Method of and apparatus for the analysis of gases
First Claim
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1. A method of analyzing a gas comprising the steps of:
- (a) feeding the gas to be analyzed into a first zone of known volume and permitting the gas in said zone to escape in a Knudsen flow through a first cross section into a second zone at a predetermined pressure;
(b) permitting the gas flow into and from the first zone in step (a) to reach a first steady state;
(c) measuring a parameter of the gas in said first zone at said first steady state;
(d) spontaneously changing the flow cross section through which said gas escapes from said first zone upon attainment of said first steady state and permitting the gas flow into said first zone and through the changed cross section to reach a second steady state;
(e) measuring said parameter of the gas at said second steady state; and
(f) deriving from said measurements values of the difference between the measurements at said steady states and the gradient of the measured value upon the spontaneous change in the cross section, the molecular weight of the gas and the mean molecular velocity thereof being functions of said difference and gradient.
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Abstract
The mean molecular velocity or molecular weight of an unknown gas is determined by admitting the gas at a constant flow rate into an evacuated chamber of known volume, the gas being permitted to escape through a first flow cross section in a Knudsen flow. After a first steady state is reached, the gas density is measured and then a second flow cross section is opened between the evacuated chamber and a low-pressure zone. The measurement is repeated and the difference between the two values obtained and the gradient of the measurement is used to calculate the mean molecular velocity and the molecular weight.
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Citations
23 Claims
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1. A method of analyzing a gas comprising the steps of:
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(a) feeding the gas to be analyzed into a first zone of known volume and permitting the gas in said zone to escape in a Knudsen flow through a first cross section into a second zone at a predetermined pressure; (b) permitting the gas flow into and from the first zone in step (a) to reach a first steady state; (c) measuring a parameter of the gas in said first zone at said first steady state; (d) spontaneously changing the flow cross section through which said gas escapes from said first zone upon attainment of said first steady state and permitting the gas flow into said first zone and through the changed cross section to reach a second steady state; (e) measuring said parameter of the gas at said second steady state; and (f) deriving from said measurements values of the difference between the measurements at said steady states and the gradient of the measured value upon the spontaneous change in the cross section, the molecular weight of the gas and the mean molecular velocity thereof being functions of said difference and gradient. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An apparatus for analyzing a gas, comprising:
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a vacuum chamber having a defined volume; means for feeding said chamber with a gas to be analyzed at a constant flow rate; means for evacuating said chamber; valve means defining a first flow cross section and a second flow cross section and connecting same selectively between said evacuating means and said chamber whereby a first Knudsen flow is established through at least one of said cross sections and the other cross section is selectively openable and closable to change the Knudsen cross-section at which gas escapes from said chamber; and a sensor for gas density in said chamber. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification