Chromium, nickel and cobalt contents of some Australian cements

The total chromium, nickel and cobalt concentrations of 8 Australian Portland cements ranged from 49 to 99 micrograms/g, 5 to 54 micrograms/g and < or = 1 to 13 micrograms/g, respectively. The water-soluble chromate concentrations of the cements ranged from 0.2 to 8.1 micrograms/g, and the sodium sulphate-extractable chromates from 1.4 to 9.7 micrograms/g. Results for water-soluble nickel (< or = 0.2 microgram/g) and cobalt (< or = 0.05 microgram/g) indicate that the metals are present only as water-insoluble compounds. The significance of the various data is considered from a dermatological point of view. Cement extracts for the analysis of water-soluble hexavalent chromium (chromates) are stable for at least 12 days. The optimum extraction time for hexavalent chromium in cement appears to be 1 h. Almost 100% reduction of hexavalent chromium is possible after 1 h using 100x the stoichiometric value of iron (II) sulphate. The chromates can become gradually insolubilized when the solution from the water added is in direct contact with the cement, i.e., over a period of > 60 min to 7 days, even without the addition of iron (II) sulphate.