BS EN ISO 9913-2 pdf free download

BS EN ISO 9913-2 pdf free download. Optics and optical instruments – Contact lenses – Part 2: Determination of oxygen permeability and transmissibility by the coulometric method.
3? Terms and definitions For the purposes of this part of ISO 991 3, the terms and definitions given in ISO 8320 apply, together with the following. 3.1 oxygen flux j net volume of oxygen gas passing through a unit area of sample contact lens material per unit time under specified conditions, including temperature, sample thickness, and partial pressures of oxygen on both sides of the sample NOTE? A convenient unit of oxygen flux for contact lens materials is ?l/(cm 2 ? s). In terms of measurement using the coulometric method, j is equal to the rate of oxygen flow past the coulometric oxygen sensor q V divided by the area of sample (A) through which the oxygen has passed. 3.2 oxygen permeability Dk oxygen flux (j) under specified conditions through contact lens material of unit thickness when subjected to unit pressure difference NOTE 1 ? Oxygen permeability is stated in traditional units of (cm 2 /s) ? [ml O 2 /(ml ? mmHg)], which is equivalent to (cm 3 O 2 ? cm)/(cm 2 ? s ? mmHg). The units are (cm 2 /s) ? [ml O 2 /(ml ? hPa)], or (cm 3 O 2 ? cm)/(cm 2 ? s ? hPa) when the hectopascal (hPa) is used instead of mmHg. To express Dk units in terms of hPa instead of mmHg, multiply Dk magnitudes using mmHg in the denominator by 0,750 06. To express Dk units in terms of mmHg instead of hectopascals, multiply Dk magnitudes using hectopascals in the denominator by 1 ,333 22. NOTE 2? In terms of measurement using the coulometric method, Dk is equal to the oxygen transmissibility (Dk/t) multiplied by the sample thickness (t). Oxygen permeability is a physical property of the material and is not a function of the shape or thickness of the material sample.3.3 oxygen transmissibility Dk/t oxygen permeability divided by the thickness (t), in centimetres, of the measured sample under specified conditions NOTE 1 ? Oxygen transmissibility is stated in traditional units of (cm/s) ? [ml O 2 /(ml ? mmHg)], which is equivalent to (cm 3 O 2 )/(cm 2 ? s ? mmHg). The units are (cm/s) ? [ml O 2 /(ml ? hPa)], or (cm 3 O 2 )/(cm 2 ? s ? hPa) when the hectopascal (hPa) is used instead of mmHg. To express Dk/t units in terms of hPa instead of mmHg, multiply Dk/t magnitudes using mmHg in the denominator by 0,750 06. To express Dk/t units in terms of mmHg instead of hectopascals, multiply Dk/t magnitudes using hectopascals in the denominator by 1 ,333 22. NOTE 2? In terms of measurement using the coulometric method, Dk/t is equal to the oxygen flux (j) divided by the difference in oxygen tension (partial pressure of oxygen) between atmospheres at the two exposed surfaces of the sample contact lens. Oxygen transmissibility is a property of the lens material and lens thickness; it depends on the design of the contact lens. 3.4 thickness t radial thickness within the central area of the test sample, as measured according to ISO 9339-1 , or the harmonic mean thickness of the area of test sample exposed to oxygen flow NOTE? To be consistent with other definitions and equations in this part of ISO 991 3, t should be expressed in centimetres (cm).BS EN ISO 9913-2 pdf download.