Tanbark oak (Quercus densiflora) is found in southern Oregon and southward to Mariposa county, California. The tree is also known locally as chestnut oak. The bark contains 9 to 22 per cent of tannin and averages about 18 per cent. The foliage and twigs contain about 5 per cent of tannin.
The barks of other American oaks contain considerable tannin. White oak (Quercus alba) contains 3 to 9 per cent; red oak (Q. rubra), 3 to 5 per cent ; black oak (Q. nigra), largely used as a source of quercitron, a dyestuff, but of little value for tanning ; California black oak (Q. Cali formica), about 10 per cent of tannin ; Highland oak (Q. Wislizeni), about 7 per cent ; California white oak (Q. lobata), about 12 per cent ; Canyon live-oak (Q. chryso lepis), about 10 per cent ; Pacific post oak (Q. Garryana), about 8 per cent.
Other oak barks used largely abroad are the following : English oak (Qaercus pedunculata), common in Eng land, Ireland, Scotland and Slavonia. It is used for making oakwood extract. The bark contains 8-15 per cent of tannin. Q. sessiliflora, the bark of which con tains 10-14 per cent of tanning matter, possibly both catechol and pyrogallol groups. The yield of tannin is less from trees over twenty-five years of age, and cop pice barks, from absence of roes, are often strong, and also contain less coloring matter and more fermentable sugar. Oakwood contains only a very small percentage (2-4 per cent) of tannin, practically identical with that of chestnut. Turkey oak (Q. Cerris), of southern Europe ; Q. pubescens, in mountain districts and scattered in south ern Europe, 8-15 per cent of tannin ; Evergreen oak (Q. Ilex), south Europe and Algeria, 5-11 per cent of dark colored tannin, well adapted to sole leather ; cork oak (Q. Sober), the outer bark of which is cork ; the interior bark contains 12-15 per cent of tannin, which is redder than that of ordinary oak ; African oak (Q. pseudosuber), of Algeria, 10-14 per cent of tannin ; Q. Mirbecki, of Algeria, 8 per cent of tannin in the bark ; Q. Toga, of the Pyrenees and south France, 14 per cent of tannin in the bark ; Kermes oak (Q. coccifera), of south Europe
and Algeria, has an average of 10-18 per cent of tannin, giving a firm, dark, sole leather.
Valonia (from Quercus _,Egilops and probably other species, Q. macrolepis, Grwca, Ungeri, cocc(era), is the commercial name of the acorn cups of these several kinds of oaks. Best Smyrna valonia contains up to 40 per cent, Greek 19-30 per cent, Candia valonias up to 41 per cent, and Caramanian 17-22 per cent of pyrogallol tannins or pyrogallol derivatives, and deposit a great deal of bloom consisting of ellagic acid. The acorn contains a considerable amount of fermentable sugar and but little tannin. Valo nia is hand-picked in three grades. The beard sometimes contains over 40 per cent of tannin. Valonia is especially suitable for the manufacture of sole-leather. It deposits much bloom, and is used as a dusting material. It makes the leather solid and compact, but leaves the grain some what rough and bard to work. In mixture with gambier and other materials, as it is generally used, it is an excel lent tannin for dressing leather, and with proper manage ment deposits little or no bloom.
"Nut galls" is the term applied to the excrescences on plants produced by insects for the purpose of deposit ing their eggs. "Turkish" or Aleppo galls, from Q. in fectoria, are developed from the young shoot of the oak, and are best before the insect has escaped, as they contain in this stage np to 50 or 60 per cent of gallotannic acid. These galls and those of Rhus semis lata are the principal sources of the pure tannin of commerce. Q. infectoria also bears a large gall like an apple, called "Ap ples of Sodom," or, ' rove," caused by a different insect, which contains 24-34 p e r cent of gallotannic acid.
Knoppern are galls produced on the im mature acorns of vari ous species of oaks, principally Quercus Cerris in Hungary,and contain up to 35 per cent of gallotannic acid. Like all purely gallotannic materials, they naturally give a soft and porous tannin, ill-adapted for sole leather.
The bark of a number of Indian oaks yields tannin, Q.
incana containing about 22 per cent.
The chestnuts.