scope:

This part of ISO 649 specifies requirements for five basic series of g lass hydrometers of constant mass which are graduated to indicate density (kg/m or g/m3 ) at 20 ° C. Each series comprises hydrometers which between them cover the interval 600 to 2000 kg/m3 or 0,6 to 2,0 g/ml. The hy drometers are graduted 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 densily at either 20° C or 15 ° C. These hydrometers have smaller tolerances on scale error, are limited to the range 600 to 1100 kg/m3 or 0,6 to 1,1 g/ml and are for use in liquids of low surface tension.