Permeability of rubber to gases . ospheric pressure (760 mmof mercury) on one side of the fabric and the gas in question at anexcess pressiu-e of 30 mm of water on the other side. 1 J. D. Edwards, Determination of Permeability of Balloon Fabrics, B. S. Tech. Paper No. 113; 1918. 2 Phil. Mag., 82, p. 401; 1866. Edwards 1Pickeringi Permeability of Rubber to Gases1. METHODS 329 Most of the different types of apparatus available for the deter-mination of permeability have been described in TechnologicPaper No. 113, to which reference has been made. Certain otherapparatus developed recently will be
Permeability of rubber to gases . ospheric pressure (760 mmof mercury) on one side of the fabric and the gas in question at anexcess pressiu-e of 30 mm of water on the other side. 1 J. D. Edwards, Determination of Permeability of Balloon Fabrics, B. S. Tech. Paper No. 113; 1918. 2 Phil. Mag., 82, p. 401; 1866. Edwards 1Pickeringi Permeability of Rubber to Gases1. METHODS 329 Most of the different types of apparatus available for the deter-mination of permeability have been described in TechnologicPaper No. 113, to which reference has been made. Certain otherapparatus developed recently will be mentioned in connectionwith the experimental work. What may be called the standard apparatus of the Bureau ofStandards is shown in diagram in Fig. i. The rubber sample tobe tested is held in the permeabihty cell a, which is maintained ata constant temperature in an air or water bath h. The cell con-sists of two circular plates with a shallow chamber in each. Thetest piece is held between the flanges of the cell and separates the. Fig, I.—Standard apparatus for determining permeability of rubber to gases two chambers; it is supported by a series of crossed wires in theform of a screen. A constant concentration of the gas whosepermeability is to be measured is maintained in one gas which penetrates the exposed area of rubber passes intothe other chamber, from which it is continuously removed by astream of air or other gas and determined quantitatively. Because of the common use of hydrogen in balloons, the per-meability to hydrogen is the property most often determined inthe case of balloon fabrics. For this reason, and because of theaccuracy with which the permeability to hydrogen can be deter-mined, the permeability to any other gas will be referred to itspermeability to hydrogen as the standard of comparison. 330 Scientific Papers of the Bureau of Standards [ In determining the permeability to hydrogen a current of pm-e,dry hydrogen is passed over one side
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