Magnesium sulfate

Magnesium nitrate hexahydrate, Mg(N03)2-6H20, is prepared by dissolving magnesium oxide, hydroxide, or carbonate in nitric acid followed by evaporation and crystallization at room temperature. Magnesium nitrate is soluble in methanol and ethanol and also forms addition compounds with pyridine, urea, and aniline. 

Dehydration of the hexahydrate above its melting point results in hydrolysis and the formation of basic nitrates such as Mg(N03)2-4 Mg(OH)2. Heating the hexahydrate salt to above 400°C results in the complete conversion to MgO and oxides of nitrogen. 

The MgS04-H20 system is complex due to a number of metastable phases that can coexist at the same time within an aqueous solution at a given temperature. The heptahydrate is stable from about —5 to 48.2°C, the hexahydrate from 48.2 to 67.5°C, and the monohydrate above 67.5°C all the other hydrates are metastable. 

The thermal decomposition of the hydrated salts begins at about 150°C and is accompanied by hydrolysis, which gives rise to oxysulfates. In the presence of carbon, decomposition occurs at about 750°C according to reaction (14.1)  

Economic Importance. The worldwide production of magnesium sulfate products including potassium magnesium sulfate (fertilizer) was 3.4 10 t/a in the mid-1970 s of which 2.3 10 t was kieserite MgS04 H2O (a byproduct of the potash industry). The main producer countries are the USA and the Federal Republic of Germany. The USA consumption in 1996 excluding natural kieserite was 57-10 t. 

Applications Magnesium sulfate is utilized in the potassium chemicals industry for the manufacture of potassium sulfate (from potassium chloride), sodium sulfate and potash magnesia (potassium magnesium sulfate). Magnesium sulfate, particularly as kieserite, is used as a fertilizer (ca. 80% of total consumption). It is also used in the textile industry, in the manufacture of building and refractory materials, in the pulp industry and in the production of animal feedstuffs and motor oil additives. 

Main applications of MgS04 products (kieserite, potassium magnesium sulfate)  

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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... 

The combined organic solutions were washed five times with saturated sodium chloride solution and subsequently dried Over magnesium sulfate. After concentration of the extract in a water-pump vacuum the residue was distilled through... 

Exp. 4) with cooling to about -20°C. The addition was carried out in about 10 min. Ten minutes later the solution was cooled to -60°C and a mixture of 0.20 mol of dimethyl disulfide and 50 ml of diethyl ether was added in 15 min with efficient cooling, so that the temperature could be kept below -40°C. Five minutes after the addition the mixture was poured into ice-water and three extractions with diethyl ether were carried out. The combined solutions were dried over magnesium sulfate and concentrated in a water-pump vacuum. Distillation of... 

To a mixture of 50 ml of dry THF and 0.050 mol of l-tert.-butoxy-2-pentyne (prepared by ethylation of HC-CCH O-tert.-Ci,H9 in liquid ammonia was added 0.055 mol of butyilithium in about 35 ml of hexane in 10 min at -30°C. After stirring for 20 min at -25°C the solution was cooled to -50°C and 0.06 mol of methyl iodide was added in one portion, followed 10 min later by 50 ml of water. The aqueous layer was separated and extracted twice with diethyl ether. The solutions were dried over magnesium sulfate and concentrated in a water-pump vacuum. 

The solution was then poured into 200 ml of saturated ammonium chloride solution. After vigorous shaking the upper layer was separated off and the aqueous layer was extracted three times with diethyl ether. The combined ethereal solutions were dried over magnesium sulfate and then concentrated in a water-pump vacuum. 

The combined solutions were dried over magnesium sulfate and subsequently concentrated in a water-pump vacuum. Distillation of the residue through a 30-cm Vigreux column gave the silylated propargyl sulfide, b.p. 65°C/18 mmHg, n ... 

To absolution of 1.00 mol of ethyl lithium in 800-900 ml of diethyl ether (see Chapter II, Exp. 1) was added, with cooling between -20 and -10°C, 0.50 nol of dry propargyl alcohol, dissolved in 100 ml of diethyl ether. Subsequently 1.1 mol of trimethylchlorosilane was introduced over a period of 25 min with cooling between -15 and +5°C. After stirring for an additional 2 h at about 30°C the suspension was poured into a solution of 30 g of acetic acid in 150 ml of water. After stirring for 1 h at room temperature the layers were separated and the aqueous layer v/as extracted four times with diethyl ether. The combined ethereal solutions were washed with sodium hydrogen carbonate solution in order to neutralize acetic acid, and were then dried over magnesium sulfate. The diethyl ether was removed by evaporation in a water-pump vacuum and the residue distilled... 

HCl and 50 ml of water. The upper layer was separated off and the aqueous phase was extracted five times with small portions of THF. After drying the combined solutions over magnesium sulfate the solvent was removed in a water-pump vacuum. The residue was distilled through a 30-cm Vigreux column, connected to an air condenser. After a preliminary aqueous fraction of the carboxylic acid the main fraction passed over at 100°C/15 mmHg. The compound solidified in the receiver and (partly) in the condenser. The yield was almost quantitative. 

R = tert.-CijHg). The combined organic solutions were dried over magnesium sulfate... 

To a solution of 0.40 mol of butyllithium in about 280 ml of hexane were added 280 ml of dry THF with cooling below -10°C. Subsequently 0.40 mol of 1,1-diethoxy--2-propyne (see Chapter V, Exp. 28) was introduced in 15 min at -30 to -10°C. To the solution obtained was then added in 15 min with cooling at about -15°C 0.40 mol of chloromethyl ethyl ether (note 2). After the addition stirring was continued for 1 h without cooling. The mixture was then shaken with concentrated ammonium chloride solution and the ethereal layer was separated off. The aqueous layer was extracted twice with diethyl ether. After drying the ethereal solutions over magnesium sulfate the diethyl ether was evaporated in a water-pump vacuum. 

After drying the combined pentane layers over magnesium sulfate the solvents were removed by evaporation in a water-pump vacuum. Distillation of the residue in an oil-pump vacuum (< 0.5 nriHg) in the apparatus shown in Fig. 5 (receiver cooled... 

A solution of 0.21 mol of butyllithium in about 140 ml of hexane (note 1) was cooled below -40°C and 90 ml of dry THF ivere run in. Subsequently a cold (< -20 C) solution of 0.25 nol of propyne in 20 ml of dry THF was added with cooling below -20°C and a white precipitate was formed. A solution of 0.10 mol of anhydrous (note 2) lithium bromide in 30 ml of THF was added, followed by 0.20 mol of freshly distilled cyclopentanone or cyclohexanone, all at -30°C. The precipitate had disappeared almost completely after 20 min. The cooling bath was then removed and when the temperature had reached 0°C, the mixture was hydrolyzed by addition of 100 ml of a solution of 20 g of NHi,Cl in water. After shaking and separation of the layers four extractions with diethyl ether were carried out. The extracts were dried over magnesium sulfate and the solvents removed by evaporation in a water--pump vacuum. Careful distillation of the remaining liquids afforded the following... 

To a vigorously stirred suspension of 2 mol of lithium amide in 2 1 of liquid atimonia (see II, Exp. 11) was added in 15 min 1 mol of propargyl alcohol (commercial product, distilled in a partial vacuum before use). Subsequently, 1 mol of butyl bromide was added dropwise in 75 min. After an additional 1.5 h, stirring was stopped and the ammonia was allovied to evaporate. To the solid residue were added 500 ml of ice-water. After the solid mass had dissolved, six extractions with diethyl ether were performed. The (unwashed) combined extracts were dried over magnesium sulfate and then concentrated in a water-pump vacuum. Distillation of the residue through a 40-cm Vigreux column afforded 2-heptyn-l-ol, b.p. 

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