JIS B 7525:1997

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This Japanese Industrial Standard specifies requirements for five basic series of glass hydrometers of constant mass which are graduated to indicate density (kg/m*3 or g/cm*3) at 20 degrees C. Each series comprises hydrometers which between them cover the interval 600 kg/m*3 to 2000 kg/m*3 or 0.6 g/cm*3 to 2.0 g/cm*3. The hydrometers are graduated appropriately for use in liquids of low, medium or high surface tension. It also specifies three sub-series of hydrometers which are graduated to indicate density at either 20 degree C or 15 degree C. These hydrometers having smaller tolerances on scale error are limited to the range 600 kg/m*3 to 1100 kg/m*3 or 0.6 g/cm*3 to 1.1 g/cm*3 and are for use in liquids of low surface tension. This Standard does not cover hydrometers with a built-in thermometer. These hydrometers comply with the requirements of ISO 387. A table of standard categories of surface tension is given in Annex 1. A table of recommended stem diameters is given, for guidance in manufacture, in Annex 2. In addition to five series and three sub-series, Annex 3 describes J series. Further, the requirements for specific gravity hydrometers as specified in former Standard is given in Table 4. Examples of shape of density hydrometer are shown in Fig.1.