Desiccants sodium sulfate

The dry methosulfate, dissolved in about 30 ml. of water, is made alkaline with 2-3 ml. of 10% sodium hydroxide, and the solution is then extracted exhaustively with successive 15-ml. portions of chloroform until no more blue substance is remov ed from the aqueous solution (Note 12). The combined chloroform solutions are extracted three times with 20-ml. portions of 5% hydrochloric acid. The combined acid extracts are made alkaline to phenolphthalein with 10% sodium hydroxide and reextracted exhaustively with 25-ml. portions of chloroform until no more blue substance is removed from the aqueous solution (Note 12). The combined chloroform solutions are dried over anhydrous sodium sulfate and decanted, and the chloroform is removed by distillation under reduced pressure. The blue crystalline residue is recrystallized by dissohnng it in the least possible amount of water at 60° and then cooling the solution in an ice bath. The product is filtered on a 5-cm. Buchner funnel and dried in the dark in a v acuum desiccator over calcium chloride. The yield is 1.35 g. (58%) of dark blue needles that melt at 133° (Note 13). 

If propynol and similar acetylenic compounds are dried with alkali before distillation, the residue may explode (probably owing to acetylenic salt formation). Sodium sulfate is recommended as a suitable desiccant. 

Lead tetraacetate is added in small quantities, with stirring, to an ice-cold suspension of 11 g. of ethyl 3-(D-arabino-tetrahydroxybutyl)-5-methyl 4-furoate in 100 ml. of benzene plus 40 ml. of glacial acetic acid. Addition is stopped when there is a positive reaction with potassium iodide-starch paper. The mixture is stirred for a further ten minutes, filtered, and the benzene solution washed twice with water. The benzene layer is then dried with anhydrous sodium sulfate, filtered, and the filtrate evaporated to dryness. The residue (6 g.) is mixed with a solution of 7.5 g. of sodium hydroxide plus 20 g. of silver nitrate in 40 ml. of water, and heated for 40 minutes on a steam bath. The aqueous solution is filtered, acidified to Congo Red while being cooled with ice, and the crystals formed are removed by filtration, washed with ice-cold water, and dried over phosphorus pentoxide in the vacuum desiccator yield, 2.2 g. After recrystallization from water, the product has m. p. 234r-235°. 

The organic layers are combined, washed with brine, dried over anhydrous sodium sulfate, filtered, then concentrated under reduced pressure on a rotary evaporator. The residue is stirred with 2-propanol-hexane (1 1,60 mL) for several minutes. The solid product is collected by filtration. The filtrate is concentrated on a rotary evaporator, and the residue is again stirred with 2-propanol-hexane (1 1, 5 mL). The precipitate is collected by filtration. The two lots of the products are dried in a desiccator over phosphorus pentoxide (P2O5) under reduced pressure for 12 hr. (4R,5S)-3-(Methoxyethyl)-4,5-diphenyl-2-oxazolidinone (22.2 g, 89.3%) (Note 12) is obtained as a diastereomeric mixture. In some runs, small amounts of impurities remained after trituration. These impurities can be carried through the next step without a problem although final yields will be reduced. 

The insoluble material was removed by centrifuging at 5000 rpm for 15 min in a Beckman Model No J-6B centrifuge. This extraction with alkali was repeated twice more and the solutions of sodium salts of acids were collected. Humic acids were precipitated from the combined NaOH solutions by adjusting the pH to 1 with 2N HCl slowly with stirring and the mixture was left overnight. The precipitated humic acids were collected by filtration through Whatman IMM paper and washed with O.IN HCl. The filtrates were extracted three times with ethyl acetate and the extracts dried over sodium sulfate and evaporated, the residue constituting the fulvic acids. Buth fulvic and humic acids (precipitates) were air-dried, and then dried in a vacuum desiccator over phosphorus pentoxide at room temperature. 

Filter the solution through a folded filter and set it aside in a quiet place to crystallize. The crystals are glassy in appearance and should not be too large or grown together. Drain them on a Witte plate and evaporate the mother liquor for a second crop. They may be obtained as needles as lath-shaped crystals or in a compact, many-sided form. The last named is the most desirable form, and conditions should be varied to avoid supersaturation (Exercise 6) until such crystals are obtained. Meanwhile, prepare some effloresced sodium sulfate by gently warming about 100 g. of the crude crystals until they fall into white powder. Place this powder in the bottom of an empty desiccator and... 

Obviously, the condensation of a carbonyl group with a diol produces 1 mol of water and because of the reversibility of the reaction (hydrolysis of the acetal), yields are lowered if this by-product is not removed. For such a purpose, there are essentially two possibilities (1) the continuous removal of water by an azeotropic distillation with a solvent mainly chosen for its boiling point (petroleum ether, benzene, toluene, xylene, for instance) (2) the presence of a desiccant (the most commonly taken is copper(II)sulfate, but sodium sulfate or molecular sieves have been also used) molecules known to be water scavengers, such as ortho-esters or dialkylsulfites, have also been suggested, even if they are seldom used in carbohydrate chemistry. 

Maintaining environmental samples in their original wet state is regarded as the most appropriate approach for preparing samples. Homogenized samples should be mixed with a desiccant such as sodium sulfate or celite to bind water. 

Dry the combined organic phase with anhydrous sodium sulfate. Filter off the desiccant and remove the volatiles on a rotary evaporator to give the aminoazide (30.2 g, 82%) as an amber oil. 

Pour the reaction mixture into water (100 mL) and extract with dichlorometh-ane (3 x 100 mL). Combine the washings and dry with anhydrous sodium sulfate, filter off the desiccant then remove the volatiles at reduced pressure using a rotary evaporator. 

Sodium Sulfate. Granular, anhydrous. Before use, heat to 400°C in a shallow tray for approximately 4 hours, cool in a desiccator, and store in a glass jar. 

CHAPTER 4 THE PREPARATION OF METAL AZIDES, FULMINATES, AND NITRIDES room temperature for 24 hours. Thereafter, slowly heat the mixture to about 80 Celsius with rapid stirring, and then carefully add 120 grams of 95% ethanol while stirring the reaction mixture. After the addition of the alcohol, remove the heat source, and allow the reaction mixture to cool to room temperature. Afterwards, rapidly filter-off the precipitated copper fulminate, wash with several hundred milliliters of cold water, and then dry in a desiccator filled with anhydrous magnesium sulfate. Should be stored in a desiccator over sodium sulfate in a refrigerator. 

This compound is readily prepared by bubbling dry gaseous methylamine through pure 2,4-pentanedione. The resultant oily product is taken up in ether. The ethereal solution is dried over sodium sulfate for 2 hours and filtered. The solvent is evaporated completely, leaving a residue which crystallizes on cooling to 10°. Recrystallization of this material from petroleum ether (b.p. 40-60°) 3nelds colorless crystals, m.p., 43-45°, (literature, 45°) in 70-80% yield. The compound should be stored in a desiccator or used immediately after purification. 

Procedure. The chlorosulfonic acid in a beaker is cooled to —15°. The thiophene is added, with stirring (manual stirring rod) over a period of eight minutes, during which time the temperature rises to —5°. This mixture is immediately poured into 100 g. of crushed ice and the temperature of the quenched mixture is held below 30° by means of external cooling. The mixture is then neutralized with 325 ml. of 20% sodium hydroxide solution at a temperature below 40°. The aqueous solution is extracted three times with petroleum ether and then evaporated to dryness on a drum drier. The residue is extracted with boiling anhydrous methanol to remove the product from sodium sulfate and the alcoholic solution is dried on the drum drier (or the alcohol is evaporated and the product dried in a vacuum desiccator). The product is a white hygro-... 

The precipitated methacrylamide contains varying amounts of sodium sulfate. It is essential to obtain a dry product for the benzene extraction. The desiccator should be evacuated with an oil pump to about 5 mm. several times during 24-36 hours in order to obtain a sufficiently dry material. 

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