Specific gravity balance (specific gravity scale)

Japanese: 比重てんびん(比重天秤) - ひじゅうてんびん（英語表記）specific gravity balance

A balance used to measure the buoyancy of a solid in liquid and determine the specific gravity of the solid or liquid. Measurements can be easily made by attaching a hook for hanging a solid to a normal balance (Figure). When a solid with mass M _s and specific gravity d _s is hung in a liquid of specific gravity d _l and weighed, the result is M _s (1 - d _l / d _s ). M _s is known, and when either d _l or d _s is known, the other can be determined. In the case of a solid, the sample is weighed in air as W , then hung in a liquid of specific gravity d _l on a thin suspension wire w and weighed as W _l . Knowing the specific gravity ρ of the air being measured and correcting for air buoyancy, the specific gravity d _s is then given as:

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

液体中にある固体の浮力を測定し，固体，液体の比重を知るためのてんびん。通常のてんびんに固体をつるすためのかぎをつければ容易に測定できる(図)。質量M_s，比重d_sの固体を比重d_lの液体中につって秤量するとM_s(1－d_l/d_s)となる。M_sは既知であり，d_lかd_sの一方が知られているとき他方がわかる。固体の場合，試料を空気中でWと秤量し，次に細いつり線wで比重d_lの液体中につり，W_lと秤量し，測定中の空気の比重ρを知り，空気浮力の補正を施せば，比重d_sは，となる。

出典　株式会社平凡社世界大百科事典第２版について　情報

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