» Butane contains not less than 97.0 percent of n-butane (C4H10).
[CautionButane is highly flammable and explosive. ]
Packaging and storage Preserve in tight cylinders, and prevent exposure to excessive heat.
A: The IR absorption spectrum of it exhibits maxima, among others, at about the following wavelengths, in µm: 3.4 (vs), 6.8 (s), 7.2 (m), and 10.4 (m).
B: The vapor pressure of a test specimen, obtained as directed in the General Sampling Procedure under Propellants (see Aerosols, Nasal Sprays, Metered-Dose Inhalers, and Dry Powder Inhalers 601), determined at 21 by means of a suitable pressure gauge, is between 205 and 235 kPa absolute (30 and 34 psia).
Water: not more than 0.001%, determined as directed for Water Content under Aerosols, Nasal Sprays, Metered-Dose Inhalers, and Dry Powder Inhalers 601.
High-boiling residues: not more than 5 µg per mL, determined as directed for High-Boiling Residues, Method II, under Aerosols, Nasal Sprays, Metered-Dose Inhalers, and Dry Powder Inhalers 601.
Acidity of residue Add 10 mL of water to the residue obtained in the test for High-boiling residues, mix by swirling for about 30 seconds, add 2 drops of methyl orange TS, insert the stopper in the tube, and shake vigorously: no pink or red color appears in the aqueous layer.
Limit of sulfur compounds Carefully open the container valve to produce a moderate flow of gas. Do not direct the gas stream toward the face, but deflect a portion of the stream toward the nose: the odor is free from the characteristic odor of sulfur compounds.
Chromatographic system Under typical conditions, the gas chromatograph is equipped with a thermal-conductivity detector and contains a 3-mm × 6-m aluminum column packed with 10 weight percent of liquid phase G30 on nonacid-washed support S1C, helium is used as the carrier gas at a flow rate of 50 mL per minute, and the temperature of the column is maintained at 33.
System suitability The peak responses obtained for n-butane in the chromatograms from duplicate determinations agree within 1%.
Procedure Connect 1 Butane cylinder to the chromatograph through a suitable sampling valve and a flow control valve downstream from the sampling valve. Flush the liquid specimen through the sampling valve, taking care to avoid entrapment of gas or air in the sampling valve. Inject a suitable volume, typically 2 µL, of Butane into the chromatograph, and record the chromatogram. Calculate the percentage purity by dividing 100 times the n-butane response by the sum of all of the responses in the chromatogram.