In chemical processing, the wood is either burned by the process of dry distillation, with no air present, or else is decomposed by various chemical agents.
Originally, it was burned by the primitive method of the charcoal-stack, which yielded only charcoal used in the melting of ores and iron working. All other valuable products escaped either into the ground or the atmosphere. Today, it is distilled by modern methods, and it is the by-products, such as wood alcohol, vinegar, acetone and pitch oils - and not charcoal - that are of prime importance. It is mainly the hardwoods such as beech, oak, birch, maple and hornbeam which are used for industrial processing.
The chief product of the chemical decomposition of wood is cellulose, used in the manufacture of paper, textiles, guncotton and other products. The wood of spruce, fir, various pines, and poplar and, to a lesser degree, that of beech and birch is used mostly for this purpose.
The proportion of wood processed by chemical means is growing rapidly. The papermills of the developed countries, for example, consume large areas of forest every month. Other raw materials yielded by trees are essential oils, rosin and turpentine. These are obtained from live trees by boring holes in the outer layer of wood or bark, and catching the oils in containers placed beneath them.
The favoured wood of the building industry is that of conifers: spruce, pine, fir and larch. It is long, light, well suited for beams, columns, sawn wood, doors, window-boxes and in building ships and transport vehicles.
About fifteen years ago a stand of bristle-cone pine (Pious aristata Engelm.) was discovered in the Rocky Mountains of Nevada, in which the oldest trees had 4200 annual rings.
Originally, it was burned by the primitive method of the charcoal-stack, which yielded only charcoal used in the melting of ores and iron working. All other valuable products escaped either into the ground or the atmosphere. Today, it is distilled by modern methods, and it is the by-products, such as wood alcohol, vinegar, acetone and pitch oils - and not charcoal - that are of prime importance. It is mainly the hardwoods such as beech, oak, birch, maple and hornbeam which are used for industrial processing.
The chief product of the chemical decomposition of wood is cellulose, used in the manufacture of paper, textiles, guncotton and other products. The wood of spruce, fir, various pines, and poplar and, to a lesser degree, that of beech and birch is used mostly for this purpose.
The proportion of wood processed by chemical means is growing rapidly. The papermills of the developed countries, for example, consume large areas of forest every month. Other raw materials yielded by trees are essential oils, rosin and turpentine. These are obtained from live trees by boring holes in the outer layer of wood or bark, and catching the oils in containers placed beneath them.
The favoured wood of the building industry is that of conifers: spruce, pine, fir and larch. It is long, light, well suited for beams, columns, sawn wood, doors, window-boxes and in building ships and transport vehicles.
About fifteen years ago a stand of bristle-cone pine (Pious aristata Engelm.) was discovered in the Rocky Mountains of Nevada, in which the oldest trees had 4200 annual rings.
About the Author:
Garden planning for the urban front garden often has to provide parking space. While it is difficult totally to hide parked cars, sensible planting can offer partial screening.
0 comments:
Post a Comment