MIL-PRF-25369D
6.8.1 Accelerated gravimetric method. Determine the increase in weight of phosphorus
pentoxide (P2O5) when subjected to a flow of a measured volume of carbon dioxide as follows:
Connect the carbon dioxide container to the test apparatus by means of a length of bent, seamless,
stainless-steel tubing, a high-pressure union, a needle valve, and a glass-to-metal joint. Rubber
connections are not acceptable; however, a sleeve joint secured with TygonTM or equivalent is
acceptable. Connect a mercury safety valve between the low-pressure outlet of the needle valve
and the first absorber. Use steel tubing of a fabrication that will have a capability of first passing
through a water bath at room temperature and then into a second bath at a temperature above the
critical temperature of liquid carbon dioxide. Use an apparatus consisting of three U-tube
absorbers in a series, each 4 inches high and 1/2 inch in diameter, containing P2O5 on glass wool,
and connected through a water-saturator to a calibrated wet test meter of 1/20-cubic-foot size
equipped with a 1-liter dial. Flush the needle valve connecting the container to the absorber with
carbon dioxide so that only gas discharged from the container will pass through the absorber.
Bring the absorbers to constant weight in a stream of dry carbon dioxide before weighing, so that
when the absorbers are weighed they will be at all times filled with carbon dioxide. Before each
weighing of the absorbers, open the absorbers momentarily to the air, and then close, clean, and
expose to radiation from a quartz mercury arc for 2 minutes to remove static charges. Discharge
100 liters through the apparatus at a rate not to exceed 0.4 liter per minute. Calculate the gas
volume corresponding to the gain in weight to 760 mm of mercury and 70 ºF. Compute the
moisture content in terms of milligrams per liter.
6.9
Changes from previous issue. Marginal notations are not used in this revision to identify
changes with respect to the previous issue due to the extent of the changes.
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