Potassium hydroxide, preparation

LYE sometimes refers to solutions of soda ash or potash. It is also used for solutions of CAUSTIC SODA sodium hydroxide) and CAUSTIC POTASH (potassium hydroxide), prepared by mixing milk of lime with soda ash or potash. This mixing produces a solution of caustic soda, or caustic potash, and a limestone precipitate. A medieval recipe for caustic soda crystals calls for 1 part each of slaked lime and soda ash with 7 parts water, boiled until the volume is halved, filtered and decanted 10 times then evapouiated. 

Caustic Solution, 1 M potassium hydroxide prepared in distilled/deionized water. 

The benzene used in this preparation should be reasonably free from toluene therefore use a sample of benzene supplied by dealers as crystalUsable benzene, i.e.y one which crystallises readily when cooled in ice-water. It should preferably be dried over calcium chloride and, immediately before use, filtered through a fluted filter-paper. The pyridine should also preferably be dried over solid potassium hydroxide and redistilled. 

The cost of this preparation (particularly for large classes) can be appreciably reduced by using a solution of 20 g. of sodium hydroxide in 25 ml. of water, in place of the potassium hydroxide solution. In this case, however, the product on standing overnight forms a very hard mass, which should be dissolved in tcarm water. The yields of alcohol and acid are unchanged. 

Since the silver salts of the carboxylic acids are usually soluble in dilute nitric acid, they must be prepared by treating an aqueous solution of a neutral salt of the acid (and not the free acid itself) with silver nitrate solution. It is not practicable to attempt to neutralise the acid with sodium or potassium hydroxide solution, because the least excess of alkali would subsequently cause the white silver salt to be contaminated with brown silver oxide. The general method used therefore to obtain a neutral solution j to dissolve the acid in a small excess of ammonia solution, and then to boil the solution until all free... 

There are no liquid alkynes whieh can be conveniently prepared by the elementary student. Some of the properties of aeetylenie hydrocarbons may be studied with the gas, aeetylene. Although the latter may be prepared in moderate 3deld by the addition of ethylene dibromide to a boiling aleoholic solution of potassium hydroxide or of sodium ethoxide,... 

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. 

The independent preparation of potassium phthabmide (from a solution of phthalimide in absolute ethanol and potassium hydroxide in 75 per cent, ethanol) may be avoided in many cases by boiling phthalimide with the halide in the presence of anhydrous potassium carbonate. The N-substituted phthalimide (I) is frequently cleav with difficulty this is often facilitated by reaction with hydrazine hydrate to give an intermediate product, which is easily decomposed by hydrochloric acid to 3deld the insoluble hydrazide of phthaUc acid (II) and the primary amine (III) ... 

Phenylbenzoyldiazomethane may be prepared by the oxidation of benzil-monohydrazone with mercuric oxide in the presence of dry etber as a solvent Tbe addition of a little alcoholic potassium hydroxide serves to catalyse the reaction ... 

Method A. Cool a solution of the nitrate-free dichloride, prepared from or equivalent to 5 0 g. of palladium or platinum, in 50 ml. of water and 5 ml. of concentrated hydrochloric acid in a freezing mixture, and treat it with 50 ml. of formahn (40 per cent, formaldehyde) and 11 g. of the carrier (charcoal or asbestos). Stir the mixture mechanically and add a solution of 50 g. of potassium hydroxide in 50 ml. of water, keeping the temperature below 5°. When the addition is complete, raise the temperature to 60° for 15 minutes. Wash the catalyst thoroughly by decantation with water and finally with dilute acetic acid, collect on a suction filter, and wash with hot water until free from chloride or alkali. Dry at 100° and store in a desiccator. 

Method B. For some purposes a shghtly more active catalyst is obtained when it is prepared in more concentrated solutions. The procedure is the same as above, but the volumes of solution for 5 g. of metal are dilute acid, 25 ml. formaldehyde, 35 ml. potassium hydroxide, 32 g. in 32 ml. of water. 

An ethereal solution of diazomethane free from alcohol may be prepared as follows such a solution is required, for example, in the Amdt-Eistert reaction with acid chlorides (compare Section VI,17). In a 100 ml. longnecked distilling flask provided with a dropping funnel and an efficient downward condenser, place a solution of 6 g. of potassium hydroxide in... 

Styrene may be conveniently prepared in the laboratory by heating p-phenylethyl alcohol (Section IV,204) with sohd sodium or potassium hydroxide when an almost quantitative dehydration occurs ... 

Diethylene glycol method. Place 0-5 g. of potassium hydroxide pellets, 3 ml. of diethylene glycol and 0 5 ml. of water in a 10 or 25 ml. distilling flask heat the mixture gently until the alkali has dissolved and cool. Add 1-2 g. of the ester and mix well. Fit the flask with a thermometer and a small water-cooled condenser in the usual way. Heat the flask over a small flame whilst shaking gently to mix the contents. When only one liquid phase, or one hquid phase and one solid phase, remains in the flask, heat the mixture more strongly so that the alcohol distils. Identify the alcohol in the distillate by the preparation of the 3 5 dinitrobenzoate (Section 111,27,2). 

The most widely used method for the preparation of carboxylic acids is ester hydrolysis. The esters are generally prepared by heterocyclization (cf. Chapter II), the most useful and versatile of which is the Hantzsch s synthesis, that is the condensation of an halogenated a- or /3 keto ester with a thioamide (1-20). For example ethyl 4-thiazole carboxylate (3) was prepared by Jones et al. from ethyl a-bromoacetoacetate (1) and thioformamide (2) (1). Hydrolysis of the ester with potassium hydroxide gave the corresponding acid (4) after acidification (Scheme 1). 

The last step in the synthesis of divinyl ether (used as an anesthetic under the name Vinethene) involves heating CICH2CH2OCH2CH2CI with potassium hydroxide Show how you could prepare the necessary starting material CICH2CH2OCH2CH2CI from ethylene... 

Alkali AletalIodides. Potassium iodide [7681-11-0] KI, mol wt 166.02, mp 686°C, 76.45% I, forms colorless cubic crystals, which are soluble in water, ethanol, methanol, and acetone. KI is used in animal feeds, catalysts, photographic chemicals, for sanitation, and for radiation treatment of radiation poisoning resulting from nuclear accidents. Potassium iodide is prepared by reaction of potassium hydroxide and iodine, from HI and KHCO, or by electrolytic processes (107,108). The product is purified by crystallization from water (see also Feeds and feed additives Photography). 

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