Vacuum drying


The combined aqueous layers were extracted twice with pentane or hexane and the extracts were subsequently washed twice with water. The combined organic solutions were concentrated in a water-pump vacuum (drying is not necessary). To the remaining liquid were added 150 ml of methanol and 3 ml of 362 hydrochloric acid. The mixture was warmed for 10 min at 60°C and subsequently the volatile compounds were removed in a water-pump vacuum (rotary evaporator). The residue was dissolved in 200 ml of diethyl ether and the ethereal solution was stirred for 20 min at 20°C with 25 g of machine-powdered KOH (note 3). After addition of water, extraction with diethyl ether and drying over magnesium sulfate, the solvent was removed by evaporation in a water-pump vacuum and the remaining liquid was distilled through a 25-cm Vigreux column to give the allenic alcohol, b.p. 88 /12 mmHg, n 1.4760, in an overall yield of 822.  [c.31]

The main features in which the Radford process differs from the batch operation are in thermal dehydration and compounding. Water-wet nitrocellulose on a continuous vacuum belt filter is vacuum-dried followed by hot air transfusion (80°C) to reduce the moisture to less than 2%. After cooling, alcohol is sprayed on the nitrocellulose to a concentration of 15—20%. The alcohol-wet nitrocellulose is then transferred from a surge feeder to a compounder by a continuous weigh-belt along with the other ingredients of the composition, which are also weighed and added automatically.  [c.44]

The shaping and dehydration line is a long bank of pipes connected by short-radius U-shaped bends that are hot-water jacketed to provide a gradually increasing temperature of ca 60 to 80°C. On passage through the pipe, the viscosity of the particles decreases, and they become spherical and are dehydrated by the dissolved salt present to ca 10% entrained water. The large percentage of entrained solvent is removed by passing the lacquer—water through a series of evaporators. The propellant slurry is then passed over a screen and vacuum filtered in series to recycle the salt and coUoid solution and to wash residual coUoid from the grains. After washing, the propeUant may be vacuum-dried to remove excess water. It is size classified on a series of continuously rotating screens, and may then be impregnated with nitroglycerin ethyl acetate is removed by vacuum distUlation. The product is coated with deterrent, and roUed if necessary, by the same methods used in the batch process. Moisture is removed by a series of continuous vibrated semifluidized-bed dryers. Surface coatings are appUed in a continuous dmm or a batch barrel blender. Blending is carried out in a static internal tube-type blender or a large barrel blender. The propeUant is packed in dmms for shipment.  [c.47]

Degumming and Dewaxing. Some oils, such as soybean, contain appreciable amounts of phosphohpids. These materials are often referred to as gums because of high viscosity and sticky texture. Hydratable phosphatides are removed by treating the cmde oil with hot water or dilute acid. In older plants, hydration is carried out as a batch process. The hydrated oil is allowed to stand in a tank and then the precipitated phosphohpids are skimmed from the top. In modem plants, the oil is hydrated continuously and the phosphatides are removed in a centrifuge. The vacuum-dried sludge from soybean processing is known as lecithin. This material may be used cmde or may be further purified. Lecithin (qv) is a surfactant with several appHcations in foods or specialty chemical products.  [c.124]

Sodium fluoroacetate is usually made by displacing the halogen from an ester of bromo- or chloroacetic acid with potassium fluoride or, in one instance, antimony fluoride, followed by hydrolysis with aqueous sodium hydroxide (15—17). A commercial process for its manufacture from ethyl chloroacetate and potassium fluoride has been described (18). The ester, purified by distillation to remove traces of acid and water, is treated with oven-dried, finely powdered potassium fluoride in a weU-stirred autoclave at 200°C for 11 hours. The resulting ethyl fluoroacetate [459-72-3] is then distilled into an agitated tank containing sodium hydroxide dissolved in methanol. The soHd product is isolated by centrifugation, followed by vacuum drying. Through this process, all Hquids are handled in a closed system of pipes and vessels, carefully inspected for leaks before each mn. This is important since the intermediate fluoroacetate is highly toxic, and the starting chloroacetate is a lacrimator.  [c.307]

Vacuum drying is done by spreading the leather grain on a smooth, heated, stainless steel surface. A cover is placed over the drying surface and the drying chamber evacuated. The advantage of vacuum drying is the speed at which each piece is dried using low temperatures. The vacuum drying system is beneficial for the production of some types of quaHty shoe leather. The equipment is expensive, however, and is only found in modem, weU-financed tanneries.  [c.84]

The wet soap is put into the drying operation where moldable soHd soap is created by reducing the water content in the wet soap from around 30% to between 7 and 15%. This drying step can be attained through three typical approaches atmospheric flash drying, vacuum drying, and chilled surface drying. For all three approaches the wet soap stream is first superheated in a high pressure steam heat exchanger of either a plate-and-frame or tube-and-sheU design. The amount of heating the soap undergoes depends on the drying needs.  [c.156]

Vapor-recompression forced-circulation evaporators consist of a crystallizer a compressor, and a vapor scmbber. Feed brine enters the crystallizer vessel, where salt is precipitated. Vapor is withdrawn, scmbbed, and compressed for reuse in the heater. Ultimately, weak brine from the process is recycled to the solution-rnined cavern. Crystallized salt is removed from the elutriation leg as a slurry. Recompression evaporators are more energy-efficient than multiple-effect evaporators but require higher cost electrical power for energy input. The development of single-stage compressors has significantly reduced costs. The salt slurry from either type of evaporator is dewatered first by centrifuging or vacuum drying and then in kiln or fluidized-bed dryers, where moisture content of the final product is reduced to 0.05% or less. During the twentieth century, salt producers have made significant advances in lowering energy consumption and in reducing salting and scaling in evaporators.  [c.181]

In vacuum drying or other processes containing atmospheres of 100 percent vapor, the temperature of liquid vaporization will equal or exceed the saturation temperature of the liquid at the system pressure. (When a free liquid or wetted surface is present, drying will occur at the saturation temperature, just as free water at I0I.325 kPa vaporizes in a 100 percent steam atmosphere at I00°C.)  [c.1175]

Comparison Data—Plate Dryers Comparative studies have been done on products under both atmospheric and vacuum drying conditions. See Fig. 12-79. These curves demonstrate (1) the improvement in drying achieved with elevated temperature and (2) the impact to the drying process obtained with vacuum operation. Note that cui ve 4 at 90°C, pressure at 6.7 kPa absolute, is comparable to the atmospheric cui ve at 150°C. Also, the comparative atmospheric cui ve at 90°C requires 90 percent more diying time than the vacuum condition. The dramatic improvement with the use of vacuum is important to note for heat-sensitive materials.  [c.1217]

Use alternate drying method (ex. vacuum drying instead of atmospheric drying vacuum tray dryer, freeze drying, cryogenic CO2 drying, instead of vacuum rotary dryer) where material is subdivided in multiple locations  [c.72]

The elements thus formed are then inserted into a sheet steel container, vacuum dried and impregnated, with suitable non-PCB dielectric, which may be an oil dielectric or epoxy resin. The capacitor shell is then hermetically sealed, in oil dielectrics, to avoid any leakage of dielectric during operation.  [c.811]

D-Arabinose [10323-20-3, 28697-53-2 (pyranoside)] M 150.1, m 164 , [a]s46 -123 (c 10, H2O after 24h), pK 12.54. Crystd three times from EtOH, vacuum dried at 60° for 24h and stored in a vacuum desiccator.  [c.115]

Diphenylguanidine [102-06-7] M 211.3, m 148°, pK 10.12. Crystd from toluene, aqueous acetone or EtOH, and vacuum dried.  [c.225]

Sodium hydroxide (anhydrous) [ 1310-73-2] M 40.0, m 323 , b 1390 , d 2.13. Common impurities are water and sodium carbonate. Sodium hydroxide can be purified by dissolving lOOg in IL of pure EtOH, filtering the solution under vacuum through a fine sintered-glass disc to remove insoluble carbonates and halides. (This and subsequent operations should be performed in a dry, C02-free box.) The soln is concentrated under vacuum, using mild heating, to give a thick slurry of the mono-alcoholate which is transferred to a coarse sintered-glass disc and pumped free of mother liquor. After washing the crystals several times with purified alcohol to remove traces of water, they are vacuum dried, with mild heating, for about 30h to decompose the alcoholate, leaving a fine white crystalline powder [Kelly and Snyder 7 Am Chem Soc 73 4114 1951],  [c.472]

High speed automatic mechanical pressing is commonly used to volumetricaHy load small quantities of primary explosives into blasting caps and detonators and to make small explosive components. Primary explosives may be mixed with graphite to improve flow and antistatic properties, or may be desensitized with waxes, stearates, or polymeric compounds. Secondary explosives and explosive mixtures may be pressed to form booster pellets or to load components directiy as in the case of armor-penetrating projectiles. Where the explosive is too sensitive in its pure crystalline state to permit press loading or lacks the requited mechanical properties in its compressed state for subsequent use, it is coated with polymeric materials such as polystyrene and polybutadiene, to form mol ding powders, often referred to as plastic-bonded explosives. Desensitization is obtained when the explosive crystals are thoroughly and uniformly coated. A typical procedure for making PBX-type explosives involves making a lacquer of a solution of the organic polymer in a solvent, eg, ethylacetate, and a dding it to a water slurry of the explosive. The solvent is distilled off under vacuum while the mix is agitated, precipitating the polymer on the explosive. The coated explosive forms small agglomerates as the solvent removal process continues. It is filtered, washed, and vacuum dried to form a free-fiowing, dustiess, high density powder. Bi- or trimodal size distributions of spherical shaped explosive particles are often used to improve the flow characteristics and packing density of the mol ding powder. Antistatic agents (qv) such as carbon black may be added to prevent dust explosions. In another coating technique, the requited amount of low melting wax is added to a water slurry of the explosive at a temperature high enough to melt the wax. After agitation to distribute the wax on the crystals, the temperature is lowered, the water decanted, and the remaining mass filtered and dried.  [c.20]

The physical and chemical properties are less well known for transition metals than for the alkaU metal fluoroborates (Table 4). Most transition-metal fluoroborates are strongly hydrated coordination compounds and are difficult to dry without decomposition. Decomposition frequently occurs during the concentration of solutions for crysta11i2ation. The stabiUty of the metal fluorides accentuates this problem. Loss of HF because of hydrolysis makes the reaction proceed even more rapidly. Even with low temperature vacuum drying to partially solve the decomposition, the dry salt readily absorbs water. The crystalline soflds are generally soluble in water, alcohols, and ketones but only poorly soluble in hydrocarbons and halocarbons.  [c.167]

Drying. The retanned leather is stretched to increase the area for the best yield and to produce a flat leather surface. The leather is then dried. There are several drying (qv) systems used which depend on the type and thickness of the leather. Thin garment leathers, made soft by retanning and fatHquoring, may be dried by hanging in a dry loft. Soft leathers can be reworked by mechanical means to the softness desired when dry. For shoe uppers the leather should be held in a stretched condition. Two or three types of drying are commonly in use in the industry toggle drying, paste drying, and vacuum drying. In toggle drying the leather is held in an extended condition with clamps on the edge of the leather stretched on a screen. The screens are placed in a temperature and humidity controUed dryer until the leather is dry.  [c.84]

The esterification reaction in making ester oils is commonly carried out with a catalyst at about 210°C while removing excess water as it forms (32). Excess acid or alcohol is then stripped off, and unreacted acid is neutrali2ed with calcium carbonate or calcium hydroxide before final vacuum drying (qv) and filtration (qv).  [c.245]

Other direct tests for measuring the fat in milk and dairy products include the Mojonnier method, which employs thermostatically controUed vacuum drying ovens and hot plates together with desiccators whose temperature is controUed by circulating water the Gerber test, developed and used extensively in Europe (21,22), which employs sulfuric acid to dissolve soHds other than fat, amyl alcohol [71-41-0] to prevent charring of fat, and centrifuging to separate the fat into the caHbrated neck of the Gerber test bottle and the DPS detergent test, based on the principle that the selected detergent(s) dissolves readily in both fat and water phases of milk and then leaves the solution upon appHcation of heat and/or salt, thereby Hberating the accumulated fat for measurement. The official AO AC Te Sa test, a rapid detergent method using alkaline buffering agents and test bottles fitted with a side arm and plunger, is essentially a chemical extraction method appHcable to a variety of animal and vegetable fat products. These fat tests are described (23).  [c.364]

The one-part sealant bases require drying the ingredients. Predrying the ingredients before manufacturing is cumbersome and expensive. Other alternatives include vacuum drying during manufacture, a2eotropic distillation to remove water before moisture-sensitive components are added, and use of desiccants (qv). The most common method is through the use of the desiccant barium oxide (8). The mixing is done on equipment as described except the processes are carried out under an atmosphere of dry nitrogen and the final step is to combine the pastes into a single mix.  [c.458]

The beneficial effect of anticholinergics in asthma rehes upon bronchial smooth muscle exhibiting a cholinergicaHy mediated tone (resting state tension) (112,113). Receptors in the cholinergic nervous system are divided into two main classes, muscarinic (M) and nicotinic (113). Anticholinergic agents exert their bronchodilating effect by blocking the muscarinic-receptors found in bronchial smooth muscle. This blockade inhibits the normal cholinergic-induced tone. In addition, it has been shown that cholinergic receptor stimulation results in inhibition of adenylate cyclase, thereby reducing cychc AMP levels (114). Blockade of this effect should result in indirect bronchodilatation (Fig. 2). Although atropine is effective in preventing exercise-induced asthma (103), it and other anticholinergic agents have no effect on bronchial hyperesponsiveness, the release of other mediators, or on the inflammatory process (115,116). Significant dose related side-effects such as blurred vision, dry mouth, and inhibition of gastric motility occur. These side effects result from systematic distribution of the dmgs, including penetration into the central nervous system and their widespread antagonism of other muscarinic receptors.  [c.443]

Processing conditions can have a dramatic effect on sealant rheology, cure time, and physical properties. Typical processing variables are mixer speed (rpm), time, temperature, and vacuum. Order of ingredient addition is also important. For one-part moisture-curing sbicones, it is important to keep the raw materials dry and to minimize exposure of the finished sealant to moist air. Fabure to do so can result in the formation of small cured gels in the sealant. Dry raw materials are also critical when manufacturing one-part urethanes and polysulfides. The isocyanate end of the prepolymer is very reactive with moisture and can lead to gassing from carbon dioxide formation. The catalysts used to cure one-part polysulfides are moisture-sensitive and must be protected from moisture during manufacture. Three methods used to dry urethane and polysulfide raw materials are azeotropic distillation with toluene, vacuum drying, and addition of a desiccant to the formulation. Stoichiometry of the urethane prepolymers is critical for achieving the desired sealant properties. Specifically, this means closely controlling the ratio of isocyanate to hydroxyl.  [c.313]

Vacuum drying is similar to atmospheric drying but does not require as high a temperature to drive the moisture loss it can be performed in a considerably smaller tower. Wet soap, heated to around 130—150°C in a low pressure heat exchanger, is sprayed onto the walls of an evacuated tower using a nozzle. The nozzle can either be unidirectional, mounted on a rotating shaft, or statically mounted and multidirectional. Cooling and drying is achieved in one step through the rapid release of moisture as vapor, which occurs upon introduction of superheated soap into the vacuum chamber (foule-Thompson cooling). The dried, cooled soap is scraped off the tower wall with a scraper blade mounted on a rotating shaft. The moisture in the dried soap is dependent on the flow rate, the temperature of the soap, and the pressure in the vacuum chamber the last also controls the final temperature of the soap. The dried soap is obtained at the bottom of the tower in the form of small pellets through an airlock created by the screw extmsion of the soap through a multiholed orifice plate. Vacuum drying has a number of advantages over atmospheric flash drying, including the lower pressure steam requirements, lower overall temperatures, and the more compact drying system/tower.  [c.156]

Thiamine chloride hydrochloride [67-03-8] (thiamine hydrochloride) C 2H gN40SCl2 (2), crystallizes as colorless monoclinic needles, mp 248—250°C (with decomposition), which in bulk appear white and have an approximate density of 0.4 kg/L. Several polymorphic crystal forms have been reported. The salt has a characteristic thiazole meat-like odor and a slightly bitter taste. On exposure to air of average humidity, the hydrochloride (2) can adsorb up to one mole of water (more typically slightly less, to about 4% by weight), which may be removed by heating to 100°C or by vacuum drying. It is very soluble in water (over 1 kg/L at 25°C), soluble in glycerol (0.056 kg/L), propylene glycol, and methanol, sparingly soluble in 95% ethanol (0.01 kg/L), and practically insoluble in less polar organic solvents. In 1—5% solutions in water it shows a pH of 3— 3.5 (6,7).  [c.85]

Calcium hypochlorite is made by drying a filter cake of neutral calcium hypochlorite dihydrate containing 30—50% water depending on the type of filter used. This material is usually prepared from hydrated lime, caustic, and chlorine. The cake can be air or vacuum dried. During air drying some reaction with CO2 occurs resulting in formation of CaC03. Some loss of available chlorine also occurs lea ding to formation of chlorate, chloride, oxygen, chlorine, and possibly HOCl and CI2O. Control of moisture and mechanical treatment (preforming) during drying results in a free-flowing essentially dusfless granular product (182,239). Slurries containing about 45% soHds can be sprayed into a fluidized bed of granular Ca(OCl)2 (240). The intermediate product containing about 20% water can be dried further by conventional means.  [c.473]

The vacuum plate drwer is provided as pari of a closed system. The vacuum dryer has a cylindrical housing and is rated for fiill-vacuum operation (typical pressure range 3-27 kPa absolute). The exhaust vapor is evacuated try a vacuum pump and is passed through a condenser for solvent recovery. There is no purge-gas system required for operation under vacuum. Of special note in the vacuum-drying system  [c.1216]

Until now complex compounds of iron and hydroxylamine haven t been received. It is connected with liability of complex compounds of iron with monodentant amines and complication of interaction in the system of Fe-VFe - NH OH. Usual methods that are used to synthesis hydroxylamine complexes in this case turned out to be non-effective. For depression of oxidation-reduction processes and hydrolisation we used the method of synthesis in anaerobic conditions - in atmosphere of argon. Outlet FeCl, was received using the method of high-temperature synthesis. NH OH HCl passed vacuum drying process. Absolute low alcohols were used as solutions. We have received two kinetic unstable complex of iron (II) and hydroxylamine in solution dark-green (pH 3,0 -6,0) (I) and brown-red (pH 6,5 - 7,5) (II). Absorption spectrums of complexes were made, spectral lines were assigned. For the (I) parameter 10 Dg - 9756 cm was found. The character of spectrums shows that I high spin complex of Fe (II) and II is low-spin complex. Using the method A.K. Babko -constants of compounds was counted.  [c.42]

During development of drying circuits for the rests of primary processing grapes, the element content of received raw material components was studied. The initial material was processed in vacuum drying installation at the fixed temperatures in a range 40-60°C. The gamma-activation analysis with help of the high-current electron accelerator was applied to measurements. The content of elements Ca, Mn, Ni, Zn, Rb, Zr, Mo, I and U in skins and seeds of white grapes Aligote and of red grapes Moldova was determined.  [c.441]

In the post-impregnated system, although the coils are formed as above, they are inserted into the slots when they are still in a flexible state. They are now easy to handle and cause no damage to their own insulation or the insulation of the slots while being inserted into the slots. The process up to the winding stage of the stator is thus faster and economical. The stator is then vacuum dried to remove trapped moisture, followed by immersion in a resin bath. It is kept immersed under vacuum so that resin can fill the voids. The bath is then pressurized to compress the resin so that it penetrates deeply into the slots, crevices and voids. Figure 9..3 illustrates the lowering of a stator s pre-formed windings into a resin impregnating tank. The stator is then cured in an oven under controlled conditions. The overall vacuum impregnating system may be expensive in view of the equipment required to dip the bulk of the stator into the impregnating resin to create a very high vacuum, but the excellent properties of postvacuum impregnation may compensate this initial cost.  [c.223]

Crown-6 [17455-13-9] M 264.3, m 37-39 . Recrystd from acetonitrile and vacuum dried. Purified by pptn of 18-crown-6/nitromethane 1 2 complex with Et20/nitromethane (10 1 mixture). The complex is decomposed in vacuum and distilled under reduced pressure. Also recrystd from acetonitrile and vacuum dried.  [c.174]

Diacetyl benzene [1009-61-6] M 162.2, m 113-5-114.2 . Crystd from benzene and vacuum dried over CaCl2. Also dissolved in acetone, treated with Norit, evapd and recrystd from MeOH [Wagner et al. J Am Chem Soc 108 7727 1986].  [c.187]

Recrysts slowly from aqueous 80% EtOH, then vacuum dried over P2O5. Alternatively, crystd from water at 55°, then dried for 6h in a vacuum oven between 60-70° at 2mm.  [c.251]

The propionamide can be dried over CaO. H2O and unreacted propionic acid were removed as their xylene azeotropes. It was vacuum dried. Material used as an electrolyte solvent (specific conductance less than 10 ohm cm" ) was obtained by fractional distn under reduced pressure, and stored over BaO or molecular sieves because it readily absorbs moisture from the atmosphere on prolonged storage. [Hoover Pure Appl Chem 37 581 I974 Recommended Methods for Purification of Solvents and Tests for Impurities, Coetzee Ed., Pergamon Press, 1982.]  [c.299]

Alternatively, it is dissolved in twice its weight of water at 55-60°, filtered, coned to half its volume and poured slowly, with stirring, into about twice the volume of EtOH. The crystals which separate on cooling to 3-4° are filtered off, washed with a little MeOH, air dried by suction, then finally ground and dried in a vacuum desiccator over P2O5. It has also been crystd from water, MeOH or aq MeOH, and vacuum dried at 80° for 2 days.  [c.382]

Potassium bromate [7758-01-2] M 167.0, m 350°(dec at 370°), d 3.27. Crystd from distilled H20(2mL/g) between 100° and 0°. To remove bromide contamination, a 5% soln in distilled H2O, cooled to 10°, has been bubbled with gaseous chlorine for 2h, then filtered and extracted with reagent grade CCI4 until colourless and odourless. After evaporating the aqueous phase to about half its volume, it was cooled again slowly to about 10°. The crystalline KB1O3 was separated, washed with 95% EtOH and vacuum dried [Boyd, Cobble and Wexler J Am Chem Soc 74 237 7952]. Another way to remove Br" ions was by stirring several times in MeOH and then dried at 150° [Field and Boyd J Phys Chem 89 3767 1985],  [c.453]

Sodium ethylsulfate [546-74-7] M 166.1. Recrystd three times from MeOH-Et20 and vacuum dried.  [c.470]

Sodium hexafluorophosphate [21324-39-0] M 167.9, pK - 0.5, pK 2 5.12 (for fluorophosphoric acid H2PO3F). Recrystd from acetonitrile and vacuum dried for 2 days at room temperature. It is an irritant and is hygroscopic. [Delville et al. J Am Chem Soc 109 7293 1987.]  [c.471]


See pages that mention the term Vacuum drying : [c.139]    [c.227]    [c.230]    [c.481]    [c.70]    [c.415]    [c.191]    [c.192]    [c.247]    [c.354]    [c.470]    [c.513]    [c.574]   
Advanced organic synthesis (1971) -- [ c.183 ]