312. Purity.--The most important alcohols are methyl alcohol and ethyl alcohol. The former, wood spirit, is obtained in an impure state by distilling wood; it is used to dissolve resins, fats, oils, etc., and to make aniline. It is poisonous, as are the others. Ethyl alcohol, spirit of wine, is the commercial article. It is prepared by fermenting glucose, and distilling the product. It boils at 78 degrees, vaporizing 22 degrees lower than water, from which it can be separated by fractional distillation. By successive distillations of alcohol ninety-four per cent can be obtained, which is the best commercial article, though most grades fall far below this. Five per cent more can be removed by distilling with CaO, which has a strong affinity for water. The last one per cent is removed by BaO. One hundred per cent constitutes absolute alcohol, which is a deadly poison. Diluted, it increases the circulation, stimulates the system, hardens the tissues by withdrawing water, and is the intoxicating principle in all liquors.--It is very inflammable, giving little light, and much heat, and readily evaporates. Beer has usually three to six per cent of alcohol; wines, eight to twenty per cent. The courts now regard all liquors having three per cent, or less, of alcohol, as not intoxicating. In Massachusetts it is one per cent. CHAPTER LVII. OILS, FATS, AND SOAPS. 313. Sources and Kinds of Oils and Fats.--Oils and fats are insoluble in water; the former are liquid, the latter solid. Most fats are obtained from animals, oils from both plants and animals. Oils are classified as fixed and essential. Castor oil is an example of the former and oil of cloves of the latter. Fixed oils include drying and non-drying oils. They leave a stain on paper, while essential, or volatile oils, leave no trace, but evaporate readily. Essential oils dissolved in alcohol furnish essences. They are obtained by distilling with water the leaves, petals, etc., of plants. Drying oils, as linseed, absorb O from the air, and thus solidify. Non-drying ones, as olive, do not solidify, but develop acids and become rancid after some time. Oils and fats are salts of fatty acids and the base glycerin. The three most common of these salts are olein, found in olive oil, palmitin, in palm oil and human fat, and stearin, in lard. The first is liquid, the second semi-solid, the last solid. Most fats are mixtures of these and other salts. Olefin = Glyceryl) ( oleic) oleate ) ( ) Pahnitin = Glyceryl)salts from (palmitic)acid and glyceryl hydrate. palmitate) ( ) Stearin = Glyceryl) (stearic ) stearate) 314. Saponification consists in separating these salts into their acids and the base glycerin; soap-making is the best illustration. To effect this separation, a strong soluble base is used, KOH for soft, and NaOH for hard soap. Study this reaction: