Purification of Ethyl Alcohol

To prepare absolute alcohol, 100 gms. of freshly burnt quicklime in the form of small lumps are placed in a 500-c.c. distilling flask, and 300 gms. of rectified spirits added. After 8 hours the alcohol is distilled off on a water bath until a thermometer in the neck of the flask indicates 80°. The alcohol so obtained still contains about 3% of water. 

To further purify the alcohol the above product is shaken with finely divided silver oxide. This oxidises any aldehyde present to acetic acid. Caustic soda is added to bind the acid, and the alcohol distilled, using a good column (see p. 22). The portion passing over at constant temperature is then treated with calcium turnings in the same way as methyl alcohol (see above). The anhydrous alcohol is very hygroscopic, and must not be exposed to air. 

For the removal of the last traces of water the alcohol ihay be refluxed several hours with small quantities of sodium and ethyl succinate or phthalate. (J. C. 8., 1927, 1288 Am. Soc., 1931, 1106.) 

If the presence of methyl alcohol is permissible an effective method of drying consists in refluxing for several hours with magnesium methylate. (0. S., VII., 37.) 

Colourless liquid spirituous odour miscible with water in all proportions binary mixture with water contains 75-57% alcohol, and boils at 78-1° at 760 mms. B.P. 760 pure alcohol, 78-3° B.P. 2113° D. 0-790. It forms a ternary mixture with benzene and water, and this property is utilised in the manufacture of industrial absolute alcohol. (J. C. S., 81, 707 see Preparation 198 B., 38, 3612.) 

---