LINEN-BT EACIIING. The process employed for removing colors from linen is similar to that employed for cotton. although the natural im purities are greater in the thix-fibre than in the cotton. These are rendered soluble by alkaline boilings, after which the coloring matters that still remain are oxidized and destroyed by baths of bypoehlorites. or bleaehing-powder. It is sometimes found desirable. especially when linen (loth is bleached, to introduce a step called grassing, which consists in exposing the material in a field to the action of air. light. and moisture for several days. It is believed that by this method the full strength of the fibre is more completely retained. in linen-bleaching the treatment of the yarn varies slightly from the treatment of the cloth, the latter being somewhat more extended.
\\oor.-BLEAciliNG. The special feature in which this differs from the preceding methods is in the preliminary process, which is called scouring. Wool-fibre usually contains from 15 to 70 per cent. of foreign matter, consisting of dirt, and especially of fatty matters secreted by the ani mal, called yolk. This is divided into two parts: (1) 'Aloof perspiration.' which is soluble in water, and consists essentially of potassium com pounds of oleic and slcurie acids, thus constitut ing an important source of potash; and (2) a compound insoluble in water and composed of cholesterin in combination with fatty acids. The
scouring process consists in dipping the loose wool on a frame into dilute alkaline solutions which form emulsions with the yolk, or in treat ing the wool to the successive action of fat sol vents, such as carbon disulphide, and washing. When the wool-yarn is scoured the process is similar, although the machinery is somewhat dif ferent. Wool cloth is scoured by passing the material as an endless band through the scouring liquid, and then through a pair of squeezing roll ers. Even after scouring, wool cloth retains a faint yellow tint, which is then removed by bleaching. This is accomplished by the action of sulphurous acid, which is formed by burning sulphur in a closed chamber while the scoured and washed material, still wet, is suspended on poles, or the woolen material may be immersed and moved about in a solution of sulphurous acid. After bleaching the materials are well washed, and any persistent yellow tint is neu tralized by the addition of a preparation of bluing.