Bleaching, a process of whitening fabric by removal of natural colour, such as the tan of linen, is usually carried out by means of chemicals selected according to the chemical composition of the fibre. Chemical bleaching is usually accomplished by oxidation, destroying colour by the application of oxygen, or by reduction, removing colour by hydrogenation. Cotton and other cellulosic fibres are usually treated with heated alkaline hydrogen peroxide; wool and other animal fibres are subjected to such acidic reducing agents as gaseous sulfur dioxide or to such mildly alkaline oxidizing agents as hydrogen peroxide. Synthetic fibres, when they require bleaching, may be treated with either oxidizing or reducing agents, depending upon their chemical composition. Cottons are frequently scoured and bleached by a continuous system.
The flour milling process begins with cleaning the grain and tempering it by adding water. The tempered grain is ground in a series of rollermills to remove the bran and to cut the endosperm. Between each rollermill cycle, the ground grain is sifted and separated into various sizes. Middle-size material is sent to a purifier, or shaking sifter, and on to another set of rollermills for further reduction and sifting into a variety of flours and flour blends. These are then stored in large bins.
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Bleaching
Bleaching, a process of whitening fabric by removal of natural colour, such as the tan of linen, is usually carried out by means of chemicals selected according to the chemical composition of the fibre. Chemical bleaching is usually accomplished by oxidation, destroying colour by the application of oxygen, or by reduction, removing colour by hydrogenation. Cotton and other cellulosic fibres are usually treated with heated alkaline hydrogen peroxide; wool and other animal fibres are subjected to such acidic reducing agents as gaseous sulfur dioxide or to such mildly alkaline oxidizing agents as hydrogen peroxide. Synthetic fibres, when they require bleaching, may be treated with either oxidizing or reducing agents, depending upon their chemical composition. Cottons are frequently scoured and bleached by a continuous system.
The flour milling process begins with cleaning the grain and tempering it by adding water. The tempered grain is ground in a series of rollermills to remove the bran and to cut the endosperm. Between each rollermill cycle, the ground grain is sifted and separated into various sizes. Middle-size material is sent to a purifier, or shaking sifter, and on to another set of rollermills for further reduction and sifting into a variety of flours and flour blends. These are then stored in large bins.