Packaging and storage—
Preserve in cylinders.
NOTES—The following tests are designed to reflect the quality of Carbon Dioxide in both its vapor and liquid phases, which are present in previously unopened cylinders. Reduce the container pressure by means of a regulator. Withdraw the specimens for the tests with the least possible release of Carbon Dioxide consistent with proper purging of the sampling apparatus. Measure the gases with a gas volume meter downstream from the detector tubes in order to minimize contamination or change of the specimens. Perform tests in the sequence in which they are listed.
The various detector tubes called for in the respective tests are listed under Reagent Specifications in the section Reagents, Indicators, and Solutions.
Identification—
Pass 100 ± 5 mL, released from the vapor phase of the contents of the container, through a carbon dioxide detector tube at the rate specified for the tube: the indicator change extends throughout the entire indicating range of the tube.
Water—
Flush the regulator that has been flushed with 5 L or more of the gas specimen. Pass 50 ± 5 L, released from the vapor phase, through a water vapor detector tube connected to the regulator with a minimum length of metal or polyethylene tubing. Measure the gas passing through the detector tube with a gas flowmeter set at a flow rate of 2 L per minute. The indicator change corresponds to not more than 150 mg per cubic meter.
Limit of ammonia—
Proceed with Carbon Dioxide as directed in the test for
Nitrogen dioxide, except to pass 1050 ± 50 mL of this gas through an ammonia detector tube at the rate specified for the tube: the indicator change corresponds to not more than 0.0025%.
Limit of hydrogen sulfide—
Pass 1050 ± 50 mL, released from the vapor phase, through a hydrogen sulfide detector tube at the rate specified for the tube: the indicator change corresponds to not more than 1 ppm.
Limit of nitric oxide—
Pass 550 ± 50 mL, released from the vapor phase, through a nitric oxide-nitrogen dioxide detector tube at the rate specified for the tube: the indicator change corresponds to not more than 2.5 ppm.
Carbon monoxide—
Pass 1050 ± 50 mL, released from the vapor phase of the contents of the container, through a carbon monoxide detector tube at the rate specified for the tube: the indicator change corresponds to not more than 0.001%.
Nitrogen dioxide—
Arrange the container so that when its valve is opened, a portion of the liquid phase of the contents is released through a piece of tubing of sufficient length to allow all of the liquid to vaporize during passage through it, and to prevent frost from reaching the inlet of the detector tube. Release into the tubing a flow of liquid sufficient to provide 550 mL of the vaporized specimen plus any excess necessary to assure adequate flushing of air from the system. Pass 550 ± 50 mL of this gas through a nitric oxide-nitrogen dioxide detector tube at the rate specified for the tube: the indicator change corresponds to not more than 2.5 ppm.
Sulfur dioxide—
Proceed with Carbon Dioxide as directed in the test for
Nitrogen dioxide, except to pass 1050 ± 50 mL through a sulfur dioxide detector tube at the rate specified for the tube: the indicator change corresponds to not more than 5 ppm.
Assay—
[NOTE—Sampling for this assay may be done from the vapor phase for convenience, but this results in more residual volume. If the specification of 1 mL is exceeded from the vapor phase, a liquid specimen may be taken.
] Assemble a 100-mL gas buret provided with a leveling bulb and two-way stopcock to a gas absorption pipet of suitable capacity by connecting the pipet to one of the buret outlets. Fill the buret with slightly acidified water (turned pink with methyl orange), and fill the pipet with potassium hydroxide solution (1 in 2). By manipulation of the leveling bulb and leveling water, draw the potassium hydroxide solution to fill the pipet and capillary connection up to the stopcock, and then fill the buret with the leveling water and draw it through the other stopcock opening in such a manner that all gas bubbles are eliminated from the system. Draw into the buret 100.0 mL of specimen taken from the liquid phase as directed in the test for
Nitrogen dioxide. By raising the leveling bottle, force the measured specimen into the pipet. The absorption may be facilitated by rocking the pipet or by flowing the specimen between pipet and buret. Draw any residual gas into the buret, and measure its volume: not more than 1.0 mL of gas remains.
