Condensation prevention

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Passing warm water through the condenser prevents blockage by solid product otherwise pressure may build and force the joints apart. As an alternative, steam may be passed through the condenser periodically. 

Some years ago, at Professor Debye s suggestion, I set up in the Zurich laboratory an apparatus by means of which the temperature variation of dielectric constants can be measured for a constant number of molecules. Various defects in the apparatus, in particular the use of ordinary brass condensers, prevented the dielectric constants being determined with the accuracy necessary for an accurate calculation of the electric moment, so that the moments could only be determined to about o i. io e.s.u. 

During the first part of the run, the circulation of brine through the reflux condenser system must be limited to avoid crystallizing the acetic acid. As chlorination proceeds, the quantity of acetic acid distilling off decreases, and the circulation of brine can be increased accordingly. Since the reflux condenser prevents the passage of any considerable quantity of acetic acid vapors to the return condenser, the latter may be kept at approximately 0 C to ensure the condensation of acetyl chloride. 

Excessive condensation in the drum during wintv r jeatedfy caused buildup of ethane, until the stripper flooded. Ke ing drum warm 1 cutting cooling to the condenser prevented recurrence. 

Wines high in sulfur dioxide should be treated for its removal before distillation. Got (1947) showed that wines of 15% to 18% alcohol and 200 to 400 p.p.m. of sulfur dioxide yielded results 0.2% to 0.5% low. Use of concentrated alkali in a bubble cap in the condenser prevents sulfurous acid from distilling over and gives a better distillate for the determination of alcohol, according to Rocques (1950). 

Make sure that the steam condensate level in the reboiler channel head is below the bottom row of tubes. Also check that the reboiler steam supply has been completely desuperheated with clean steam condensate. Preventing water submergence of tubes and using desuperheated steam results in cooler reboiler tubes. This slows down corrosion and particulate generation. 

The basic requirements for an excellent water condensation prevention material are ... 

Si02-Al203 Oxopolymers. The large difference in reactivity of aluminium and silicon alkoxides towards hydrolysis and condensation prevents the formation of many Si-O-Al bonds even when Si(OR)4 is prehydrolyzed before mixing with... 

Dehydration can be performed by a number of methods cooling, absorption and adsorption. Water removal by cooling is simply a condensation process at lower temperatures the gas can hold less water vapour. This method of dehydration is often used when gas has to be cooled to recover heavy hydrocarbons. Inhibitors such as glycol may have to be injected upstream of the chillers to prevent hydrate formation. 

Although it is hard to draw a sharp distinction, emulsions and foams are somewhat different from systems normally referred to as colloidal. Thus, whereas ordinary cream is an oil-in-water emulsion, the very fine aqueous suspension of oil droplets that results from the condensation of oily steam is essentially colloidal and is called an oil hydrosol. In this case the oil occupies only a small fraction of the volume of the system, and the particles of oil are small enough that their natural sedimentation rate is so slow that even small thermal convection currents suffice to keep them suspended for a cream, on the other hand, as also is the case for foams, the inner phase constitutes a sizable fraction of the total volume, and the system consists of a network of interfaces that are prevented from collapsing or coalescing by virtue of adsorbed films or electrical repulsions. 

Meanwhile assemble the apparatus shown in Fig. 62, or that in Fig. 23(D), p. 45, having a distilling-flask of at least 500 ml. capacity in either case. If an ordinary condenser C (Fig. 62) is employed, fit the lower end of the condenser by means of a short piece of rubber tubing to a small inverted funnel. Arrange the latter so that its lip is just below the surface of 25 ml. of concentrated hydrochloric acid diluted with 75 ml. of water contained in a 250 ml. beaker B the hydro-. chloric acid is thereby prevented from being sucked back into the... 

Place 8 0 g. of magnesium turnings or ribbon and 80 ml. of the dry benzene in the flask. Prepare a solution of 9-0 g. of mercuric chloride in 50 ml. of the dry acetone, transfer it to the dropping-funnel, and then allow it to enter the flask slowly at first, and then more rapidly, so that the addition takes about 3-5 minutes. The reaction usually starts shortly after the initial addition of the mercuric chloride solution if it is delayed, it may then start vigorously, and the flask may have to be cooled in water to prevent escape of acetone through the condenser. 

Hydrolysis of />-Tolunitrile. As in the case of benzonitrile, alkaline h> drolysis is preferable to hydrolysis by 70% sulphuric acid. Boil a mixture of 5 g. of p-tolunitrile, 75 ml. of 10% aqueous sodium hydroxide solution and 15 ml. of ethanol under a reflux water-condenser. The ethanol is added partly to increase the speed of the hydrolysis, but in particular to prevent the nitrile (which volatilises in the steam) from actually crystallising in the condenser. The solution becomes clear after about i hour s heating, but the boiling should be continued for a total period of 1-5 hours to ensure complete hydrolysis. Then precipitate and isolate the p-toluic acid, CH3CgH4COOH, in precisely the same way as the benzoic acid in the above hydrolysis of benzonitrile. Yield 5 5 g. (almost theoretical). The p-toluic acid has m.p. 178°, and may be recrystallised from a mixture of equal volumes of water and rectified spirit. 

It may occasionally happen, particularly if the solution is approaching saturation, that a small quantity of the crystalline solute separates at the top of the tube H in the zone Z, i.e, immediately above the source of the heat. This may be prevented by placing a narrow oblong piece of asbestos paper, with slots cut in each end, horizontally between the tubes H and D, the slots fitting over the lower narrow ends of the condenser C and the cup F. 

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