About 0.5 g of iodine is placed in a small flask fitted with a long reflux air condenser and 15 cm of fuming nitric acid (b.p. 380 K) are added. The mixture is then heated on a water bath at 385-390 K in a fume cupboard until the reaction seems to be complete. This takes about an hour. The solution is then transferred to an evaporating basin and evaporated to dryness on a steam bath. The iodic acid  [c.350]

Concentrate each of the two solutions (or eluates) to about 20 ml, by distilling off the greater part of the benzene, the distilling-flask being immersed in the boiling water-bath. Then pour the concentrated solution into an evaporating-basin, and evaporate the remaining benzene (preferably in a fume-cupboard) in the absence of free flames, i.e., on an electrically heated water-bath, or on a steam-bath directly connected to a steam-pipe. Wash the dry residue from the first eluate with petrol and then dry it in a desiccator pure o-nitroaniline, m.p. 72°, is obtained. Wash the second residue similarly with a small quantity of benzene and dry pure />--nitroaniline, m.p. 148" , is obtained. Record the yield and m.p. of each component.  [c.50]

Now place 35 ml. of the mixed solvent (C) in the clean cylinder E, and suspend the strip, as described above, to the horizontal arm of G (Fig. 25(A)) adjust the position of the strip so that, when the bung is firmly in position, the bottom of the paper-strip is about 5 mm. above the solvent. Place the cylinder for 5-8 hours in a draught-free place, such as a cupboard, where the temperature is reasonably constant.  [c.53]

Then remove the strip and dry it in a stream of cold air, either from a blower, or by pinning it to the lower edge of a fume-cupboard window having a vigorous draught already in operation. Then spray the strip lightly but uniformly with the ninhydrin solution (D) in a fume-cupboard, and dry as before.  [c.53]

Next day, hang the paper from the edge of the fume-cupboard window in the full draught of the fan to dry, and immediately mark the position of the solvent front.  [c.54]

The Winchester bottle should then be closed by a rubber stopper carrying a calcium chloride tube (to allow escape of hydrogen) and the ether allowed to stand for a further 24 hours. It should then be decanted into a large distilling-flask, a few small pieces of freshly cut sodium preferably added, and the flask connected with a double- surface water-condenser having a receiver cooled in ice water. Ether in these quantities should always be distilled in a fume-cupboard having an efficient draught, so that there is no possibility of any uncondensed vapour escaping into the laboratory. The flask itself should be heated  [c.82]

Owing to the copious evolution of nitrous fumes, this preparation must be carried out in a fume-cupboard having an efficient draught. Place 20 g. of coarsely powdered cane sugar (sucrose) in a 750 ml. flat-bottomed flask, add too ml. of concentrated nitric acid and heat the flask on a boiling water-bath. As the mixture becomes warm, the greater part of the sugar dissolves and a vigorous but harmless reaction, accompanied by a tremendous evolution of nitrous fumes, takes place. Immediately the evolution of gas starts, remove the flask from the water-bath and place it on a wooden block or some similar non-conducting surface. When the reaction subsides (after about 15 minutes) pour the hot solution into an evaporating-basin, wash out the flask with about 20 ml. of concentrated nitric acid, and then evaporate the acid solution on the water-bath until it has a volume of about 20 ml. Some oxidation continues in the solution during the evaporation, which is comparatively rapid. Now add about 40 ml. of water to the solution, and again evaporate to about 20 ml. Cool the solution thoroughly in ice-water oxalic acid rapidly crystallises. When crystallisation is complete, filter at the pump, and then recrystallise from a small quantity of hot water. Dry by pressing between pads of drying-paper, or in an atmospheric desiccator, but not in an oven where partial loss of water of crystallisation may occur. Yield, 7 g. The hydrated acid has m.p. 101° the anhydrous acid decomposes on heating. Oxalic acid is poisonous.  [c.112]

Since glycerol is a very hygroscopic substance, it may be necessary to ensure that the sample used is anhydrous. For this purpose, place about 70 ml. in a porcelain evaporating-basin, and heat it carefully over a gauze (preferably in a fume-cupboard), stirring it steadily with a thermometer until the temperature is 175-180 then maintain this temperature for a further 5 minutes. Allow the glycerol to cool, but while it is still warm i.e.y before it becomes viscous) pour 50 ml. (63 g.) into a 250 ml. distilling-flask containing 40 g. of pow dered crystalline oxalic acid. Fit a thermometer in the flask so that the bulb is completely immersed in the glycerol mixture, and then fit a water-condenser to the flask. Heat the mixture carefully over a gauze so that the temperature rises to 110-120°, and then adjust the heating so that the temperature remains within these limits. A vigorous effervescence of Carbon dioxide occurs, and the aqueous formic acid begins slowly to distil over. When the effervescence tends to subside, remove the Bunsen flame and allow the temperature to fall to 70-80° then add a further 40 g. of powdered oxalic acid, and continue the heating as before. Ultimately 25-30 ml. of distillate are obtained, the total period of heating being about i hour. W hile the distillation is proceeding, withdraw a few ml. of the distillate and apply Tests 2, 3 and 4 for formic acid given on p. 350-351.  [c.113]

Add 15 g, of chloroacetic acid to 300 ml. of aqueous ammonia solution d, o-88o) contained in a 750 ml. conical flask. (The manipulation of the concentrated ammonia should preferably be carried out in a fume-cupboard, and great care taken to avoid ammonia fumes.) Cork the flask loosely and set aside overnight at room temperature. Now concentrate the solution to about 30 ml. by distillation under reduced pressure. For this purpose, place the solution in a suitable distilling-flask with some fragments of unglazed porcelain, fit a capillary tube to the neck of the flask, and connect the flask through a water-condenser and receiver to a water-pump then heat the flask carefully on a water-bath. Make the concentrated solution up to 40 ml. by the addition of water, filter, and then add 250 ml. of methanol. Cool the solution in ice-water, stir well, and set aside for ca. I hour, when the precipitation of the glycine will be complete.  [c.130]

CAUTION. The vapour of selenium dioxide is poisonous, and all operations involving the hot material, alone or in solution, should be performed in a fume-cupboard. If lumps of selenium dioxide have to be powdered in a mortar, the latter should also be in a fume-cupboard, with the window lowered as far as possible, to avoid inhaling the fine dust. (cf. p. 191)  [c.147]

In this preparation, the ( + ) or dextro-rotatory (natural) camphor or the ( ) or racemic (synthetic) camphor can be used. Perform the oxidation in a fume-cupboard.  [c.148]

Lithium aluminium hydride if carelessly manipulated may be dangerous for two distinct reasons. The material is caustic, and should not be allowed to touch the skin it is particularly important that the finely divided material should be kept away from the lips, nostrils and eyes, and consequently pulverisation in a mortar must be carried out with the mortar in a fume-cupboard, and with the window drawn down as far as possible in front of the operator. This danger from handling has however been greatly reduced, for the hydride is now sold in stated amounts as a coarse powder enclosed in a polythene bag in a metal container this powder dissolves readily in ether, and preliminary pulverisation is unnecessary.  [c.155]

Assemble in a fume-cupboard a 3-necked flask fitted with a stirrer, a reflux condenser, and a dropping-funnel, the apparatus  [c.155]

This preparation must be performed in a fume-cupboard, because nitrous fumes are evolved during the nitration. A ground-glass flask and air condenser (Fig. 22(a) and (c), p. 43) should preferably be used.  [c.161]

Weigh out 8 g. of phenol into a dry 750 ml. flat-bottomed flask, add 10 ml. (18-5 g.) of concentrated sulphuric acid, and shake the mixture, which becomes warm. Now heat the flask on a briskly boiling water-bath for 30 minutes to complete the formation of the phenol-sulphonic acid, and then chill the flask thoroughly in an ice-water mixture. Place the flask on a wooden block (or on some similar non-conducting surface) in an efficient fume-cupboard, and without delay, /.e., whilst the phenol-sulphonic acid is still a cold viscous syrup, add 30 ml. of concentrated nitric acid and at once thoroughly mix the liquids by shaking for a few seconds. Then allow the mixture to stand undisturbed. Usually within one minute a vigorous (but harmless) reaction occurs, and red fumes pour out of the flask. When the action subsides, heat the flask on a boiling water-bath for hours, with occasional shaking. During this period the heavy oil, which is present at the beginning, ultimately forms a mass of crystals. When the heating is complete, add 100 ml. of cold water, mix well and then chill thoroughly in ice-water. Filter the yellow crystals at the pump, wash thoroughly with water to eliminate all inorganic acid and drain. Recrystallise from a mixture of i volume of ethanol and 2 volumes of water, about 90 ml. of the mixed solvent being required. Picric acid is obtained in pale yellow leaflets, m.p. 122 . Dry by pressing between sheets of drying-paper, or in a desiccator. Yield of recrystallised material.  [c.173]

Place 0 5 ml. of the pyridine in a 200 ml. round- or flat-bottomed flask and add 34 ml. (30 g.) of benzene. Fit the flask with a reflux water-condenser, and then place it in a cold water-bath. If the experiment is conducted in a fume-cupboard, the top of the condenser can be closed with a calcium chloride tube bent downwards (as in Fig. 61, p. 105 or in Fig. 23(A), p. 45, where the outlet-tube A will carry the calcium chloride tube) and the hydrogen bromide subsequently allowed to escape if, however, the experiment is performed in the open laboratory, fit to the top of the condenser (or to the outlet-tube A) a glass delivery-tube which leads through a piece of rubber tubing to an inverted glass funnel, the rim of which dips just below the surface of some water  [c.175]

Place 10 ml. (10-3 g.) of aniline in a 150 ml. conical flask, and add slowly 20 ml. (37 g.) of concentrated sulphuric acid shake the mixture gently during the addition, and keep it cool by immersing the flask occasionally in cold water. White lumps of aniline hydrogen sulphate separate. Add cautiously 20 ml. of 10% fuming sulphuric acid concentrated sulphuric acid containing io% of dissolved sulphur trioxide), and then heat the mixture in an oil-bath at 180-190° for i hour, preferably in a fume-cupboard. Allow the product to cool, and pour it carefully into about 200 ml. of cold water, stirring the mixture vigorously during the addition. Allow to stand for about 5 minutes, and then filter off at the pump the sulphanilic acid which has crystallised out, wash it well with water, and drain. The crystals so obtained should be almost colourless. Purify by recrystallising from about 250 ml. of boiling water filter the hot solution through a Buchner funnel and flask which have been preheated by the filtration of boiling distilled water. If, however, the temperature of the reaction mixture has been allowed to rise above 190°, the crude sulphanilic acid may be greyish-brown in colour in this case, boil the aqueous solution obtained during the recrystallisation with about 2 g. of animal charcoal for 10-15 minutes (see p, 23), and then filter the hot solution through the preheated Buchner funnel. The sulphanilic acid rapidly separates from the filtrate in colourless crystals when the filtrate is quite cold, filter off the crystals at the pump, wash with a small quantity of cold water and drain thoroughly. Dry the crystals by pressing between sheets of drying-paper, or by placing in an atmospheric calcium chloride desiccator. In a vacuum desiccator the sulphanilic acid loses its water of crystallisation, and hence its crystalline form. Yield, about 10 g.  [c.180]

Apart from the diazotisation, the whole of the following preparation up to the completion of the steam-distillation must be carried out in a fume-cupboard having a vigorous draught.  [c.191]

For this preparation, which must be performed in the fume-cupboard, assemble the apparatus shown in Fig. 67(A). C is a 150 ml. distilling-flask, to the neck of which is fitted a reflux single-surface water-condenser D, closed at the top E by a calcium chloride tube. The side-arm of C carries a cork F which fits the end E of the condenser for subsequent distillation. The side-arm of C is meanwhile plugged by a small rubber cork, or by a short length of glass rod. (Alternatively, use the ground-glass flask and condenser (Fig. 22 (a) and (c), p. 43), and  [c.240]

Assemble in a fume-cupboard the apparatus shown in Fig. 67(A). Place 15 g. of 3,5-dinitrobenzoic acid and 17 g. of phosphorus pentachloride in the flask C, and heat the mixture in an oil-bath for hours. Then reverse the condenser as shown in Fig. 67(B), but replace the calcium chloride tube by a tube leading to a water-pump, the neck of the reaction-flask C being closed with a rubber stopper. Now distil off the phosphorus oxychloride under reduced pressure by heating the flask C in an oil-bath initially at 25-30, increasing this temperature ultimately to 110°. Then cool the flask, when the crude 3,5-dinitro-benzoyl chloride will solidify to a brown crystalline mass. Yield, 16 g., i.e,y almost theoretical. Recrystallise from caibon tetrachloride. The chloride is obtained as colourless crystals, m.p. 66-68°, Yield, 13 g Further recrystallisation of small quantities can be performed using petrol (b.p. 40-60°). The chloride is stable almost indefinitely if kept in a calcium chloride desiccator.  [c.243]

Place 30 g. of anhydrous finely powdered aluminium chloride in a 300 ml. dry round-bottomed bolt-head Rask, and add 75 ml. of dry benzene (free from toluene). Fit a water-condenser to the flask, and then in turn fit a small dropping-funnel securely in the top of the condenser by means of a cork having a shallow V-shaped groove cut vertically in the side to give open access to the air. (Alternatively use the apparatus shown in Fig. 23(A), p. 45, the outlet-tube A being closed with a calcium chloride tube.) Cool the contents of the flask in a basin of cold water (ice-water must not be used, in case the benzene crystallises) now place 20 ml. (22 g.) of acetyl chloride in the dropping-funnel, and allow it to run slowly down the condenser into the flask, the latter being shaken from time to time to ensure thorough mixing of the contents. When all the acetyl chloride has been added, heat the flask in a water-bath at 50° for i hour in order to complete the reaction, a vigorous evolution of hydrogen chloride occurring meanwhile. The heating should therefore be carried out in the fume-cupboard, the dropping-funnel being replaced by a calcium chloride tube, bent downwards as in Fig. 61, p. 105. Alternatively, the heating may be carried out in the open laboratory, in which case a delivery-tube should be securely fitted at one end to the top of the condenser (or to the outlet-tube A in Fig. 23(A)), and at the other end to the stem of an inverted glass filter-funnel, the latter being placed in a beaker of water so that the rim dips/wj/ below the surface the hydrogen chloride is thus absorbed without  [c.255]

Mix 6 2 ml. (6 4 g.) of pure ethyl acetoacetate and 5 ml. of pure phenylhydrazine in an evaporating-basin of about 75 ml. capacity, add 0 5 ml. of acetic acid and then heat the mixture on a briskly boiling water-bath (preferably in a fume-cupboard) for I hour, occasionally stirring the mixture with a short glass rod. Then allow the heavy yellow syrup to cool somewhat, add 30-40 ml. of ether, and stir the mixture vigorously the syrup may now dissolve and the solution shortly afterwards deposit the crystalline pyrazolone, or at lower temperatures the syrup may solidify directly. Note. If the laboratory has been inoculated by previous preparations, the syrup may solidify whilst still on the water-bath in this case the solid product when cold must be chipped out of the basin, and ground in a mortar with the ether.) Now filter the product at the pump, and wash the solid material thoroughly with ether. Recrystallise the product from a small quantity of a mixture of equal volumes of water and ethanol. The methyl-phenyl-pyrazolone is obtained  [c.271]

The first part of this preparation (as far as the solidification of the sodium cyanoacetate) must be carried out in the fume-cupboard. Add 30 g. of monochloroacetic acid to 60 ml. of water contained in a wide evaporating-basin (about 12-15 diameter)  [c.272]

Ethyl bromoacetate is lachrymatory, and the preparation should therefore be carried out in a fume-cupboard.  [c.287]

This preparation should be carried out in a fume-cupboard.  [c.290]

Add 60 ml. of concentrated hydrochloric acid with shaking to 30 ml. of aniline in the flask, cool the mixture to about 50, and then add 45 ml. of paraldehyde and some fragments of unglazed porcelain assemble the apparatus without delay in a fume-cupboard with the condenser inclined at an angle of about 60°.  [c.301]

Note. The chloroacetone, which should be freshly distilled (b.p. 119°), is lachrymatory, and therefore the distillation and the preparation should be performed in a fume-cupboard.  [c.305]

Some alcohols react readily with phenylisocyanate at room temperature, and others require heating, preferably in petroleum. Phenylisocyanate is poisonous and should not be heated outside a fume-cupboard except under a condenser.  [c.336]

Place about 1 g. of the nitro-hydrocarbon in a boiling-tube and add 5 ml. of cone. HCl and several pieces of granulated tin. Warm the mixture and shake continuously to break up the oily drops of the nitro-compound. When all the oil has disappeared (about 3 minutes heating) pour off the liquid from any undissolved tin into a 100 ml. conical flask. Cool and add cautiously 30% aqueous NaOH solution until the precipitate formed redissolves to give a dark-coloured solution. Cool the latter thoroughly and shake well with about 15 ml. of ether. Separate the ethereal layer in a separating-funnel, wash with water and evaporate the ether in a basin on a previously heated water-bath in a fume-cupboard atoay from all flames. The residue is either  [c.385]

Although these nitrations proceed smoothly, attempted nitration of an unidentified substance should always be carried out with extreme care, e.g., by working in a fume-cupboard and pointing the boiling-tube away from the operator. Many organic substances e.g., alcohols and phenols) react with great violence with a mixture of nitric and sulphuric acids.  [c.391]

Bromoform. Commercial bromoform should be shaken thoroughly with water, separated, dried over powdered anhydrous sodium sulphate and then fractionally distilled under reduced pressure using a water-condenser. It should be stored in a dark cupboard. It is an excellent solvent, has the advantage of a high Constant, and very seldom causes association of the solute.  [c.435]

Assemble in a fume-cupboard the apparatus shown in Fig. 6i. A is a wide-necked round-bottomed 100 ml. flask to which the reflux water-condenser B is fitted by means of a rubber stopper. The latter carries also an inlet tube C (which should not be too narrow in diameter), by means of which a current of hydrogen chloride, dried by passage through the sulphuric acid wash-bottle D, can be passed down to the bottom of A. The hydrogen chloride is best generated by means of a Kipp s apparatus charged with solid ammonuim chloride and concentrated sulphuric acid. I he top of the condenser B is fitted with a calcium chloride tube R, preferably bent downwards as shown drops of water tend to collect in the end of E as hydrogen chloride steadily escapes during the experiment, and are thus prevented from running back and so fouling the calcium chloride. (Alternatively, the flask, condenser and inlet-tube can be replaced by the apparatus shown in Fig.  [c.104]

Add 10 g. of powdered acetanilide to 10 ml. (io-6g.) of glacial acetic acid contained in a 100 ml. beaker, and then to the well-stirred mixture add 20 ml. (37 g.) of concentrated sulphuric acid. The mixture becomes hot and a clear solution is rapidly obtained. Place the beaker in an intimate mixture of salt and crushed ice until the temperature of the reaction-mixture falls to about 0-5°. Now, whilst stirring the viscous mixture continuously with the thermometer, add 4 ml. of ordinary fuming nitric acid d, 1 5) cautiously drop by drop from a burette (preferably in a fume-cupboard), so that the temperature of the mixture does not rise above 25° this operation should take 10-15 nainutes. Then remove the beaker from the freezing mixture, allow it to stand for 30 minutes at room temperature, and pour the contents on to about 100 g. of crushed ice, whereby the crude nitro-acetanilide is at once precipitated finally rinse out the beaker with 50 ml. of water containing a few fragments of ice, adding the solution to the main bulk of the product. Allow the mixture to stand for about 20 minutes, and then filter at the pump, wash thoroughly with cold water to remove acid, and drain.  [c.167]

The preparation of />-tolunitrile illustrates the method employed for the diazotisation of amines the hydrochlorides of which are only moderately soluble in cold water. Dissolve 24 g. of powdered />-toluidine in a warm mixture of 55 ml. of concentrated hydrochloric acid and 180 ml. of water, and then chill the solution thoroughly in ice-water during the cooling, stir the mixture continuously in order to ensure that the p-toluidine hydrochloride crystallises out as small feathery crystals which will subsequently redissolve readily during the diazotisation. Now continue precisely as in the above preparation of benzonitrile (p. 191), observing the same precautions against inhaling cyanogen and using the same quantities of all the reagents, f.e., diazotising with a solution of 17 g. of sodium nitrite in 40 ml. of water, and pouring the diazotised solution into the potassium cupro-cyanide solution prepared as before. During the addition of the diazotised solution, however, the potassium cupro-cyanide mixture must be occasionally warmed on a water-bath in the fume-cupboard in order to keep the temperature between 60° and 70 .  [c.194]

While this solution is standing, dissolve 17 g. of anhydrous sodium carbonate in 70 ml. of warm water in a 800 ml. beaker, and then add 115 g. of finely powdered crystalline sodium sulphite (NajSOajyHaO) and continue warming the solution at 40-50° for a few minutes, so that the greater part of the sulphite dissolves. Then cool the solution in ice-water until the temperature is between 5° and 10°, some of the sulphite meanwhile crystallising out again. Now add the diazonium solution slowly to the well-stirred sulphite solution the mixture becomes red in colour, and a deep red oil separates and later solidifies as orange-coloured crystals (sometimes the orange crystals separate without the intermediate formation of the oil). When the addition of the diazo solution is complete, continue stirring the mixture for 5-10 minutes, and then warm it to 30° on a water-bath (in a fume-cupboard) and pass in a stream of sulphur dioxide from a syphon until the solution is saturated and no more gas is absorbed the excess of sodium sulphite and the orange crystals dissolve up at this stage. Now heat the solution to 70° and add 150 ml. of concentrated hydrochloric acid with stirring. Within a few minutes, crystals of phenylhydrazine hydrochloride separate out cool the mixture in ice-water for 15 minutes with occasional stirring and then filter at the pump and drain thoroughly.  [c.198]

Fit a 500 ml. flask (preferably by means of a three-necked adaptor) with a stirrer having a rubber-sleeved or mercury seal, a dropping-funnel and, by means of the third outlet, with a calcium chloride tube. Place 250 ml. of dry toluene and 40 g. of aluminium chloride in the flask, and cool the latter in an ice-water bath inside a fume-cupboard. (Ensure that the aluminium chloride is a fresh sample, i.e., that it has not been long stored in a previously opened bottle, and pulverise it if necessary immediately before use.) When the mixture has been thoroughly cooled, place 35 ml. of acetyl chloride in the dropping-funnel, and allow it to run drop-wise into the flask over a period of 30 minutes, maintaining the stirring and cooling throughout. Hydrogen chloride is steadily evolved. When the addition of the acetyl chloride is complete, replace the ice-bath by a water-bath, and maintain the temperature of the latter at 20-25 2 hours with constant stirring.  [c.290]

Formation of nitrosaminey RgN NO. (a) From monomethylaniline. Dissolve I ml. of monomethylaniline in about 3 ml. of dil. HCl and add sodium nitrite solution gradually with shaking until the yellow oil separates out at the bottom of the solution. Transfer completely to a smdl separating-funnel, add about 20 ml. of ether and sh e. Run off the lower layer and wash the ethereal extract first with water, then with dil. NaOH solution, and finally with w ter to free it completely from nitrous acid. Evaporate the ether in a basin over a previously warmed water-bath, in a fume cupboard with no flames near. Apply Liebermann s reaction to the residual oil (p. 340).  [c.376]

Nitration. Mix together in a boiling-tube 2 ml. of cone. HNO, and 2 ml. of oonc. H1SO4. Add 1 ml. of nitrobenzene with shaking and then heat the mixture over a small flame with constant shaking in a fume-cupboard for a  [c.385]

See pages that mention the term Chipboard : [c.471]    [c.2849]    [c.2850]    [c.351]    [c.305]    [c.83]    [c.181]    [c.182]    [c.257]    [c.299]    [c.315]    [c.322]    [c.388]   
Plastics materials (1999) -- [ c.678 ]