Alcoholic potassium hydroxide solution

The 0 -S.V alcoholic potassium hydroxide solution Is prepared by dissolving 16g. of potassium hydroxide pellets in 500 ml. of alcohol (or industrial spirit) contained in a bottle closed by a cork. After standing for 24 hours, the clear solution is decanted or filtered from the residue of potassium carbonate. It is said that a solution in methyl alcohol has better keeping qualities than that in ethyl alcohol. 

It is essential to standardise the alcoholic potassium hydroxide solution immediately before use by titration with standard 0-5N or 0-25N hydrochloric or sulphuric acid using phenolphthalein as indicator. 

A solution of 130 g. (0.52 mole) of this ester in 400 cc. of ethyl alcohol is placed in a two-necked 2-I. flask, carrying a dropping funnel and a reflux condenser, and is heated to boiling. Then one-third of a solution (Note 2) of 78.5 g. (1.4 moles) of potassium hydroxide in 400 cc. of alcohol is added from the dropping funnel, and the alcoholic solution is boiled until it becomes clear. Then a second third of the alkali solution is added, and the reaction mixture is again boiled until any precipitate disappears. Finally, the last third of the alcoholic potassium hydroxide solution is added. The addition of the alkali requires about twenty minutes. The reaction mixture is then boiled for forty minutes longer. 

If the entire amount of alcoholic potassium hydroxide solution is added at this point, there is precipitated a colorless solid, which does not dissolve even on prolonged heating. 

Benzohydrol has been obtained by reducing benzophenone with sodium amalgam,1 with metallic calcium and alcohol,2 with hydrogen in the presence of a catalyst,3 with zinc, aluminium or sodium in strongly alkaline solutions,4 with zinc dust and alcoholic potassium hydroxide solution,5 and electrolytically.6... 

To 15.0 g. (0.50 mole) of paraformaldehyde (Eastman Organic Chemicals) and 100 g. (0.75 mole) of propiophenone (Eastman Organic Chemicals) in a 250-ml. Erlenmeyer flask, 10 ml. of IN alcoholic potassium hydroxide solution was added with stirring. After a few minutes a clear solution formed, and the temperature rose to 35° and then fell slowly. The yellow solution was stirred for 5.5 hours at room temperature, during which time the solution became turbid. The turbid solution was poured into 150 ml. of water, and the mixture was acidified with concentrated hydrochloric acid (Congo red indicator). 

Experiment.—Boil a few drops of benzyl chloride with (halogen-free) alcoholic potassium hydroxide solution for a few minutes in a test tube on the water bath. Then dilute with water, acidify with nitric acid, remove undissolved material by extraction with ether, and add a few drops of silver nitrate solution. 

Analysis of the Benzyl Chloride.—The quantitative determination of halogen in substances containing halogen in aliphatic combination is not carried out in a sealed tube by the Carius method (cf. p. 69), but by hydrolysis with standard alcoholic potassium hydroxide solution. Since this method is very often used, a check on the purity of the present preparation may be combined with practice in this method of analysis. 

The hydrolysis of the esters is carried out by prolonged heating with aqueous mineral acids or solutions of alkali hydroxides. See saponification of fats on p. 149. Alcoholic potassium hydroxide solution is an... 

Carbon Disulphide.f — Thoroughly mix 50 cc. of benzene with 50 gin. of alcoholic potassium hydroxide solution (11 gm. of potassium hydroxide in 90 gm. of absolute alcohol), and allow the mixture to stand several hours at a temperature of about 20° C. Shake with about 100 cc. of water, remove the aqueous solution from the benzene, neutralize the latter with acetic acid, and add copper-sulphate solution. No precipitate should form. 

In a 500-cc. three-neck flask, fitted with a reflux condenser and a mechanical stirrer (Note t), is placed 45.5 g. (0.25 mole) of 2,4-dinitrotoIuene (Note 2), 85 g. (1.5 moles) of iron (Note 3), and 100 cc. of 50 per cent (by weight) ethyl alcohol (Note 4). The mixture is heated to boiling on a water bath, the stirrer is started (Note 5) and a solution of 5.2 cc. (0.06 mole) of concentrated hydrochloric acid in 25 cc. of 50 per cent (by weight) ethyl alcohol is added slowly (Note 6). The mixture is refluxed for two hours after addition of the acid is complete. At the end of this time the apparatus is disconnected and the hot mixture is made just alkaline to litmus by the addition of the calculated amount of 15 per cent alcoholic potassium hydroxide solution (Note 7). Without allowing the mixture to cool, the iron is removed by filtration and the reaction flask is rinsed with two 50-cc. portions of 95 per cent ethyl alcohol the same alcohol is used to wash the iron residue. To the filtrate is added 84 cc. of 6 N sulfuric acid the normal sulfate of 2,4-diaminotoluene precipitates. The mixture is cooled to 250 and filtered by suction. The product is washed with two 35-rc. portions of 95 per... 

Test for Nitrobenzene.—About 25 grams of the substance are digested for some hours with 30 c.c. of cold alcohol, the mass being then filtered, and the filtrate diluted with an equal volume of water and heated on a water-bath with a little zinc dust and about 3 grams of caustic potash until the bulk of the alcohol is expelled. The residual aqueous liquid is decanted off and extracted with an equal volume of ether, the ethereal layer being separated and evaporated and the residue dissolved in 3 c.c. of water. This solution is heated with a few drops of chloroform and alcoholic potassium hydroxide solution in presence of aniline, derived from nitrobenzene in the marzipan, the characteristic odour of phenyl-carbylamine is emitted. 

This is a method for obtaining di-secondary glycols from certain aldehydes by means of alcoholic potassium hydroxide solution.41... 

Caution. Bromosilane is potentially hazardous since it is spontaneously inflammable in air. All manipulations involving this compound must be carried out in a vacuum system. Unused bromosilane may be destroyed by condensing it in small portions into a large quantity of alcoholic potassium hydroxide solution. The hydrogen which is liberated during the ensuing reaction should be pumped away continuously as it is evolved. 

Ester Value Prepare an alcoholic potassium hydroxide solution by dissolving 11.2 g of potassium hydroxide in 250 mL of alcohol and diluting with 25 mL of water. Add 10.0 mL of this solution to the neutralized solution retained in the test for Acid Value (above). Add 5 drops of phenolphthalein TS, connect a suitable condenser, and reflux for 2 h. Cool, add 5 additional drops of phenolphthalein TS, and titrate the excess alkali with 0.1 A sulfuric acid. Perform a blank determination (see General Provisions) using 10.0 mL of the alcoholic potassium hydroxide solution, and make any necessary correction. Calculate the ester value by the formula... 

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