Part 5
V. _From Alcohol._ (ALCOHOL VINEGAR, GERMAN ACETIC ACID.) In a bell-glass, or an oblong glass case, perforated shelves are arranged, a few inches apart, one above another, on which are placed a number of small flat dishes of porcelain, earthenware, or wood. These dishes are filled with spirit of wine or dilute alcohol; and over each is suspended a watch-glass or capsule containing a portion of platinum-black; the whole being arranged so that the platinum-black and the surface of the alcohol are not more than 1-1/2 to 2 inches apart. Strips of porous paper are next so hung in the case, that their bottom edges are immersed in the spirit, to promote evaporation; and lastly, the apparatus, loosely covered, is set in a light place at a temperature of from 70° to 90° Fahr.--the sunshine, when convenient. In a short time the temperature of the platinum rises, and the formation of acetic acid begins; and the condensed vapour trickles down the sides of the glass and collects at the bottom of the case, whence it is removed once or twice a day. (See _engr._) The product of a case of twelve cubic feet content, with 7 or 8 oz. of platinum-powder, is capable of producing daily, if well managed, nearly 1·31 lb. of hydrated acetic acid from 1 lb. of absolute alcohol; 25 lbs. of platinum-powder and 300 lbs. of alcohol will, in like manner, furnish a daily supply of nearly 350 lbs. of pure acid, and of other strengths in proportion. Theoretically, the product should be 130 parts of the hydrated acid for every 100 parts of alcohol consumed; but this is never quite obtained in practice, owing to a small portion of the alcohol mixing with the newly formed acid, and escaping decomposition; and from another small portion of both the alcohol, and of the newly formed aldehyd, being carried off by the air that permeates the apparatus. The platinum-powder does not waste, and the most inferior spirit may generally be employed.
_Rationale._ In this process, the alcohol (as in other cases of acetification) is first converted into aldehyd; and this, as rapidly as formed, absorbs oxygen and passes into hydrated acetic acid. The simultaneous formation of aldehyd during the oxygenation of that already formed, may be detected by its odour.
_Obs._ During the mutual action of the platinum-black and the vapour of alcohol, the temperature increases, and continues to do so until all the oxygen contained in the air enclosed in the case is consumed, when the acetification stops. On opening the case for a short time, to admit of a fresh supply of air, the operation recommences, thus showing its dependence on the oxygen of the atmosphere. For this transmutation, 100 grains of alcohol require 71 grains (equal to 200 cubic inches) of oxygen, or about 1000 cubic inches of atmospheric air. To render the process continuous and rapid, a fresh supply of air must, therefore, be constantly provided. This may be effected by either having a loosely covered opening at the top of the case, and several much smaller ones near its lower part; or (and preferably) by means of two small glass tubes passing through the lid or cover, one of which terminates just below the point of insertion, whilst the other divides into branches which reach to within a short distance from the bottom, as shown in the _engraving_. In this way a very slow current of fresh air will always be kept up in the apparatus.
In practice, we find, that by loosely spreading the platinum-black on pieces of platinum-gauze, and supporting these on small tripods or bars of glass or porcelain (or even wood), the watch-glasses and their troublesome suspension may be dispensed with; as also may be the strip of porous paper, provided a temperature of not less than 90° Fahr. be maintained in the case or acetifier, which may easily be done by the application of artificial heat in the absence of sunshine. On the large scale, a case of wood with a glass roof, or even a well-seasoned cask or vat may be employed, in which case the temperature of the apparatus must be kept up either by means of steam-pipes or flues, or by the supply of warm air. On the small scale, a hand bell-glass placed on a dish, with a single watch-glass or piece of platinum-gauze, and a single capsule containing alcohol, may be used, provided the bell-glass be supported on three very small wedges, to admit of a supply of air. A modification of this is sometimes employed, in which the alcohol is supplied, in drops, to the platinum-black, by means of a long, tubular funnel passing through the mouth of the bell-glass, and having its lower extremity drawn to a very fine point, as shown in the _engr._ To ensure success, the platinum-black should be either fresh-prepared, or recently washed and very gently heated, before placing it in the acetifier. Spongy platinum, though ordered by many chemical compilers, does not answer well for this process.
By the above elegant and economical process, perfectly pure acetic acid of considerable strength may be produced from even impure alcohol; but it is impossible in this way to obtain a concentrated acid without a subsequent operation, because the action of platinum-black on absolute alcohol, or even on strong alcohol, is so violent that the platinum soon begins to glow, and inflammation ensues. Unfortunately the revenue laws of this country, until lately, stood in the way of the adoption of this beautiful process, unless duty-paid alcohol or methylated spirit be employed; but there is no statute that prevents an individual employing pure spirit, of any strength, on the small scale, for private consumption. In Germany, and in the United States of America, vinegar is manufactured on this plan, and from the low price of crude alcohol there, it will no doubt prove ultimately to be the cheapest source of both pure acetic acid and culinary vinegars.
VI. _Miscellaneous Formulæ_:--
1. An excellent acetic acid, of considerable strength, may be made by soaking fresh-burnt and perfectly dry charcoal in common vinegar, and then subjecting it to distillation. The water comes over first, and on increasing the heat, the acid follows. Vinegar-bottoms and waste vinegar may be used.
2. By exposing vinegar, or dilute acetic acid, to the air in very cold weather, or to freezing mixtures, the water separates in the form of ice, and the strong acetic acid may be obtained by draining it into suitable glass vessels, observing to do so at a temperature sufficiently low to keep the water solid. Said to answer well in cold climates.
3. Acetic acid containing 20% of water may be deprived of a good deal of its superfluous water by standing over dry sulphate of soda. (Liebig.) It may then be used either with or without distillation.
4. Acetic acid, of ordinary strength, may be concentrated to any degree, by rectification once, or oftener, from dry acetate of potash or soda, rejecting the first and last portions. The same acetate may be used repeatedly. The temperature need not exceed 400°, and must not rise above 570° Fahr.
ACETIC ACID. (B. P.) _Syn._ ACIDUM ACETICUM. Water mixed with 33% of hydrated acetic acid. Prepared by distilling acetate of soda with sulphuric acid. Colourless sour liquid. Sp. gr. 1·044.
_Prop._ Pure hydrated acetic acid is a thin, colourless liquid above 62 Fahr.; at 50° to 55° it crystallises in large, brilliant, colourless, transparent needles and plates, and even at 60° if a crystal of the acid be dropped in; at 40° it is a solid crystalline mass. Sp. gr.--liquid, 1·063 (Mollerat) to 1·0635 (Mohr);[3]--crystallised, 1·135 at 55° Fahr. (Ure). Odour, intensely pungent when concentrated, but grateful, fragrant, and refreshing, when diffused; taste, intensely sour and acrid, becoming agreeable and refreshing, on sufficient dilution with water; volatile; inflammable, burning with a white flame; vapour of boiling acid highly combustible; dissolves camphor, resins, gum resins, volatile oils, gelatin, gliadin, coagulated albumen, and fibrin (as muscle or the crassamentum of the blood); it coagulates casein, but not liquid albumen (as the serum of the blood and white of egg): miscible with alcohol, ether, and water in all proportions; boils at 248° Fahr.;[4] and is decomposed at a red heat. Its salts are called ACETATES (which _see_).
[Footnote 3: 1·064--H. M. Witt (Ure's '_Dict., of Arts, M. & M._,' 5th ed.); 1·063 to 1·065--Muspratt ('_Chemistry, Theor. & Prac._,' p. 2); 1·06296--Pereira (4th ed.); 1·0629--Brande; 1·062--Ure; 1·057--Berzelius ('_Jahr. ber._,' xvi, 192):--variations evidently arising from difference of purity in the acid examined, or from difference of temperature. The sp. gr. 1·080, with other numbers given by Prof. Lehmann ('_Chemistry_,' Day's Transl.), is probably a misprint.]
[Footnote 4: This is the boiling-point given by the best authorities, and confirmed by Gerhardt ('_Chimie Organique_,' i, 718). Ure made it 230°(an error corrected in 5th ed.), Lehmann says 243·140, and others give it at 235°, 240°, &c. An acid of about 80% (sp. gr. 1·073 to 1·0743), its maximum density, boils at 219° to 220° Fahr.]
_Char., Tests, &c._--1. Free acetic acid reddens litmus paper, like the other acids; and may be readily recognised by its odour and volatility:--2. Sesquichloride of iron being added, and the acid then nearly saturated with ammonia, the fluid acquires a deep dark-red colour.
_Estim._ See ACETIMETRY. Organic mixtures that cannot be thus tested, or from which the acid cannot be obtained by simple distillation, may be neutralised, if acid, with carbonate of lime, boiled for a few minutes, cooled, filtered, the lime precipitated with dilute sulphuric acid, and the whole submitted to distillation, when the acid contents of the distillate may be estimated as above.
_Pur._ By heat, it escapes (entirely) in vapour; nothing is precipitated on the addition of either hydrosulphuric acid, nitrate of silver, or chloride of barium. Sometimes it is contaminated with sulphurous acid, which may be recognised by putting a fluid drachm of the acid, mixed with an ounce of distilled water and half a drachm of pure hydrochloric acid, also a few pieces of granulated zinc, into a flask. While effervescence continues suspend a slip of white blotting-paper, moistened with solution of sub-acetate of lead, in the upper part of the flask above the liquid, for about five minutes. The paper should not be discoloured, and thus indicate the absence of sulphurous acid.
_Adult._ The acetic acid of the shops is chiefly adulterated with water. Sulphurous acid and lead are accidental contaminations; that of the latter often reaches 2%, making the acid poisonous.
_Phys. eff., &c._ In its concentrated state it is a corrosive and an acrid poison. Taken internally, it acts by dissolving the animal tissues, and by thus destroying the organisation causes death, like the other acids. In the dilute form it acts as a stimulant, rubefacient, alterative, refrigerant, and escharotic.
_Uses._ Acetic acid is much employed by the chemist and pharmaceutist, in the manufacture of various preparations, and in analysis; by the perfumer, in the composition of several of his most refreshing and agreeable scents; and in medicine, as an antiseptic, stimulant, rubefacient, alterative, refrigerant, and escharotic. Acetic acid (B. P.) applied by means of a piece of rag tied to the end of a small stick, is a nearly certain cure for ring-worm and scaldhead--one or two applications generally effecting a cure, and the severe smarting it causes is only of short duration; as a caustic, it removes warts and corns; a piece of lint or blotting-paper wetted with it and applied to the skin (evaporation being prevented), forms a useful extemporaneous blister. It was once employed as a disinfectant; but is now only used as a fumigation, to disguise the unpleasant smell of the sickroom and crowded assemblies. It is a popular refreshing scent in faintings, asphyxia, and nervous headache; and is a valuable rubefacient, astringent, and local stimulant. It is also used as a rubefacient and caustic in veterinary practice.
In the _arts_, the commercial acid (pure pyroligneous acid) is used by the engraver to etch his plates; as an antiseptic in pickling and preserving animal and vegetable substances used as food, and anatomical preparations; in dyeing and calico printing, and in the manufacture of medicated vinegars and other pharmaceutical preparations.
In the dilute state, its properties and applications are similar to those of ordinary vinegar, and are noticed under that head.
_Poisoning_ from acetic acid is rare. When concentrated, it is capable, by its corrosive and solvent action, of perforating the coats of the stomach and digestive canal; and it colours the mucus of these organs by the chemical action it exerts upon the blood. Vinegar in an excessive quantity acts in a similar way, but in a slighter degree. The _treatment_ and _antidotes_ are similar to those directed in cases of poisoning by the other acids. See POISONS.
_Duty, Excise, &c._ See VINEGAR.
_Gen. commentary._ Acetic acid, on the large scale, is principally prepared from acetate of soda, which yields by a comparatively inexpensive, and not a difficult operation, an acid sufficiently strong and pure for commercial purposes, without the necessity of rectification. In this process shallow vessels of wood or of copper formed without rivets or solder (except silver solder) in those parts exposed to the action of the acid, are generally employed for the purpose of the distillation. A coil of drawn copper pipe, heated by steam having a pressure of 30 to 40 lbs. to the inch, traverses the bottom of the apparatus, to impart the necessary heat. The refrigerator consists of well-cooled earthenware, Berlin ware, or glass vessels; and the adopter pipe is also of the same materials. Another common form, which is even still more convenient, is a stout copper still, furnished with a cast-iron jacket to hold high-pressure steam, the usual refrigeratory being employed. In a few instances the space between the still and jacket is filled with sand, oil, tallow, or fusible metal; in which case the apparatus is set in brickwork, and heated by a naked fire. Stills of earthenware are also frequently employed; and even worms and condensers of silver, or silvered copper, are sometimes used, and with advantage. With a leaden worm the product is always contaminated with a little of that metal; the efforts of the manufacturer to the contrary, by the exclusion of air, and by rejecting the first and last portions of the distillate, only lessening and not preventing this evil. A lute (if any) composed of linseed meal and water, with or without a little powdered plaster of paris, may be employed; but flat bands and short tubes of well-seasoned vulcanised india rubber are infinitely more convenient and efficacious. The ingredients being placed in the still, and well but hastily stirred together with a wooden spatula, the head is luted on, and the distillation soon afterwards commenced. The chief care now should be to increase the heat gradually as the distillation proceeds; and when a steam-heat is not used, to carefully avoid over-firing, particularly towards the close of the operation. A little acetic ether is added by some manufacturers. In this way 4 lbs. of acid of the sp. gr. 1·050, is obtained for every 3 lbs. of acetate of soda employed. Should rectification be had recourse to, the addition of about 2 or 3% of bichromate of potash, peroxide of manganese, or red oxide of lead, will remove empyreuma, if present. The first of these substances is the most effective; the power of the others being in the order in which they are printed. In distilling the weaker acids and vinegars, it is found useful to add from 25 to 30% of chloride of sodium, which, by raising the boiling-point of the liquid, allows the acid the more freely to pass over (Stein); but this addition proves disadvantageous when any sulphuric acid is present, in which case sulphate of soda may be employed instead. If this addition be not made, the whole of the acid cannot be obtained without distillation to dryness, and the generation of empyreuma.
On the small scale, glass retorts are usually directed to be used, but glass alembics or flasks are more convenient and safe, as already noticed. In the preparation of the pure acid, care should be taken that the acetate of soda does not contain common salt, as the carbonate of soda prepared by calcination, and frequently used to form the acetate, is generally contaminated with it, and yields up its hydrochloric acid or chlorine during the process of distillation, thus vitiating the product. In all the methods given the product becomes more concentrated in proportion to the dryness of the acetate and the strength of the oil of vitriol or muriatic acid employed. By using the one dry, and the other concentrated, glacial acid may always be obtained by collecting separately the last two fifths that come over, and submitting this to refrigeration.
According to Melsens, pure GLACIAL ACETIC ACID is most advantageously obtained by distilling pure and dry acetate of potash with an excess of strong and moderately pure acetic acid, rejecting that which first passes over.
Acetate of soda may be safely dried at a temperature of 400° to 450°, provided care be taken to avoid ignition from contact with sparks. A less heat is, however, quite sufficient to drive off the whole of its water of crystallisation. It is known to be dry by its assuming the appearance of a smooth oily liquid whilst hot. If, whilst heated, it emits fumes, it is suffering decomposition. The same applies to the other commercial acetates. Crystallised acetate of soda loses about 2/5ths of its weight by thorough drying.
When acetate of soda and sulphuric acid are the ingredients employed in the production of acetic acid, sulphate of soda is formed, which, in the large way, the chemist returns to the manufacturer of acetate of soda (_i. e._ to the pyroligneous acid maker), who employs it in the decomposition of fresh acetate or pyrolignite of lime. In this way the same soda-salt is employed over and over again, acting merely as the vehicle for the separation of the crude acetic acid in the solid form, and its easy and cheap transportation from one point to another. This ingenious method of mutual assistance resulting from the application of chemical science to provide for the wants of everyday life, offers some explanation of the extraordinarily low price at which acetic acid may now be purchased.
The acetic acid of commerce (pure pyroligneous acid) is almost wholly obtained from the acetates of soda and lime. The principal supply of crude acetate (pyrolignite) of soda is from America, Norway, and Sweden; but much is also obtained from our home manufactories. See ACETIFICATION, ACETIMETRY, FERMENTATION, PYROLIGNEOUS ACID, SODIUM, (Acetate of), VINEGAR, &c.
More recently, acetic acid has been obtained by decomposing with hydrochloric acid the double salt of chloride of calcium and acetate of lime, mentioned by Fritzsche ('Ann. de Poggend,' xxviii, 123). For this purpose, solutions of acetate of lime and chloride of calcium are mixed and evaporated, the combined salts readily crystallising in large needles. These are freed from the mother-liquor and distilled with common muriatic acid.
The acid furnished by this method requires redistillation, and is, moreover, contaminated with some of the fatty products always present in the crude pyrolignite.
=Anhydrous Acetic Acid.= _Syn._ ACETIC ANHYDRIDE. Acetic acid deprived of the elements of water.
Acetic Acid. Water. Acetic Anhydride. 2C_{2}H_{4}O_{2} - H_{2}O = C_{4}H_{6}O_{3}.
=Aromat'ic Acetic Acid.= _Syn._ AROMATIC VINEGAR; A. SPIRIT OF V.; ACIDUM ACE'TICUM AROMAT'ICUM, L.--_Prep._ 1. (Ph. E. 1839.) Dried rosemary and origanum, of each 1 oz.; lavender flowers, 1/2 oz.; bruised cloves, 1/2 dr.; acetic acid (sp. gr. 1·068), 1-1/2 pint; macerate for 7 days, express, and filter. A fragrant and refreshing perfume. Omitted in Ph. E. 1841 and P. B. 1867.
2. (Ph. E. 1817.) As the last, but using distilled vinegar instead of the strong acid of the Pharmacop[oe]ia. Inferior.
3. (P. Cod. 1839) Camphor, 2 oz.; oil of lavender, 10 gr.; oil of cinnamon, 20 gr.; oil of cloves, 30 gr.; concentrated acetic acid, 1 pint. Very fragrant and refreshing.
4. (Ph. Bor. 1847; Cod. Med. Hamb. 1845.) Oil of cloves, 1 dr.; oils of lavender and citron, of each 2 scrup.; oils of bergamot and thyme, of each 1 scrup.; oil of cinnamon, 10 drops; strongest acetic acid, 1 oz.; mix. Limpid; yellow-brown; highly fragrant and refreshing. See ACETIC ACID (Camphorated), and VINEGAR (Aromatic).
=Beaufoy's Acetic Acid.= A superior commercial acetic acid (_i. e._ purified pyroligneous acid), having a sp. gr. of about 1·044; or containing about 28% of real acetic acid, or 32 to 33% of the hydrated acid. Same strength, &c., as ACETIC ACID P. B.
=Cam'phorated Acetic Acid.= _Syn._ CAMPHORATED VINEGAR; ACIDUM ACE'TICUM CAMPHORA'TUM, L.--_Prep._ 1. (Ph. E. 1841.) Camphor, 1/2 oz.; pulverise it by means of a few drops of spirit of wine, and then dissolve it in acetic acid (Ph. E.), 6-1/2 fl. oz.
2. (Ph. D. 1850.) Camphor, 1 oz.; rectified spirit, 1 fl. dr.; pulverise, and dissolve in strong acetic acid (acid. acet. fort. Ph. D.), 10 fl. oz.
_Obs._ This preparation is intended as a substitute for the aromatic acetic acid of the shops and previous pharmacop[oe]ias. It is also useful as an embrocation, in rheumatism and neuralgia; as an extemporaneous vesicant and counter-irritant; and as a fumigation in fevers, &c.
=Dilute' Acetic Acid.= _Syn._ ACIDUM ACETICUM DILU'TUM, L. Acetic acid, 1 pint; distilled water, 7 pints; mix, Sp. gr. 1·006. One fluid ounce corresponds to 16 grains of anhydrous acid (3·63 per cent.).
=Glacial Acetic Acid.= _Syn._ ACIDUM ACETICUM GLACIALE. Acetate of soda, 20 oz., is liquefied by a gentle heat, stirred till it becomes pulverulent, and then further heated until it fuses; it is at once removed from the fire, and, when cool, the mass is broken up, placed in a 3-pint stoppered retort connected with a Liebig's condenser, and then treated with sulphuric acid, 8 fl. oz. When the distillation slackens heat is to be applied, and the process continued until 6 fl. oz. of acetic acid have passed over. If a little of the product strikes a blue colour when mixed with a solution of iodate of potassium containing mucilage of starch, the whole product must be agitated with perfectly dry black oxide of manganese, 1/4 oz., and redistilled. Sp. gr. 1·065; contains 85% of anhydrous acid.
=ACETIC ANHYDRIDE.= See ANHYDROUS ACETIC ACID.
=ACETICA.= [L.] Medicated vinegars.
=ACETIDUX, Dr DELFER'S.= Made by Döllinger, of Berlin. For the radical and painless removal of warts, corns, hard skin, &c. A solution of 5 grms. of chromic acid in 15 grms. of water. (Schädler.)
=ACETIFICATION.= _Syn._ ACETIFACIO, L.; ACETIFICATION, Fr.; ESSIGMACHEN, EINSAÜERN, Ger. In _chemistry_, the act or process of converting into vinegar; also the state of undergoing such conversion.