Mercury origin

Of all the metals in the periodic table, mercury, Hg (atomic number 80), is the only one to exist as a liquid at ambient temperatures. Mercury is also volatile, which means that uncontained mercury atoms evaporate into the atmosphere. Today, the atmosphere carries a load of about 5000 tons of mercury. Of this amount, about 2900 tons are from current human activities, such as the burning of coal, and 2100 tons appear to be from natural sources, such as outgassing from Earth s crust and oceans. Since the mid-igth century, however, humans have emitted an estimated 200,000 tons of mercury into the atmosphere, most of which has since subsided onto the land and sea. It is probable, therefore, that a large portion of the mercury emitted from "natural" sources is actually the re-emission of mercury originally put there by humans over the last 150 years. 

Recent estimates indicate that of the approximately 200000 tons of mercury emitted to the atmosphere since 1890, about 95% resides in terrestrial soils, about 3% in the ocean surface waters, and 2% in the atmosphere (Expert Panel on Mercury Atmospheric Processes 1994). Some 20-30% of the current oceanic emissions are from mercury originally mobilized by natural sources (Eitzgerald and Mason 1996). Similarly, a potentially large fraction of terrestrial and vegetative emissions consists of recycled mercury from previously deposited anthropogenic and natural emissions (Expert Panel on Mercury Atmospheric Processes... 

Mercury is ubiquitously present in the environment. Some of the mercury originates from natural sources, some is the result of pollution. A detailed discussion of environmental aspects of mercury can be found in a recent review (WHO. 1989a). Here only aspects relevant to human exposure will be briefly reviewed. 

Headspace mercury was sequentially analyzed as a function of time, temperature, and bottle equilibration procedure (Table 9). The 40 pg/kg THg (liquid) concentration exhibited by oil US 19-4 represented its residual non-volatile mercury concentration as demonstrated by the low values of mercury found in headspace measurements, in constructed samples, the mercury that partitioned to the bottle headspace and then retrieved in successive headspace analyses originated from elemental mercury added to the sample. The initial attempt to measure mercury in the headspace of the US19-C12/Hg sample bottle produced an off scale response by the detector, and thus the amount lost in the first attempt at measurement is not known but is certainly high. Leaving the bottle open for 24 h was sufficient to deplete the elemental mercury originally added to the bottle. 

Methods have been described for the determination of organo-mercury dusts and vapours in air, Hamilton and Ruthven draw the sample of air through a furnace at 800°C in which the organomercury compounds are decomposed to metallic mercury, and finally through an ultra-violet spectrophotometer in which total mercury (original organo- and metallic mercury) is determined. A two-way stopcock permits the sample to by-pass the furnace metallic mercury only is then measured, and the organomercury is calculated by difference,... 

Using the curve given by the square points in Fig. XVI-2, make the qualitative reconstruction of the original data plot of volume of mercury penetrated per gram versus applied pressure. 

The electrode potential of aluminium would lead us to expect attack by water. The inertness to water is due to the formation of an unreactive layer of oxide on the metal surface. In the presence of mercury, aluminium readily forms an amalgam (destroying the original surface) which is. therefore, rapidly attacked by water. Since mercury can be readily displaced from its soluble salts by aluminium, contact with such salts must be avoided if rapid corrosion and weakening of aluminium structures is to be prevented. 

These elements formed Group IIB of Mendeleef s original periodic table. As we have seen in Chapter 13, zinc does not show very marked transition-metaf characteristics. The other two elements in this group, cadmium and mercury, lie at the ends of the second and third transition series (Y-Cd, La-Hg) and, although they resemble zinc in some respects in showing a predominantly - - 2 oxidation state, they also show rather more transition-metal characteristics. Additionally, mercury has characteristics, some of which relate it quite closely to its immediate predecessors in the third transition series, platinum and gold, and some of which are decidedly peculiar to mercury. 

If, on the other hand, the thermometer has previously been used at some temperature below the freezing-point of benzene, when the bulb is originally placed in the beaker of water at 7-8 C., the mercury will rise in the capillary and ultimately collect in the upper part of the reservoir at a. When the expansion is complete, again tap the thermometer sharply at R so that this excess of mercury drops down into b, and then as before check the success of the setting by placing the thermometer m some partly frozen benzene. In either case, if the adjustment is not complete, repeat the operations, making a further small adjustment, until a satisfactory result is obtained. 

Mercury porosimetry is a technique which was originally developed to enable pore sizes to be determined in the macropore range where, as pointed out in... 

In their original work Drake and Ritter found that the curves of volume against pressure for the penetration and withdrawal did not coincide. Numerous investigations since then have confirmed that hysteresis is a general feature of mercury porosimetry. 

Selective solution of the aluminum from the ahoy using a volatile metal, such as mercury, lead, bismuth, cadmium, magnesium, or zinc, has been investigated. After extracting the aluminum from the original ahoy into the volatile metal, the volatile metal is distilled, leaving pure aluminum. Neither electrolysis nor volatile metal extraction can extract aluminum from iron aluniinide [12004-62-3J, EeAl, titanium aluniinide [12004-78-3] TiAl, or Al C. ... 

Mercury is widespread in the environment, originating both from natural (natural gassing of the Eailh s cmst, leaching from rocks) and industrial sources (e.g. production of caustic soda and chlorine, electrical industry, biocides, etc.). 

The Minamata disaster in Japan, when 52 people died in 1952, occurred because fish, which formed the staple diet of the small fishing community, contained abnormally high concentrations of mercury in the form of MeHgSMe. This was found to originate from a local chemical works where Hg salts were used (inefficiently) to catalyse the production of... 

Vinyl acetate was originally produced hy the reaction of acetylene and acetic acid in the presence of mercury(II) acetate. Currently, it is produced hy the catalytic oxidation of ethylene with oxygen, with acetic acid as a reactant and palladium as the catalyst ... 

The original IlkoviC equation neglects the effect on the diffusion current of the curvature of the mercury surface. This may be allowed for by multiplying the right-hand side of the equation by (1 + ADl/2 t1/6 m 1/3), where A is a constant and has a value of 39. The correction is not large (the expression in parentheses usually has a value between 1.05 and 1.15) and account need only be taken of it in very accurate work. 

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