MIL-DTL-38741A
A × N × (0.0809 × 106 )
ppm Acid halides (as HBr) =
W
where: A = Amount of NaOH solution in milliliters.
N = Normality of NaOH solution.
W = Weight of bromochlorodifluoromethane sample in grams.
4.4.3 Free halogen. The free halogen shall be treated with an excess of potassium iodide and
the iodide liberated titrated with sodium thiosulfate solution.
4.4.3.1 Reagents.
a. Sodium thiosulfate, 0.01N solution: Prepare a 0.1N solution by dissolving 25 grams of
sodium thiosulfate (Na2S2O3>5H2O) and 0.5 gram of sodium carbonate in 1 liter of distilled water.
Standardize against 0.1N potassium dichromate solution. From this 0.1N solution of sodium
thiosulfate, prepare a 0.01N solution as follows: Pipet a 10 mL aliquot of the standard 0.1N
sodium thiosulfate solution into a 100 mL volumetric flask and dilute to the mark with distilled
water and mix. Prepare the 0.01N sodium thiosulfate solution fresh daily.
b. Sulfuric acid, 1:4 solution in water.
c. Potassium iodide, 10 percent solution in water.
d. Starch indicator.
4.4.3.2 Procedure. Pour 100 mL of 10 percent potassium iodide solution into a 250 mL
Erlenmeyer flask. Add 10 mL 1:4 sulfuric acid and 1 mL of starch indicator solution. Bubble 100
grams of bromochlorodifluoromethane vapor through the potassium iodide solution. Titrate any
liberated iodine with standard 0.01N sodium thiosulfate solution. Run a reagent blank along with
the sample. Calculate the free halogen, as bromine, as follows:
( A - B) × N × (0.0799 × 106 )
ppm Free halogen (as Br) =
W
Where: A
=
Milliliters of sodium thiosulfate solution required for titration of the sample.
=
Milliliters of sodium thiosulfate solution required for titration of the blank.
B
=
Normality of sodium thiosulfate solution.
N
=
Weight of bromochlorodifluoromethane sample used in grams.
W
4.4.4 Nonvolatile residue. Add 100 mL of bromochlorodifluoromethane to an evaporating
dish which has been weighed to nearest milligram. Allow to evaporate to dryness in a hood.
After evaporation is complete, dry for 15 minutes in a drying oven at 105 °C. Cool the
evaporating dish in a desiccator and reweigh to nearest milligram. Calculate the non-volatile
residue as follows:
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