Decanting losses

Decanting losses were much higher than anticipated. In an attempt to minimize losses, the chemical composition of the precipitation batches was varied to increase the oxalate/aluminum ratio. These variables had little effect on product losses because the solubility losses were very low (<15% of the actual loss). Apparently, Am-Cm oxalate solids are being suspended prior to and during decanting (perhaps due to the decay heat of Cm) and a portion of the suspended precipitate was decanted. A new decant jet, which had a plate welded across the bottom and holes drilled around the pipe above the plate to provide horizontal rather than vertical suction, was fabricated and installed after the fifth batch. Losses, however, remain unchanged. 

Power for each Hquid and the soHd phase must be added to get Pp. P, the soHds process power, = T -AN for scroU decanters, where = conveyor torque and AN = differential speed between bowl and conveyor. Pp is the friction power, ie, loss in bearings, seals, gears, belts, and fluid couplings. P, the windage power, = K and fi = viscosity of surrounding gas p = density of gas D = rotor outside diameter N = rpm and K = shape... 

Zinc-Copper Couple A 500-ml Erlenmeyer flask equipped for magnetic stirring is charged with a mixture of zinc powder (49.2 g, 0.75 g-atom) and hydrochloric acid (40 ml of 3 % aqueous solution). The contents of the flask are rapidly stirred for 1 minute, and the liquid is decanted. Similarly, the zinc is washed with the following three times with 40 ml of 3% hydrochloric acid solution, five times with 100 ml of distilled water, five times with 75 ml of 2 % aqueous copper sulfate solution, five times with 100 ml of distilled water, four times with 100 ml of absolute ethanol, and five times with 100 ml of absolute ether. These last ethanol and ether washes are decanted onto a Buchner funnel to prevent loss. The residue is collected by suction filtration, washed again with anhydrous ether, and dried in air. Finally, the zinc-copper couple is stored (20-24 hours) in a vacuum desiccator over phosphorous pentoxide. 

In some circumstances, separation of solid from a liquid is better achieved by use of a centrifuge than by filtration, and a small, electrically driven centrifuge is a useful piece of equipment for an analytical laboratory. It may be employed for removing the mother liquor from recrystallised salts, for collecting difficultly filterable precipitates, and for the washing of certain precipitates by decantation. It is particularly useful when small quantities of solids are involved centrifuging, followed by decantation and re-centrifuging, avoids transference losses and yields the solid phase in a compact form. Another valuable application is for the separation of two immiscible phases. 

Wash solutions for precipitates, 426 Washing of precipitates 118, 426 by decantation. 119 solubility losses in, 119, 427 Washing soda D. of sodium carbonate in, 295 Water absorbents for, 477 ammonia-free, 679 deionised, 90 D. of hardness, 332 D. of total cation concentration, 210 D. with Karl Fischer reagent 637 distilled, 90 high purity, 91 ionic product of, 36 types and standards for, (T) 90 volume of 1 g at various temperatures, (T)87... 

Mix 130 g. of the crude thiomorpholide with 270 ml. of glacial acetic acid, 40 ml. of concentrated sulphuric acid and 60 ml. of water raise the temperature of the mixture carefully to the boiling point and reflux for 6 hours. Decant the solution from a little tarry matter into 2 litres of water and keep overnight. Collect the solid by suction filtration and wash it well with cold water. Digest the solid with a solution of 50 g. of sodium hydroxide in 1 litre of water, filter and acidify the filtrate with hydrochloric acid filter off the crude p-naphthylacetic acid, wash with water and dry. The yield of the crude acid, m.p. 137-140°, is 75 g. RecrystaUisation from benzene raises the m.p. to 142-143° the loss is about 10 per cent. 

Water and ethanol form a low boiling point azeotrope. So, water cannot be completely separated from ethanol by straight distillation. To produce absolute (100 per cent) ethanol it is necessary to add an entraining agent to break the azeotrope. Benzene is an effective entrainer and is used where the product is not required for food products. Three columns are used in the benzene process. Column 1. This column separates the ethanol from the water. The bottom product is essentially pure ethanol. The water in the feed is carried overhead as the ternary azeotrope of ethanol, benzene and water (24 per cent ethanol, 54 per cent benzene, 22 per cent water). The overhead vapour is condensed and the condensate separated in a decanter into, a benzene-rich phase (22 per cent ethanol, 74 per cent benzene, 4 per cent water) and a water-rich phase (35 per cent ethanol, 4 per cent benzene, 61 per cent water). The benzene-rich phase is recycled to the column as reflux. A benzene make-up stream is added to the reflux to make good any loss of benzene from the process. The water-rich phase is fed to the second column. 

In an ideal case, an ionic liquid dissolves the catalyst and displays a partial miscibility with the reactants under reaction conditions (giving a relatively high reaction rate) and negligible miscibility with the product (giving enhanced selectivity and yield). At the termination of the reaction, the product can be removed by simple decantation without the need to extract the catalyst. This mode of operation eliminates heating and therefore results in reduced loss of catalyst by thermal decomposition (/). 

Two-phase systems in which an insoluble organic substrate is reacted with a catalyst dissolved in an ionic liquid show promise for commercial use (Chauvin and Helene, 1995 Freemantle, 1998). One such system is a nickel-catalyzed olefin dimerization. The dimers are produced selectively and decanted from the ionic liquid. The catalyst/ ionic liquid phase is recycled without loss of activity. Other reactions investigated include ... 

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