ISO 649-1:1981

Laboratory glassware — Density hydrometers for general purposes — Part 1: Specification

The requirements for basic series and sub-series of glass hydrometers of constant mass without built-in thermometer are specified. They are graduated to indicate density at 20 degrees centigrade and 15 degrees centigrade, respectively. Standard categories of surface tension are tabled in annex A, recommended stem diameters in annex B.