Filter solution

Carbon disulphide should never be used if any alternative solvent is available, as it has a dangerously low flash-point, and its vapours form exceedingly explosive mixtures with air. Ether as a solvent for recrystallisation is much safer than carbon disulphide, but again should be avoided whenever possible, partly on account of the danger of fires, and partly because the filtered solution tends to creep up the walls of the containing vessel and there deposit solid matter by complete evaporation instead of preferential crystallisation. 

The hot filtered solution is then without delay poured into a lipped beaker or a conical flask not into an evaporating-basin, since it is crystallisation and not evaporation which is now required), the beaker covered with a watch-glass, and then cooled in ice-water. As cooling proceeds, the solution should be stirred from time to time to facilitate crystallisation, and when crystallisation appears complete, the cooling should be continued for at least another 15 minutes. 

The camphorquinone can be purified in either of two ways, (i) To save time, the drained but still damp material can be recrystallised from water containing 10% of acetic acid, the hot filtered solution being cooled and vigorously stirred. The quinone separates as brilliant yellow crystals (yield, 2 5 g.), m.p. 192-194 , increased to 196-197 by a second reciystal-lisation. (ii) The crude camphorquinone can be dried in a vacuum desiccator (weight of dry quinone, 5 g.), and then recrystallised from petroleum (b.p. 100-120 ), the hot solution being filtered through a fluted paper in a pre-heated funnel. The quinone separates in beautiful crystals, m.p. 196-197 , 2 8 g. 

Pour the reaction mixture cautiously into 400 g. of crushed ice and acidify it in the cold by the addition of a solution prepared by adding 55 ml. of concentrated sulphuric acid to 150 ml. of water and then coohng to 0°. Separate the ether layer and extract the aqueous layer twice with 50 ml. portions of ether. Dry the combined ethereal solutions over 50 g. of anhydrous potassium carbonate and distil the filtered solution thror h a Widmer column (Figs. II, 17, 1 and II, 24, 4). Collect separately the fraction boihng up to 103°, and the dimethylethynyl carbinol at 103-107° Discard the high boiling point material. Dry the fraction of low boihng point with anhydrous potassium carbonate and redistil. The total 3 ield is 75 g. 

Difluorodiphenyl. Bis-diazotise a solution of 46 g. of benzidine (Section IV,88) in 150 ml. of concentrated hydrochloric acid and 150 ml. of water by means of a solution of 35 g. of sodium nitrite in 60 ml. of water add about 200 g. of crushed ice during the process (compare p-Fbtorotoluene above). Filter the solution and add it to a filtered solution of 85 g. of sodium borofluoride in 150 ml. of water. Stir for several minutes, collect the precipitated bis-diazonium borofluoride by suction filtration, wash with 5 ml. of ice-cold water, and dry at 90-100°. Place the dry salt in a flask fitted with an air condenser, immerse the flask in an oil bath, and slowly raise the temperature to 150° (Fume Cupboard ). When decomposition of the salt is complete, steam distil the mixture collect the 4 4 difluoro-diphenyl which passes over and recrystallise it from ethanol. The yield is 21 g., m.p. 92-93°. 

Dissolve 14 g. of p-phenetidine (2) in 240 ml. of water to which 20 ml. of 5N hydrochloric acid (or 9 ml. of the concentrated acid) have been added stir the solution with about 5 g. of decolourising carbon for 5 minutes, warm, and filter the solution with suction. Transfer the cold filtered solution of p-phenetidine hydrochloride to a 700 ml. conical flask, add 13 g. (12 ml.) of acetic anhydride and swirl the contents to dissolve the anhydride. Immediately add a solution of 16 g. of crystallised sodium acetate in 50 ml. of water and stir (or swirl) the contents of the flask vigorously. Cool the reaction mixture in an ice bath, filter with suction and wash with cold water. RecrystaUise from hot water (with the addition of a little decolourising carbon, if necessary), filter and dry. The yield of pure phenacetin, m.p. 137°, is 12 g. 

The speciation scheme of Batley and Florence requires eight measurements on four samples. After removing insoluble particulates by filtration, the solution is analyzed for the concentration of anodic stripping voltammetry (ASV) labile metal and the total concentration of metal. A portion of the filtered solution is passed through an ion-exchange column, and the concentrations of ASV metal and total metal are determined. A second portion of the filtered solution is irradiated with UV light, and the concentrations of ASV metal... 

In 1990, appioximately 66,000 metric tons of alumina trihydiate [12252-70-9] AI2O2 3H20, the most widely used flame retardant, was used to inhibit the flammabihty of plastics processed at low temperatures. Alumina trihydrate is manufactured from either bauxite ore or recovered aluminum by either the Bayer or sinter processes (25). In the Bayer process, the bauxite ore is digested in a caustic solution, then filtered to remove siUcate, titanate, and iron impurities. The alumina trihydrate is recovered from the filtered solution by precipitation. In the sinter process the aluminum is leached from the ore using a solution of soda and lime from which pure alumina trihydrate is recovered (see Aluminum compounds). 

Excess calcium hydroxide is precipitated by usiag carbon dioxide and the calcium carbonate, calcium hydroxide, and calcium phosphite are removed by filtration. The filtered solution is treated with an equivalent amount of sodium sulfate or sodium carbonate to precipitate calcium sulfate or carbonate. Sodium hypophosphite monohydrate [10039-56-2] is recovered upon concentration of the solution. Phosphinic acid is produced from the sodium salt by ion exchange (qv). The acid is sold as a 50 wt %, 30—32 wt %, or 10 wt % solution. The 30—32 wt % solution is sold as USP grade (Table 12) (63). Phosphinic acid and its salts are strong reduciag agents, especially ia alkaline solution (65). 

A carbonated slurry of cyanamide solution, solid calcium carbonate, and graphite is cooled to remove the heat of reaction. Part of the slurry is recycled to faciUtate temperature control whereas the remainder is filtered yielding cyanamide solution and a cake of calcium carbonate and graphite. The filtered solution is also recycled ia order to control the soHds content. The final concentration of cyanamide is normally maintained at 25%. 

A filtered solution of the crude product in 200 cc. of hot absolute alcohol is treated with 250 cc. of concentrated hydrochloric acid. Most of the hydrochloride precipitates at once and is filtered, washed with alcohol and dried. The filtrate is cooled in an ice-salt bath and again filtered, and the prccijiitatc is... 

In a copper or iron kettle of 4-I. capacity is placed a solution of 200 g. of d-tartaric acid and 700 g. of sodium hydroxide in 1400 cc. of water. A 12-I. flask through which cold water is run is placed in the mouth of the kettle in order to prevent loss of water vapor, and the mixture is boiled gently over an open flame for four hours. The solution is now transferred to a 12-I. flask or crock and partially neutralized with 1400 cc. of commercial hydrochloric acid (density 1.19). To the still alkaline solution is now added just enough sodium sulfide to precipitate all the iron or copper which has been dissolved from the kettle (Note i). The filtered solution is then just acidified with hydrochloric acid, boiled to expel all hydrogen sulfide, and made very faintly alkaline to phenolphthalein with sodium hydroxide solution. To the hot solution is then added a concentrated solution of 300 g. of anhydrous calcium chloride which causes an immediate precipitation of calcium tff-tartrate and mesotartrate. 

Diethyl ether (about 1.41.) is added to a warm filtered solution of 100 g. of the crude nitroso compound in ca. 0.7 1. of dichloromethane until the solution becomes slightly turbid. The nitrosocarbamate is collected after cooling overnight at — 20°, and is dried under reduced pressure at 0°, providing 88-93 g. of yellow crystals with a pink luster, m.p. 87-89. 

If very pure amine is desired the product described above is dissolved with 1.04 parts of crystalline oxalic acid in eight parts of hot water. After clarification with Norite, the filtered solution on cooling deposits crystals of the acid oxalate. About 5 g. of the salt remains in each 100 cc. of the mother liquor most of this can be obtained by evaporation and further crystallization. The amine is liberated from the pure oxalate with potassium hydroxide, distilled with steam, and purified as described above. When a known amount of amine is desired in water solution (as for optical resolution) a weighed amount of the (anhydrous) oxalate is decomposed and the amine is distilled quantitatively with steam. 

The reaction mixture is not cooled during the addition of the last two or three portions of phenyl isocyanate, so that the final temperature is near 25° this procedure prevents separation of the sodium salt of cyanophenylurea, which crystallizes readily at low temperatures. For the same reason, the filtered solution of the salt is not precooled, but rather is cooled during the precipitation of the free cyanourea. 

Detailed information on the emission characteristics of various sources and the transmission properties of glasses and filter solutions can be found in A J. Gordon and R. A. Ford, The Chemist s Companion, Wiley-Interscience, New York, 1972, pp. 348-368 and in S. L. Murov, I. Carmichael, and G. L. Hug, Handbook of Photochemistry, 2nd ed., Marcel Dekker, New Vbrk, 1993. 

The ethereal solution of crude quinidine and cinchonidine, obtained as described under cinchonine, is shaken with dilute hydrochloric acid, the excess acid neutralised with ammonia and sodium potassium tartrate added. The base is recovered from the precipitated tartrate by dissolving the latter in dilute acid and pouring the filtered solution in a thin stream, slowly and with constant stirring, into excess of ammonia solution. The crude alkaloid is converted into the neutral sulphate, and this recrystallised... 

B Immersion well (quartz or pyrex), fitted with inlet (a) and outlet b) for cooling liquid (water or filter solution), and with ground joint (c) to C Reaction flask, fitted with gas inlet d) and outlet (e adapted to hold, e.g., a reflux condenser). 

Figure 13-2 Preparative Photoreactor Equipped for Filter Solutions. ...

Ultrafiltration is an improvement on the dialysis principle. Filters having pore sizes over the range of biomolecular dimensions are used to filter solutions to select for molecules in a particular size range. Because the pore sizes in these filters are microscopic, high pressures are often required to force the solution through the filter. This technique is useful for concentrating dilute solutions of macromolecules. The concentrated protein can then be diluted into the solution of choice. 

IB.2 grams of a-phenylbutyric acid chloride are dissolved in 25 ml of toluene. To this solution, there is slowly added a solution of 16.1 grams of diethylaminoethoxyethanol in 25 ml of toluene, the reaction mixture thereby becoming hot. It is then heated for B hr under reflux. The reaction mixture, after cooling, is carefully poured onto 75 grams of ice and made alkaline with dilute ammonia. After thorough shaking of the solution, the toluene layer is removed and washed until neutral with water. The toluene solution is treated with carbon and dried over sodium sulfate. The toluene is distilled off from the filtered solution. 

The calcium carbonate precipitate was removed by filtration, and the filtered solution was found to contain 1,436 g of fructose as determined by optical rotation. A small amount of calcium bicarbonate was present as an impurity in solution and was removed by the addition of oxalic acid solution until a test for both calcium and oxalic acid was negative. The insoluble calcium oxalate precipitate was removed by filtration. 

A hot, filtered solution of 2.27 grams of pyrvinium chloride dihydrate in 250 ml of water is added slowly to a solution of 2.25 grams of sodium pamoate monohydrate in 50 ml of water. A red precipitate immediately forms. The mixture is heated at about 90°-100°C for 5 minutes more and then filtered. The reaction product is washed with hot water and dried at about 75°C in a vacuum. This preparation melts at about 210°-215°C with prior softening from about 190°C. 

The viscous reaction mixture is then poured into 1.5 liters of ice water and agitated to form a uniform solution. The solution is treated with activated carbon and filtered. Thereafter, 80% acetic acid is added until the filtered solution remains acidic to litmus. The precipitate formed is filtered and washed thoroughly with distilled water. The product is air-dried at a temperature of 95° to 100°C for 48 hours to yield 133 grams of 5-allyl-5-(1-methylbutyl)-2-thiobarbituric acid having a melting point of 132° to 133°C and assaying at 99.5% pure, from U.S. Patent 2,876,225. 

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