Pyroligneous acid

When wood is heated without an excess of air to temperatures in excess of 250°C, it decomposes into charcoal and a volatile fraction, which condenses on cooling. The aqueous phase of this condensate is known as pyroligneous acid. The chief component is water containing about 10% of acids, mainly formic, acetic and propionic. 

---

Acid—Base Chemistry. Acetic acid dissociates in water, pK = 4.76 at 25°C. It is a mild acid which can be used for analysis of bases too weak to detect in water (26). It readily neutralizes the ordinary hydroxides of the alkaU metals and the alkaline earths to form the corresponding acetates. When the cmde material pyroligneous acid is neutralized with limestone or magnesia the commercial acetate of lime or acetate of magnesia is obtained (7). Acetic acid accepts protons only from the strongest acids such as nitric acid and sulfuric acid. Other acids exhibit very powerful, superacid properties in acetic acid solutions and are thus useful catalysts for esterifications of olefins and alcohols (27). Nitrations conducted in acetic acid solvent are effected because of the formation of the nitronium ion, NO Hexamethylenetetramine [100-97-0] may be nitrated in acetic acid solvent to yield the explosive cycl o trim ethyl en etrin itram in e [121 -82-4] also known as cyclonit or RDX. 

Until World War 1 acetone was manufactured commercially by the dry distillation of calcium acetate from lime and pyroligneous acid (wood distillate) (9). During the war processes for acetic acid from acetylene and by fermentation supplanted the pyroligneous acid (10). In turn these methods were displaced by the process developed for the bacterial fermentation of carbohydrates (cornstarch and molasses) to acetone and alcohols (11). At one time Pubhcker Industries, Commercial Solvents, and National Distillers had combined biofermentation capacity of 22,700 metric tons of acetone per year. Biofermentation became noncompetitive around 1960 because of the economics of scale of the isopropyl alcohol dehydrogenation and cumene hydroperoxide processes. 

Commercial acetic acid is manufactured fiom pyroligneous acid obtained in the destructive distillation of wood. The latter is neutralised with lime, and separated by distillation from wood-spirit and acetone. The crude calcium acetate, which has a dark colour, is then distilled with the requisite quantity of concentrated hydrochloric acid. Anhydrous or glacial acetic acid is obtained by distilling fused sodium acetate with concentrated sulphuric acid. 

Brenz-holzsaure, /. pyroligneous acid, -kate-chtn, n. pyrocatechol, pyrocatechin. -kate-chingerbstoff, m. pyrocatechol tannin. 

Synonyms Acetasol Acetic acid (aqueous solution) AcOH AI3-02394 BRN 0506007 CCRIS 5952 EINECS 200-580-7 Ethanoic acid Ethylic acid FEMA No. 2006 Glacial acetic acid HAc Methane-carboxylic acid NSC 132593 Pyroligneous acid UN 2789 UN 2790 Vinegar acid Vosol. 

Pyridylamine, see 2-Aminopyridine a-Pyridylamine, see 2-Aminopyridine p-Pyrine, see Pyrene Pyrinex, see Chlorpyrifos Pyroacetic acid, see Acetone Pyroacetic ether, see Acetone Pyrobenzol, see Benzene Pyrobenzole, see Benzene Pyrofax, see Butane Pyroligneous acid, see Acetic acid Pyromucic aldehyde, see Furfural Pyropentylene, see Cyclopentadiene Pyrophosphoric acid, tetraethyl ester, see Tetraethyl pyrophosphate... 

Acetic acid is one of the oldest known chemicals. Dilute acetic acid, vinegar, has been made by aerobic bacterial oxidation of ethanol. It has also been reclaimed by extraction or extractive distillation from pyroligneous acid, which was obtained from the extractive distillation of wood (J ). In the early nineteen hundreds, oxidation of acetaldehyde became the main source of acetic acid. The acetaldehyde has been obtained from acetylene ( ). ethylene (3) or ethanol as indicated below. 

Vinegar and Pyroligneous Acid. Vinegar (acetic acid) is mentioned several times in the Bible, as, for example, in Proverbs 10, 26 As vinegar to tire teeth and as smoke to the eyes, so is the sluggard to them that send him. It was known to Theophrastus three centuries before the birth of Christ, and was used in tire manufacture of white lead and verdigris and in extracting mercury from cinnabar (I). 

German chemist who detected sodium sulfate (Glauber s salt, the enixum of Paracelsus) in water from a spring near Vienna and introduced its use into medicine. His Description of New Philosophical Furnaces contains methods for the preparation of pyroligneous acid and the mineral acids. 

Charcoal was a valued commodity in antiquity. The ancient Egyptians used the volatile product of hardwood distillation, pyroligneous acid, for embalming. Before synthetic organic chemistry became well established, destructive hardwood distillation provided several important industrial chemicals, among these were acetone, acetic acid, and methanol (still often referred to as wood alcohol). Charcoal is a fine, smokeless fuel, prized for its smokeless nature and used extensively for outdoor cooking. Acetone was originally made by the dry distillation of calcium acetate made from wood-derived acetic acid, but better, cheaper sources are also available. 

Synonyms Acid methane carboxylic, Ethanoic acid, Purified pyroligneous acid, Vinegar. Appearance Clear, colorless liquid strong pungent odor. 

When wood is heated in the absence of air or with only limited amounts of air, thermal degradation takes place. This begins at about 100°C and increases with rising temperature. At about 270°C exothermic reactions set in, causing a rise in temperature (usually held at 400-500°C) bringing about complete carbonization. The products are charcoal, condensable liquids, and noncondensable gases.39 The condensable liquids separate into aqueous (pyroligneous acid) and oil and tar... 

On the other hand, methyl ethyl ketone, the primary material in the preparation of this war gas, is easily obtainable even in wartime, for it is a by-product in the manufacture of acetone from pyroligneous acid. The monobromo- derivative of methyl ethyl ketone has similar aggressive properties to bromoacetone and was used by both the French and the Germans in the war of 1914-18,... 

The only ketone which we shall consider is acetone, CH3—CO— CH3, or propanone, also called di-methyl ketone. Acetone is a liquid that boils at 56.5°. It has a peculiar odor, and is soluble in all proportions in water. It is a valuable solvent for many organic substances, and is used in the manufacture of explosives and in important synthetic reactions. It is the third important constituent of crude wood alcohol or pyroligneous acid, being formed as a product of the dry distillation of wood. Table XIII gives the names, formulas and boiling" points of a few of the more common and important ketones. 

---