble matter. Dry a filtering crucible of sufficient pore size to prevent clog-
ging to constant weight at 100° to 110°C. Cool in a desiccator and weigh to the nearest 0.1 mg.
Weigh to the nearest 0.1 g approximately 50 g of the specimen and dissolve in approximately 800
mL of water. Filter the solution through the weighed crucible and wash the residue with 5 por-
tions of hot water. Retain the filtrate for subsequent determinations. Dry the crucible and resi-
due for 3 hours at 100° to 110°C. Cool in a desiccator and weigh to the nearest 0.1 mg.
Calculate the percent water --- insoluble matter as follows:
Percent water --- insoluble matter = 100A
W
where: A = Weight in grams of residue, and
W = Weight in grams of specimen
4.4.5 pH of water --- soluble matter. Cool the filtrate from 4.4.4 to room temperature. Trans-
fer to a 1 liter volumetric flask and dilute with water to the mark. Determine the pH of a portion
of this solution by means of a suitable standardized pH meter. Save the remaining solution for
later use.
4.4.6 Hypochlorites. To a 200 mL aliquot of the solution from 4.4.5, add a strip of potassium
iodide --- starch paper. There shall be no immediate appearance of a blue color which indicates
the presence of hypochlorites. If the test for hypochlorites is negative, retain this solution for
4.4.7, if required. Disregard the test for chlorites if hypochlorites are present.
4.4.7 Chlorites. If a negative test for hypochlorites was obtained in 4.4.6, add 5 mL of 0.1N
sulfuric acid to the solution and test with a fresh strip of potassium iodide --- starch paper. There
shall be no immediate presence of a blue color which indicates the presence of chlorites.
4.4.8 Chlorides. To a 100 mL aliquot of the solution from 4.4.5, add 1 mL of a 5 percent
solution of potassium chromate and titrate to a permanent faint blood --- red tinge with 0.1N sil-
ver nitrate solution. Calculate the percent chlorides as KCl as follows:
Percent chlorides = 7.456AB
W
where: A = Milliliters of silver nitrate solution used,
B = Normality of silver nitrate solution, and
W = Weight in grams of specimen in aliquot from 4.4.5.
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