The Tanner's Key to a New System of Tanning Sole Leather, Or, the Right Use of Oak Bark (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1824. Excerpt: ... CHAP. IX. FOREIGN TANNIN, Sfc. $c. AT HALF THE PRICE OF BARK, &C. ACCORDING TO VARIOUS EXPERIMENTS, BY EMINENT CHEMISTS-SIR JOSEPH BANKS, SIR H. DAVY, MR. KERR, &c Credite operibus. The present duties are, viz.--s. d. Oak Bark 0 8 per cwt. Valonia, or acorn cups...26 Do. Sumac 17 Do. Terra Japonica or Catechu lOrf. per lb. except for tanners, and then only 'is. per cwt. Solid vegetable extracts from oak bark or other vegetable substances to be used for the purpose of tanning leather, and for no other purpose whatever, 3. per cwt. The legislature have evidently seen, and' wisely felt the necessities to admit all possible substitutes for tannin, by these last-mentioned enactments, and considerable importations of extracts of tannin have been made, even at 100 per ton, while native substitutes have been overlooked, and several foreign tannins seldom or never used for that purpose. I particularly allude to the Indian tree, styled Acacia Catechu, or Terra Japonica, i. e. Japan earth, or Cutch. According to Ure's Chemical Dictionary, it is a brown astringent substance--it is a dry extract prepared from the wood of a species of sensitive plant; the mimosa catechu, imported from Bombay and Bengal into England. According to Sir H. Davy, who analysed it, 200 grains of picked catechu from Bombay afforded 109 Grains of Tannin 66 Extractive Matter 13 Mucilage 13 Residuum chiefly Sand and calcareous earth. That from Bengal did not prove quite so strong. The Hindoos prefer the lightest colored, which has probably most sweetness, to chew with the betel nut. Of all astringent substances known, catechu appears to contain the largest proportion of tannin, and Mr. Purkis found one pound of catechu equal to 7 or 8 lbs. of oak bark for tanning leather. Sir H. Davy made ...