MIL-DTL-248D
4.4.2 Determination of solidification point. The solidification point shall be determined
in accordance with Method 210.1 of MIL-STD-650 except that a National Bureau of Standard
Thermometer with a range of 79-82 degrees Centigrade shall be used. (See Figure 1).
4.4.3 Moisture. The moisture shall be determined in accordance with MIL-STD-650,
Method 101.4.
4.4.4 Acidity. Transfer an accurately weighed portion of 10.0 grams of sample to 250
mL glass-stoppered iodine flask or equivalent. Add 40 ml methylene chloride from a graduated
cylinder to the sample and also to an empty flask which will serve as a blank. Stopper the flask.
Swirl the sample flask until dissolution is complete. Put 0.75 ml (approx. 20 drops) of
bromothymol blue indicator in a 100 ml graduated cylinder and dilute to the mark with CO2 -
free distilled water. Stopper the flask containing the CO2 - free water. Transfer the 100 ml of
water containing the indicator to the blank flask and replace stopper. Repeat this procedure with
the sample flask. Swirl both sample and blank flasks vigorously for 10-20 seconds to ensure
interaction of methylene chloride and water layers.
NOTE: Too vigorous swirling or shaking must be avoided or an emulsion will be produced
which may take hours to disperse.
Titrate the blank solution first. If the lower (aqueous) layer is blue, add a measured amount of
0.01 N H2SO4 dropwise until it turns green or yellow and add an equal amount to the sample. If
the solution is green or yellow at the start, begin to titrate with 0.01 N NaOH. Add the NaOH
dropwise, stoppering the flask after each addition and swirling vigorously for 5-10 seconds (see
note above). The end point is taken as a blue color which persists for 2 minutes after the
methylene chloride and water ha ve separated into distinct layers and which persists after one
additional 5-10 second swirling.
NOTE: The blue color may fade somewhat or acquire a trace of green coloring after the final
swirl but this is acceptable.
The sample is now titrated in a manner similar to that of the blank titration. The end point is a
persistent blue color as described in the blank determination but care must be taken to look
through the aqueous layer horizontally against a white or colorless background since transmitted
or reflected light from the yellow methylene chloride solution will cause a green coloration. In
addition, incomplete separation of methylene chloride and water may result in a cloudiness
which may also impart a slight green cast to the aqueous layer.
Experience with the method should allow a determination of the end point to within ± 0.05 ml
NAOH.
Where:
A = ml NaOH for sample
B = ml NaOH for blank
N = Normality of NaOH
W= Sample wt., grams
14
For Parts Inquires submit RFQ to Parts Hangar, Inc.
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business