There will be no abrupt changes in the cross section of the hydrometer, that will hinder cleaning or drying or permit air bubble to be trapped. The graduation of hydrometer will be on the basis of liquid having a surface tension of 55 dynes/cm. The graduation lines will be at intervals of 0.0005, every alternate line will extend beyond the shortest lines; every tenth graduation will exceed that of all the intervening lines and will be numbered in full. The basis of the scale will be density (g/ml) at 27' deg C. The maximum permissible scale error on the hydrometer is plus or minus one scale division.

Hydrometer Jar (IS 2720, Part-IV, 1985, section 5.2.1.2)

It will be transparent glass with uniform thickness and base size. It will have a mark of 1000 ml capacity with 7 cm dia at a height of 330 mm_+5 mm. Over all height of the cylinder will be about 400 mm without spout