World Health Organization Discontinues Its Drinking-Water Guideline for Manganese

Background: The World Health Organization (WHO) released the fourth edition of Guidelines for Drinking-Water Quality in July 2011. In this edition, the 400-µg/L drinking-water guideline for manganese (Mn) was discontinued with the assertion that because “this health-based value is well above concentrations of manganese normally found in drinking water, it is not considered necessary to derive a formal guideline value.

Intermediate phases and products of thermal decomposition of the compound Tl₂Pb[Cu(NO₂)₆]

The stoichiometry of the thermal decomposition of the compound Tl2Pb[Cu(NO2)6] has been studied. It is shown that the composition of the intermediate phases depends on the atmosphere in the reaction space, the composition of the intermediate phases being different when the decomposition is carried out in nitrogen or in air. As intermediate phases produced during decomposition under a nitrogen atmosphere, Cu2O and Pb(NO3)2 were formed at 280-degrees-C. At the same temperature in an air atmosphere there were identified TlNO3, Pb6O5(NO3)2 and Tl5.1PbO9.15 as intermediates. Further heating of this system led to the subsequent crystallization of Tl2O3, CuO and, probably, Tl6Pb2O5 (520-degrees-C). As the final product of the decomposition a mixture of CuO, Tl2O and PbO was identified