Magnesium control

In all applications, the chelant may have been added for a variety of purposes. As discussed in Section 10.2, chelants can have roles where calcium and magnesium control is key, such as detergency or scale inhibition. Alternatively, transition metal ion control could be the target, for example, in bleach stabilization. Some applications require both properties simultaneously. Chelants can also act as biocide potentiators or as antioxidants, to prevent trace metal ions from causing oxidative spoilage. This may require that metal concentrations be kept below certain... 

Alterations in magnesium-controlled, monovalent cation permeability pathway Inhibition of calcium transport Formation of hydrogen peroxide... 

In an electrolytic zinc plant, magnesium contained in the zinc concentrate becomes soluble and would accumulate in the electrolyte. Different techniques have been employed, such as the selective zinc precipitation process and the releaching of concentrates, to reject magnesium from the zinc circuit (2,3). The original design for magnesium control at the Pasminco Clarksville Zinc Plant was to strip the zinc content in the electrolyte from 55 g/l to about 25 g/l and then to bleed the stripped electrolyte, approximately 100 mVday, to the... 

I. G. Matthew, O. M. G. Newman and D. J. Palmer, Water Balance and Magnesium Control in Electrolytic Zinc Plants Using the E. Z. Selective Zinc Precipitation Process , TMS Paper Selection A-79-15. 1979. 

Surface cracking tearing of the surface of the part, especially with high temperature alloys, aluminum, zinc, magnesium. Control of the billet temperature, extrusion speed and friction are important. 

Uses Utilized in calcium and magnesium control process aid in detergent mfg. ... 

Equip a 1-litre three-necked flask with a powerful mechanical stirrer, a separatory funnel with stem extending to the bottom of the flask, and a thermometer. Cool the flask in a mixture of ice and salt. Place a solution of 95 g. of A.R. sodium nitrite in 375 ml. of water in the flask and stir. When the temperature has fallen to 0° (or slightly below) introduce slowly from the separatory funnel a mixture of 25 ml. of water, 62 5 g. (34 ml.) of concentrated sulphuric acid and 110 g. (135 ml.) of n-amyl alcohol, which has previously been cooled to 0°. The rate of addition must be controlled so that the temperature is maintained at 1° the addition takes 45-60 minutes. AUow the mixture to stand for 1 5 hours and then filter from the precipitated sodium sulphate (1). Separate the upper yellow n-amyl nitrite layer, wash it with a solution containing 1 g. of sodium bicarbonate and 12 5 g. of sodium chloride in 50 ml. of water, and dry it with 5-7 g. of anhydrous magnesium sulphate. The resulting crude n-amyl nitrite (107 g.) is satisfactory for many purposes (2). Upon distillation, it passes over largely at 104° with negligible decomposition. The b.p. under reduced pressure is 29°/40 mm. 

Method 2. Equip a 1 htre thre necked flask with a double surface reflux condenser, a mechanical stirrer and a separatory funnel, and place 12 -2 g. of dry magnesium turnings, a crystal of iodine, 50 ml. of sodium-dried ether and 7-5 g. (5 ml.) of a-bromonaphthalene (Section IV,20) in the flask. If the reaction does not start immediately, reflux gently on a water bath until it does remove the water bath. Stir the mixture, and add a solution of 96 g. (65 ml.) of a-bromonaphthalene in 250 ml. of anhydrous ether from the separatory funnel at such a rate that the reaction is vmder control (1 -5-2 hours). Place a water bath under the flask and continue the stirring and refluxing for a further 30 minutes. The Grignard reagent collects as a heavy oil in the bottom of the flask ... 

To a solution of 0.35 mol of allenyllithium in 240 ml of hexane and 200 ml of THF (see Chapter II, Exp. 13) were added 25 g of dry HMPT at -80°C. Subsequently 0.30 mol of l-bromo-3-chloropropane were added in 10 min. The reaction was very exothermic, but could be kept under control by occasional cooling in a bath with liquid nitrogen. After an additional 10 min the cooling bath was removed and the temperature was allowed to rise to -30°C. The solution was then poured into 500 ml of water. The organic layer and three ethereal extracts were dried over magnesium sulfate. The solvents were distilled off as thoroughly as possible at... 

MetaUic ions are precipitated as their hydroxides from aqueous caustic solutions. The reactions of importance in chlor—alkali operations are removal of magnesium as Mg(OH)2 during primary purification and of other impurities for pollution control. Organic acids react with NaOH to form soluble salts. Saponification of esters to form the organic acid salt and an alcohol and internal coupling reactions involve NaOH, as exemplified by reaction with triglycerides to form soap and glycerol,... 

Magaldrate is prepared by precipitation from aqueous solutions of sodium or potassium aluminate and a magnesium salt under controlled conditions of concentration and temperature. The precipitated product is collected by filtration, washed to remove soluble by-products, and dried. 

K. N. Reichek, K. J. Clark, and J. E. HiUis, Controlling the Salt Water Corrosion Peformance of Magnesium AZ91 Alloy, paper 850417, Society of Automotive Engineers, Detroit, Mich., 1985. 

D. L. Hawke, J. E. HiUis, and W. Unsworth, Preventive Practice for Controlling the Galvanic Corrosion of Magnesium Alloys, International Magnesium Association, McLean, Va., 1988. 

Instmmentation and control guidelines for processes utilizing magnesium hydroxide and other slurries have been outlined (82). An experimental deterrnination of the accuracy of magnetic dow meters for magnesium hydroxide slurries d owing in pipelines (qv) has been reported (83). 

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