ISO/TC 48/SC 4 - Density measuring instruments

This International Standard specifies requirements for a series of pyknometers for general laboratory use for the determination of the densities of liquids. Specialized pyknometers for use with particular products, or otherwise not in common use, are excluded. Sufficient details to define such pyknometers should be included in International Standards which specify or describe their use. A device suitable for adjustment of the liquid level in the neck of the Reischauer pyknometer is shown in annex A.

Glass hydrometers of constant mass which do not incorporate a thermometer are considered. Basis of scale, reference temperature, surface tension and reference levels for adjustment and reading are specified. In annex A the standard categories of surface tension are tabled, and annex B deals with the adoption of density as preferred basis of scale.

The requirements specify the instruments with an incorporated thermometer for determination the alcohol content by mass or the alcohol concentration by volume of mixture of water and alcohol. Construction, materials and scale are described. The dimensions are tabled and the values of the alcohol mass content and the alcohol concentration by density and surface tension are given in a second table.

The determination of the density is specified considering the general procedures. Apparatus and readings of the density and temperature are described and also the application of the corrections. In drawings the construction and the demensions of suitable vessels are shown.

The requirements for basic series and sub-series of glass hydrometers of constant mass without built-in thermometer are specified. They are graduated to indicate density at 20 degrees centigrade and 15 degrees centigrade, respectively. Standard categories of surface tension are tabled in annex A, recommended stem diameters in annex B.

The requirements for five series of glass hydrometers concern reference levels for adjustment and reading, materials, dimensions, form, scale and handling. The annexes deal with standard surface tensions, stem diameters and meniscus corrections.

A single conventional value is specified and it is stated how the indication of hydrometer having a thermal cubic expansion coefficient value may be corrected for use in measurement tables in the construction of which the conventional value has been used.