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APHA
SMWW 3500-Cr
Chromium
2023
5
Standard methods for the examination of water and wastewater (543.3 APHA 24th ed. Ref. Treatises&monographs FL2)
Chromium (Cr) is the first element in Group VIB in the periodic table. It has an atomic number of 24, an atomic weight of 51.99, and valences of 0 and 2 through 6. The average abundance of Cr in the earth’s crust is 122 ppm; in soils Cr ranges from 11 to 22 ppm; in streams it averages about 1 μg/L, and in groundwaters it is generally 100 μg/L. Chromium is found chiefly in chrome-iron ore (FeO · Cr2O3). Chromium is used in alloys, in electroplating, and in pigments. Chromate compounds frequently are added to cooling water for corrosion control...