One of the principal advantages of myrabolan extract, which has to a large extent replaced sumac and plant galls in European tanneries, is its acid-forming properties. It contains 3 to 5% sugars, which is much more than most other tannins contain; consequently fermentation takes place readily in the tan liquor and satisfactory plumping of the hides and skins is obtained in the early stages of tanning. Myrabolan tannin also contains a large proportion of ellagitannic acid, and thus readily deposits bloom. The disadvantages of the tannin are its slow penetration, and its tendency to produce a spongy leather of poor wearing quality. Because of these characteristics, myrabolans is usually blended with other more astringent tannins, e.g., wattle, quebracho, or mangrove, which penetrate faster.
Myrabolans is a pyrogallol class of tannin, with low viscosity, a medium pH (3.2) and salts content, and very high acids content. The tannin also contains chebulinic acid and a fairly high proportion of ellagitannin.
In addition to its used in the tanning industry, myrabolan tannin is also used as a black dye and in the manufacture of some inks. See also:VEGETABLE TANNINS . (175 , 298 , 306 )
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