MIL-DTL-38741A
b. Attach a septum to the cylinder and chill the base of the cylinder in liquid nitrogen for 15
minutes. Do not purge the cylinder when attaching the septum as this would alter the relationship
between the bromochlorodifluoromethane and the contaminants. Instead, the small amount of air
behind the septum is permitted to enter the standard when the valve is opened.
c. After verifying that the septum is still attached securely, open the valve. Keep the cylinder
in liquid nitrogen.
d. Using appropriately sized syringes, individually and in turn add the gaseous contaminants
listed in table III in the amount indicated. The indicated vapor densities are based on a laboratory
temperature of 20.0 °C and a barometric pressure of 100.0 kPa. These data must be adjusted to
reflect actual laboratory conditions.
e. Using an appropriately sized syringe, add the liquid contaminant listed in table III in the
amount indicated. For best accuracy, this contaminant and its syringe should be pre-chilled in a
freezer (approximately -20 °C) and promptly transferred. The indicated liquid density is based on
available manufacturer data and is approximate due to the absence of practical temperature
control.
TABLE III. Calibration standard impurities.
Vapor
Volume
mg
mg/kg
Total mg/kg
Present3
1
2
Component
Density,
Added,
Added
Added
mg/mL
mL
HFC-23
2.895
3.9
11.3
CFC-13
4.331
2.6
11.3
HCFC-22
3.606
3.2
11.5
Halon 1301
6.288
1.8
11.3
Halon 1201
5.355
2.1
11.2
CFC-12
5.077
2.2
11.2
Liquid
Volume
mg
mg/kg
Total mg/kg
Added1
Added2
Present3
Component
Density,
Added,
mg/µL
µL
Halon 1202
2.463
4.6
11.3
1
If necessary, correct mg added for the purity of the calibration component.
2
Values are determined during preparation of standard.
3
Column to be filled in, (see 4.4.1.5), after determining ppm present in stock components
(see 6.3).
f. Close the valve and allow the calibration standard cylinder to return to ambient
temperature. Set the cylinder aside for a minimum of 12 hours to allow all the cylinder's contents
to equilibrate.
4.4.1.5 Calibration standard analysis.
5
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