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vermilion

(Encyclopedia)vermilion, vivid red pigment of durable quality. It is a chemical compound of mercury and sulfur and is known as red sulfide of mercury; it was formerly obtained by grinding pure cinnabar but is now c...

hafnium

(Encyclopedia)hafnium hăfˈnēəm [key], metallic chemical element; symbol Hf; at. no. 72; at. wt. 178.49; m.p. about 2,227℃; b.p. 4,602℃; sp. gr. 13.31 at 20℃; valence +4. Hafnium is a lustrous, ductile, si...

neptunium

(Encyclopedia)neptunium nĕpto͞oˈnēəm [key], radioactive chemical element; symbol Np; at. no. 93; mass number of most stable isotope 237; m.p. about 640℃; b.p. 3,902℃ (estimated); sp. gr. 20.25 at 20℃; va...

formula weight

(Encyclopedia)formula weight, in chemistry, a quantity computed by multiplying the atomic weight (in atomic mass units) of each element in a formula by the number of atoms of that element present in the formula, an...

periodic law

(Encyclopedia)periodic law, statement of a periodic recurrence of chemical and physical properties of the elements when the elements are arranged in order of increasing atomic number. Such an arrangement in the for...

combining weight

(Encyclopedia)combining weight, the proportion (by weight) in which a chemical element combines with other elements to form compounds. The determination of combining weights was a very important part of early chemi...

tantalum

(Encyclopedia)tantalum tănˈtələm [key] [from Tantalus], metallic chemical element; symbol Ta; at. no. 73; at. wt. 180.94788; m.p. 2,996℃; b.p. 5,400±100℃; sp. gr. 16.65 at 20℃; valence +2, +3, +4, or +5....

nobelium

(Encyclopedia)nobelium nōbēˈlēəm [key], artificially produced radioactive chemical element; symbol No; at. no. 102; mass no. of most stable isotope 259; m.p. 827℃; b.p. and density unknown; valence +2, +3. I...

fermium

(Encyclopedia)fermium fûrˈmēəm [key] [for Enrico Fermi], artificially produced radioactive chemical element; symbol Fm; at. no. 100; mass no. of most stable isotope 257; m.p. 1,527℃; b.p. and sp. gr. unknown;...

rhenium

(Encyclopedia)rhenium rēˈnēəm [key], metallic chemical element; symbol Re; at. no. 75; at. wt. 186.207; m.p. about 3,180℃; b.p. about 5,625℃; sp. gr. 21.02 at 20℃; valence −1, +2, +3, +4, +5, +6, or +7....