MIL-DTL-11309J
subdued light.) Add approximately 25 mL of distilled water and again stopper and swirl to
ensure complete mixing and solution of KI. Titrate at once with a freshly standardized 0.15 N
sodium thiosulfate solution to light straw color. Add starch indicator, and continue titration to
end point.
4.5.2.1.1 Calculation. Calculate the result as follows:
Percent titratable chlorine = (35.45)(mL of sodium thiosulfate)(N)(100)
(grams of sample)(1000)
4.5.2.2 Acidity. Weigh 1 gram of the contents of the pouch A to the nearest milligram
and disperse in 1 liter of distilled water at 25 șC ± 1 șC. The pH, measured with a glass
electrode, shall not be lower than 2.5. Titrate the entire solution with 0.1 N NaOH. The latter
solution is added from a burette while stirring, measuring the pH with a glass electrode at
suitable increments. As the pH value approaches 5.0, the increments should be made smaller,
with pH intervals no greater than 0.2. Continue the titration until pH of 5.5 has been reached.
The number of milliliters of 0.1 N NaOH required to give a pH of 5.0 is then found by
interpolation of this data.
4.5.2.2.1 Calculation. Calculate the result as follows:
Milligrams NaOH per gram = (mL of NaOH)(N)(40)
(grams of sample)
Where:
N = Normality of NaOH
4.5.2.3 Surface active ingredient. A 1.5-gram sample of disinfectant from pouch A
weighed out to the nearest mg shall be dispersed in a 250-mL volumetric flask containing
125 mL of distilled water. Mix well and fill to volume. Mix well again. Pipette a 25-mL aliquot
of sample into a 125-mL flask. Add 2.0 N sodium arsenite drop wise. Test one drop of solution
on starch iodine test paper until all blue disappears (available chlorine is removed). Record
number of drops required. Discard. To a 250-mL stoppered graduated cylinder add 25 mL of
methylene blue indicator, 25 mL chloroform, 25 mL of distilled water, and a 25-mL portion of
the sample taken from the original flask while agitating. Add predetermined volume of sodium
arsenite plus an excess of 1 or 2 drops as determined in the pretest. Titrate with standardized
hyamine 1622 solution (0.002 N). Shake vigorously after each addition. After the mixture has
separated, note color difference between the two layers. Using the degree of difference as a
guide, continue adding hyamine in successfully smaller increments, shaking the graduated
cylinder two times after each addition. When colors are close, add the hyamine in 0.05-mL
amounts until the end point.
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