The problem with using a pressure change is that the smaller the change in azeotropic composition, the larger is the recycle in Figs. 3.86 and 3.96. If the azeotrope is not sensitive to changes in pressure, then an extraneous material can be added to the distilla-  [c.80]

At z in the curve, however (the minimum of vapour pressure), the solution and vapour are in equilibrium and the liquid at this point will distil without any change in composition. The mixture at z is said to be azeotropic or a constant boiling mixture. The composition of the azeotropic mixture does vary with pressure.  [c.48]

Bi Bismuth, biacetyl See diacetyl.  [c.59]

In aqueous solution, hydrogen chloride forms hydrochloric acid. The concentrated acid contains about 40% hydrogen chloride (about 12 M). A graph of the boiling point of hydrogen chloride-water mixtures against composition shows a maximum at about 20 % HCl hence if either the concentrated or dilute acids be distilled, then either hydrogen chloride or water respectively distil over, leaving behind constant boiling-point acid.  [c.331]

When distillation starts, the pig is so placed that the first fraction collects in C. When the second fraction starts to distil, A is rotated slightly to bring the outlet tube leading to D in the lowest position, so that the second fraction collects in D further rotation then causes the third fraction to collect in E. The apparatus however often gives unsatisfactory results, particularly in the hands of students, who frequently find that if a good vacuum is obtained in the apparatus, the pig sticks firmly around the cork F and refuses to rotate conversely, easy rotation around this cork usually means a leaky joint at this point, and an unsatisfactory and varying pressure is recorded by the manometer. (The ground-glass fitting B shown in Fig. 23(F), p. 46, avoids this trouble,)  [c.31]

Reflux Distillation Unit. The apparatus shown in Fig. 38 is a specially designed distillation-unit that can be used for boiling liquids under reflux, followed by distillation. The unit consists of a vertical water-condenser A, the top of which is fused to the side-arm condenser B. The flask C is attached by a cork to A. This apparatus is particularly suitable for the hydrolysis of esters (p. 99) and anilides (p. 109), on a small scale. For example an ester is heated under reflux with sodium hydroxide solution while water is passed through the vertical condenser water is then run out of the vertical condenser and passed through the inclined condenser. The rate of heating is increased and any volatile product will then distil over.  [c.64]

Mix 50 ml. (40 g.) of ethanol and 50 ml. (52 g.) of glacial acetic acid thoroughly in a 250 ml, round-bottomed flask, and add slowly, with cooling and shaking, 10 ml. (18 5 g.) of concentrated sulphuric acid. Ensure that the liquid is homogeneous, then fit the flask with a reflux water-condenser (Fig. 8, p. 17) and boil the mixture gently over a wire gauze for 10 minutes. Now alter the position of the condenser (Fig. 59, p. 100, or Fig. 23(D), p. 45) and distil oflF about two-thirds of the mixture and then transfer the distillate to a separating-funnel. t Add about 25 ml. of 30% sodium carbonate solution, cork the funnel and shake carefully in order to neutralise and remove the free acetic and sulphurous acids present in the crude ethyl acetate much carbon dioxide is evolved during the shaking, therefore release the pressure in the funnel at frequent intervals by cautiously removing the cork, or alternatively by inverting the securely corked funnel and momentarily opening the tap. Now allow the two layers to separate, and carefully run off and reject the lower aqueous layer, ensuring that the sodium carbonate solution is removed as completely as possible. Then prepare a solution of 25 g. of anhydrous calcium chloride in 25 ml. of water, add it to the ethyl acetate in the funnel, and again shake vigorously. The calcium chloride solution removes any unchanged ethanol present in the ethyl acetate. Allow the mixture to separate, and again run off the lower aqueous layer as completely as possible. Then run the ethyl acetate into a small conical flask, add a few lumps of  [c.97]

Now decant the dried liquid into a small distilling flask of about 10 ml, capacity (Fig. 36, p. 63). Distil the liquid and collect the fraction b.p. 74-79°. Yield, 3 g.  [c.98]

The residual liquid in the flask is a dilute alkaline solution of sodium acetate. To liberate the acetic acid, add dilute sulphuric acid until the solution is definitely acid to litmus, and then distil off about 20 ml. Perform on this aqueous distillate the tests for acetic acid given on p. 347-  [c.100]

Then filter the ethyl bromide through a small fluted filter-paper directly into a 60 ml. distilling flask. Fit the flask with a 100° thermometer, and a water-condenser having as before an ample supply of cold water then arrange the condenser so that its lower end enters the neck of a small dry weighed conical flask, supporting the latter in line with the condenser, and chilling it externally by a mixture of ice and water. Distil the ethyl bromide slowly from a water-bath, and collect the fraction boiling between 35° and 40°. Average yield, 23 g. In view of the low boiling-point of the ethyl bromide, it should be preserved in a sealed glass specimen tube (see Fig. 21, p. 41).  [c.102]

Run off the lower layer of bromide, dry it with calcium chloride (as in the above preparation of ethyl bromide) and finally distil the filtered bromide from a small flask, preferably through a short column. Collect the n-butyl bromide as a colourless liquid of b.p. 99-102°. Yield, 30 g.  [c.103]

Fit the flask with a 100° thermometer and a water-condenser, and distil the ethyl iodide carefully from a water-bath, collecting the fraction which distils between 68° and 73°. Yield, about 24 g.  [c.107]

Alternatively the semi micro apparatus shown in Fig. 38 (p. 63) may be used. Heat the anilide and sulphuric acid under reflux for 15 minutes in such a manner that the vapour does not rise higher than half-way up the vertical condenser through which water is passed. Then dilute the solution in the flask with 5 ml. of water. Empty the vertical condenser and run cold water through the inclined condenser. Now increase the rate of heating and distil off 1-2 ml. of aqueous acetic acid.  [c.109]

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]

A considerable amount of the formic acid, however, still remains behind in the distilling-flask as the unhydrolysed monoformate. Therefore, if time allows, dilute the residue in the flask with about an equal volume of water, and then steam-distil, the monoformate ester being thus completely hydrolysed and the formic acid then driven over in the steam. Collect about 400 ml. of distillate. Add this distillate to that obtained by direct heating of the reaction mixture and then treat with lead carbonate as described above. Total yield of lead formate is now about 40 g.  [c.114]

Place 21 g. (a 20% excess) of powdered anhydrous sodium acetate in a 100 ml. round-bottomed flask fitted with a reflux water-condenser, and cool the flask in ice-water. Place 15 ml. (16-5 g.) of acetyl chloride in a dropping-funnel fitted into the top of the condenser by means of a grooved cork cf. Fig. 53, p. 76, or Fig. 23(A), p. 45). Now allow the acetyl chloride to run slowly down into the chilled sodium acetate, thoroughly mixing the contents by shaking as soon as the product becomes sufficiently liquid. Then heat the flask on a boiling water-bath for 10 minutes to complete the reaction. Next disconnect the condenser and fit it by means of a knee-tube Fig. 59, p. 100, or Fig. 23(0), p. 45) to the flask for distillation. Heat the flask with a luminous smoky Bunsen flame (without a gauze), waving the flame around the base of the flask to ensure uniform heating and to minimise risk of cracking continue heating until no more distillate passes over. Now fractionally distil the crude acetic anhydride slowly from a 40 ml. distilling-flask, preferably using an air-condenser. A small quantity passes over at 130-135° (due to traces of free acetic acid) and the major fraction at 135-140 . Yield, 18 g.  [c.116]

In view of the small volume of nitromethane to be manipulated, the crude nitromethane may be extracted from the aqueous distillate with ether (30-40 ml.). Dry the ethereal extract over sodium sulphate, filter through a fluted filter-paper, and then distil off the ether on a water-bath with the usual precautions (Fig. 64, p. 163 Fig, 23(E), p. 45) finally distil the residual nitromethane.  [c.132]

Dissolve I g. of pinacol (preparation, p. 148) in 20 ml. of water, and add 20 ml. of the 5% aqueous sodium periodate solution. After 15 minutes, distil the clear solution, collecting the first 5 ml. of distillate. Treat this distillate with 2,4-dinitro-phenylhydrazine solution A (p. 263). Acetone 2,4-dinitrophenyl-hydrazone rapidly separates from the solution when filtered off, washed with a small quantity of ethanol, and dried, it has m.p. 126-127°, and after recrystallisation from ethanol it has m.p. 128°.  [c.146]

C4HgN202. Colourless needles m.p. 234 "C, sublimes at 215°C. Prepared by the action of hydroxylamine on diacetyl, or by treating methyl ethyl ketone with ethyl nitrite and hydrochloric acid to which gives diacetyl monooxime which with sodium hydroxylamine monosulphonate gives dimethylglyoxime. It slowly polymerizes condenses with o-pheny-lenediamine to give quinoxaline derivatives. Forms a dark-red crystalline nickel salt. Under appropriate conditions dimethylglyoxime can also be used for the detection and estimation of Bi, Cu, Co and Pd. Also used for rot-proofing of some fibres.  [c.141]

Figure Bl.2.11. Biologically active centre in myoglobin or one of the subunits of haemoglobin. The bound CO molecule as well as the proximal and distal histidines are shown m addition to the protohaeme unit. From Rousseau D L and Friedman J M 1988 Biological Applications of Raman Spectroscopy vol 3, ed T G Spiro (New York Wiley). Reprinted by pennission of John Wiley and Sons Inc. Figure Bl.2.11. Biologically active centre in myoglobin or one of the subunits of haemoglobin. The bound CO molecule as well as the proximal and distal histidines are shown m addition to the protohaeme unit. From Rousseau D L and Friedman J M 1988 Biological Applications of Raman Spectroscopy vol 3, ed T G Spiro (New York Wiley). Reprinted by pennission of John Wiley and Sons Inc.
To use such a column, the crude liquid is placed in a round-t ottomed flask C having a short wide neck, the usual fragments of unglazed porcelain are added, and the column then fixed in position, great care being taken to ensure that it is mounted absolutely vertically, again in order to avoid channelling. A water-condenser is then fitted in turn to the side-arm of the column, particularly when the components of the mixture have low boiling-points. The mixture is then heated with a very small flame, carefully protected from draughts to ensure a uniform supply of heat. It is essential that the initial heating of the liquid in C (while it is still mounting the cold column) should not be hurried, as considerable extra condensation occurs while the column is warming up, and the latter may easily choke when once distillation has started, and a thermal equilibrium has been established between the column and its surroundings, the tendency to choke should disappear. The heating is then adjusted until the distillate is issuing from the side-arm of the column not faster than about i drop every 4-5 seconds. In these circumstances, so efficient a fractionation should be obtained that, when the lowest-boiling fraction has distilled over, distillation completely ceases, as the next lower fraction is refluxing definitely below the side-arm of the column. The heating is then cautiously increased, and a sharp rise in boiling-point (and therefore a sharp fractionation) should occur as the second fraction starts to distil. Although in Fig. 12(B) a condenser is shown fitted to the side-arm of the column, this is required only for low-boiling components for most mixtures, however, the above rate of distillation, necessary for efficient fractionation, will be accompanied by complete condensation in the side-arm of the column, from which the successive fractions may be collected directly.  [c.27]

Experiment 6. Fractional Distillation of a Mixture of Benzene and Toluene. Fractionally distil about 40 ml. of a mixture of equal volumes of benzene and toluene, using the type of fractionating column shown in Fig. ii(b), in which about 18-20 cm. of the column are actually filled with glass sections, but in which the cotton-wool lagging is not used. Distil very slowlyy so that the total distillation occupies about hours. Shield the apparatus very carefully from draughts. Collect the fractions having the b.ps (a) 80-85°, ( ) 85-107°, (c) 107-111°. A sharp separation should be obtained, e.g.y these fractions should have volumes of about 19, 2, and 17 ml. respectively.  [c.28]

When distillation starts, the taps D and E are open, and G is turned so as to give direct access from J to J . The first fraction therefore runs from C through E, and collects in F. Directly the second fraction starts to distil, E is closed, so that this fraction collects in C. Meanwhile G is turned to allow air to enter through J to F, which can then be detached and a new receiver F added. If a pump of good capacity is being used, it is sufficient now to turn G so as to give direct access again between J and J, thus evacuating the new receiver F, which is then ready to receive the second fraction which has been accumulating in C. If a rather weak pump is in use, however, this sudden admission of the air from the new receiver F into the rest of the apparatus may cause a moderate rise in the pressure, and a temporary cessation in the distillation, and in these circumstances bumping frequently starts (and persists) when distillation recommences. To avoid this, the tap G, before being turned, should be connected to a supplementary pump, which will evacuate the new receiver F rotation of G as before now serves to cut off the supplementary pump and simultaneously reconnect the two parts of the apparatus through JJ.  [c.32]

Then detach and reverse the condenser, and reconnect it to the flask through a knee-tube for direct distillation, as shown in Fig. 60, p. 101, or Fig. 23(0), p. 45. Distil the mixture, by direct heating over a gauze, until about 8 ml. of distillate have been collected. Acetic acid is volatile in steam and an aqueous solution of the acid, containing, however, some acetaldehyde, is thus obtained. With a very small portion of this solution, perform the tests for acetic acid given on p. 347.  [c.76]

Add dil. HjS04 to the residue in the flask until definitely acid to litmus. Distil off 1 2 ml., and perform tests on this aqueous distillate for acetic acid.  [c.100]

One disadvantage of using acetic anhydride is that with primary amines, traces of the diacctyl compound, RN(COCH3)2, niay be formed the chances of this secondary acetylation are, however, usually remote, and recrystallisation from an aqueous solvent will generally hydrolyse the diacetyl derivative rapidly back to the mono-acetyl compound.  [c.107]

The crude acetonitrile contains as impurity chiefly acetic acid, arising from the action of phosphoric acid on the acetamide. Therefore add to the nitrile about half its volume of water, and then add powdered dry potassium carbonate until the well-shaken mixture is saturated. The potassium carbonate neutralises any acetic acid present, and at the same time salts out the otherwise water-soluble nitrile as a separate upper layer. Allow to stand for 20 minutes with further occasional shaking. Now decant the mixed liquids into a separating-funnel, run off the lower carbonate layer as completely as possible, and then pour off the acetonitrile into a 25 ml, distilling-flask into which about 3-4 g. of phosphorus pentoxide have been placed immediately before. Fit a thermometer and water-condenser to the flask and distil the acetonitrile slowly, collecting the fraction of b.p. 79-82°. Yield 9 5 g. (12 ml.).  [c.122]

Dissolve 50 g. of monochloroacetic acid in 100 ml. of water contained in a 500 ml. round-bottomed bolt-head flask, and then neutralise the solution by the cautious addition of 30 g. of finely potcdered anhydrous sodium carbonate, For this purpose, add the sodium carbonate in small quantities (about i g.) at a time, preferably with the aid of a spatula, and shake the solution gently around after each addition to facilitate the evolution of carbon dioxide a clear solution is thus maintained throughout, whereas the rapid addition of large quantities of the carbonate produces lumps of material which are subsequently difflcult to dissolve. Now dissolve 36-5 g. of sodium nitrite in 50 ml. of water with gentle heating, cool the solution thoroughly in ice-water, and then add it with shaking to that of the sodium mono-chloroacetate. Add some fragments of unglazed porcelain, and then fit the flask with a delivery-tube of moderately wide bore connected in turn to a water-condenser (as in Fig. 59, p. 100, or, better, in Fig. 23(0), p. 45). Support the flask over a gauze, and then heat it gejitly with a small Bunsen flame. The solution slowly becomes yellow in colour, then greenish and finally a yellowish-brown, when a vigorous eftervescence starts at once remove the Bunsen flame, and allow the reaction to proceed spontaneously, carbon dioxide being evolved and the solution boiling vigorously. When the reaction subsides, replace the Bunsen flame and maintain a steady boiling. Nitromethane distils over in the steam and separates as a colourless oil at the bottom of the distillate since nitromethane is slightly soluble in water, stop the distillation as soon as drops of nitromethane can no longer be detected in the distillate leaving the condenser. Transfer the distillate to a separating-funnel, and carefully run off the lower layer of nitromethane and then dry it over anhydrous sodium sulphate for 30 minutes. Filter the dry nitromethane (preferably through a small dry Buchner funnel), transfer it to a 30 ml. distilling-flask fitted with a water-condenser, and then slowly distil, collecting the fraction of b.p. 100-102°.  [c.132]

See pages that mention the term Dicacodyl : [c.11]    [c.130]    [c.141]    [c.163]    [c.266]    [c.296]    [c.414]    [c.235]    [c.9]    [c.58]    [c.75]    [c.81]    [c.91]    [c.98]    [c.103]    [c.105]    [c.109]    [c.110]    [c.112]    [c.115]    [c.118]    [c.123]    [c.129]   
Chemistry of the elements (1998) -- [ c.2 , c.4 , c.583 , c.584 ]