Decolorizing solutions

The procedure described above provides a sufficient quantity of bis[copper(I) trifluoromethanesulfonate] benzene complex for several reactions at the scale used in Part C. If bis[copper(I) trifluoromethanesulfonate] benzene complex for a single reaction is desired, the same procedure can be followed at the appropriate scale without the use of the glove bag. In this case, the decolorized solution is not filtered but instead is cooled, and the product is allowed to crystallize in the reaction vessel. The supernatant benzene is decanted, and the crystals are washed in the flask with fresh benzene. The bis[copper(I) trifluoromethanesulfonate] benzene complex is then used without drying hj the same flask. 

In the 19th century, various carbons were studied for their ability to decolorize solutions and adsorb compounds from gases and vapors. Commercial applications of activated carbon began early in the 20th century. Solutions containing phenols, acetic acid, herbicides, dyes, chlorophenols, cyanide and chromium have been successfully treated by carbon adsorption ( ). 

A solution of methyl 3-rnethylbicyclo[1.1.0]butane-l-carboxylate (0.63 g, 5 mmol) and 1-phenyl-1,2,4-lriazoline-3,5-dione (0.87 g, 5 mmol) in CH2C12 (25 raL) was sLirred at 25 C. After 1 h, the decolorized solution was stripped, and the yellow gum (1.4 g) was repeatedly washed with petroleum ether until washes were colorless. Recrystallization (CC14) gave the product yield 0.76 g (64%) mp 86-90 C. 

Most alkenes decolorize solutions of bromine in carbon tetrachloride (Section 8-10). The red bromine color disappears as bromine adds across the double bond. When bromine is added to benzene, no reaction occurs, and the red bromine color remains. 

Remove the cations by treatment with Dowex 50 in the following manner Add 350 ml of moist Dowex 50 in the H+ form (prepared by the instructor) to the decolorized solution and stir gently for 5 min before separating by vacuum filtration. Do not use filter aid when removing the Dowex use only Whatman filter paper. 

Evidence for the production of ascorbic acids is that, after irradiation, the solution was able to decolorize solutions of 2,6-dichlorophenolindophenol and to produce a red color with an alkaline solution of triphenyltetrazolium chloride. The solution also displayed an absorption maximum at 245 m/u similar to that of L-ascorhic acid, and paper chromatography indicated the presence of a product running identically with L-ascorbic acid. The yield of the ascorbic acid was a function of the concentration, rising from G 0.16 at 5 X 10 ilf to G 0.95 at 4 X 10 M for a dose of 2.8 X 10 e.v. ml. of x-rays. The route to the ascorbic acid from the lactone may involve abstraction of a hydrogen atom at C-2 or C-3, followed by enoliza-tion. 

Place 12 ml of chloroaeetate buffer in a 25-ml standard flask. Add 2.5 ml of the iron-sulphosalicylate reagent, then add the analyte solution (distillate) eontaining not more than 1 mg of F, and make up to the mark with water. Measure the absorbance of the partly decolorized solution at 500 nm using water as the referenee. 

This section describes batchwise fixed-bed adsorbers in which the adsorbent is replaced with fresh material, or removed and regenerated after it is exhausted, then reinstalled. Commercial examples include columns used for chemical feedstock purification, decolorizing solutions, and wastewater treatment. The goal is generally to employ material balance and rate equations to predict adsorber performance, possibly to analyze experimental data (e.g., breakthrough curves and temperature histories), to diagnose problems, or to assess properties or conditions. Unfortunately, various conditions often result in nearly identical behavior, so diagnosing causes may be difficult. 

Liquid phase adsorption is used mainly to bind turbid substances, to purify and decolor solutions, and to separate organic pollutants. Grained active carbon is employed as an adsorbent, mixed in a pulverized form with the liquid or as particles in a percolation process. 

The combined method utilizes the advantages of the above two methods. The filter is precoated with a layer of fresh active carbon, and a dose of active carbon can be added to the sugar solution. The decolorized solution is refiltered through a bed of diatomaceous earth, which serves to remove active carbon that might have passed through a damaged filter, cloth, or channel in the filter cake. Without refil-teration, the final product may have a gray color. 

This technique for decolorizing solutions works because colored impurities as well as the compound being purified are adsorbed on the surface of the carbon particles. For electronic reasons, the colored substances adsorb more strongly to the surface. You should avoid using too much decolorizing carbon because the desired product itself may be adsorbed by it, so less product will be recovered. 

If the filtrate and washings contain residual bromine, as evidenced by a yellow color, add saturated aqueous sodium bisulfite until the solution is colorless. Flush the decolorized solution down the drain. 

Carefully flood smear with the decolorizing solution until the solvent runs colorlessly from the slide (30 to 60s). 

Addition of aldehydes, e.g., an aqueous solution of acetaldehyde, to the decolorized solution causes the color to reappear. The alkali salts of the N-sulfinic acid of -fuchsin-leuco-sulfonic acid are formed by the action of neutral sulfites. 

Procedure. A drop of the acid test solution is treated with a drop of bromine water in a depression of a spot plate. If the color is discharged, the addition is continued until a permanent yellow is obtained. The excess bromine is removed by adding a little solid sulfosalicylic acid. A drop of starch-cadmium iodide solution is added to the decolorized solution. Depending on the amount of thallium present, a deep or a light blue appears immediately. 

Procedure One drop of the tested alcohol is mixed with one drop of 5% phosphoric acid, then another drop of 5% KMn04, and, after 1 min of standing, with the saturated sodium hydrogen sulfate solution, just the amount necessary for decoloration (if part of the brown precipitate remains undissolved, some dilute H3PO4 and NaHS03 solution is added). To the decolorized solution 10—20 mg of chromotropic acid are added, and then, dropwise, 5 ml of cone, sulfuric acid. The solution is heated in a 60 ""C warm water bath for 10 min. The violet color of the solution is proof of the presence of methanol in the sample. 

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