Problems Mercuric oxide

Replacing zinc with cadmium produces a cell with an OCV of 0.90 V, with characteristics very similar to those of the zinc-mercuric oxide system described above, but which is able to be stored and operated at extreme temperatures (—55 to 80°C) due to the low solubility of cadmium oxide even in concentrated KOH. Cells have been successfully operated at 180°C. Note that hydrogen generation does not occur at a cadmium anode. Because of cost and disposal problems, such cells are used only for applications where their special properties can be exploited, e.g. telemetry from internal combustion, jet or rocket engines. 

Hanafi ZM, Ismail EM (1988) Colour problem of mercuric oxide photoconductivity and electrical conductivity of mercuric oxide. Z phys Chem 158 8-86... 

Cardiac pacemakers are generally employed when the cardiac rhythm is either abnormal or too slow. To rectify this problem, doctors prescribe implanted pacemakers that detect the slow heart rate and send impulses to stimulate the muscle using microelectronic circuits. The life of these devices developed before 1973 and incorporating zinc-mercuric-oxide (Zn-HgO) batteries was only between 12 and 18 months. When Li-l2 batteries became available around 1975, the battery life was extended to more than 10 years. The life of devices with batteries developed after 2008 could be more than 15 years. 

During the last several years, the market for mercuric oxide batteries has almost completely evaporated, due mainly to environmental problems associated with mercury and cadmium and few are manufactured. They have been removed from the International Electrotechnical Commission (lEC) and the American National Standards Institute (ANSI) standards. In applications, they have been replaced by alkaline-manganese dioxide, zinc/air, silver oxide and lithium batteries. 

This problem differs from the preceding one. Here we must calculate the nitric acid concentration, which must be added so that no mercuric oxide exists. This calculation must take into account the fact that the dissolution of mercuric oxide is accompanied by acid-base equilibria. The latter are... 

Samples with particulate matter may present quite serious problems, and it may be desirable to remove particles, for example, by centrifugation, and examine this fraction by procedures applicable to solid phases which are discussed in Section 2.2.5. Tangential-flow high-volume filtration systems have been used for analysis of particulate fractions (>0.45 jum) where the analytes occur in only low concentration (Broman et al. 1991). Attention has already been drawn to artifacts resulting from reactions with cyclohexene added as an inhibitor to dichloromethane. It has also been suggested that under basic conditions, Mn2+ in water samples may be oxidized to Mn(III or IV) which in turn oxidized phenolic constituents to quinones (Chen et al. 1991). Serious problems may arise if mercuric chloride is added as a preservative after collection of the samples (Foreman et al. 1992) since this has appreciable solubility in many organic solvents, and its use should therefore be avoided. 

FOLLOW-UP PROBLEM 2.9 Give the systematic names for the formulas or the formulas for the names of each compound (a) lead(lV) oxide (b) CU2S (c) FeBr2 (d) mercuric chloride. 

The structural elucidation of multiphase polymers is a continuing problem as, at times, the few commonly used staining reagents are not satisfactory. Osmium tetroxide has the widest range of applicability, but there are polymers that cannot be differentiated by this stain. Mercuric trifluoroacetate has been described for the staining of several polymers [154] polystyrene, poly(2,6-dimethyl-l,4-phenylene oxide) and saturated styrene-butadiene-styrene block copolymers (Kraton G, trademark. Shell Oil Company). 

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