Laboratory decantation

The first ten runs were conducted on a laboratory decanter of 150 mm diameter. The following year, tests were conducted on a small plant with a pilot plant size decanter of 425 mm bowl diameter. The plant capacity was limited, but results (runs 13-29) were sufficiently encouraging to warrant work on a larger plant the following year (runs 31-34). 

The laboratory decanter was limited by its small gearbox torque, and by its relatively small pond depth. However, its performance was sufficiently encouraging to warrant the larger scale tests and was confirmed in practice. The last laboratory test recorded stretched the limits of the decanter to demonstrate the feasibility of extra dryness. Because of the lower recoveries of the last three test runs, these are not included in the graphs. For the first pilot plant series, no centrate samples were analysed, but adjudged good and so a nominal figure is used for the sake of the calculations. 

Bulk displacement may be caused by fluid flow or direct mechanical conveying of a complete phase or fraction from one location or vessel to another. Consider, for example, the mechanical decantation of the upper phase from vessel A to vessel B. In vessel B, additional separation takes place because of the redistribution of components of the upper phase in vessel A between itself and the lower phase in vessel B (Figure 3.1.1). But all the components in the upper phase of vessel A are displaced to the new vessel B at the same rate and in a nonselective fashion. Such a procedure is followed in laboratory decantations as well as in industrial decanters. 

Conduct the preparation in the fume cupboard. Dissolve 250 g. of redistilled chloroacetic acid (Section 111,125) in 350 ml. of water contained in a 2 -5 litre round-bottomed flask. Warm the solution to about 50°, neutralise it by the cautious addition of 145 g. of anhydrous sodium carbonate in small portions cool the resulting solution to the laboratory temperature. Dissolve 150 g. of sodium cyanide powder (97-98 per cent. NaCN) in 375 ml. of water at 50-55°, cool to room temperature and add it to the sodium chloroacetate solution mix the solutions rapidly and cool in running water to prevent an appreciable rise in temperature. When all the sodium cyanide solution has been introduced, allow the temperature to rise when it reaches 95°, add 100 ml. of ice water and repeat the addition, if necessary, until the temperature no longer rises (1). Heat the solution on a water bath for an hour in order to complete the reaction. Cool the solution again to room temperature and slowly dis solve 120 g. of solid sodium hydroxide in it. Heat the solution on a water bath for 4 hours. Evolution of ammonia commences at 60-70° and becomes more vigorous as the temperature rises (2). Slowly add a solution of 300 g. of anhydrous calcium chloride in 900 ml. of water at 40° to the hot sodium malonate solution mix the solutions well after each addition. Allow the mixture to stand for 24 hours in order to convert the initial cheese-Uke precipitate of calcium malonate into a coarsely crystalline form. Decant the supernatant solution and wash the solid by decantation four times with 250 ml. portions of cold water. Filter at the pump. 

An equihbrium, or theoretical, stage in liquid-liquid extraction as defined earlier is routinely utilized in laboratory procedures. A feed solution is contacted with an immiscible solvent to remove one or more of the solutes from the feed. This can be carried out in a separating funnel, or, preferably, in an agitated vessel that can produce droplets of about 1 mm in diameter. After agitation has stopped and the phases separate, the two clear liquid layers are isolated by decantation. 

A test run is conducted to evaluate the performance of a 50,000 bpd (331 m /hr) FCC unit. The feed to the unit is gas oil from the vacuum unit. No recycle stream is processed however, the off-gas from the delayed coker is sent to the gas recovery section. Products from the unit are fuel gas, LPG, gasoline, LCO, and decanted oil (DO). Tables 5-2 and 5-3 contain stream flow rates, operating data, and laboratory analyses. The meter factors have been adjusted for actual operating conditions. 

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. 

Once equilibrium in the reagent mixture is attained, centrifugation in a common laboratory centrifuge, followed by decantation of the supernatant is all that is required for separation of bound and free label. 

Various experimental conditions have been used for oxidations of alcohols by Cr(VI) on a laboratory scale, and several examples are shown in Scheme 12.1. Entry 1 is an example of oxidation of a primary alcohol to an aldehyde. The propanal is distilled from the reaction mixture as oxidation proceeds, which minimizes overoxidation. For secondary alcohols, oxidation can be done by addition of an acidic aqueous solution containing chromic acid (known as Jones reagent) to an acetone solution of the alcohol. Oxidation normally occurs rapidly, and overoxidation is minimal. In acetone solution, the reduced chromium salts precipitate and the reaction solution can be decanted. Entries 2 to 4 in Scheme 12.1 are examples of this method. 

When the samples were returned to the laboratory the pH was adjusted to approximately pH 8 using concentrated ammonia (Ultrapure, G. Frederick Smith). Chelating cation exchange resin in the ammonia form (20 ml Chelex 100,100 - 200 mesh, Bio-Rad) was added to the samples and they were batch extracted on a shaker table for 36 hours. The resin was decanted into columns, and the manganese eluted using 2N nitric acid [129]. The eluant was then analysed by graphite furnace atomic absorption spectrophotometry. Replicate analyses of samples indicate a precision of about 5%. 

Several days later, Natividad Rosa brought us a whole basket of leaves, for which she was paid fifty pesos. The business seemed to have been discussed, for two other women brought us further quantities of leaves. As it was known that the expressed juice of the leaves is drunk in the ceremony, and this must therefore contain the active principle, the fresh leaves were crushed on a stone plate, squeezed out in a cloth, the juice diluted with alcohol as a preservative, and decanted into flasks in order to be studied later in the laboratory in Basel. I was assisted in this work by an Indian girl, who was accustomed to dealing with the stone plate, the metate, on which the Indians since ancient times have ground their corn by hand. 

Its laboratory method of ptepn, given in Ref 8, p 192 and in PATR 1448, p 9, consists of two steps prepn of Pb hydroxide and of LDNR, Basic. To a soln of 18.96g of pb acetate in 67 ml of warm distd w add gradually, with stirring, 4.0 g of NaOH dissolved in 67 ml of w and continue stirring for 5 mins. After allowing to settle, wash the white ppt of Pb hydroxide, by decantation three times with 100ml of distd w, and use immediately for the next operation... 

Tor use in the laboratory, hydrate of potassa, prepared as above, is treated with rectified spirit of wine in a stoppered bottle. The solution is allowed to deposit, decanted and evaporated in a silver dish, until fumes coase to be evolved, adding from time to time during the evaporation some water to prevent blacken-... 

YOU DECIDE ON THE SECOND WAY, USING THE STEPS SHOWN ON THE BOTTOM OF THESE PAGES. IN DOING THIS, YOU DO WHAT THE CURIES DID IN EXTRACTING RADIUM AND LEARN, IN THE PROCESS, THE IMPORTANT LABORATORY TECHNIQUES OF SOLUTION, DECANTATION, FILTRATION. EVAPORATION, AND CRYSTALLIZATION. 

The sample should be sent as rapidly as possible to the laboratory, and when the analysis is not to be carried out immediately the bottles are stored horizontally and in a cool, but not excessively cold, place. Turbid samples are either left for some time and then decanted or filtered prior to analysis, the residue being examined separately if necessary. The determination of sulphur dioxide should be made before filtration and as soon as the bottle is opened. 

Copper powder is prepared by dissolving 100 grams of recrystallised copper(n) sulphate in 350 ml of hot water in a 1-litre beaker a magnetic stirrer is provided. After cooling to the laboratory temperature, the stirrer is set in motion and 35 g (or more, if necessary) of purified zinc powder (see 4.2.80, Zinc) are gradually added until the solution is decolourised. The precipitated copper is washed by decantation with water. Dilute hydrochloric acid (5%) is added to the precipitate in order to remove the excess of zinc, and stirring is continued until the evolution of hydrogen ceases. The copper powder is filtered, washed with water and kept in a moist condition (as a paste) in a stoppered bottle. 

Method 2. It is often convenient to prepare the powdered sodium in the flask in which the subsequent reaction is to be carried out this is usually a three-necked flask. Into a 1-litre three-necked flask fitted with a reflux condenser (protected by a drying tube containing soda lime), a sealed stirrer and a dropping funnel are placed 23 g of clean sodium and 150-200 ml of sodium-dried xylene. The flask is surrounded by a mantle and heated until the sodium has melted. The stirrer is started and, after the sodium is suitably granulated, the mantle is removed. When the contents of the flask have cooled to the laboratory temperature, the stirrer is stopped. The xylene may then be decanted, and the sodium washed with two 100 ml portions of sodium-dried ether to remove traces of xylene as in Method 1. Large quantities of molecular sodium may be prepared by this method. 

Wear neoprene gloves,17 laboratory coat, and eye protection. Cover spill with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand. Scoop into a beaker or pail. In the fume hood, slowly add the acid mixture to a pail of cold water. When reaction ceases, neutralize with more sodium carbonate if necessary. When solids have settled, decant liquid into drain with 50 times its volume of water. Discard solid residue with normal refuse. Ventilate site of spillage well to evaporate remaining liquid and dispel vapor.18,19... 

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