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(A) Tanning extracts of vegetable origin.
These are vegetable extracts used mainly for the tanning of hides or skins. They are generally prepared by extraction with warm water (sometimes acidulated) from the vegetable material (wood, barks, leaves, fruits, roots, etc.) previously ground or shredded. The liquid obtained is filtered or centrifuged and then concentrated and sometimes treated with sulphites, etc. The extracts thus obtained are liquid but may be further concentrated to paste or solid forms. All these extracts contain varying proportions of tannin as well as other substances such as sugar, mineral salts, organic acids, etc. They are generally brown, yellow or reddish in colour.
The principal tanning extracts are those from oak, chestnut, quebracho, pines, wattle (mimosa), sumach, myrobalans, vallonia, gambier, mangrove or divi-divi.
The heading does not include :(a) Raw vegetable materials, whether dried, shredded, powdered or not, of a kind used primarily in the production of tanning extracts (heading 14.04). (b) Tanning extracts mixed with synthetic tanning substances (heading 32.02). (c) Residual lyes from the manufacture of wood pulp, whether or not concentrated (heading 38.04). (B) Tannins and their salts, ethers, esters and other derivatives.
Tannins (tannic acids) are the main active constituents of vegetable tanning materials. They are obtained by extraction with ether or alcohol from the raw vegetable materials of heading 14.04 or from the extracts covered by Part (A) above. The heading also covers gall-nut extracts (water-extracted gall-nut tannins) which are of lesser strength than those extracted with organic solvents.
The heading covers tannins (pyrogallol and catechol tannins) whether or not containing impurities from the extraction process.
The most common variety is gall-nut tannin (gallotannic acid).
Other tannins include oak bark tannin (quercitannic acid), chestnut wood tannin (castaneotannic acid), quebracho tannin, mimosa tannin, etc.
All these tannins are generally in the form of white or yellowish amorphous powders which turn brown on exposure to air. They may sometimes be in the form of scales or needle-like crystals, etc. They are used principally as mordants in dyeing, in the manufacture of inks, for the clarification of wines or beers, in pharmacy and photography.
The tannates classified in this heading include those of aluminium, bismuth, calcium, iron, manganese, zinc, hexamethylenetetramine, phenazone or orexine. Other derivatives of tannins include acetyltannin and methyleneditannin. These derivatives are usually employed in medicine. The heading does not include : (a) Precious metal tannates or other precious metal compounds (heading 28.43) or tannin derivatives of headings 28.44 to 28.46 and 28.52. (b) Gallic acid (heading 29.18). (c) Tannates and other tannin derivatives of products of headings 29.36 to 29.39 or 29.41. (d) Synthetic tanning substances, whether or not mixed with natural tanning materials (heading 32.02). (e) Tannates and other tannin derivatives of proteins of headings 35.01 to 35.04, for example, casein tannate (heading 35.01), albumin tannate (heading 35.02), gelatine tannate (heading 35.03).
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