Magnesium density

It is clear that these alloys, from the point of view of lightness, are more important the more magnesium (density 1 -75) they contain. 

Magnesium, density 1.7 g cm , is one of the least dense metals. It has an hexagonal crystal structure with a = 0.320 nm, c = 0.520 nm, and da = 1.624. The basal plane is close-packed and the axial ratio is only slightly greater than the theoretical value for incompressible spheres (Emley, 1966). The atomic diameter is 0.320 nm, so there is a favorable size factor with a diverse range of the solute elements Aluminum (Al), Zinc (Zn), Cerium (Ce), Yttrium (Y), Silver (Ag), Zirconium (Zr), and Thorium (Th) (Pol-mear, 1989). 

In Fig. III-7 we show a molecular dynamics computation for the density profile and pressure difference P - p across the interface of an argonlike system [66] (see also Refs. 67, 68 and citations therein). Similar calculations have been made of 5 in Eq. III-20 [69, 70]. Monte Carlo calculations of the density profile of the vapor-liquid interface of magnesium how stratification penetrating about three atomic diameters into the liquid [71]. Experimental measurement of the transverse structure of the vapor-liquid interface of mercury and gallium showed structures that were indistinguishable from that of the bulk fluids [72, 73]. 

Mix 31 g. (29-5 ml.) of benzyl alcohol (Section IV, 123 and Section IV,200) and 45 g. (43 ml.) of glacial acetic acid in a 500 ml. round-bottomed flask introduce 1 ml. of concentrated sulphuric acid and a few fragments of porous pot. Attach a reflux condenser to the flask and boil the mixture gently for 9 hours. Pour the reaction mixture into about 200 ml. of water contained in a separatory funnel, add 10 ml. of carbon tetrachloride (to eliminate emulsion formation owing to the slight difference in density of the ester and water, compare Methyl Benzoate, Section IV,176) and shake. Separate the lower layer (solution of benzyl acetate in carbon tetrachloride) and discard the upper aqueous layer. Return the lower layer to the funnel, and wash it successively with water, concentrated sodium bicarbonate solution (until effervescence ceases) and water. Dry over 5 g. of anhydrous magnesium sulphate, and distil under normal pressure (Fig. II, 13, 2) with the aid of an air bath (Fig. II, 5, 3). Collect the benzyl acetate a (colourless liquid) at 213-215°. The yield is 16 g. 

Magnesium hydroxide is white, has an average particle size of 1—10 p.m, density of 2.36 g/mL, refractive index of 1.58, and Mohs hardness of 2.00. Water loss on ignition is 31.8 wt %. Magnesium hydroxide contains 1.0 wt % Ca(OH)2 and is made by Solem Industries and Morton Thiokol (25). 

Light or heavy magnesium carbonate is exposed to a red heat, and carbon dioxide and water are expelled leaving light or heavy magnesium oxide. The density is also influenced by the calcining temperature higher temperatures yield more compact forms. 

Lithium magnesium alloys, developed during World War 11, have found uses in aerospace appHcations. Lithium alters the crystallization of the host magnesium from the normal hexagonal stmcture to the body-centered cubic stmcture, with resultant significant decreases in density and increases in ductibiHty. 

Bulk density is 1.49 kg/L for 57% solids slurry with a Mg(OH)2 loading of 0.85 kg/L. The properties of some magnesium hydroxide slurries are given in Table 12. 

Anhydrous magnesium nitrate [10377-60-3] Mg(N02)2, is very difficult to isolate. The commercial product is the deUquescent hexahydrate [13446-18-9] Mg(N02)2 6H20. As illustrated in the solubiUty curve in Figure 7, the hexahydrate is the stable soHd phase between —18 and 55—56°C. Properties are given in Table 17 (1 4). The unit ceU contains two formula units and the calculated density is 1.643 g/cm. ... 

Magnesium Methylate. Magnesium methoxide [109-88-6] Mg(OCH2)2, mol wt, 86.3, is an almost white powder powder density 0.5 g/mL ... 

Piebaked anodes aie produced by molding petroleum coke and coal tar pitch binder into blocks typically 70 cm x 125 cm x 50 cm, and baking to 1000—1200°C. Petroleum coke is used because of its low impurity (ash) content. The more noble impurities, such as iron and siUcon, deposit in the aluminum whereas less noble ones such as calcium and magnesium, accumulate as fluorides in the bath. Coal-based coke could be used, but extensive and expensive prepurification would be required. Steel stubs seated in the anode using cast iron support the anodes (via anode rods) in the electrolyte and conduct electric current into the anodes (Fig. 3). Electrical resistivity of prebaked anodes ranges from 5-6 Hm anode current density ranges from 0.65 to 1.3 A/crn. ... 

Betterton-KroIIProcess. MetaHic calcium and magnesium are added to the lead bullion in a melt and form ternary compounds that melt higher than lead and are lower in density. By cooling the lead bath to a temperature close to the melting point of lead, the intermetalHc compounds high in bismuth content soHdify and float to the top where they are removed by skimming. 

FIG. 20-78 Reaction in compacts of magnesium carbonate when pressed (P = 671 kg/cnr ). (a) Stress contour levels in kilograms per square centimeter, (h) Density contours in percent solids, (c) Reaction force developed at wedge responsible for stress and density patterns. [Tf ain, Trans. Inst. Cbem. Eng. (London), 35, 258 (1957).]... 

Because carbon dioxide is about 1.5 times as dense as air and 2.8 times as dense as methane, it tends to move toward the bottom of the landfill. As a result, the concentration of carbon dioxide in the lower portions of landfill may be high for years. Ultimately, because of its density, carbon dioxide will also move downward through the underlying formation until it reaches the groundwater. Because carbon dioxide is readily soluble in water, it usually lowers the pH, which in turn can increase the hardness and mineral content of the groundwater through the solubilization of calcium and magnesium carbonates. 

Concentration limits of the diphosphate-ion, admissible to determination of magnesium and cobalt, manganese and cobalt, zinc and cobalt by spectrophotometric method with application of the l-(2-pyridylazo)-resorcinol (PAR) are presented. Exceeding maintenance of the diphosphate-ion higher admissible supposes a preliminary its separation on the anionite in the H+-form. The optimum conditions of cobalt determination and amount of the PAR, necessary for its full fastening are established on foundation of dependence of optical density of the cobalt complex with PAR from concentration Co + and pH (buffer solutions citrate-ammoniac and acetate-ammoniac). 

No fewer than 14 pure metals have densities se4.5 Mg (see Table 10.1). Of these, titanium, aluminium and magnesium are in common use as structural materials. Beryllium is difficult to work and is toxic, but it is used in moderate quantities for heat shields and structural members in rockets. Lithium is used as an alloying element in aluminium to lower its density and save weight on airframes. Yttrium has an excellent set of properties and, although scarce, may eventually find applications in the nuclear-powered aircraft project. But the majority are unsuitable for structural use because they are chemically reactive or have low melting points." ... 

Figure 6-7 shows the effect of water conductivity on the rest potential of type AZ63, and M2 as well as of zinc and aluminum [23]. In cold waters with chlorides or sulfates, the polarization of magnesium anodes is low — even in the case of high current densities. This is demonstrated for 70°C with current-density vs. 

Cathodic protection with magnesium anodes can be just as economical as impressed current anode assemblies for pipelines only a few kilometers in length and with protection current densities below 10 xA m" e.g., in isolated stretches of new pipeline in old networks and steel distribution or service pipes. In this case, several anodes would be connected to the pipeline in a group at test points. The distance from the pipeline is about 1 to 3 m. The measurement of the off potential... 

At the relatively low protection current density of 200 llA m and with the anode positioned on one side, it is to be expected that with this storage tank sufficient reduction in potential would be achieved on the other side of the tank from the anode. The off potential was measured using a measurement point at a depth of about 2 m as f/cu-cuso4 = -0.88 V at the tank. At the other side of the tank as well as above it, off potentials of-0.90 to -0.94 V were found. These potentials were measured with a protection current of 10 mA (anode 1 6 mA, anode 2 4 mA) with an additional resistance of 8 Q in the protection current circuit (see Fig. 11-2). With a direct connection between the tank and the group of magnesium anodes, the initial current was about 16 mA, which after 1 h of polarization decreased to about 14 mA. The reserve current, based on a long-term current of 10 mA, amounted to ca. 40% in the operation of the cathodic protection installation. 

Galvanic or impressed current anodes are used to protect these components. The anode material is determined by the electrolyte zinc and aluminum for seawater, magnesium for freshwater circuits. Platinized titanium is used for the anode material in impressed current protection. Potential-regulating systems working independently of each other should be used for the inlet and outlet feeds of heat exchangers on account of the different temperature behavior. The protection current densities depend on the material and the medium. 

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