Potassium hydroxide purification

The purification train. The oxygen is led from the cylinder through Ordinary flexible rubber condenser tubing to the constant level device A (Fig. 85). This consists of two concentric tubes (approximately 2 cm. and 0-5 cm. respectively, in diameter the inner tube being narrowed and curved at the bottom as shown) immersed in 50% aqueous potassium hydroxide contained in the outer vessel (diameter 3-5 cm.). Then by adjusting the liquid level in A the pressure of oxygen may be kept constant, and at a maximum of about... 

The cmde phthaUc anhydride is subjected to a thermal pretreatment or heat soak at atmospheric pressure to complete dehydration of traces of phthahc acid and to convert color bodies to higher boiling compounds that can be removed by distillation. The addition of chemicals during the heat soak promotes condensation reactions and shortens the time required for them. Use of potassium hydroxide and sodium nitrate, carbonate, bicarbonate, sulfate, or borate has been patented (30). Purification is by continuous vacuum distillation, as shown by two columns in Figure 1. The most troublesome impurity is phthahde (l(3)-isobenzofuranone), which is stmcturaHy similar to phthahc anhydride. Reactor and recovery conditions must be carefully chosen to minimize phthahde contamination (31). Phthahde [87-41-2] is also reduced by adding potassium hydroxide during the heat soak (30). 

The use of potassium hydroxide rather than sodium hydroxide is dietated by solubility characteristics which make purification of the sodium alkoxide difficult. 

According to the literature, the product obtained in this manner may contain ethyl adipate. To remove this, the product is cooled to 0° and run slowly into 600 cc. of 10 per cent potassium hydroxide solution maintained at 0° with ice-salt. Water is added until the salt which separates has dissolved, and the cold alkaline solution is extracted twice with 200-cc. portions of ether. The alkaline solution, kept at 0°, is run slowly into 900 cc. of 10 per cent acetic acid solution with stirring, the temperature remaining below 1° (ice-salt). The oil which separates is taken up in 400 cc. of ether, and the aqueous solution is extracted with four 250-cc. portions of ether. The ether extract is washed twice with cold 7 per cent sodium carbonate solution and dried over sodium sulfate. After removal of the ether the residue is distilled, b.p. 7g-8i°/3 mm. The recovery is only 80-85 per cent, and in a well-conducted preparation the ethyl adipate eliminated amounts to less than one per cent of the total product. Unless the preparation has proceeded poorly the tedious purification ordinarily is best omitted. 

A solution of the acylated thiocyanatohydrin in a minimal amount of 5% potassium hydroxide in diglyme (other solvents such as methanol, ethanol or tetrahydrofuran have also been used) is stirred for 2 days at room temperature. Water is added to the reaction mixture to precipitate the product which is filtered or extracted with ether (or chloroform). The ether extract is washed several times with water, dried (Na2S04), and concentrated under vacuum. The thiirane usually can be crystallized from an appropriate solvent pair. Chromatography over alumina has been used for the purification of episulfides. 

This crude product is dissolved in 100 ml of dilute hydrochloric acid, the acid solution is extracted with ether, and the aqueous layer is made basic with sodium hydroxide solution (3N) in the presence of ether (approximately 250 ml). The ether layer Is separated, dried over potassium hydroxide and evaporated to a white solid. Additional purification by repeating the formation of the hydrochloric acid salt and reprecipitation of the base is carried out. When purified in this manner, followed by drying at 80°C in vacuo over phosphorus pentoxide, 2-chloro-11-(4-methyl-1-piperazinyl)dibenz[b,f] [1,4]oxazepine, li/IP 109° to 111°C, is obtained. 

Potassium hydroxide was purchased from Mallinckrodt Chemical Company and used without further purification. 

In contrast to other organothallium(I) compounds, cyclopentadienyl-thallium(I) is a remarkably stable compound. Samples can be stored in sealed bottles for months without appreciable decomposition occurring it is unaffected by water and dilute alkali and it is only slowly oxidized by air at room temperature. Cyclopentadienyltballium(I) was first prepared by Meister in 1956 by addition of freshly distilled cyclopentadiene to a suspension of thallium(I) sulfate in dilute potassium hydroxide solution 101, 102). A number of variations of this procedure have been described (5, 25, 34, 56), and the compound has been made in other ways 35, 56,110, 164), but Meister s preparation, in which the yield of crude product is greater than 90%, remains the method of choice. Purification of crude cyclopenta-dienylthallium(I) is best accomplished by vacuum sublimation, and purity of samples can readily be assessed by gas-liquid chromatography on silicone oil at 170° C using hydrogen as carrier gas (7). 

It is necessary that the acetylene entering the reaction flask be of high purity. The acetylene purification train illustrated in Fig. 12 consists of three 500-ml. round-bottomed traps, each containing 250 ml. of concentrated sulfuric acid, followed by a 3-ft. column containing potassium hydroxide and a drying agent such as anhydrous calcium sulfate (Drierite). Empty flasks... 

As an alternative purification procedure, the checkers have esterified the crude acid by refluxing it for 2 hours with three times its weight of methanol and 2 ml. of 98% sulfuric acid. The solution is poured into 10 volumes of water and extracted with the minimum amount of chloroform required to give a clean separation of layers. The chloroform solution is washed with water, dried over calcium chloride, and distilled from a Claisen flask with an indented neck. Methyl 1-adamantanecarboxylate is collected at 77-79° (1 mm.) m.p. 38-39°. Hydrolysis of the ester with the calculated amount of 1A potassium hydroxide followed by acidification yields 1-adamantanecarboxylic acid m.p. 175-176.5° 90% overall recovery. 

The submitters used pentane " petroleum spirit (b.p. 25-40°) available from Hopkin Williams Ltd., Hadwell Heath, England, and anhydrous diethyl ether available from May Baker Ltd., Dagenham, England. Both solvents were each distilled over solid potassium hydroxide before use. The checkers purchased pentane from Phillips Petroleum Company and distilled it over solid potassium hydroxide. Anhydrous diethyl ether supplied by Mallinckrodt Chemical Works was used without further purification. 

Dunn and Stich [78] and Dunn [79] have described a monitoring procedure for polyaromatic hydrocarbons, particularly benzo[a]pyrene in marine sediments. The procedures involve extraction and purification of hydrocarbon fractions from the sediments and determination of compounds by thin layer chromatography and fluorometry, or gas chromatography. In this procedure, the sediment was refluxed with ethanolic potassium hydroxide, then filtered and the filtrate extracted with isooctane. The isooctane extract was cleaned up on a florisil column, then the polyaromatic hydrocarbons were extracted from the isoactive extract with pure dimethyl sulphoxide. The latter phase was contacted with water, then extracted with isooctane to recover polyaromatic hydrocarbons. The overall recovery of polyaromatic hydrocarbons in this extract by fluorescence spectroscopy was 50-70%. 

Without purification, the mixture of acetates is placed in a 250-mL round-bottomed flask and 150 mL of a 10% potassium hydroxide solution in aqueous methanol is introduced at room temperature. After 24 hr of stirriqg, the brown mixture is poured into a separatory funnel, diluted with 200 mL of water, and extracted with four 150-mL portions of ether. The combined ethereal fractions are dried over anhydrous magnesium sulfate, filtered, and concentrated to give a mixture of alcohols (Note 6) as a light yellow oil. 

Methylenecyclohexane oxide has been prepared by the oxidation of methylenecyclohexane with benzonitrile-hydrogen peroxide or with peracetic acid by treatment of 1-chlorocyclo-hexylmethanol with aqueous potassium hydroxide and by the reaction of dimethylsulfonium methylide with cyclohexanone. This reaction illustrates a general method for the conversion of ketones and aldehydes into oxiranes using the methylene-transfer reagent dimethyloxosulfonium methylide. The yields of oxiranes are usually high, and the crude products, in most cases, are of sufficient purity to be used in subsequent reactions (e.g., rearrangement to aldehydes) without further purification. 

In the preparation described here, the alkaline reagent of choice is potassium hydroxide because it is more soluble in methanol than is sodium hydroxide. In the final purification of the product, residues of potassium salts and potassium hydroxide are also more easily removed than sodium analogs. Commercially, sodium methoxide is often used as the catalyst for hydrolysis, but handling of this reagent calls for a somewhat more complex procedure. 

The submitters used prepurified nitrogen, obtained from Matheson Company, Inc., East Rutherford, New Jersey, without further purification. The checkers passed Linde (H. P. Dry) nitrogen successively through chromous chloride solution, solid potassium hydroxide, Ascarite, and solid phosphorus pentoxide. 

Technical-grade tetrahydrofuran, available from BASF-A G or Fisher Scientific Company, is dried by distillation, first from potassium hydroxide and then from lithium aluminum hydride. This tetrahydrofuran is used for all operations in this procedure. For a warning note regarding the purification of tetrahydrofuran, see Org. Syn., Coll. Vol. 5, 976 (1973). 

As to salts, this last recipe above, taken from the literature, is the only claim of a valid hydrochloride salt of DMT. In the original synthesis, by Manske, the following description appears. "The hydrochloride could be obtained only as a pale yellow resin which, when dried in a vacuum desiccator over potassium hydroxide, became porous and brittle." I have found no attempts at its synthesis in the literature, and I have personally had no success at all. The picrate salt is well defined, used mostly for isolation and purification. The oxalate is used occasionally in animal studies. Early human studies involving the injection of solutions of the hydrochloride apparently made by dissolving DMT base in dilute aqueous HCI, and neutralizing this with base to achieve an end pH of appropriate 6. The fumarate is the salt specifically approved by the FDA for human studies, and this was the form used for human intravenous injection employed in the recent New Mexico studies. 

The purification of the alkali hydroxides.—Numerous impurities have been reported in commercial sodium and potassium hydroxides. Several have commented on the presence of peroxide, particularly in caustic potash.19 Various salts—carbonate, sulphate, nitrate, nitrite, chloride, and phosphate—as well as alumina, silica, organic matters, and metal oxides—e.g. arsenic, vanadium, iron, etc., have been reported. More or less of the other alkalies may also be present. 

Sulphur Hexafluoride, SF6.—Sulphur hexafluoride, the first hexahalide to be discovered, is prepared by submitting sulphur to the action of fluorine in a copper tube. The issuing gas on condensation in a spiral tube of the same metal at —80° C. becomes partly solidified by allowing the solid to vaporise gradually and passing the vapours through potassium hydroxide solution and solid potassium hydroxide successively, the substance is rendered purer, complete purification being effected subsequently by re-solidification followed by fractional evaporation.4... 

Hafnium tetrachloride, nitric acid, and potassium hydroxide solutions were prepared using doubly-distilled water from an all borosilicate glass still. The chemicals were of the highest purity grade commercially available and were used without further purification. 

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