Abstract
Water is conventionally and widely used as a reference standard to measure physical quantities such as the density, volume, internal volume, and concentration. Water is also used as a standard for other physical properties such as the specific heat and surface tension. However, water density is influenced depending on its isotopic composition and content of dissolved gases. Researches on density measurement using solid material with stable density such as silicon single-crystals were therefore started in the 1970s. Demands have been raised from industry for densimetric technology to improve reliability of product and to maintain traceability of measurement. With this background, AIST established a new density standard using silicon single-crystals. Shifting the density standard from liquid to solid will not only improve the accuracy but also promotes development of new material evaluation technology for thin films as well as metrological standard technology for next generation.
