| Pyrogallols. | Catechols. |
| Myrobalans (Terminalia Chebula). | Gambier (Uncaria Gambir). |
| Chestnut wood (Castanea vesca). | Hemlock (Abies canadensis). |
| Divi-divi (Caesalpinia Coriaria). | Quebracho (Quebracho Colorado). |
| Algarobilla (Caesalpinia brevifolia). | Mangrove or Cutch (Rhizophora Mangle). |
| Sumach (Rhus Coriaria). | Mimosa or Golden Wattle (Acacia Pycnantha). |
| Oakwood (Quercus family). | Larch (Larix Europaea). |
| Chestnut oak (Quercus Prinus). | Canaigre (Rumer Hymenosepalum). |
| Galls (Quercus Infectoria). | Birch (Betula alba). |
| Willow (Salix arenaria). | Cutch Catechu (Acacia Catechu). |
Subsidiary.
| Oakbark (Quercus Robur). Valonia (Quercus Aegilops). |
Myrobalans are the fruit of an Indian tree. There are several different qualities, the order of which is as follows, the best being placed first: Bhimley, Jubbalpore, Rajpore, Fair Coast Madras and Vingorlas. They are a very light-coloured material, containing from 27 % to 38 % of tannin; they deposit much “bloom,” ferment fairly rapidly, supplying acidity, and yield a mellow leather.
Chestnut comes on the market in the form of crude and decolorized liquid extracts, containing about 27 % to 31 % of tannin, and yields a good leather of a light-brown colour.
Oakwood reaches the market in the same form; it is a very similar material, but only contains 24 % to 27 % of tannin, and yields a slightly heavier and darker leather.
Divi-divi is the dried seed pods of an Indian tree containing 40 % to 45 % of tannin, and yielding a white leather; it might be valuable but for the tendency to dangerous fermentation and development of a dark-red colouring matter.
Algarobilla consists of the seeds of an Indian tree, containing about 45 % of tannin, and in general properties is similar to divi-divi, but does not discolour so much upon fermentation.
Sumach is perhaps the best and most useful material known. It is the ground leaves of a Sicilian plant, containing about 28 % of tannin, and yielding a nearly white and very beautiful leather. It is used alone for tanning the best moroccos and finer leather, and being so valuable is much adulterated, the chief adulterant being Pistacia lentiscus (Stinko or Lentisco), an inferior and light-coloured catechol tannin. Other but inferior sumachs are also used. There is Venetian sumach (Rhus cotinus) and Spanish sumach (Colpoon compressa); these are used to some extent in the countries bordering on the Mediterranean. R. Glabra and R. Copallina are also used in considerable quantities in America, where they are cultivated.
Galls are abnormal growths found upon oaks, and caused by the gall wasp laying eggs in the plant. They are best harvested just before the insect escapes. They contain from 50 % to 60 % of tannin, and are generally used for the commercial supply of tannic acid, and not for tanning purposes.