Mercury alloys

Dental amalgams, mainly silver—tin—mercury alloys, have been used as fillings for many years (see Dental MATERIALS). The most common alloy contains 12 wt % tin. 

B. Amalgamated, Zinc [Mercury alloy (Hg, Zn)]. Zinc powder (206 g., 3.15 moles) is placed in a 1-1. beaker, covered with 250 ml. of aqueous 10% hydrochloric acid, and stirred for 2 minutes. The acid is then decanted and replaced by distilled water, the mixture is stirred, and the supernatant is decanted. Washing is continued in this way until the water is neutral to litmus. A warm solution of 40 g. (0.15 mole) of mercuric chloride [Mercury chloride (HgCl2)] in 250 ml. of distilled water is then poured onto the zinc, and the mixture is stirred gently for 10 minutes. After filtration, the powder is washed with 250 ml. of distilled water, five 250-ml. portions of 95% ethanol, and five 250-ml. portions of anhydrous ether. Drying under vacuum gives 196 g. of zinc amalgam. 

It may be mentioned that the possibility of bivalence of tin in grey tin and the mercury alloy, suggested by the bipositive oxidation state of the element in many of its compounds, is ruled out because it leads to too small a value of R 1)—smaller than that for quadrivalent tin, whereas a larger value would be expected as the result of the appropriation of much of the s orbital by the unshared pair. 

Thalhum and its compounds have limited apphcations. It is used in insecticides and rodenticides. Thalhum-mercury alloys are used for switches and closures for use at sub-zero temperatures. Another application is in making low melting glasses for electronic encapsulation. Thallium sulfide is used in photocells. 

Various processes separate rare earths from other metal salts. These processes also separate rare earths into specific subgroups. The methods are based on fractional precipitation, selective extraction by nonaqueous solvents, or selective ion exchange. Separation of individual rare earths is the most important step in recovery. Separation may be achieved by ion exchange and solvent extraction techniques. Also, ytterbium may be separated from a mixture of heavy rare earths by reduction with sodium amalgam. In this method, a buffered acidic solution of trivalent heavy rare earths is treated with molten sodium mercury alloy. Ybs+ is reduced and dissolved in the molten alloy. The alloy is treated with hydrochloric acid, after which ytterbium is extracted into the solution. The metal is precipitated as oxalate from solution. 

Composition Dependence of Alloy Viscosity. Attempts have been made to calcnlate the viscosity of a dilnte liquid alloy from a theoretical standpoint, but with little success. This is primarily due to the fact that little is known about the interaction of dissimilar atoms in the liquid state. Empirical relationships for the viscosity of dilute liquid alloys have been developed, but these are generally limited to specific alloy systems—for example, mercury alloys with less than 1% impurities. The viscosities of binary liquid alloys have been empirically described using a quantity called the excess viscosity, (not to be confused with the excess chemical potential), which is defined as the difference between the viscosity of the binary mixture (alloy), pa, and the weighted contributions of each component, xipi and X2P2-... 

Mercury (Hg) Mercury is a silvery white liquid metal. Because of its high density, mercury is used in sphygmomanometers. It is also found in some thermometers. Before its toxic nature was fully understood, mercury compounds had been used in medical applications ranging from treatment of syphilis to constipation. Mercury alloys well with many other metals, and alloys containing mercury are known as amalgams. 

As the metal dissolves, it gives up two electrons which reduces the C=0 bond. The mercury alloyed with the zinc does not participate in the reaction it serves only to provide a clean active metal surface. The mechanism of reduction s is not very clear, but it is believed to proceed as shown in Scheme 6.27. 

An alloy of thallium and mercury can be used to make low-temperature thermometers. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals. The thallium-mercury alloy remains liquid at —76°F (—60°C). At that temperamre, a mercury-only thermometer would freeze solid. 

Combines with many metals to form mercury alloys called amalgams... 

Use Thallium salts, mercury alloys, low-melting glasses, rodenticides, photoelectric applications, electrodes in dissolved oxygen analyzers. 

EINECS 231-138-1 HSDB 4496 Ramor Thallium Thallium, elemental Thallium, metallic. Metallic elem-ent thallium salts, mercury alloys, low-melting glasses, rodenticides, photoelectric applications, electrodes in dissolved oxygen analyzers, mp = 303° bp = 1457° d = 11.85. Atomergic Chemetals, Cerac Noah Cham. Sigma-Aldrich Fine Chem. 

M. Simon et al., Mercury, Mercury Alloys and Mercury Compounds , Ullmann s. ... 

The metals commonly used in medical devices are stainless steel (Types 316 and 316 L), cobalt-chromium-based alloys, titanium, and titanium-based alloys. Metals are used extensively in orthopedic surgery for load-bearing devices, such as artificial joints and fixation devices (wires, pins, screws fracture plates, etc.). Other metals include tantalum, gold, and mercury alloys the latter two are used predominantly in dentistry. 

It s used in thallium-mercury alloys for applications in switches that are used at sub-zero temperatures, and it can be used in laboratories as a low temperature thermometer because it extends the freezing point of Hg to -60 C. This can be used by engineers to monitor conditions at such low temperatures. 

For these reasons, potential measurements of alloys are frequently made at higher temperatures with solid electrolytes or by using molten salt electrolytes. Measurements in aqueous electrolytes and at room temperatures were mostly restricted to mercury alloy (amalgam) electrodes. 

Definition A sodium/mercury alloy contg. 2-20% sodium... 

Precaution Flamm. as dust exposed to heat or flame violent reaction with F2 Hazardous Decomp. Prods. Forms toxic compds. on contact with moisture heated to decomp., emits toxic fumes of Tl Uses Thallium salts mercury alloys low-melting glasses, lenses, prisms rodenticide fungicide photoelectric applications electrodes in dissolved oxygen analyzers Manuf./Distrib. Aldrich http //www.sigma-aldrich.com Atomergic Chemetals... 

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