Pouring Procedures

Fig. 27.4 Details of the experimental setup (a) longitudinal aspect of the model, (b) wall face instrumentation - Config. 2, (c), (d) pairs of accelerometers on shaking table and upper ring, (e) backfill accelerometer, (f) sand pouring procedure, (g), (h) back and front view of the wall...

Pouring procedures require no special apparatus. The necessary amount of adsorbent is weighed out and shaken to a homogeneous suspension with a suitable solvent. A previously determined volume of this is rapidly poured in one movement on to the middle of the plate to be coated. By gentle tilting and shaking, the suspension is distributed over the plate which is then dried in a horizontal position. 

A strip of adhesive tape (Tesafilm, Scotch tape), 1—2 cm wide, is stuck all round the outside of the plate to be able to prepare thicker layers on glass plates, using the pouring procedure. The adsorbent suspension is poured into the shallow trough thus formed. The adhesive strip can be torn off after the layer has dried. 

The layers are best prepared by the standard procedure, using a spreader (p. 56, 85). Pouring procedures are used successfully in many... 

Oleum is marketed in all strengths up to ca. 70 per cent. SO3. From 0 to 40 per cent, free SO3, it is a liquid from 40 to 60 per cent, free SO3, it is a solid from 60 to 70 per cent, free SO3, it is liquid above 70 per cent, free SO3, it is a solid. The acid must be kept in ground glass stoppered, thick-walled bottles. If it is required to melt the acid, the stopper is removed, a watch glass placed on the mouth of the bottle, and the bottle placed in a layer of sand in an air bath which is warmed with a small flame. The bottle is fitted with a wash bottle attachment, and any desired quantity of acid is forced out by gentle air pressure from a hand or foot bellows (the mouth must not be used) this procedure is far more satisfactory than that of pouring the liquid acid from the bottle. 

The acid, if monobasic, can usually be distilled directly from the reaction mixture. If this procedure is not possible, the reaction mixture is poured into excess of crushed ice, and the acid is isolated by ether extraction or by other suitable means. The acid is then characterised (Section 111,85). The addition of hydrochloric acid (as sodium chloride say 5 per cent, of the weight of sulphuric acid) increases the rate of the reaction. 

Procedure 1. Dissolve 1 g. of the compound in 5 ml. of chloroform in a test-tube and cool in ice. Add 5 ml. of chlorosulphonic acid CA UTION in handhng) dropwise and with shaking. When the initial evolution of hydrogen chloride subsides, remove the reaction mixture from the ice and, after 20 minutes, pour it into a 50 ml. beaker filled with crushed ice. Separate the chloroform layer, wash it well with water, and evaporate the solvent. Recrystallise the residual aryl sulphonyl chloride from light petroleum (b.p. 40-60°), chloroform or benzene this is not essential for conversion into the sulphonamide. 

Procedure 2. Follow Procedure 1 except that no solvent is employed. Pour the s3Tupy reaction mixture on to crushed ice, remove the resulting aryl sulphonyl chloride and/or sulphone, if a sohd, by filtration with suction and, if a hquid, by means of a small separatory funnel or dropper, and wash with water. 

Because of the great solubility of sulphonic acids in water and the consequent difficulty in crystallisation, the free sulphonic adds are not usually isolated but are converted directly into the sodium salts. The simplest procedure is partly to neutralise the reaction mixture (say, with solid sodium bicarbonate) and then to pour it into water and add excess of sodium chloride. An equilibrium is set up, for example ... 

An alternative procedure, more suitable for the preparation of somewhat larger quantities of the bromo derivative, is the following. Dissolve 10 g, of the compovmd in 10-15 ml. of glacial acetic acid, cautiously add 3-4 ml. of hquid bromine, and allow the mixture to stand for 15-20 minutes. Pour into 50-100 ml. of water, filter off the bromo compound at the pump, and wash with a httle cold water. Recrystallise from dilute alcohol. 

Place 125 ml. of glacial acetic acid, 7 -5 g. of purifled red phosphorus (Section II,50,d) and 2 5 g. of iodine in a 500 ml, round-bottomed flask fitted with a reflux condenser. Allow the mixture to stand for 15-20 minutes with occasional shaking until aU the iodine has reacted, then add 2 5 ml. of water and 50 g, of benzilic acid (Section IV,127). Boil the mixture under reflux for 3 hours, and filter the hot mixture at the pump through a sintered glass funnel to remove the excess of red phosphorus. Pour the hot filtrate into a cold, weU-stirred solution of 12 g. of sodium bisulphite in 500 ml, of water the latter should be acid to litmus, pro duced, if necessary, by passing sulphur dioxide through the solution. This procedure removes the excess of iodine and precipitates the diphenyl-acetic acid as a fine white or pale yellow powder. Filter the solid with suction and dry in the air upon filter paper. The yield is 45 g., m.p. 

Method 2. The procedure described under Benzenesulphonyl Chloride, Method 2 (Section IV,206) may be used with suitable adjustment for the difierence in molecular weights between sodium p-toluenesulphonate (Section IV,30) and sodium benzenesulphonate. When the reaction product is poured on to ice, the p-toluenesulphonyl chloride separates as a sohd. This is filtered with suction it may be recrystaUised from hght petroleum (b.p. 40-60°) and then melts at 69°. 

A simplified procedure is possible by using polyphosphoric acid as the condensing agent. Add 160 g. of polyphosphoric acid to a solution of 11 g. of resorcinol in 13 g. of ethyl acetoacetate. Stir the mixture and heat at 75-80° for 20 minutes, and then pour into ice-water. Collect the pale yellow solid by suction filtration, wash with a little cold water, and dry at 60°. The yield of crude 4-methyl-7-hydroxycoumarin, m.p. 178-181°, is 17 g. Recrystalbsation from dilute ethanol yields the pure, colourless compound, m.p. 185°. 

Step 3. The neutral components. The ethereal solution (E remaining after the acid extraction of Step 2 should contain only the neutral compounds of Solubility Groups V, VI and VII (see Table XI,5). Dry it with a little anhydrous magnesium sulphate, and distil off the ether. If a residue is obtained, neutral compounds are present in the mixture. Test a portion of this with respect to its solubility in concentrated sulphuric acid if it dissolves in the acid, pour the solution slowly and cautiously into ice water and note whether any compound is recovered. Examine the main residue for homogeneity and if it is a mixture devise procedures, based for example upon differences in volatility, solubility in inert solvents, reaction with hydrolytic and other reagents, to separate the components. 

Safrole from the Grignard reagent Keeping the apparatus from the above reaction, pour 60g of allylbromide into the sep funnel. As with the ingredients of the last procedure the allylbromide must be dried over sodium sulphate. This stuff is really nasty, use a mask at least or a fume cupboard if you can get access to one or fill the sep funnel outdoors. The fumes are invisible and pretty lethal -please be warned. 

Top-Feed Procedure The sequence of operations with a top-feed leaf test is the same as in a bottom-feed test, except that the leaf is not immersed in the sluriy. The best method for transferring the slurry to the top-feed leaf is, of course, a function of the characteristics of the sluriy. If the particles in the sluriy do not settle rapidly, the feed can usually be transferred to the leaf from a beaker. If, however, the particles settle veiy rapidly, it is virtually impossible to pour the slurry out of a beaker satisfactorily. In this case, the best method is to make use of an Erlenmeyer flask, preferably one made of plastic. The slurry is swirled in the flask until it is completely suspended and then abruptly inverted over the leaf. This technique will ensure that all of the sohds are transferred to the leaf. 

B. a-Ketoglularic acid. The ester obtained by the foregoing procedure is mixed with 600 ml. of concentrated hydrochloric acid and left overnight. The mixture is concentrated by distillation (Note 5) until the temperature of the liquid reaches 140°. It is poured into an evaporating dish and allowed to cool. The solid mass, weighing 11(3-112 g., is then pulverized. The yield of a-ketoglutaric acid is 92-93% of the theoretical for the last step, or 75-77% based upon diethyl succinate. The light tan product, obtained as described above, is suitable for most purposes, but a purer add, m.p. 109-110° (corr.) may be obtained by recrystallization from an acetone-benzene mixture. 

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