Acetic acid has been produced by synthesis from carbon disulphide. Carbon disulphide plus chloroform gives carbon tetrachloride, CCI. This body, under treatment with metallic sodium, gives ethylene chloride, CH,Cl, and eventually ethane hexachloride, C,Cl. Ethane hexachloride treated with water yields trichloracetic acid, CCI,COOH, and this, by reduction, gives acetic acid. Of course, the above method is of purely theoretic interest, the actual manufacture of acetic acid being either from the distillation. of wood or by the oxidation of alcohol. The latter, when diluted and under the influence of the mother of vinegar, Mycoderma aceti, is converted into vinegar, which represents a weak acetic acid. The commercial acetic acid, however, is produced by the destructive distillation of wood. As already explained on p. 645, wood, on being subjected to heat, yields a tarry distillate, called crude pyroligneous acid (pyros, meaning fire, and lignum, wood), which is composed chiefly of wood alcohol, acetic acid, and acetone. The separation of acetic acid from this distillate has already been given, so suffice it to say that a very large quantity of acid is produced by such treatment of wood, and it has been found that the great heat formerly thought necessary to decompose same is unnecessary. Acetic acid can best be prepared by cutting oak wood in appropriate sized billets, putting into a retort, and heating under 218° C.; at this temperature wood does not char, and except for darkening in color after the process, appears as original wood. The residue is simply dried and is then sold for fuel. Acetic acid is official in three distinct strengths. ACIDUM ACETICUM GLACIALE. Glacial Acetic Acid. A liquid containing not less than 99 per cent., by weight, of absolute Acetic Acid [CH,.COOH=59.58] and not more than 1 per cent. of water. A clear, colorless liquid, of a strong, vinegar-like odor, and a very pungent, acid taste. Specific gravity: not above 1.049 at 25° C. (77° F.). At a temperature somewhat below 15° C. (59° F.) the Acid becomes a crystalline solid. At 117° to 118° C. (242.6° to 244.4° F.) it boils, evolving inflammable vapors. Glacial Acetic Acid should respond to the tests of purity given under Acidum Aceticum; but the tint produced by the addition of 2 drops of tenth-normal potassium permanganate V.S. to 2 Cc. of the Acid diluted with 10 Cc. of water, contained in a clean, glass-stoppered bottle, should not be changed to brown within two hours. Tests for Identity.-Given above. Impurities. See Acetic Acid. Assay.-Details in Part V. Remarks. This glacial acetic acid must contain at least 99 per cent. CH,COOH, and is called "glacial," because at temperatures below 15° C. it becomes solid, like ice. Some manufacturers have put upon the market an acetic acid labeled "glacial," but on careful examination of the label it is found that in smaller type are the words 80 per cent. That such procedure is dishonest goes without saying. Glacial acetic acid is very valuable as a solvent for a great diversity of substances; thus it dissolves resins, glue, and a large number of other organic bodies. Its use in this way, however, must be with caution, as there is strong likelihood of its forming chemical combina A liquid composed of not less than 36 per cent., by weight, of absolute Acetic Acid [CH.COOH=59.58] and about 64 per cent. of water, and obtained by the oxidation of ethyl alcohol or by the destructive distillation of wood. A clear, colorless liquid, having a strong, vinegar-like odor, a purely acid taste, and a strongly acid reaction. Specific gravity: about 1.045 at 25° C (77° F.). Miscible with water or alcohol in all proportions. When heated, the Acid is volatilized without leaving a residue. On adding to Acetic Acid enough ammonia water to neutralize it or to leave the Acid in slight excess, and then ferric chloride T.S., the liquid will require a blood-red color, which is discharged by strongly acidulating with sulphuric acid. When the Acid is slightly supersaturated with ammonia, the liquid should not have a bluish tint (absence of copper), nor should any residue be left after evaporating the alkaline liquid on a water-bath (absence of other fixed impurities). If 5 Cc. of the Acid be supersaturated with 10 Cc. of ammonia water, and 5 Cc. of tenth-normal silver nitrate V.S. be added, and the mixture boiled for one or two minutes, no dark deposit should be produced (absence of formic or sulphurous acids). When the Acid is slightly supersaturated with potassium hydroxide T.S., the liquid should not develop a smoky odor or taste. If 5 drops of tenth-normal potassium permanganate V.S. be mixed with 2 Cc. of the acid, previously diluted with 10 Ce. of water, and contained in a clean, glass-stoppered vial, the pink tint should not change to brown at once, and should not become entirely brown, or free from pinkishbrown, in less than a half minute (limit of empyreumatic substances). Tests for Impurity.-See above. Impurities. Copper, fixed impurities; formic acid, sulphurous acid; excess of empyreumatic substances. Details above. Heavy metals, sulphuric acid, hydrochloric acid. Details in Part V. Assay.-Details in Part V. Remarks. Acetic acid contains 36 per cent. absolute acetic acid, and should be ordered as 36 per cent. acid. The ordinary commercial acetic acid, familiarly called "No. 8," is not the pharmacopoeial acid. It contains but 29 to 30 per cent. of absolute acetic acid. The fact that No. 8 acetic acid is not pharmacopoeial was learned by a friend of the writer at considerable expense, inasmuch as he dispensed No. 8 acid when acetic acid was called for, and afterward had to answer the charge of violation of the Pure Food Laws of his State. This should warn all pharmacists residing in States having Pure Food and Drug Laws to exercise the utmost caution in dispensing commodities under pharmacopoeial names, unless they are exactly the standard prescribed by the pharmacopoeia, it being usually considered in interpretation of such laws that when a pharmacist labels a substance with the pharmacopoeial name, he means pharmacopoeial strength. Thus to dispense essence of vanilla containing tonka bean, labeled "essence of vanilla," would be the ground for legal action. No. 8 acetic acid is so called because one part of same with eight parts of water is supposed to give the strength of dilute vinegar. Vinegar is a 3 to 5 per cent. solution of acetic acid, more or less impure, and it is assumed that it is always made by the fermentation of alcoholic liquids. Thus a dilute white wine or cider, when fermented, will yield vinegar. A quick method for making vinegar is Schutzenbach's method; percolating diluted alcohol over oak shavings. Authorities state that by any of these methods no vinegar containing more than 15 per cent. acetic acid can be made, and as on the market there are a large number of so-called cider vinegars, as strong as 20 to 25 per cent., the conclusion is obvious that such are made from wood vinegar. The commercial grading of vinegar is by the awkward denomination of so many "grains," and this means the number of grains of alkali necessary exactly to neutralize one ounce of the vinegar. This is even more vague than the average commercial standard, as different authorities say the alkali is sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate respectively. Then it is uncertain whether the ounce means troy, avoirdupois, or fluid. If the alkali is potassium bicarbonate, and the "ounce" means fluidounce, "100-grain vinegar" should contain about 12 per cent. acetic acid; 50-grain should contain about 6 per cent. of acetic acid. Acetic acid is interesting as one liquid of which the specific gravity is not a criterion of strength. Thus at 15° glacial acetic acid has a specific gravity of 1.0562; 85 per cent. has a specific gravity of 1.0747; 81 per cent. is 1.0755; 80 per cent. has a specific gravity of 1.0756, which same specific gravity is possessed by the 79 per cent., 78 per cent., and 77 per cent.; 76 per cent. has a specific gravity of 1.0755, and from that point on a gradual diminution of specific gravity occurs until 43 per cent. has a specific gravity of 1.056-the same specific gravity as the glacial. The high specific gravity exhibited by acid containing 77 per cent. to 80 per cent. CH,COOH is supposed be due to the formation, in the solution, of hydroxide of acetic acid. The tests for acetic acid are as follows: When the acid (or an acetate), alcohol, and sulphuric acid are heated together, the mixture gives the pleasant odor of acetic ether. On the other hand, any acetate, when fused with arsenic acid on a platinum foil, gives the disgusting odor of cacodyl. This substance is really a mixture of cacodyl, As,(CH,),, and cacodyl oride, As,(CH,),O; the graphic formulas of the two bodies being respectively: These substances, on treatment with mercuric oxide, yield cacodylic acid: Sodium cacodylate, (CH3),AsONa3H2O, the sodium salt of the above, is considerably used as a mild arsenical preparation. Dose, to 2 grains. ACIDUM ACETICUM DILUTUM. Diluted Acetic Acid. It should contain not less than 6 per cent., by weight, of absolute Acetic Acid [CH,.COOH=59.58] and about 94 per cent. of water. Recipe. Acetic Acid, one hundred grammes.. Mix them. 100 Gm. 500 Gm. To make six hundred grammes.. 600 Gm. Specific gravity: about 1.009 at 25° C. (77° F.). It should respond to the tests of purity given under Acidum Aceticum. Tests for Identity.-See above. Impurities.-See Acetic Acid. Assay.-Details in Part V. Remarks.-Diluted acetic acid, contrary to the general rule for diluted acids (that they be 10 per cent.), contains 6 per cent. absolute acetic acid. A monobasic organic acid [CCI,.COOH], usually obtained by the oxidation of hydrated chloral with nitric acid. It should be kept in dark amber-colored, wellstoppered bottles, in a cool place. White, deliquescent, rhombohedral crystals, having a slight characteristic odor. Very soluble in water, alcohol, and ether. The aqueous solution, on boiling, is decomposed, with the formation of chloroform and carbon dioxide. Heated to 52° C. (125.6° F.) it melts, and at 195° C. (383° F.) it boils and vaporizes without leaving a residue. An aqueous solution of Trichloracetic Acid has an acid reaction upon blue litmus-paper. On heating with potassium hydroxide T.S., it is decomposed, with the formation of chloroform and pota si a carbonate. If to its aqueous solution (1 in 10) ferric chloride T.S. be added, a faint reddish color is developed. Tests for Identity.-See above. Remarks. As chloral represents aldehyde with three hydrogen atoms replaced by three chlorine atoms, so the trichloracetic acid represents acetic acid with three hydrogen atoms replaced by three chlorine atoms, viz.: Again, as acetic acid can be made by the oxidation of aldehyde (see p. 665), so chloral hydrate on oxidation yields trichloracetic acid. Trichloracetic acid is used in dentistry for hardening the gums. Glycocoll, or amidoacetic acid, and taurin, or amidoethylsulphuric acid, must be given passing notice as constituents of oxgall (p. 941). The graphic formulas of these two bodies are: The polybasic acids are derivatives of the hydrocarbons containing more than one carboxyl group. Thus an acid corresponding to the general formula Ri (COOH),, called dibasic acid, and Rii (COOH)3, called the tribasic acids, are both illustrations of polybasic acids. The simplest of these is the one which can be considered as derived from ethane. Oxalic Acid (COOH),.-This body was long known in the past as the potassium oxalate, which is the constituent of the leaves of several plants, notably Oxalis perennis, from which the acid derives its name. It was Scheele, in 1776, who first gave the acid a thorough chemical examination. Oxalic acid can be made synthetically by several methods. Thus cyanogen, when treated with water, forms ammonia and oxalic acid by the following reaction: This is stated because it represents the real method of the synthesis of any acid, the same being formed from hydrocarbons containing one less carbon atom than the acid desired by converting same into chloride, then replacing the chlorine group by the cyanogen group (CN), and then converting the cyanogen group into the carboxyl group by the reaction given above, which is considered as a variety of saponification. The commercial manufacture of oxalic acid is by the oxidation of either sugar or starch by nitric acid, or by fusing cellulose (sawdust) with potassium hydroxide. The latter is the popular method, the yield being 50 per cent. as much as the sawdust employed. Oxalic acid is not official, although mentioned in the pharmacopoeia as a test solution, both in qualitative testing and in volumetric analysis. It is poisonous, and its antidote is any convenient preparation of lime, thus forming insoluble calcium Of the above, the alcohols have no pharmaceutic interest, it being necessary only to call attention to the fact that two isomeric forms of propyl alcohol are known-the primary and the secondary. The former yields on oxidation propylic aldehyde, while the secondary gives, under the same treatment, the ketone, acetone. Both of these alcohols yield, with the appropriate acids, esters. Propionic aldehyde can be dismissed on the simple statement that it, on oxidation, yields propionic acid, CH,CH,COOH. |