GENERAL PROPERTIES OF THE ALCOHOLS. 177 The method answers with aniline, which is thus converted into carbolic acid; but it does not answer with the true alcohol bases. Properties.-The alcohols present themselves in the form of liquids or solids which are lighter than water. The lower terms of the series are freely soluble in water, but they become less soluble as the proportion of carbon and hydrogen increases, the higher terms becoming successively more viscid and oily, whilst those which are solid at ordinary temperatures are insoluble in water, and resemble the fats in appearance. The lower terms may be volatilized without experiencing decomposition. The boiling point of each alcohol is about 72° (40° C.) lower than that of the fatty acid which it yields by oxidation. The following table contains most of the bodies at present known, which belong to the class of substances homologous with vinic alcohol; but there can be no doubt that as science progresses this list will be extended, and that ultimately an alcohol will be found corresponding to each term of the series of the volatile acids represented by the general formula, H. Alcohols. 2n Formula. Specific Gravity. €nHg+,g Liquid. Vapour. 12. Laurylic alcohol 16. Ethal, or cetylic. 27. Cerotin, or cerylic 30. Melissin, or melissylic 16H 34 Ꮎ €27H 56 30H630 H The formula of each of these substances, it will be seen, contains one atom of oxygen, combined with quantities of carbon and hydrogen in which the number of atoms of hydrogen always exceeds by two, twice the number of atoms of carbon. The monatomic alcohols may all be regarded as compound oxides of hydrogen and of a peculiar hydrocarbon, of which the general formula is H2n+1, or as formed from a molecule of water Ꮎ in which H one-half of the hydrogen has been displaced by an equivalent of a hydrocarbon; they retain therefore but a single atom of typical hydrogen; ordinary alcohol being represented upon this view as 5 10. He. The typical atom of hydrogen admits of being displaced Н by potassium, sodium, and other metallic bodies, and under certain circumstances by a second equivalent of a hydrocarbon either identical with or analogous to the first, thus giving rise either to a simple or to a mixed ether (1139), or it may be displaced by an acid radicle, in which case a compound ether is formed. The general formula of an alcohol, therefore, may be represented as Є„H2n+2, or (ЄH2 I2n+1)HO. Notwithstanding the possibility of thus displacing hydrogen in definite quantity from the molecule of alcohol by sodium or potassium, the alcohols are not to be regarded as acids, from which class of compounds they differ in a marked manner. One of the most characteristic differences between an alcohol and an acid consists in the fact that an alcohol is convertible by the action of hydrochloric acid into a hydrochloric ether, with elimination of water: whilst a reaction exactly the reverse takes place in the case of the acids; for the chlorides of the acid radicles are decomposed by water into the free acid and hydrochloric acid; as for example: The reactions by which a passage is effected from one series. to a higher or lower term by the addition or removal of an atom of carbon are particularly interesting: for example, the addition of carbon, as in the passage from the ethylic to the tritylic series, may be effected as follows, by acting on sodium ethyl with carbonic anhydride (1184): Methyl iodide, by exchange of cyanogen for iodine, furnishes methyl cyanide, which is identical with acetonitrile : ¤H2I + KЄN = KI + ¤H„‚¤N (or (¤‚H ̧)'''N); and acetonitrile, by the process of Mendius, digesting it with zinc and an alcoholic solution of hydrochloric acid, furnishes hydrochlorate of ethylia, from which, by distillation with caustic potash, the base ethylia is isolable. The researches of Kolbe (Liebig's Annal. cxxxii. 102), of Butlerow, and others, have rendered it probable that the homologous terms of the alcohols and their derivatives are all referable to the methylic alcohol, ordinary alcohol being wood spirit containing an atom of methyl in the place of one of the atoms of hydrogen in methyl; and each successive term being produced by the substitution successively for the same atom of hydrogen of an atom of ethyl, trityl, tetryl, &c., in the original molecule of wood spirit:_* Alcohols formed on this type Kolbe terms primary alcohols, these being the ordinary or true alcohols. By the substitution of another atom of an alcoholic radicle for a second atom of hydrogen in the original atom of methyl, a new set of alcohols, termed by Kolbe secondary alcohols, may be obtained; and by a substitution of the third atom of hydrogen in methyl by an alcohol radicle, tertiary alcohols would be obtained, as may be illustrated by the following formulæ : At present only one secondary alcohol is known with certainty: this is isomeric with tritylic alcohol, and was obtained by Friedel by acting upon acetone (1259) with nascent hydrogen; and but one tertiary alcohol is known; this is isomeric with tetrylic alco * The homology of the normal alcohols is explained by Kolbe and by Butlerow on the hypothesis that the radicles ethyl, trityl, tetryl, amyl, &c., are each formed from methyl by successive substitutions of methyl EH, for an atom of hydrogen within the methyl group; as for instance each successive group of methyl which is introduced becoming methylated by successive substitution of a fresh atom of methyl for an atom of hydrogen. 180 METHYLIC ALCOHOL, OR WOOD SPIRIT. hol, it was obtained by Butlerow by acting upon the product of zinc-methyl (1182) on acetyl-chloride (1266) with water. There is reason to believe that many if not all the pseudoalcohols of Wurtz (1201) when more fully examined will be found to be referable to the secondary or to the tertiary group. The true alcohols by partial oxidation lose two atoms of hydrogen, and then furnish aldehyds; and these bodies, by the further absorption of oxygen, yield acids; the latter contain the same number of atoms of carbon as the alcohol from which they were procured, but two atoms less of hydrogen and one atom more of oxygen than the alcohol; (vide table, page 40). The potassium salts of these fatty acids may be obtained by heating the alcohol with caustic potash: ethylic alcohol, for instance, yields an acetate of the basyl whilst hydrogen es capes: 2 The alcohols are further characterized by yielding, when treated with sulphuric acid and other dehydrating compounds, a class of substances termed ethers, which formerly were regarded as alcohols, minus H.; though, as will hereafter be explained (1139), there can be no doubt that this does not truly represent the mode of their formation. By a still more complete dehydration the alcohols give rise to the hydrocarbons of the olefine series. (Hon). 4 (1125) 1. WOOD SPIRIT; Methylic Alcohol, or Pyroxylic Spirit (ЄH2 or C2H12=32). Sp. gr. of liquid at 32°, 0·8179; of vapour 1*12; Rel. wt. 16; Boiling pt. 149° 9 (65° ·5C.)—Wood spirit is the alcohol of the methylic series, which derives its name, not very appropriately, from uéu, wine. This alcohol has not as yet been procured by any process of fermentation; it is found amongst the volatile products obtained by the destructive distillation of wood at a high temperature in closed vessels, accompanied by a large quantity of impure acetic acid, acetate of ammonium, methyl acetate, tarry matter, and various hydrocarbons. It has also been obtained artificially by Berthelot, by acting upon marsh gas by chlorine, and decomposing the chloride thus obtained by means of a solution of potash: ЄH,Cl+KHO becoming €Ꮋ Ꮎ + KCl. Purification. In order to isolate methylic alcohol, the crude products of the distillation of wood are rectified by the heat of a water bath, and the product is distilled from quicklime, which retains the acetic acid, the water, and tarry matter. The wood METHYLIC ALCOHOL, OR WOOD SPIRIT. In 181 naphtha of commerce is simply rectified from chalk: as thus prepared it is a mixture consisting chiefly of methylic alcohol and methyl acetate, with certain oily hydrocarbons insoluble in water, and which may be separated from it by mixture with water. order to free it from these impurities it is mixed with an equal volume of concentrated solution of potash, and allowed to stand for some hours; any oily matters which may have risen to the surface are removed, and it is then distilled; the alkali decomposes the methyl acetate, usually present in large quantity, and forms potassic acetate whilst wood spirit is produced; after this it may be in great measure deprived of water by adding potassic carbonate as long as it is dissolved: the upper stratum of liquid is then decanted and may be saturated with chloride of calcium, which forms with pyroxylic spirit a compound not decomposable at the temperature of boiling water; the mixture is subjected in a retort to the heat of a steambath, and the volatile portions, containing acetone and methylic acetal, are thus expelled. The residue, which retains the wood spirit, is mixed with an equal weight of water, by which the spirit is displaced from its combination with the chloride; and on renewing the application of heat, methylic alcohol, mixed with a little water, passes over; a second rectification from quicklime furnishes it in a state of purity. Wöhler obtains wood spirit in a pure state more readily by converting it first into methyloxalic ether (1169) which being a solid may be purified by crystallization; when this ether is simply distilled with water it is converted into oxalic acid and wood spirit: the latter may then be rectified from quicklime, by which means it is obtained pure and in the anhydrous form. Properties. Wood spirit is a limpid, inflammable, colourless liquid, of a penetrating spirituous odour, and a disagreeable burning taste; the empyreumatic smell commonly observed is due to impurities in the product. It has a sp. gr. of 0.798 at 68° (20° C.). It is soluble in water, alcohol, and ether, in all proportions. After it has been mixed with water the two liquids occupy less bulk than when separate. It is very inflammable, and burns with a pale flame, furnishing carbonic anhydride and water. When pure it does not reduce the mercurous nitrate if mixed with its solution. Methylic alcohol mixes readily with the essential oils, and dissolves many fatty bodies and resins with facility. Its principal application in the arts, as crude wood naphtha, is founded upon its power of dissolving the resins, which, when thus dissolved, are employed as varnishes. A solution of shell-lac and other resins in wood naphtha, is extensively |