Botanical List of Tanning Materials.[135]
[135] The percentage of tannin given where the source of information is not stated must in many cases be regarded as uncertain, many analyses having been made before the introduction of modern methods, but those quoted as having been done in the author’s laboratory are of recent date and have been made by the latest methods.
CONIFERÆ, Pines, Cypresses, mostly containing Catechol tans, yielding reds.
Abies excelsa, Lam. (Pinus Abies, Pinus Picea, Picea vulgaris, Link.), Norway Spruce. Fr. Faux sapin; Ger. Fichte, Rottanne. The source of the so-called larch-extract, and a principal tanning material of Austria. Contains 7-13 per cent. of a catechol-tannin and much fermentable sugar, and on this account is useful for swelling and colouring, but does not tan heavily. English and Scandinavian bark does not seem much utilised. Best bark 2-8 mm. thick; smooth, yellow inside, with reddish-brown ross outside. For detailed description of structure see von Höhnel, ‘Die Gerberinden,’ p. 35.
Abies pectinata, Silver Fir. Fr. Sapin; Ger. Edeltanne, Silbertanne, Weisstanne. Used to a limited extent, but apt to be confused with spruce. Contains 6-15 per cent. iron-blueing tannin. Used in Styria, Austria, Russia. Without “ross,” but silver-grey and smooth outside. (Von Höhnel, ‘Die Gerberinden,’ p. 40; ‘Gerber,’ 1875, p. 375.)
Abies (Pinus, Tsuga) canadensis, Hemlock Fir ([Fig. 44]). The principal American tanning material, and source of hemlock extract; averages 8-10 per cent. of a catechol-tannin, but variable, 18 per cent. reported, possibly from a different species. Abundant in Canada and the Northern and North-western States of America. The bark of old trees, which is principally used for tanning and extract-making, is 2-4 cm. thick, smooth and yellow within, greyish and deeply fissured without. The ross, which is red and thick, contains a considerable quantity of tannin, with much dark-red phlobaphen. It does not differ in structure from the inner living and yellow “flesh.” The bark is easily recognisable by its well-marked concave lamellæ of cork, cutting off successive layers of “ross” of several millimetres in thickness. (Von Höhnel, ibid., p. 42.)
Fig. 44.[136]—Hemlock Fir (Tsuga canadense).
[136] Bastin and Trimble’s American Coniferæ, American Journal of Pharmacy.
Abies alba (Picea alba), White Spruce, North America. In character of tree and bark very similar to Norway spruce.