【国外标准】 Standard Specification for Laboratory Glass Graduated Burets

This specification covers requirements for glass burets of precision and general-purpose grades suitable for laboratory use. Burets are classified as: class A - precision grade buret, and class B - general purpose burets. Burets shall be calibrated to deliver the intended volume at 20°C. No after-drainage period is allowed. Self-zeroing burets shall have an ungraduated, tapered, interior extension that terminates with an overflow orifice. Burets may be equipped with a filling tube. All burets shall have permanently attached stopcocks. The stopcock's handle shall be located to the right. Stopcock plugs shall be provided with a retaining device. 1.1 This specification covers requirements for glass burets of precision and general-purpose grades suitable for laboratory use. 1.1.1 Class A—Each buret of precision grade may be marked with the letter “A” to signify compliance with applicable construction and accuracy requirements in Table 1 and Table 2. Each buret may be marked with a permanent serial number at the option of the manufacturer. 1.1.2 Class B—General purpose burets are of the same basic design as Class A burets. However, volumetric tolerances for Class B burets shall be within twice the specified range allowed for Class A burets. These burets need not be marked with their class designation or serial number. See Table 1 and Table 3 for tolerances and dimensional requirements. Note 1: The Twelfth General (International) Conference on Weights and Measures redefined the litre as a “special name for the cubic decimetre,” but agreed to permit continuance of the terms litre, millilitre, and mL, except in association with measurements of the highest precision. For volumetric glassware the difference between the old and new meanings of litre is negligible. Therefore, either mL or cm3 may be marked on ware covered by this standard. 1.1.3 Product with a stated capacity not listed in this standard may be specified Class A Tolerance when product conforms to the tolerance range of the next smaller volumetric standard product listed in Table 1. 1.2 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.