Temperatures, industrial acid cooling

Place 5.3 g (0.025 mol) of benzil (Expt 6.143), 3.0 g (0.05 mol) of urea, 15 ml of 30 per cent aqueous sodium hydroxide solution and 75 ml of ethanol in a 100-ml round-bottomed flask. Attach a reflux condenser and boil under reflux using an electric heating mantle for at least 2 hours. Cool to room temperature, pour the reaction product into 125 ml of water and mix thoroughly. Allow to stand for 15 minutes and then filter under suction to remove an insoluble by-product. Render the filtrate strongly acidic with concentrated hydrochloric acid, cool in ice-water and immediately filter off- the precipitated product under suction. Recrystallise at least once from industrial spirit to obtain about 2.8 g (44%) of pure 5,5-diphenylhydantoin, m.p. 297-298 °C. 

Dinitroanthraquinones are industrially prepared by nitration of anthraquiaone in mixed nitric—sulfuric acid at 0—50°C. The reaction mixture is then heated to a temperature slightly higher than the nitration reaction temperature to enrich the content of 1,5-dinitroanthraquinone in soHd phase, and then cooled and filtered to obtain the 1,5-dinitroanthraquinone wet cake. Mother Hquor is concentrated by distillation of nitric acid and crystallised 1,8-isomer is separated. The filtrate is again distilled, and precipitated ( -isomers are filtered off and filtrate is recycled to the nitration step (72—74). 

Corrosion of industrial alloys in alkaline waters is not as common or as severe as attack associated with acidic conditions. Caustic solutions produce little corrosion on steel, stainless steel, cast iron, nickel, and nickel alloys under most cooling water conditions. Ammonia produces wastage and cracking mainly on copper and copper alloys. Most other alloys are not attacked at cooling water temperatures. This is at least in part explained by inherent alloy corrosion behavior and the interaction of specific ions on the metal surface. Further, many dissolved minerals have normal pH solubility and thus deposit at faster rates when pH increases. Precipitated minerals such as phosphates, carbonates, and silicates, for example, tend to reduce corrosion on many alloys. 

In the electroplating industry, the use of titanium as hooks " and as heating and cooling coils for temperature control of certain acidic liquors has improved the control of plating baths Perhaps the most significant... 

On an industrial scale, PA-6 is synthesized from e-caprolactam with water as the initiator. The process is very simple if the reaction is earned out at atmospheric pressure. The polymerization is earned out in a VK-reactor (Fig. 3.23), which is a continuous reactor without a stirrer, with a residence time of 12-24 h at temperatures of 260-280°C.5,28 Molten lactam, initiator (water), and chain terminator (acetic acid) are added at the top and the polymer is discharged at the bottom to an extruder. In this extruder, other ingredients such as stabilizers, whiteners, pigments, and reinforcing fillers are added. The extruded thread is cooled in a water bath and granulated. The resultant PA-6 still contains 9-12%... 

DR. PATEL One reason for much of the interest which prevails in this area right now, especially with iron ll), has to do with the corrosion of steel in industry and also in nuclear reactors. Normally one thinks of forming precipitates or particles by adding base to a solution and cooling it down. If iron(III) solutions are made more acidic and if you raise the temperature, these conditions lead to the formation of very, very well-defined particles. A very important event in this is the proton transfer kinetics that lead to the formation of the hydrolysis of many of these trivalent ions. 

Dissolve 34 g (0.25 mol) of o-nitroaniline in a warm mixture of 63 ml of concentrated hydrochloric acid and 63 ml of water contained in a 600-ml beaker. Place the beaker in an ice-salt bath, and cool to 0-5 °C while stirring mechanically the o-nitroaniline hydrochloride will separate in a finely divided crystalline form. Add a cold solution of 18 g (0.26 mol) of sodium nitrite in 40 ml of water slowly and with stirring to an end-point with potassium iodide-starch paper do not allow the temperature to rise above 5-7°C. Introduce, while stirring vigorously, a solution of 40 g (0.36 mol) of sodium fluoroborate in 80 ml of water. Stir for a further 10 minutes, and filter the solid diazonium fluoroborate with suction on a Buchner funnel. Wash it immediately once with 25 ml of cold 5 per cent sodium fluoroborate solution, then twice with 15 ml portions of rectified (or industrial) spirit and several times with ether in each washing stir the fluoroborate well before applying suction. The o-nitrobenzenediazonium fluoroborate weighs about 50 g (86%) the pure substance melts with decomposition at 135 °C. 

Place a solution of 50 g (0.25 mol) of p-bromoacetophenone (Expt 6.122) in 100 ml of glacial acetic acid in a 500-ml flask. Add very slowly (about 30 minutes) from a dropping funnel 40 g (12.5 ml, 0.25 mol) of bromine (CAUTION) shake the mixture vigorously during the addition and keep the temperature below 20 °C. p-Bromophenacyl bromide commences to separate as needles after about half of the bromine has been introduced. When the addition is complete, cool the mixture in ice-water, filter the crude product at the pump and wash it with 50 per cent alcohol until colourless (about 100 ml are required). Recrystallise from rectified (or industrial) spirit (c. 400 ml). The yield of pure p-bromophenacyl bromide (colourless needles, m.p. 109 °C) is 50 g (72%). 

Fig. 21.1. Heat transfer flowsheet for single contact, sulfur burning sulfuric acid plant. It is simpler than industrial plants, which nearly always have 4 catalyst beds rather than 3. The gaseous product is cool, S03 rich gas, ready for H2S04 making. The heat transfer product is superheated steam. All calculations in this chapter are based on this figure s feed gas composition and catalyst bed input gas temperatures. All bed pressures are 1.2 bar. The catalyst bed output gas temperatures are the intercept temperatures calculated in Sections 12.2, 15.2 and 16.3.

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