Wash-over equipment

Over 22.7 million kg (50 million lb) of zinc sulfate are used annually in the U.S. for the manufacture of approximately 454 million kg (one billion lb) of viscose rayon. Zinc is used as a regeneration retardant in the acid spinning bath. Because it is not consumed in any of the viscose reactions, these 22.7 million kg (50 million lb) of zinc represent process losses, through dragout by the filaments to the subsequent wash streams, filter backwashing, splashes, leaks, and the washing of equipment.14... 

This cleaning procedure requires that the solvent boil in a vaporizer. Then as the hot solvent vapor condenses and washes over a cooler component, the soluble contaminants are carried away. This action can occur by placing components inside a vapor degreaser chamber into which the solvent vapor rises from a vaporizer chamber. (See Fig. 11-9.) Alternatively, if a vessel is to be cleaned, hot solvent vapor can be piped from a vaporizer into the vessel, on whose inner walls condensation and cleaning will occur. In this case, the equipment should be positioned and connected so that the condensate can be thoroughly drained from the system. Continuous removal of the condensate and its trans-... 

Allyl Chloride. Comparatively poor yields are obtained by the zinc chloride - hydrochloric acid method, but the following procedure, which employs cuprous chloride as a catalyst, gives a yield of over 90 per cent. Place 100 ml. of allyl alcohol (Section 111,140), 150 ml. of concentrated hydrochloric acid and 2 g. of freshly prepared cuprous chloride (Section II,50,i one tenth scale) in a 750 ml. round-bottomed flask equipped with a reflux condenser. Cool the flask in ice and add 50 ml. of concen trated sulphuric acid dropwise through the condenser with frequent shaking of the flask. A little hydrogen chloride may be evolved towards the end of the reaction. Allow the turbid liquid to stand for 30 minutes in order to complete the separation of the allyl chloride. Remove the upper layer, wash it with twice its volume of water, and dry over anhydrous calcium chloride. Distil the allyl chloride passes over at 46-47°. 

Equip a 1-litre three-necked flask with a powerful mechanical stirrer, a separatory funnel with stem extending to the bottom of the flask, and a thermometer. Cool the flask in a mixture of ice and salt. Place a solution of 95 g. of A.R. sodium nitrite in 375 ml. of water in the flask and stir. When the temperature has fallen to 0° (or slightly below) introduce slowly from the separatory funnel a mixture of 25 ml. of water, 62 5 g. (34 ml.) of concentrated sulphuric acid and 110 g. (135 ml.) of n-amyl alcohol, which has previously been cooled to 0°. The rate of addition must be controlled so that the temperature is maintained at 1° the addition takes 45-60 minutes. AUow the mixture to stand for 1 5 hours and then filter from the precipitated sodium sulphate (1). Separate the upper yellow n-amyl nitrite layer, wash it with a solution containing 1 g. of sodium bicarbonate and 12 5 g. of sodium chloride in 50 ml. of water, and dry it with 5-7 g. of anhydrous magnesium sulphate. The resulting crude n-amyl nitrite (107 g.) is satisfactory for many purposes (2). Upon distillation, it passes over largely at 104° with negligible decomposition. The b.p. under reduced pressure is 29°/40 mm. 

Place a mixture of 25 5 g. of n-valerio acid (Sections 111,83 and 111,84), 30 g. (37 -5 ml.) of dry n-propyl alcohol, 50 ml. of sodium-dried benzene and 10 g. (5-5 ml.) of concentrated sulphuric acid in a 250 ml. round-bottomed flask equipped with a vertical condenser, and reflux for 36 hours. Pour into 250 ml. of water and separate the upper layer. Extract the aqueous layer with ether, and add the extract to the benzene solution. Wash the combined extracts with saturated sodium bicarbonate solution until effervescence ceases, then with water, and dry with anhydrous magnesium sulphate. Remove the low boiling point solvents by distillation (use the apparatus of Fig. II, 13,4 but with a Claisen flask replacing the distilling flask) the temperature will rise abruptly and the fi-propyl n-valerate will pass over at 163-164°. The yield is 28 g. 

Place 84 g. of iron filings and 340 ml. of water in a 1 - 5 or 2-litre bolt-head flask equipped with a mechanical stirrer. Heat the mixture to boiling, stir mechanically, and add the sodium m-nitrobenzenesulphonate in small portions during 1 hour. After each addition the mixture foams extensively a wet cloth should be applied to the neck of the flask if the mixture tends to froth over the sides. Replace from time to time the water which has evaporated so that the volume is approximately constant. When all the sodium salt has been introduced, boU the mixture for 20 minutes. Place a small drop of the suspension upon filter paper and observe the colour of the spot it should be a pale brown but not deep brown or deep yellow. If it is not appreciably coloured, add anhydrous sodium carbonate cautiously, stirring the mixture, until red litmus paper is turned blue and a test drop upon filter paper is not blackened by sodium sulphide solution. Filter at the pump and wash well with hot water. Concentrate the filtrate to about 200 ml., acidify with concentrated hydrochloric acid to Congo red, and allow to cool. Filter off the metanilic acid and dry upon filter paper. A further small quantity may be obtained by concentrating the mother liquid. The yield is 55 g. 

In a 2 litre bolt-head flask, equipped with an efficient mechanical stirrer, place 60-5 g. (50 ml.) of pure nitrobenzene and a solution of 30 g. of ammonium chloride in 1 litre of water. Stir vigorously and add 75 g. of a good quality zinc powder (about 90 per cent, purity) in small portions over a period of 5 minutes. The main reaction occurs about 5 minutes after the addition and the temperature rises. When the temperature reaches about 65°, add enough ice to the weU-stirred mixture to reduce the temperature to 50-55°. Filter the solution through a Buchner funnel twenty minutes after the first portion of zinc powder was introduced wash the zinc oxide residues with 600-700 ml. of boiling water. 

Place a mixture of 125 ml. of A.R. benzene and 32 -5 g. of di-re-butyl d-tartrate (1) in a 500 ml. three-uccked flask, equipped with a Hershberg stirrer (Section 11,7) and a thermometer. Stir the mixture rapidly and add 58 g. of lead tetra-acetate (Section 11,50,15) in small portions over a period of 20 minutes whilst maintaining the temperature below 30° by occasional cooling with cold water. Continue the stirring for a further 60 minutes. Separate the salts by suction filtration and wash with two... 

The purified commercial di-n-butyl d-tartrate, m.p. 22°, may be used. It may be prepared by using the procedure described under i o-propyl lactate (Section 111,102). Place a mixture of 75 g. of d-tartaric acid, 10 g. of Zeo-Karb 225/H, 110 g. (136 ml.) of redistilled n-butyl alcohol and 150 ml. of sodium-dried benzene in a 1-litre three-necked flask equipped with a mercury-sealed stirrer, a double surface condenser and an automatic water separator (see Fig. Ill, 126,1). Reflux the mixture with stirring for 10 hours about 21 ml. of water collect in the water separator. FUter off the ion-exchange resin at the pump and wash it with two 30-40 ml. portions of hot benzene. Wash the combined filtrate and washings with two 75 ml. portions of saturated sodium bicarbonate solution, followed by lOu ml. of water, and dry over anhydrous magnesium sulphate. Remove the benzene by distillation under reduced pressure (water pump) and finally distil the residue. Collect the di-n-butyl d-tartrate at 150°/1 5 mm. The yield is 90 g. 

Because dimethyl sulfate looks like water, operations are preferably not performed when water is present, eg, wet floors or rain. Any spills or leaks should not be left unattended they should be contained, and mnoff to sewers should be avoided. Minor spills should be flooded with water to dilute and hydroly2e the dimethyl sulfate. The area should then be covered with a dilute (2—5 wt %) caustic solution or a dilute (2—5 wt %) ammonia solution, or soda ash may be sprinkled over the neat liquid and the mix wetted with a gende spray of water. The neutrafi2ing agent should remain on the affected area for 24 h and then should be washed away. Only personnel wearing protective equipment should perform these operations. The product bulletins should be consulted for procedures to be followed for more severe spills. Concentrated ammonia should not be used with neat dimethyl sulfate because explosions have resulted after their contact (128). 

A. Heptoic anhydride enanthic anhydride). In a 250-ml. round-bottomed three-necked flask, equipped with a stirrer, dropping funnel, and thermometer, are placed 15.8 g. (16.1 ml., 0.2 mole) of dry pyridine (Note 1) and 25 ml. of dry benzene (Note 2). I hen 14.8 g. (15.5 ml., 0.1 mole) of heptoyl chloride (Note 3) is added rapidly to the stirred solution. The temperature rises only slightly, and a pyridinium complex separates. While stirring is continued, 13.0 g. (14.1 ml., 0.1 mole) of heptoic acid (Note 3) is added from the dropping funnel over a period of 5 minutes. The temperature rises rapidly to 50-65° (Note 4), and pyridine hydrochloride is formed. After stirring for 10 minutes, the solid is collected on a chilled Buchner funnel and washed twice with 25-ml. portions of dry benzene (Note 5). 

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