Specifies long, medium and short hydrometers in five series for measuring and indicating the density of liquids in kilograms per cubic metre. It also specifies two special purpose hydrometers for use mainly in petroleum technology. Appendices cover the procedure for determination of density by means of a hydrometer, notes on the design of hydrometers, the measurement of liquids in bulk, and vessels for hydrometric observations. It does not apply to hydrometers for measuring the density of LP gas or the acid in lead-acid accumulators.