Ethyl alcohol iodoform test

Reaction.—A delicate test for ethyl alcohol is the lodofornt reaction. Pour a few drops of alcohol into a test-tube and add about 5 c.c of a solution of iodine in potassium iodide, and then dilute caustic soda solution until the iodine colour vanishes. Shake up and narm very gently to about 6o°. If no turbidity 01 precipitate appears at once, set the test-tube aside for a time. Yellow crystals of iodoform will ultimately deposit, which have a peculiar odoui, and a characteiistic star shape nhen viewed under the microscope. The same reaction is given with... 

Iodoform test. This test is more specific than the previous two tests. Only ethanol (ethyl alcohol) and alcohols with the part structure CH3CH(OH) react. These alcohols react with iodine in aqueous sodium hydroxide to give the yellow precipitate iodoform. 

The preparation of dimethylaniline is carried out in an iron autoclave withstanding 60 atmospheres of pressure, provided with a cast iron lin- ing, a manometer and an oil bath. The methyl alcohol used for the alkylation must be free from all traces of acetone and ethyl alcohol, because these compounds, as impurities, cause a very great increase in the pressure. The purity of the methyl alcohol should be established by an iodoform test. 

Hypoiodites are used for qualitative tests for methyl ketones (Lieben test). For this purpose, a compound to be tested is stirred with an aqueous solution of sodium hydroxide (80 mol/mol of methyl ketone). Iodine (4.5 mol of 12) is added portionwise with stirring, and the mixture is set aside for 20 min at 25 °C before acidification. In the presence of a methyl keto group, a yellow heavy precipitate of iodoform settles at the bottom of the test tube. Iodoform can be identified easily not only by its characteristic smell but also by its melting point (120-123 °C) [1173], This test applies not only to methyl ketones but to any compound that can be converted in the reaction medium into a species containing the COCH3 group, for example, isopropyl or ethyl alcohol. 

Water may be tested for by anhydrous copper sulphate or by aluminium ethylate. Alcohol may be detected by the iodoform reaction, but acetaldehyde also gives this reaction. Acetaldehyde gives a greyish precipitate of mercury with Ncssicr s reagent. 

Ethyl alcohol is best identified by means of its boiling point and that of the bromide, iodide,-or benzoate (463) prepared from it. Aconvenie nt test for alcohol which is often used, is made by adding to a warm aqueous solution of the substance a solution of sodium carbonate and iodine iodoform, CHI3, precipitates as a yellow powder and can be recognized by its characteristic odor. The reactions involved will be described later (266). The formation of iodoform is not a positive proof of the presence of ethyl alcohol as other substances are converted into iodoform under the conditions used in the test. ... 

Iodoform, CHI3, tri-iodomethane, is formed when alcohol and certain other compounds (66) are treated with iodine in the presence of an alkali. It can be prepared by adding iodine to a warm aqueous solution of alcohol or acetone which contains sodium carbonate. The iodoform, which separates as a yellow precipitate, is purified by crystallization from dilute alcohol. It crystallizes in yellow, lustrous, six-sided plates, which melt at 119 , and have a peculiar, very characteristic odor. The reactions by which alcohol is converted into iodoform are analogous to those as the result of which chloroform is obtained from alcohol. The formation of iodoform is often used as a test for ethyl alcohol, but as other substances, such as acetone, isopropyl alcohol, and aldehyde yield iodoform when warmed in alkaline solution with iodine, the test is not reliable unless it is known that the other substances which respond to it are absent. Most of the compounds which yield iodoform when treated in this way contain the group CH3.C linked to oxygen. 

Ethyl Alcohol.— The detection of ethyl alcohol in urine may be important in the diagnosis of intoxications. Distil carefully 50-100 ml. of the urine, and apply the iodoform test and the nitro chromic test (p. 109) to 5 ml. samples of the distillate. Alcohol gives a positive reaction with both tests. Acetone, if present, will also come over in the distillate, and give a positive iodoform reaction, but does not give a blue colour with the nitro chromic reagent. 

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