Group IV.: C, Si, Ge, Zr, Th, tetravalent; Ti, tetravalent and hexavalent; Sn, Pb, divalent and tetravalent; Ce, trivalent and tetravalent.
Group VI.: 0, usually divalent, but tetravalent and possibly hexavalent in oxonium and other salts; S, Se, Te, di-, tetraand hexa-valent; Cr, di-, triand hexa-valent; Mo, W, di-, tri-, tetra-, pentaand hexa-valent.
Group VIII.: Fe, Co, divalent and trivalent; Ni, divalent; Os, Ru, hexavalent and octavalent; Pd, Pt, divalent and tetravalent; Ir, tri-, tetraand hexa-valent.
On heavy metals: lead, mercury, cadmium and hexavalent chromium will be banned from vehicle components by 1 January 2003.
hexavalent chromium will be banned from vehicle components by 1 January 2003.
hexavalent chromium compounds in a number of in vitro tests in bacteria.
hexavalent chrome which currently ends up in the foul sewer or in the exhaust from the stack.
hexavalent form of chromium (Cr 6+) is more toxic, it is not normally found in food.
The message was clear change from the carcinogenic hexavalent form to less hazardous trivalent form where possible or face increasing restrictions and controls.
For example, one study found hexavalent chromium in a product which is the toxic and carcinogenic form of the mineral.
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