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Rh,symbol for the element rhodiumrhodium
, metallic chemical element; symbol Rh; at. no. 45; at. wt. 102.90550; m.p. about 1,966°C;; b.p. 3,727±100°C;; sp. gr. 12.41 at 20°C;; valence +2, +3, +4, +5, or +6.
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1. Abbr. for relative humidity.
2. Abbr. for “right hand.”
3. Abbr. for “round head.”
Rockwell hardness number—the higher the number, the harder the material.A measure of the resistance of a material to indentation; determined by use of a machine which presses a steel ball or a spheroconical ball indentor into the material under arbitrarily fixed test conditions; expressed by the