Desiccants sulfuric acid

By-product water formed in the methanation reactions is condensed by either refrigeration or compression and cooling. The remaining product gas, principally methane, is compressed to desired pipeline pressures of 3.4—6.9 MPa (500—1000 psi). Einal traces of water are absorbed on siHca gel or molecular sieves, or removed by a drying agent such as sulfuric acid, H2SO4. Other desiccants maybe used, such as activated alumina, diethylene glycol, or concentrated solutions of calcium chloride (see Desiccants). 

Liquid Desiccants. Glycols and sulfuric acid are the principal examples. 

Equilibrium moisture content of a hygroscopic material may be determined in a number of ways, the only requirement being a source of constant-temperature and constant-humidity air. Determination may be made under static or dynamic conditions, although the latter case is preferred. A simple static procedure is to place a number of samples in ordinaiy laboratoiy desiccators containing sulfuric acid solutions of known concentrations which produce atmospheres of known relative humidity. The sample in each desiccator is weighed periodically until a constant weight is obtained. Moisture content at this final weight represents the equilibrium moisture content for the particular conditions. 

Methods for removing water from solids depends on the thermal stability of the solids or the time available. The safest way is to dry in a vacuum desiccator over concentrated sulfuric acid, phosphorus pentoxide, silica gel, calcium chloride, or some other desiccant. Where substances are stable in air and melt above 100°, drying in an air oven may be adequate. In other cases, use of an Abderhalden pistol may be satisfactory. 

Reagents such as water, ammonia, hydrochloric acid, nitric acid, perchloric acid, and sulfuric acid can be purified via distillation (preferably under reduced pressure and particularly with perchloric acid) using an allglass still. Isothermal distillation is convenient for ammonia a beaker containing concentrated ammonia is placed alongside a beaker of distilled water for several days in an empty desiccator so that some of the ammonia distils over into the water. The redistilled ammonia should be kept in polyethylene or parafrin-waxed bottles. Hydrochloric acid can be purified in the same way. To ensure the absence of metal contaminants from some salts (e.g. ammonium acetate), it may be more expedient to synthesise the salts using distilled components rather than to attempt to purify the salts themselves. 

The crude ester, after a further washing and after being dried in a vacuum desiccator over sulfuric acid, melts at 98-100 and weighs 220 g. (91 per cent of the theoretical amount). 

The product is again collected by filtration, washed with water, resuspended in 225 ml. of water, collected, and pressed as dry as possible. The filter cake is thoroughly dispersed in 160 ml. of absolute alcohol, then filtered, air-dried, and finally dried in a vacuum desiccator over concentrated sulfuric acid. The bright-yellow solid is pulverized and redried. The yield is 115-135 g. (60-71%). When this product is inserted in a bath preheated to 210 and the temperature is increased at a rate of 1° per 10 seconds, decomposition with evolution of gas occurs at 219-220° (cor.) (Note 13). 

For these reasons many research groups prefer to dry the chromatograms in a vacuum desiccator with protection from light. Depending on the mobile phase employed phosphorus pentoxide, potassium hydroxide pellets or sulfuric acid can be placed on the base of the desiccator, to absorb traces of water, acid or base present in the mobile phase. 

About 20 grams of diamino diphenyl sulfone is dissolved in about 500 cc of ethyl alcohol (3A made up of 5 parts methyl alcohol and 100 parts of ethyl alcohol) by placing the ingredients in a flask provided with a reflux condenser and warming over a water bath. About 24 grams of pure grade, very finely powdered (40 to 60 mesh) sodium formaldehyde sulfoxylate Is then rapidly added to the alcohol solution of diamino diphenyl sulfone and the mixture refluxed in the usual manner. It was found that the mixture should be refluxed for a total of 5 hours and that a precipitate starts to form near the 3 hour period. The reaction mixture is then cooled to 15°C and kept at this temperature for about 1 hour. The precipitate formed in the filtrate is filtered off rapidly and drained as much as possible to remove mother liquor and then washed with small amounts of cold alcohol. The solid product is immediately placed in a desiccator and dried over sulfuric acid for about 20 hours. 

The ice-cold fluoboric acid solution is added rather rapidly, with stirring, to the finished tetrazo solution, the temperature being kept below io°. A thick paste of 4,4 -biphenylene-bis-diazonium borofluoride forms. The mixture is stirred at io° for twenty to thirty minutes. It is then collected on a 19-cm. Buchner funnel, and washed consecutively with about 200 cc. of cold water, 200 cc. of cold commercial methyl alcohol, and 200 cc. of commercial ether the cake is sucked as dry as possible between washings. It is then dried in a vacuum desiccator over concentrated sulfuric acid (sp. gr. 1.84). The yield of the dry solid is 393 400 g. (68-69 Per cent of the theoretical amount). The product decomposes at 135-1370. 

B) p-Nitrobenzaldehyde.—A mixture of 45 g. (0.18 mole) of crude />-nitrobenzaldiacetate, 100 cc. of water, 100 cc. of alcohol, and 10 cc. of concentrated sulfuric acid is refluxed for thirty minutes, filtered through a fluted filter, and the filtrate chilled in an ice bath. The crystals are separated by suction filtration, washed with cold water, and dried in a vacuum desiccator. The first crop weighs 22-24 g- (82-89 Per cent of the theoretical amount), m. p. 106-106.5°. A second crop amounting to 2-3 g. is obtained by diluting the filtrate with about 300 cc. of water. The total yield is 24-25.5 g. (89-94 per cent of the theoretical amount) (Note 6). 

The moist salt exploded during drying over the concentrated acid in a vacuum desiccator, (presumably owing to formation of traces of manganese heptoxide from reaction with sulfuric acid vapour). 

The reaction mixture is allowed to stand for 1 to 2 hours (or overnight, if more convenient) after this interval the solution will have assumed a clear, pale yellow color. The condenser is then set for downward distillation, stirring is resumed, and the solvent is removed by distillation from a steam bath (Note 5). After nearly all the ether has been removed, the distillation is continued under reduced pressure (40-50 mm.) until no further appearance of crystals is noted. The residue, which consists of yellow crystals of the crude product, is then allowed to stand until dry in a vacuum desiccator which contains concentrated sulfuric acid, soda lime, and anhydrous calcium chloride (Note 6). 

The selenium is dried overnight in a vacuum desiccator over concentrated sulfuric acid. 

The commercial grade (m.p. 61-63°) of monochloroacetic acid should be ground and thoroughly dried over concentrated sulfuric acid in a vacuum desiccator for two days. The yield was lowered by about 10 per cent when the chloroacetic acid was used without previous drying. 

Sufficient water is now added to the mixture to dissolve the pasty chromium salts (300-800 cc.). The mass of crystals is then rapidly filtered on a Buchner funnel and sucked as dry as possible. The crystals are then transferred to a small laboratory centrifuge and centrifuged for several minutes. The crystals are washed in the centrifuge with about 15-25 cc. of ice water, then with 10-15 cc- of cold petroleum ether, and finally centrifuged till as dry as possible. The crude dichloroacetone is dried in a vacuum desiccator over sulfuric acid overnight. It weighs about 220 g. 

Sodium azide Heavy metals, 4758 Sulfuric acid Hydrofluoric acid, 4479 Vinyl acetate Desiccants, 1532 See ASSESSMENT OF REACTIVE CHEMICAL HAZARDS... 

In a 3-1., three-necked, round-bottomed flask fitted with a powerful slow-speed stirrer having a Teflon blade, a 500-ml. dropping funnel, and a thermometer arranged to dip into the liquid is placed 588 g. (366 ml., 6 moles) of concentrated sulfuric acid. The flask is surrounded by an ice-salt mixture, the stirrer started, and 1216 g. (1170 ml., 12 moles) of acetic anhydride (Note 1) is added at such a rate that the temperature does not rise above 20° (Note 2). The separatory funnel is removed and 912 g. (6 moles) of coarsely powdered D,L-camphor is added (Note 3). The flask is then closed with a stopper and stirring is continued until the camphor is dissolved. The stirrer is replaced by a stopper, the ice bath allowed to melt, and the mixture left to stand for 36 hours (Note 4). The camphorsulfonic acid is collected on a suction filter and washed with ether (Note 5). After being dried in a vacuum desiccator at room temperature, the nearly white crystalline product weighs 530-580 g. (38-42%). It melts at 202-203° with rapid decomposition and is relatively pure (Note 6). 

Sulfur is one of the four major commodities of the chemical industry. The other three are limestone, coal, and salt. Most sulfur that is produced is used to manufacture sulfuric acid (HjSO ). Forty million tons are produced each year in the manufacture of fertilizers, lead-acid batteries, gunpowder, desiccants (drying agent), matches, soaps, plastics, bleaching agents, rubber, road asphalt binders, insecticides, paint, dyes, medical ointment, and other pharmaceutical products, among many, many other uses. Sulfur is essential to life. 

The starting dioxopiperazine (L-prolinyl-L-proline anhydride, 1) is prepared from the ethyl ester of i.-pro-line by storage over concentrated sulfuric acid in a desiccator for 3 weeks yield 59% [a]D — 137.2 (c = 3.5, CHC1,). 

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