1.1 This specification covers glass hydrometers of various scale graduation systems, as required by the ASTM Test Methods in which they are used. 1.2 This standard does not purpor This specification covers glass hydrometers of various scale graduation systems, as required by the ASTM test methods in which they are used. Hydrometers shall be of the constant-mass, variable-displacement type. Hydrometers shall be made of glass, exc