Molybdenum concentrations

About 50% of copper in food is absorbed, usually under equitibrium conditions, and stored in the tiver and muscles. Excretion is mainly via the bile, and only a few percent of the absorbed amount is found in urine. The excretion of copper from the human body is influenced by molybdenum. A low molybdenum concentration in the diet causes a low excretion of copper, and a high intake results in a considerable increase in copper excretion (68). This copper—molybdenum relationship appears to correlate with copper deficiency symptoms in cattle. It has been suggested that, at the pH of the intestine, copper and molybdate ions react to form biologically unavailable copper molybdate (69). 

The Mo/Al ratio measured by XPS always decreased upon sulfiding. Bulk analysis showed no change in molybdenum concentration upon sulfiding, indicating that no molybdenum was lost during sulfiding. 

Kuroda and Tarui [498] developed a spectrophotometric method for molybdenum based on the fact that MoVI catalyses the reduction of ferric iron by divalent tin ions. The plot of initial reaction rate constant versus molybdenum concentration is rectilinear in the range 0.01-0.3 mg/1 molybdenum. Several elements interfere, namely, titanium, rhenium, palladium, platinum, gold, arsenic, selenium, and tellurium. 

The molybdenum concentration in the reference sample is rather high and a direct determination using the cookbook conditions [710] is very straightforward. There is no difference between peak area and peak height evaluation. In spite of 1800 °C for thermal pretreatment, a small background absorption signal is present. 

Molybdenum concentrations in field collections of selected species of animals and plants... 

Table 30.1 Molybdenum Concentrations in Selected Nonbiological Materials ... 

Table 30.2 Molybdenum Concentrations in Field Collections of Selected Species of Animals and Plants (Values shown are in mg Mo/kg [ppm Mo] fresh weight [FW], dry weight [DW], or ash weight [AW].)... 

Proposed criteria for human health protection include drinking water concentrations less than 50 pg Mo/L, and daily dietary intakes less than 7 pg Mo/kg food — based on a 70-kg adult (Table 30.5). Molybdenum concentrations in blood of healthy people averaged 14.7 pg Mo/L, distributed between the plasma and erythrocytes. Anemic people had significantly lower blood molybdenum levels. In leukemia patients, molybdenum levels increased significantly in whole blood and erythrocytes but not in plasma (Shamberger 1979). Additional work is recommended on the use of blood in fish and wildlife as an indicator of molybdenum stress and metabolism (Eisler 1989). 

Osman, N.H.I. and A.R. Sykes. 1989. Comparative effects of dietary molybdenum concentration on distribution of copper in plasma in sheep and red deer (Cervus elaphus). Proc. N.Z. Soc. Anim. Product. 49 15-19. 

Suttle, N.F. 1983a. Effects of molybdenum concentration in fresh herbage, hay and semi-purified diets on the copper metabolism of sheep. Jour. Agric. Sci. (Cambridge) 100 651-656. 

Ward, J.V. 1973. Molybdenum concentrations in tissues of rainbow trout (Salmo gairdneri) and kokanee salmon (Oncorhynchus nerka) from waters differing widely in molybdenum content. Jour. Fish. Res. Board Canada 30 841-842. 

Molybdenum(O) compounds, 17 28-29 Molybdenum(II) compounds, 17 27-28 Molybdenum(IV) compounds, 17 25-26 Molybdenum(V) compounds, 17 23-25 Molybdenum(VI) compounds, 17 20-23 Molybdenum concentrate price, annual average, 17 121... 

In an equilibrium study of the adsorption of molybdenum(VI) from aqueous solution onto activated carbon it has been found that the data are best explained in terms of an absorption model comprising the three species [HMo207] , Mo03(H20)3, and [HMo04] of which the dimer predominates by far (80). Computer treatment of potentiomet-ric (81) and spectrophotometric data (82) also indicated the possible existence of [HMo207] as a minor species in aqueous solution at low molybdenum concentration ( 2 X 104 Af). However, as its assumed stability region overlaps with several other polynuclear ions more direct evidence is needed before its existence can be accepted with certainty. 

Peters (5) Has reviewed the leaching of copper, nickel, zinc, lead and molybdenum concentrates in terms of the thermodynamic stability of the sulfide minerals of these metals. Process developments associated with the most favorable decomposition paths are considered. 

Platinum electrodes were cleaned with the same procedure. Then sodiiun molybdenum oxide (Johnson Matthey, 99.998%) was added to obtain 0.01 M molybdenum concentration. Then the potential was held at 50 mV for 10 s. Then the electrode was rinseed with hydrogen saturated water and transferred to the measurement cell. The potential was set to 50 mV immediately after the transfer. 

Evaluation of the soil profile results indicates that there is a strong partitioning of copper and molybdenum into the nearsurface soil horizon. Copper and molybdenum concentrations are significantly greater in the near-surface (0 to 30 cm) B horizon soils than in the deeper C horizon soils (Fig. 1). More work is required to determine the reason for the preferential partitioning of metals into the B horizon. 

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