Magnesium dried

Uses and Economic Aspects. Magnesium bromide is used in medicine as a sedative in treatment of nervous disorders, in electrolyte paste for magnesium dry cells, and as a reagent in organic synthesis reactions. The price of magnesium bromide hexahydrate in January 1995 was 5.51/kg (33). 

Fj Preparation of 2, 4,8-Trimethylpsoralen Crude 7-acetoxy-6-(2, 3 -dibromopropyl)-4,8-dimethyIcoumarin (245.7 g, 0.57 mol) was refluxed for 1% hours with a stirred solution of sodium (65.4 g, 2.85 mols) in a magnesium-dried ethanol (2.1 liters). After standing at room temperature for 15 minutes, the reaction mixture was poured into a stirred mixture of ice (8,000 g) and a 3.5% HCI (8 liters). Twelve hours later, the precipitate had coagulated and was collected by filtration it was thoroughly washed with successive 3-liter portions of 5% NaOH, water, 0.5% HCl, and water. 

Estimation.—Ruthenium may be estimated by precipitation with magnesium from solutions of its salts. The precipitate is washed with dilute sulphuric acid to remove excess of magnesium, dried, ignited in a current of hydrogen, cooled in carbon dioxide, and weighed as metal. 

Tetrafluoroborates recrystallizcd from abs EtOH and fluorides from magnesium-dried ( superdry") EtOH. Relative ratios determined by HNMR spectroscopy (in CDCI3). 

Triphenylpyrylium fluoride (20 mmol) and the primary amine (20 mmol) in magnesium-dried EtOH/ sodium-dried benzene (lOOmL, 1 1 v/v) were heated in a Dean Stark apparaus for 12 h. The solvents were removed in vacuo (25 C/20 Torr) and the resulting oil triturated with Et20 to give w hite crystals... 

R. R. Balaguer and F. P. Schiro, New Magnesium Dry Battery Structure, in Proc. 20th Power Sources Symp., Atlantic City, N.J. 1966, p. 90. 

The magnesium dry cell consists of a magnesium anode, a manganese dioxide-carbon cathode and an electrolyte, which is usually magnesium perchlorate or magnesium bromide. The basic cell reaction is ... 

Magnesium dry batteries are now finding widespread use in military communications equipment. With inereasing use and production, the cost of these batteries has dropped significantly. For example, for the BA4386/U battery consisting of 16 long C-size cells, the cost dropped from 512.50 per battery to below 5.00 over 3 years. The equivalent zinc battery costs approximately 3.00. 

Attempts to fabricate magnesium dry cell batteries using flat cell constructions have to date been unsuccessful. This is due to an expansion problem caused by the build-up of reaction products. 

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