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|  MIL-E-19141D
(c) Oxygen drying train: This consists of a pressure reducing valve
on the oxygen supply, a needle valve and oxygen flow meter to
regulate the flow meter to regulate the flow of oxygen, a wash
bottle containing concentrated sulfuric acid (96 percent), a
spray trap and a drying tower filled with anhydrous magnesium
perchlorate.
(d) Combustion tube: A fused silica combustion tube, open at both
ends, with a devitrification point above 2000F shall be used.
About 6 inches of the tube shall project from either side of the
furnace. A plug of fine glass wool is inserted into the outlet
end of the combustion tube to filter the gases. It shall be
inserted far enough into the tube so that-it is heated 400 to
(e) Water absorption train: The water driven from the sample is col-
lected in a U-tube absorber (Schwartz) filled with anhydrous mag-
nesium perchlorate. A gas-sealing bottle containing concentrated
sulfuric acid (96 percent) is attached to the outlet end of the
moisture U-tube absorber.
3.
Temperature.
A temperature of
shall be maintained within the combustion tube
for the determination.
4.
Preparation and handling of sample.
The sample shall be a composite of the coatings from the middle portions
of three electrodes. It should be immediately transferred to a dried,
stoppered vial or sample bottle. The sample size used in each deter-
mination shall be approximately 4 grams; it shall be weighed directly
on the balance dish and transferred to the boat with forceps, weighing
the sample to the nearest 0.001 gram.
5.
Handling of combustion boat and absorption tube.
The ignited nickel boat after removal from the combustion tube shall be
transferred to a Pyrex desiccator containing anhydrous magnesium perchlo-
rate as a desiccant. The absorption tube shall be handled with lint-free
gauze at all times and shall be stored in the balance case during the
cooling period, so that it assumes the temperature of the atmosphere in
which it is to be weighed.
Dessicants.
6.
The anhydrous magnesium perchlorate and sulfuric acid shall be renewed often
enough to ensure the best performance. In the case of the absorption tube
this can be estimated roughly since it is known that anhydrous magnesium
perchlorate will absorb at least 16 percent of its weight in water, without
any noticeable loss in drying ability.
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