Vacuum condensers

Entering vacuum condensers to cut down pressure drop  [c.3]

Figure 1. Baffling and inlet bathtub are shown in this typical vacuum condenser design. Figure 1. Baffling and inlet bathtub are shown in this typical vacuum condenser design.
Another example of pressure control by variable heat transfer coefficient is a vacuum condenser. The vacuum system pulls the inerts out through a vent. The control valve between the condenser and vacuum system varies the amount of inerts leaving the condenser. If the pressure gets too high, the control valve opens to pull out more inerts and produce a smaller tube area blanketed by inerts. Since relatively stagnant inerts have poorer heat transfer than condensing vapors, additional inerts  [c.66]

The control valve allows the Jets to pull noncondensibles out of the condenser as needed for system pressure control. In addition to requiring extra surface area for control, the vacuum condenser also needs enough surface area for subcooling to ensure that the Jets do not pull valuable hydrocarbons or other materials out with the noncondensibles. To allow proper control and subcooling, some designers add approximately 50% to the calculated length.  [c.291]

The hot condensate from the heater in A can be returned to the boiler. The solution to be evaporated is fed at 195 °F into the liquor spaces of effect A at F by means of a pump or by gravity. Since the pressures in B and C are progressively lower, the solution can be drawn in sequence through the system by the pipes F and F" and finally lifted to atmospheric pressure by the pump F ". This arrangement is called parallel flow, or forward flow. In order to permit the removal of fixed gases from the heating space of all the effects, each is connected by a small pipe to the vacuum condenser or to the body of the vapor space of the same effect which is obviously at lower pressure. Where the noncondensable gas is small, the latter is better practice, as this, method acts as a safeguard against the loss of steam due to its discharge with fixed gases.  [c.116]

In direct contact heal exchange, there is no wall to separate hot and cold streams, and high rales of heal transfer are achieved. Applications include reactor off-gas quenching, vacuum condensers, desuperheating, and humidification. Water-cooling lowers are a particular example of a direct contact heal e.xchanger. In direct contact cooler-condensers, the condensed liquid is frequently used as the coolant.  [c.137]

Plate and frame e.xchangers (plate heat exchangers)-used for heating and cooling in reactor off-gas quenching, vacuum condensers, desuperheating, and humidification.  [c.173]

Vapor Treatment. The vapors from the tank space can be sent to a treatment system (condenser, absorption, etc.) before venting. The system shown in Fig. 9.1 uses a vacuum-pressure relief valve which allows air in from the atmosphere when the liquid level falls (Fig. 9.1a) but forces the vapor through a treatment system when the tank is filled (Fig. 9.16). If inert gas blanketing is required, because of the flammable nature of the material, then a similar system can be adopted which draws inert gas rather than air when the liquid level falls.  [c.260]

Since solids do not exist as truly infinite systems, there are issues related to their temiination (i.e. surfaces). However, in most cases, the existence of a surface does not strongly affect the properties of the crystal as a whole. The number of atoms in the interior of a cluster scale as the cube of the size of the specimen while the number of surface atoms scale as the square of the size of the specimen. For a sample of macroscopic size, the number of interior atoms vastly exceeds the number of atoms at the surface. On the other hand, there are interesting properties of the surface of condensed matter systems that have no analogue in atomic or molecular systems. For example, electronic states can exist that trap electrons at the interface between a solid and the vacuum [1].  [c.86]

Solid phosphorus, arsenic and antimony exist in well known allo-tropic modifications. Phosphorus has three main allotropic forms, white, red and black. White phosphorus is a wax-like solid made up of tetrahedral P4 molecules with a strained P—P—P angle of 60° these also occur in liquid phosphorus. The reactivity of white phosphorus is attributed largely to this strained structure. The rather less reactive red allotrope can be made by heating white phosphorus at 670 K for several hours at slightly higher temperatures, 690 K, red phosphorus sublimes, the vapour condensing to reform white phosphorus. If, however, red phosphorus is heated in a vacuum and the vapour rapidly condensed, apparently another modification, violet phosphorus, is obtained. It is probable that violet phosphorus is a polymer of high molecular weight which on heating breaks down into P2 molecules. These on cooling normally dimerise to form P4 molecules, i.e. white phosphorus, but in vacuo link up  [c.209]

The benzene has now to be distilled off at atmospheric pressure and the residual phenylhydrazine at reduced pressure. For this purpose, fit a small dropping-funnel to the main neck of a 60 ml. Claisen flask, cork the other neck, and fit a water-condenser to the side-arm. Run about 30 ml. of the benzene solution into the flask, and heat the latter in an oil-bath, controlling the temperature of the bath so that the benzene distils gently over. Allow the remainder of the solution to run in from the dropping-funnel as fast as the benzene itself distils over. When the benzene has been almost entirely removed, fit a capillary tube and a thermometer into the necks of the flask, and then assemble the complete apparatus for vacuum distillation, using either the simple apparatus shown in Fig. i2(a) (p. 29) or a water-condenser fitted with a pig (Fig. 13, p. 31, or Fig. 23(F), p. 46). Distil the phenylhydrazine carefully from an oil-bath and collect a fraction boiling over a range of about 3°, e.g. at i2 ]-i2o°j22 mm. The phenylhydrazine is thus obtained as a very pale yellow (almost colourless) oil, of d, i-io it has a characteristic odour and is only slightly soluble in water. Yield, 16-17 g. Pure phenylhydrazine has m.p. 23° it boils at 242-243° at atmospheric pressure with partial decomposition.  [c.199]

Thermal insulation. Even slight heat losses considerably disturb the delicate equilibrium of an efficient column, and almost perfect thermal insulation is required for the separation of components with boUing points only a few degrees apart. Theoretically, the greatest efficiency is obtained under adiabatic conditions. If the components boil below 100°, a silvered vacuum jacket is satisfactory the efficiency of such a jacket will depend upon the care with which it is cleaned, silvered and exhausted. In general, the most satisfactory insulation is provided by the application of heat to balance the heat loss. An electrically-heated jacket is fitted round the column the temperature of the jacket, which should be controlled by means of an external resistance or a variable voltage transformer (Variac), should be adjusted within 5° of the temperature of the vapour condensing at the upper end of the column,  [c.95]

The mean free i)ath of large organic molecules is shorter it is evident, therefore, that the condenser must be quite close to the evaporating surface. Strictly speaking, a molecular still may be deflned as a still in which the distance between the evaporating surface and the cold condensing surface is less than the mean free path of the molecules. The escaping molecules will, for the most part, proceed in a straight path to the condenser by maintaining the temperature of the latter comparatively low, the amount of reflection of molecules from the condensing surface is reduced. The great advantage of distillation under a high vacuum is that the boiling point is considerably reduced—in some cases by as much as 200-300°—thus rendering possible the distillation of substances which decompose at higher temperatures, of substances which are very sensitive to heat, and also of compounds of very high boiling point and large molecular weight.  [c.120]

The Stedman-type column is shown in Fig. 11, 56, 25. The characteristic features are (i) the use of a fine stainless steel wire cloth formed into conical discs, and (ii) an accurately fitting Pyrex glass jacket, produced by shrinking Pyrex glass on mandrels to the required inside dimensions. Modifications incorporating a silvered vacuum jacket and an electrically-heated jacket are marketed. This column is said to possess high efficiency but is expensive. It is generally employed in conjunction with a total-condensation variable take-off still head.  [c.219]

Method A. In a 500 ml. round-bottomed flask, fitted with a reflux condenser attached to a gas trap (Fig. II, 13, 8), place 59 g. of succinic acid and 117-5 g. (107-5 ml.) of redistilled acetyl chloride. Reflux the mixture gently upon a water bath until all the acid dissolves (1-2 hours). Allow the solution to cool undisturbed and finally cool in ice. Collect the succinic anhydride, which separates in beautiful crystals, on a Buchner or sintered glass funnel, wash it with two 40 ml. portions of anhydrous ether, and dry in a vacuum desiccator. The yield of succinic anhydride, m.p. 118-119°, is 47 g.  [c.375]

Type 77 units are the condenser and reboiler designs. One side is spiral flow and the other side is in cross flow. These SHEs provide veiy stable designs for vacuum condensing and reboiling seiwices. A SHE can be fitted with special mounting connec tions for refliix-type vent-condenser apphcations. The vertically mounted SHE directly attaches on the column or tank.  [c.1085]

Applications The common Heliflow apphcations are tank-vent condensers, sample coolers, pump-seal coolers, and steam-jet vacuum condensers. Instant water heaters, glycoLwater seivdces, and cryogenic vaporizers use the spiral tube s ability to reduce thermally induced stresses caused in these apphcations.  [c.1086]

A vacuum condenser has vacuum equipment (such as steam jets) pulling the noncondensibles out of the cold end of the unit. A system handling flammable substances has a control valve between the condenser and Jets (an air bleed is used to control nonflammable systems). The control method involves derating part of the tube surface by blajiketing it with noncondensibles that exhibit poor  [c.291]

The fact that electron beam instmments work under high vacuum prohibits the analysis of aqueous systems, such as biological materials or suspensions, or emulsions without specimen preparation as outlined above. These preparation procedures are time consuming and are often not justified in view of the only moderate resolution required to solve a specific practical question (e.g. to analyse the grain size of powders, bacterial colonies on agar plates, to study the solidification of concrete, etc). Enviromnental SEM (ESEM) and high-pressure SEM instmments are equipped with differentially pumped vacuum systems and Peltier-cooled specimen stages, which allow wet samples to be observed at pressures up to 5000 Pa [48]. Evaporation of water from the specimen or condensation of water onto the specimen can thus be efficiently controlled. No metal coating or other preparative steps are needed to control charging of the specimen since the interaction of the electron beam with the gas molecules in the specimen chamber produces positive ions that can compensate surface charges. High-pressure SEM , tlierefore, can study insulators without applymg a conductive coating. The high gas pressure in the vicinity of the specimen leads to a squirting of the electron beam. Thus the resolution-limiting spot size achievable on the specimen surface depends on the acceleration voltage, the gas pressure, the scattering cross section of the gas and the distance the electrons have to travel tlirough tlie high gas pressure zone [49]. High-pressure SEM and ESEM is still under development and the scope of applications is expanding. Results to date consist mainly of analytical and low-resolution images (e.g. [ ]).  [c.1642]

Since the AFM is connnonly used under ambient conditions, it must be home in mind that the sample is likely to be covered with multilayers of condensed water. Consequently, as the tip approaches the surface, a meniscus fonus between tip and surface, introducing an additional attractive capillary force. Depending on the tip radius, the magnitude of this force can be equal to or greater than that of the van der Waals forces and is observed clearly in the approach curve [98]. In fact, this effect has been exploited for the characterization of thin liquid lubricant films on surfaces [95]. The capillary forces may be eliminated by operation in ultrahigh vacuum, provided both tip and sample are baked, or, most simply, by carrying out the experiment under a contamination-free liquid enviromuent, using a liquid cell [99].  [c.1696]

The oxime is freely soluble in water and in most organic liquids. Recrystallise the crude dry product from a minimum of 60-80 petrol or (less suitably) cyclohexane for this purpose first determine approximately, by means of a small-scale test-tube experiment, the minimum proportion of the hot solvent required to dissolve the oxime from about 0-5 g. of the crude material. Then place the bulk of the crude product in a small (100 ml.) round-bottomed or conical flask fitted with a reflux water-condenser, add the required amount of the solvent and boil the mixture on a water-bath. Then turn out the gas, and quickly filter the hot mixture through a fluted filter-paper into a conical flask the sodium chloride remains on the filter, whilst the filtrate on cooling in ice-water deposits the acetoxime as colourless crystals. These, when filtered anddried (either by pressing between drying-paper or by placing in an atmospheric desiccator) have m.p. 60 . Acetoxime sublimes rather readily when exposed to the air, and rapidly when warmed or when placed in a vacuum. Hence the necessity for an atmospheric desiccator for drying purposes.  [c.94]

Meanwhile fit up an apparatus for ether distillation precisely similar to that shown in Fig. 64 (p. 163), except that a 100 ml. Claisen flask is used instead of the simple distillation-flask shown in the figure, f.e., as in Fig. 23(E), p. 45. The droppingTunnel is fitted to the main neck of the Claisen flask, the side-neck being corked. Filter the dry ethereal solution through a fluted filter-paper directly into the dropping-funnel, finally washing the conical flask and the calcium chloride with a few ml. of fresh ether. Then distil off the ether in the usual way, allowing the solution to fall from the droppingTunnel into the flask as fast as the ether itself distils over—observe all the usual precautions for ether distillations. When the distillation of the ether is complete and only the crude ester remains in the Claisen flask, fit up the latter for vacuum-distillation, using the simple apparatus shown in Fig. 12(a), (p. 29) or a Perkin triangle with condenser (Fig. 14, p. 31) or the condenser and pig shown in Fig. 23(F), p. 46, and heating the flask in an oil-bath. The ethyl malonate usually distils as a sharp fraction boiling over a range of about 2-3° it may be recognised from the following b.p.s 93°/i6 mm., io5°/26 mm. Yield, about 35 g. If necessary the ethyl malonate may be distilled at atmospheric pressure, at which it has b.p. 198° slight decomposition occurs in these circumstances, however, and the distillate, although colourless, has a slightly acrid odour.  [c.274]

A fractionating column consists essentially of a long vertical tube through which the vapour passes upward and is partially condensed the condensate flows down the column and is returned eventually to the flask. Inside the column the returning liquid is brought into intimate contact with the ascending vapour and a heat interchange occurs whereby the vapour is enriched with the more volatile component A at the expense of the liquid in an attempt to reach equilibrium. The conditions necessary for a good separation are —(i) there should be a comparatively large amount of liquid continually returning through the column (u) thorough mixing of liquid and vapour and (iii) a large active surface of contact between liquid and vapour. Excessive cooling should be avoided this diflBculty is particularly apparent with liquids of high boiling point and may be overcome by suitably insulating or lagging the outer surface of the column or, if possible, by surrounding it with a vacuum jacket or an electrically heated jacket. Various types of laboratory fractionating columns are described in Sections 11,15-11,18.  [c.9]

Mix 50 ml. of formalin, containing about 37 per cent, of formaldehyde, with 40 ml. of concentrated ammonia solution (sp. gr. 0- 88) in a 200 ml. round-bottomed flask. Insert a two-holed cork or rubber stopper carrying a capillary tube drawn out at the lower end (as for vacuum distillation) and reaching almost to the bottom of the flask, and also a short outlet tube connected through a filter flask to a water pump. Evaporate the contents of the flask as far as possible on a water bath under reduced pressure. Add a further 40 ml. of concentrated ammonia solution and repeat the evaporation. Attach a reflux condenser to the flask, add sufficient absolute ethyl alcohol (about 100 ml.) in small portions to dissolve most of the residue, heat under reflux for a few minutes and filter the hot alcoholic extract, preferably through a hot water fuimel (all flames in the vicinity must be extinguished). When cold, filter the hexamine, wash it with a little absolute alcohol, and dry in the air. The yield is 10 g. Treat the filtrate with an equal volume of dry ether and cool in ice. A fiulher 2 g. of hexamine is obtained.  [c.326]

METHYLAMINE HYDROCHLORIDE from Formalin) Place 250 g. of ammonium chloride and 500 g. of technical formaldehyde solution (formalin, 35-40 per cent, formaldehyde) in a 1-htre distilling flask insert a thermometer dipping well into the hquid and attach a condenser for downward distillation. Heat the flask on a wire gauze or in an air bath slowly until the temperature reaches 104° and maintain the temperature at this point vmtil no more distillate is collected (4-5 hours) (1). Cool the contents of the flask rapidly to room temperature and ter off the ammonium chloride (ca. 62 g.) which separates rapidly at the pump. Concentrate the filtrate to one half of the original volume on a water bath, when more ammonium chloride (ca. 19 g.) will crystallise out on coohng to room temperature. After filtration at the pump, evaporate on a water bath until a crystaUine scum forms on the surface of the hot solution. Allow to cool and filter off the methylamine hydrochloride (about 96 g.) (2). Concentrate again on a water bath and thus obtain a second crop (about 18 g.) of methylamine hydrochloride. Evaporate the mother liquor as far as possible on a water bath and leave it in a vacuum desiccator over sodium hydroxide pellets for 24 hours digest the semi-solid residue with chloroform (to remove the dimethyl-amine hydrochloride), filter off (2) the methylamine hydrochloride (about 20 g.) at the pump and wash it with a httle chloroform. [Upon concentrating the chloroform solution to about half the original bulk, about 27 g. of dimethylamine hydrochloride may be obtained the mother  [c.415]

Purify commercial undecylenic acid by distillation of, say, 250 g. under diminished pressure and collect the fraction, b.p. 152-154°/6 mm. this has a freezing point of 23°. Dissolve 108 g. of the purified undecylenic acid in 285 ml. of dry carbon tetrachloride (1) in a 1-litre three-necked flask provided with a mercury-sealed stirrer, a dropping funnel and a reflux condenser. Cool the flask in a freezing mixture of ice and salt, stir the solution and add 96 g. (31 ml.) of dry bromine (Section 11,49,5) during a period of 1 hour allow the mixture to gradually warm up to the temperature of the laboratory. Arrange the flask for distillation (compare Fig.//, 41, 1, but with stirrer in central neck), remove the carbon tetrachloride by heating on a water bath, and pour the residue into a large evaporating dish. Upon standing 1-2 days (more rapidly when left in a vacuum desiccator over silica gel), the dibromo acid crystalUses completely. The yield is quantitative.  [c.469]

Into a 500 ml. round-bottomed flask, fitted with a reflux condenser, place 42 g. of potassium hydroxide pellets and 120 g. (152 ml.) of absolute ethyl alcohol. Heat under reflux for 1 hour. Allow to cool and decant the liquid from the residual solid into another dry 500 ml. flask add 57 g. (45 ml.) of A.R. carbon dtsulphide slowly and with constant shaking. Filter the resulting almost solid mass, after cooling in ice, on a sintered glass funnel at the pump, and wash it with two 25 ml. portions of ether (sp. gr. 0-720), followed by 25 ml. of anhydrous ether. Dry the potassium ethyl xanthate in a vacuum desiccator over silica gel. The yield is 74 g. If desired, it ma be recrystallised from absolute ethyl alcohol, but this is usually unneceasary.  [c.499]

Place a mixture of 25 g. of benzophenone (Section IV,139), 15 g. of hydroxylamine hydrochloride, 50 ml. of rectified spirit and 10 ml. of water in a 500 ml. round-bottomed flask. Add 28 g. of sodium hydroxide (pellet form) in portions with shaking if the reaction becomes too vigorous, cool the flask with running tap water. When aU the sodium hydroxide has been added, attach a reflux condenser to the flask, heat to boiling and reflux for 5 minutes. Cool, and pour the contents of the flask into a solution of 75 ml. of concentrated hydrochloric acid in 500 ml, of water contained in a 1 litre beaker. Filter the precipitate at the pump, wash thoroughly with cold water, and dry in an electric oven at 40° or in a vacuum desiccator. The yield of benzophenone oxime, m.p. 142°, is 26 5 g. It may be recrystaUised from methyl alcohol (4 ml. per gram) but the m.p. is unaffected. The oxime is gradually decomposed by oxygen and traces of moisture into benzophenone and nitric acid it should be preserved in a vacuum desiccator filled with pure dry carbon dioxide.  [c.741]

Veratraldehyde (methyl vanillin). Place 152 g. of a good sample of commercial vanillin, m.p. 81-82°, in a 1 litre three-necked flask (or Pyrex wide-mouthed bottle), equipped with a reflux condenser, a mechanical stirrer, and two separatory funnels (one of these may be supported in the top of the reflux condenser by means of a grooved cork). Melt the vanillin by warming on a water bath and stir vigorously. Charge one funnel with a solution of 82 g. of pure potassium hydroxide in 120 ml. of water and the other funnel with 160 g. (120 ml.) of purified dimethyl sulphate (1) CAUTION conduet all operations with dimethyl sulphate in the fume cupboard). Run in the potassium hydroxide solution at the rate of two drops a second, and 20 seconds after this has started add the dimethyl sulphate at the same rate. Stop the external heating after a few minutes the mixture continues to reflux gently from the heat of the reaction. The reaction mixture should be pale reddish-brown since this colour indicates that it is alkaline should the colour change to greeu, an acid reaction is indicated and this condition should be corrected by shghtly increasing the rate of addition of the alkali. When half to three-quarters of the reagents have been added, the reaction mixture becomes turbid and separates into two layers. As soon as all the reagents have been run in (about 20 minutes), pour the yellow reaction mixture into a large porcelain basin and allow to cool without disturbance, preferably overnight. Filter the hard crystalline mass of veratraldehyde, grind it in a glass mortar with 300 ml. of ice cold water, filter at the pump and dry in a vacuum desiccator. The yield of veratraldehyde, m.p. 43-44°, is 160 g. This product is suflSciently pure for most purposes it can be purified without appreciable loss by distillation under reduced pressure, b.p. 158°/8 mm. m.p. 46°. The aldehyde is easily oxidised in the air and should therefore be kept in a tightly stoppered bottle.  [c.804]

Equip a 3-litre three-necked flask with a thermometer, mercury-sealed stirrer and a reflux condenser (Liebig pattern with a wide inner tube). Place a solution of 100 g. (106 ml.) of a-picoline (1) in 1 litre of water in the flask and heat to 70° on a water bath. Add 450 g. of potassium permanganate in 10 equal portions through the condenser over a period of 3-4 hours maintain the temperature at 70° for the first five additions and at 86-90° for the last five. Make each successive addition of potassium permanganate only after the preceding amount is decolourised and wash it down with 20-25 ml. of water. After the last charge of potassium permanganate is decolourised, raise the temperature to 95°, filter the hot reaction mixture with suction and wash the manganese dioxide cake on the filter with four 200 ml. portions of hot water allow each portion to soak into the cake without application of vacuum and finally suck dry before adding fresh wash water. Evaporate down the combined filtrate and washings to a volume of about 400 ml. allow to cool and adjust to a pH of 3 -2 (the isoelectric point) using B.D.H. narrow-range indicator paper (about 125 ml. of concentrated hydrochloric acid are required). Picolinic acid is very soluble in water (90 g. in 100 ml. of water at 9°) and therefore does not separate at this stage. The water is best removed by azeotropic distillation with benzene, a solvent which simultaneously extracts the picolinic acid.  [c.847]

JVJV-Diethylhydrazine. Fit a 1-litre three-necked flask with a double surface reflux condenser, a mercury-sealed stirrer and a dropping funnel, and insert calcium chloride guard tubes into the openings of the reflux condenser and dropping funnel. The apparatus must be dry. Place 10-0 g. of finely powdered lithium aluminium hydride and 500 ml. of sodium-dried ether in the flask, stir for 10 minutes, and add a solution of 23 -5 g. of diethyl nitrosamine (Section 111,124) in 135 ml. of anhydrous ether at the rate of 2-3 drops per second. After about 20 minutes, the ether refluxes gently and a white sohd separates henceforth adjust the rate of addition to maintain the reaction under control. After the addition of the nitrosamine is complete (about 1 hour), continue the vigorous stirring for 10 minutes, and then add an excess of ethyl acetate to decompose the residual hthium aluminium hydride. Now introduce 50 ml. of ION sodium hydroxide solution, stir for 10 minutes, filter with suction, and wash the residue with two 50 ml. portions of ether. Dry the combined filtrate and washings first over potassium hydroxide pellets and then over anhydrous calcium sulphate, distil through an efficient fractionating column (e.g.. a 10 vacuum-jacketed Widmer column) and collect the oa-diethylhydrazine at 98-99 5°. The yield is 10 g.  [c.880]

Preparation of aluminium isopropoxide. Place 27 -5 g. of clean aluminium foil in a 1 litre round-bottomed flask containing 300 ml. of anhydrous isopropyl alcohol (e.g., refluxed with and distilled from lime) and 0-5 g. of mercuric chloride. Attach an efficient (for example, double surface) reflux condenser carrying a calcium chloride (or cotton wool) guard tube. Heat the mixture on a water bath or upon a hot plate. When the liquid is boiling, add 2 ml. of carbon tetrachloride (a catalyst for the reaction between aluminium and dry alcohols) through the condenser, and continue the heating. The mixtime turns grey and, within a few minutes, a vigorous evolution of hydrogen commences. Discontinue the heating it may be necessary to moderate the reaction by cooling the flask in ice water or in running tap water. After the reaction has slowed down, reflux the mixture until all the metal has reacted (C-12 hours). The mixture becomes dark because of the presence of suspended particles. Pour the hot solution into a 500 ml. Claisen flask attached to a water condenser with a 250 ml. filter flask or distilling flask as leceiver. Add a few fragments of porous porcelain and heat the flask in an oil bath at 90° under slightly diminished pressure (water pump). When nearly all the isopropyl alcohol has distilled over, raise the temperature of the bath to 170° and lower the pressure gradually to the full vacuum of the water pump. Immediately the temperature of the distillate rises above 90°, stop the distillation and remove the condenser. Attach a 500 ml. distilling flask directly to the Claisen flask, add a few fresh boihng chips and distil use either an oil bath at 180-190° or an air bath (Fig. II, 5, 3). The aluminium isopropoxide passes over as a colourless viscid liquid at 140-150°/12 mm. the yield is 190 g. Pour the molten aluminium isopropoxide into a wide-mouthed, glass-stoppered bottle and seal the bottle with paraffin wax (or with cellophane tape) to exclude moisture. Generally the alkoxide (m.p. 118°) crystallises out, but the substance exhibits a great tendency to supercool and it may be necessary to cool to 0° for 1-2 days before solidification occurs.  [c.883]

Cholestenone. Place a mixture of 20 g. of purified cholesterol (m.p. 149°-150° dried to constant weight at 80-100°), 150 ml. of A.R. acetone and 200 ml. of sodium-dried benzene in a dry 1-litre round-bottomed flask fitted with a reflux condenser and calcium chloride guard tube. Introduce a boiling tube (Fig. 1,3, 1) to prevent bumping. Heat the mixture to boiling in an oil bath at 75-85°, add a solution of 16 g. of aluminium tert.-butoxide in 100 ml. of anhydrous benzene in one portion to the boihng solution. The mixture becomes cloudy and develops a yellow colour in 10 to 15 minutes. Continue gentle boiling at a bath temperature of 75-85° for 8 hours. Treat the cold mixture with 40 ml. of water, then with 100 ml. of 10 per cent, sulphuric acid, shake vigorously and transfer to a 1-Utre separatory funnel. Dilute the mixture with 300 ml. of water, shake for 5 minutes (filter, if necessary), then run off the yellow aqueous layer into a second separatory funnel and extract the latter with 25 ml. of benzene. Wash the combined benzene extracts thoroughly with water, dry with anhydrous magnesium sulphate and remove the solvent (steam bath final traces at 60° under vacuum of water pump). The yellow oily residue solidifies when it is cooled in an ice-salt bath and scratched with a glass rod keep a small portion for seeding in the subsequent crys-taUisation. Dissolve the solid in a warm mixture of 14 ml. of acetone and 20 ml. of methanol, allow the solution to cool very slowly and seed, if necessary. When the bulk of the solid has crystallised, keep the mixture at 0° for 24 hours, filter with suction, wash with 20 ml. of ice-cold methanol, and dry in a vacuum desiccator. The yield of almost colourless cholestenone, m.p. 79-80°, is 17 g.  [c.888]

Anthracene and maleic anhydride. In a 50 ml. round-bottomed flask fitted with a reflux condenser, place 2 0 g. of pure anthracene, I 1 g. of maleic anhydride (Section 111,93) and 25 ml. of dry xylene. Boil the mixture under reflux for 20 minutes with frequent shaking during the first 10 minutes. Allow to cool somewhat, add 0 5 g. of decolourising carbon and boil for a further 5 minutes. Filter the hot solution through a small, preheated Buchner funnel. Collect the solid which separates upon coohng by suction filtration, and dry it in a vacuum desiccator containing paraffin wax shavings (to absorb traces of xylene). The yield of adduct (colourless crystals), m.p. 262-263° (decomp.), is 2-2 g. Place the product (9 10-dihydroanthracene-9 10-cndo-ap-succinic anhydride) in a weU-stoppered tube, since exposure to air tends to cause hydration of the anhydride portion of the molecule.  [c.943]

See pages that mention the term Vacuum condensers : [c.19]    [c.42]    [c.77]    [c.202]    [c.179]    [c.267]    [c.112]    [c.139]    [c.430]    [c.461]    [c.640]    [c.695]    [c.700]    [c.763]    [c.977]   
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Rules of thumb for chemical engineers  -> Vacuum condensers