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38.07 Wood tar; wood tar oils; wood creosote; wood naphtha; vegetable pitch; brewers’ pitch and similar preparations based on rosin, resin acids or on vegetable pitch.
This heading covers products of complex composition obtained during the distillation (or carbonisation) of resinous or non resinous wood. Apart from gases, these processes give pyroligneous liquids, wood tar and wood charcoal in proportions varying according to the nature of the wood employed and the speed of the operation. Pyroligneous liquids (sometimes known as raw pyroligneous acid), which are not materials of international commerce, contain acetic acid, methanol, acetone, a little furfuraldehyde and allyl alcohol. This heading also covers vegetable pitch of all kinds, brewers’ pitch and similar compounds based on rosin, resin acids or on vegetable pitch.
The products classified here are :(A) Wood tar; wood tar oils whether or not decreosoted and wood creosote. (1) Wood tar is obtained by draining from wood (coniferous or other) during carbonisation in charcoal kilns (e.g., Swedish tar or Stockholm tar), or by distillation in retorts or ovens (distilled tars). The latter are obtained directly as a fraction settling out from the pyroligneous liquids (settled tars), or by distillation of the pyroligneous liquids in which they have been partially dissolved (dissolved tars).
Partially distilled tars from which some of the volatile oils have been removed by further distillation are also classified in this heading.
All these tars are complex mixtures of hydrocarbons, phenols or their homologues, furfuraldehyde, acetic acid and various other products.
Tars obtained from resinous woods, which differ from those obtained from non resinous woods in that they also contain products resulting from the distillation of the resin (terpenes, rosin oils, etc.), are viscous products ranging in colour from brownish orange to brown. They are chiefly employed (as obtained, after simple dehydration or after partial distillation) for impregnating ships’ cables, as plasticisers in the rubber industry, in the preparation of mastics, in medicine, etc.
Tars obtained from non resinous woods are thick brownish black liquids mainly used for the preparation, by distillation or other means, of a wide range of by products (wood creosote, guaiacol, etc.).
Cade oil, also known as juniper tar oil, used in medicine and soap making, is also covered by this heading. (2) Wood tar oils are produced during the distillation of wood tar. The light oils (containing aliphatic hydrocarbons, terpenes and higher ketones) are used for the manufacture of sheep dips and horticultural sprays, and the heavy oils (containing aliphatic and aromatic hydrocarbons, higher ketones and higher phenols) serve for impregnating wood and for the extraction of wood creosote.
Decreosoted oils obtained after extraction of the creosote are used according to their characteristics for concentrating ores by flotation, for preparing fungicides, as solvents, as fuels, etc. (3) Wood creosote is an essential constituent of wood tar. It is usually obtained by distilling tar obtained from non resinous woods, separating it from the appropriate fraction with sodium hydroxide, re acidification and re distillation. It is a colourless liquid but takes on colour under the action of air and light, has an odour of smoke, is caustic and is used in particular as a disinfectant and antiseptic. It should not be confused with creosote oil or mineral creosote which are classified in heading 27.07. (B) Wood naphtha is obtained by processing pyroligneous liquids. It is a yellowish liquid with an empyreumatic odour usually containing 70 to 90 % methanol (methyl alcohol) with varying proportions of acetone and other ketones (generally 8 to 20 %), as well as other impurities (methyl acetate, higher alcohols, tarry substances, etc.). Certain types of wood naphtha are used as denaturants for ethanol. (C) Vegetable pitch.
These are residues of the distillation or other treatment of vegetable materials. They include : (1) Wood pitch (wood tar pitch), a residue of the distillation of wood tar. (2) Rosin pitch, a residue of the preparation of rosin spirit and rosin oil by distillation of rosin. (3) Sulphate pitch, a residue after the distillation of tall oil, etc.
These pitches are usually blackish brown, reddish brown or yellowish brown. They generally soften with the heat of the hand. They are used, according to their type, for caulking ships, waterproof coating of woven fabrics, impregnating woods, preparing anti rust coatings, as binding materials, etc. (D) Brewers’ pitch and similar preparations based on rosin, resin acids or on vegetable pitch. (1) Brewers’ pitch is used hot for coating beer barrels. It is usually obtained by melting mixtures of rosin, paraffin wax and rosin oil, or mixtures of rosin and vegetable oils (such as linseed oil, cotton seed oil or colza oil). (2) Cobblers’ wax is used for waxing yarns and twine for sewing footwear and harness makers’ wares, and normally consists of a mixture of rosin, rosin oil, paraffin wax, ozokerite, etc., and contains powdered inorganic substances (such as talc or kaolin). It is usually in the form of blocks, sticks or discs. (3) Caulking pitch is used for caulking ships and is generally prepared by fusing a mixture of wood pitch, wood tar and rosin.
This heading does not cover :(a) Natural Burgundy pitch (also known as "Vosges pitch"), a natural resin obtained from certain coniferous trees, and yellow pitch which is natural Burgundy pitch purified by fusion and filtering (heading 13.01). (b) Stearin pitch (stearic pitch), wool grease pitch and glycerol pitch (heading 15.22). (c) Mineral pitch from coal, peat, petroleum, etc. (Chapter 27). (d) Methanol (methyl alcohol), pure or commercially pure, or other separate chemically defined products obtained by redistilling or further treating the primary products of wood distillation, e.g., acetic acid, acetone, guaiacol, formaldehyde, acetates, etc. (Chapter 29). (e) Sealing wax (heading 32.14 or 34.04). (f) Residual lyes from the manufacture of wood pulp (heading 38.04). (g) "Brais resineux" (heading 38.06).
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