Creosote mixed with coal-tar creosote, or fortified with pentachlorophenol. Water-gas-tar creosote is also derived from petroleum oil or shale oil, but by a different process; its distilled during the production of water gas. The tar is a by-product resulting from enrichment of water gas with gases produced by thermal decomposition of petroleum. Of the creosotes derived from oil, it is practically the only one used for wood preservation. It has the same degree of solubility as coal-tar creosote and is easy to impregnate into wood. Like standard oil-tar creosote, it has a low amount of tar acids and tar bases, and
Birch tar Birch tar Birch tar or birch pitch is a substance (liquid when heated) derived from the dry distillation of the bark of the birch tree. It is composed of phenols such as guaiacol, cresol, xylenol and creosol. Birch tar was used widely as an adhesive as early as the Middle Paleolithic to early Mesolithic era. Neanderthals produced tar through the dry distillation of birch bark as early as 200,000 years ago. It has also been used as a disinfectant, in leather dressing, and in medicine. 5,000-year-old chewing gum made from birch bark tar, with tooth imprints, has been found in