Iodoform is in small, lemon-yellow, lustrous crystals of the hexagonal system, with a peculiar, very penetrating and persistent odor, resembling saffron. The crystals melt at 119° C. They are very slightly soluble in water, soluble in alcohol, ether, chloroform, benzine, and fixed and volatile oils. It has a strong anæsthetic and antiseptic action, and is much used in surgery. Tetrachlor-methane, or carbon tetrachloride, CCl4, is a liquid boiling at 76.5° C. Perchlor-ethane, CaCl, forms rhombic tablets of camphor-like odor. Fuse and boil at 185°. 2. Halogen Derivatives of the Olefine Series.-These may be either substitution derivatives, in which one or more H atoms of the unsaturated hydrocarbon are replaced by halogen, the double linking of carbon atoms characteristic of the olefines remaining unchanged, or they may be addition compounds, in which case two atoms of halogen add on, In the compounds so formed the unstable double linking is broken up, and the product is in all respects identical with the dihalogen substitution derivatives of the paraffins. Thus, from ethylene, CH, we may obtain C,H,Cl, monochlor-ethylene (vinyl chloride), and C2HCl, dichlor-ethylene, or we may get by addition C2HCl, ethylene chloride, already described under the preceding class. From propylene, C,H,, we may obtain C,H,Cl, monochlor-propylene (allyl chloride), representing the substitution derivatives, or CH.Cl2, propylene chloride, representing the addition compounds. 3. Halogen Derivatives of the Acetylene Series. Here also both classes of compounds are possible,-substitution derivatives, in which the unstable treble linking still remains, and addition compounds, which pass into the class of olefine derivatives. II. ALCOHOLS, OR HYDRATES OF THE HYDROCARBON RADICALS. Alcohols are formed by the replacement of one or more hydrogen atoms of a hydrocarbon by the corresponding number of OH (hydroxyl) groups. Alcohols with 1 hydroxyl group are termed monatomic, or monacid; alcohols with 2 hydroxyl groups are termed diatomic, or diacid; alcohols with 3 hydroxyl groups are termed triatomic, or triacid. The highest of these classes as yet discovered in nature are the heptatomic alcohols, although higher ones have been obtained artificially. Two cases of isomerism may arise among the alcohols : (a) when they are derived from isomeric hydrocarbons; thus, from butane, CH. CH2. CH2. CH,, we obtain normal butyl alcohol, CH, CH-CH,, CH. CH2. CH. CH,OH, and from isobutane, CH CH, we obtain isobutyl alcohol, CH, CH-CH2OH; (b) according CH 3 : In looking at the formulas of these isomeric butyl alcohols it will be seen that we have three different types of monatomic alcohols an alcohol containing the group CH,.OH, known as a primary alcohol; an alcohol containing the group CH.OH, known as a secondary alcohol; an alcohol containing the group C(OH), known as a tertiary alcohol. We will find that these are important distinctions, as very different products are obtainable from the alcohols according as they belong to one or the other of these classes. Secondary and tertiary alcohols are also known as carbinols, and the groups combined with the carbon atoms to which the hydroxyl is attached are specially named. Thus, CHC(OH)-CH, is called trimethyl-carbinol. CH 1. Monatomic Alcohols from Saturated Hydrocarbons. General formula, C.H+1.OH. TABLE.-Continued. Name and Formula: Trimethyl carbinol, CH>C(OH).CH, Normal amyl alcohol, C4H,. CH2OH. Fermentation amyl alcohol, CH2>CH.CH2.CH2OH . Hexyl alcohol, CH18. OH Decyl alcohol, C10H21-OH CH Dodecyl alcohol, C12H25.OH Tetradecyl alcohol, C14H29.OH. Hexadecyl (cetyl) alcohol, C18H33.OH Myricyl alcohol, C30H81.OH The lower members of the series are mobile liquids soluble in water, the middle members are oily liquids only slightly soluble in water, and the higher ones are solid crystalline bodies. The lowest members possess an alcoholic odor, those over C, an odor of fusel oil, and both have a burning taste, while the highest members are odorless and tasteless solids. Among the general methods for the formation of alcohols may be mentioned: (a) The action of moist silver oxide upon the halogen derivatives of the paraffins, as C,H,I + AgOH= C2H.OH+ AgI. (b) The decomposition of the esters by boiling with caustic alkalies. This decomposition is frequently spoken of as the "saponification" of the esters, because of the well-known illustration of the decomposition of the fats: CH.OC,HO2+ Methyl Salicylate. KOH = CH3OH + CHO.OK. Potassium Salicylate. (c) The treatment of primary amines with nitrous acid : CH. NH2+ NO.OH = C2H5OH + N2+ H2O. (d) The fermentation of many of the carbohydrates (as grape sugar) with yeast will produce the lower alcohols. (See Fermentation.) Among the special methods for the formation of alcohols may be mentioned: (a) The reduction of monobasic acids and aldehydes with nascent hydrogen to form primary alcohols. (b) The reduction of ketones with nascent hydrogen to form secondary alcohols. The alcohols, it must be remembered, are hydrates of radicals which have in general a basic character. They are, therefore, weak bases. Thus, the hydrogen of the hydroxyl group is replaceable by acid radicals, forming ethereal salts or "esters." At the same time, this hydrogen is also replaceable by strong metals like Na and K, forming "alcoholates." The action of haloid acids will also replace the OH group by halogen, water forming at the same time. Thus, C2H.OH + HBr=C2H ̧Br +H2O. Oxidizing agents readily act upon them, changing primary alcohols to aldehydes and monobasic acids, and secondary alcohols to ketones, while tertiary alcohols are split up into compounds with a lesser number of carbon atoms. Methyl Alcohol, CH,. OH, derives its name from μ0ʊ, wine, and 27, wood, which idea is also conveyed in its popular name of "wood-spirit.” It occurs as salicylic ester in Gaultheria procumbens (oil of wintergreen), and is produced in the destructive distillation of wood and the "vinasse" of the beet-sugar refineries. To prepare it in 'quantity, the crude pyroligneous acid of the wood distilleries is neutralized with lime, and the volatile portions then distilled off. After repeated rectification, the methyl alcohol is finally freed from acetone and accompanying impurities by forming the crystalline oxalic ester, which is pressed, dried, and decomposed by boiling with water or ammonia. Methyl alcohol forms a colorless liquid, boiling at 66°, and with a sp. gr. o.8. It burns with a non-luminous flame, and mixes with water in all proportions. It is a solvent for fatty oils, camphors, resins, and fats. It has an intoxicating effect, and in concentrated form is poisonous. Ethyl Alcohol, C2H,.OH (Alcohol, U.S. P.).-This, the most important of the monatomic alcohols, occurs only sparingly in nature, being found as butyric ether in some plants, as the Umbellifera, and in the animal kingdom, as in diabetic urine. It may be formed in several ways: From ethane by conversion into C2HCl, and saponification of this latter (see preceding page) by moist silver oxide. From ethylene and concentrated sulphuric acid and decomposition of the resulting ethyl-sulphuric acid by water : = C2H + SO2(OH)2 CHHSO4 + H2O = C2H2OH + H2SO. It is formed, however, almost invariably by the "alcoholic fermentation" of sugar. (See Fermentation.) The reaction whereby the sugar yields alcohol and carbon dioxide, CH12O= 2C2HO+2CO,, is not a complete one, as some 5 per cent. of the sugar breaks up into other products, such as glycerin and succinic acid. A number of the homologues of ethyl alcohol are also formed, and are known collectively as "fusel oil." While alcohol may be purified by repeated distillation, it is not possible to free it from water by this means. On a large scale in the several forms of rectifying columns it is possible to bring the alcohol to 98-99 per cent., but on the small scale to not over 95 per cent. The remaining portion of water must be taken out by chemical dehydrating agents, like heated carbonate of potash, anhydrous sulphate of copper, or standing, followed by a distillation over quick-lime. The alcohol thus obtained is the Alcohol Absolutum, U. S. P. The presence of water in alcohol may be shown by admixture with benzene. This will mix to a clear liquid with alcohol containing not more than 3 per cent. of water. If the percentage begins to exceed this, the mixture becomes turbid. Anhydrous copper sulphate will also indicate the presence of water by changing from white to blue in color. Absolute alcohol boils at 78.5° C., becomes viscid at 100° C., and solidifies at -130°. Its specific gravity is 0.7937 at 15° C. It is very hygroscopic. Alcohol is a solvent for many organic compounds, such as fats, resins, and oils. A very delicate test for alcohol (although not characteristic of alcohol only) is the iodoform test. The liquid to be tested is warmed with a small quantity of iodine dissolved in iodide of potassium solution, and sodium hydrate is added until the mixture is faintly yellow. In the presence of alcohol the characteristic smell of iodoform is obtained, and gradually the fine yellow crystals separate. Benzoyl chloride, C,H,COC1, is also a delicate test for alcohol, with which it forms ethyl benzoate (benzoic ether), the smell of which is readily recognized. The commonest impurities of alcohol are aldehyde, which readily forms by oxidation, and fusel oil, |