Minerals, lead concentrations

Silver oxide lead ores have much different flotation processing characteristics. Although this ore responds to sulphidization-xanthate system, silver recovery in the lead concentrate was usually poor and amounted to about 30 40%. Floatability of lead minerals also was not satisfactory. 

If the low rade ore is a zinc mineral, then zinc concentrate obtained from the flotation process is calcined and leached with water to remove zinc. Silver and lead are left in leach residues. Residues are treated like lead concentrates and fed into lead smelters. Silver is recovered from this lead concentrate by various processes described above. 

Since 1960, it has been demonstrated by various analytical procedures that high concentrations of arsenic were present in Napoleon s hair.88 Multi-element analysis of two specimens of Napoleon s hair by ICP-MS after mineralization in concentrated nitric acid resulted in arsenic concentrations (42.1 and 37.4(xgg-1) about 40 times higher than normal values, confirming the hypothesis of a significant exposure to arsenic. However, mercury (3.3. and 4.7(xgg 1), antimony (2.1 and 1.8(xgg 1) and lead (229 and 112p,gg-1) were also detected at elevated levels. The elevated concentrations of Sb and Hg are in agreement with the data already known about the therapeutic treatments given to Napoleon (calomel and tartar emetic are compounds of mercury and antimony, respectively).88... 

Lead can be found almost exclusively in the easily-reducible and in the residual fraction (Fig. 8-11). Its main binding forms are obviously the adsorption on iron and manganese hydroxides and mineral binding. The large increase in the lead concentration from Elsterberg to Greiz is not characterized by an increase of an individual binding form. 

Lead has been also determined in wine, other beverages, and fruit slurries by a simple and rapid FIA-HG-AAS method based on the generation of PbH4 in an HN03-H202 medium [65], Lead was analyzed directly in wine samples without mineralization or preconcentration, and results were compared with those obtained by ET-AAS. The employed coupling enabled these authors to reach a characteristic mass of 0.8 ng Pb from 100 p,L injections. Lead concentrations of 59 + 1 ig L1 (FIA-HG-AAS) and 58 + 1 p,g 1 1 (ET-AAS) were reported in red wine. 

As discussed previously in this chapter, there are spots where the lead content (and the elementary composition) is higher and so-called lead enrichments are formed. Table 2.15 shows that the composition of lead enrichments can be rather different in different enrichments. Besides the increase in lead concentration, other changes in elementary composition may also occur. There are examples of lead enrichment (Figure 2.27 Sample 3 in Table 4) where the average composition remains unchanged even though the lead concentration is elevated. However, there are lead enrichments where the increase in lead concentration is accompanied by a simultaneous increase in iron (Sample 4 in Table 2.15), or a simultaneous increase of calcium and lead (Sample 2). Lead enrichment in these cases is likely due to lead coprecipitation reactions with other minerals (iron oxide and other calcium silicate phases) that were present in the sample. 

According to William Walsh of the Health Research Institute (HRI) in suburban Chicago, Beethoven s hair showed a lead concentration 100 times the normal levels. The scientists concluded that Beethoven s exposure to lead came as an adult, possibly from the mineral water he drank and swam in when he visited spas. 

The calculated weathering release of lead at HBEF is negative (- 174 g/ha/year). This pattern is likely due to changes in mineral soil lead pools over the study period. There has been marked decline in lead concentration of the forest floor concurrently with decline in atmospheric inputs during 1975-1990 (Figure 28). 

Photometric determination. The air aerosol is captured with the use of a membrane filter or in a nitric acid solution. In the case of the membrane filter, the mineralization is performed as in the preceding case. Solutions are evaporated to dryness, the dry residue is eluted with nitric acid and a reaction with dithizone and extraction with chloroform is performed in alkaline medium. The intensity of the red colour obtained is proportional to the lead concentration. The measurement is made at 520 nm [26]. 

Lead Concentrations in Common Rock-Forming Minerals (47, 356) ... 

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