BLEACHING.

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The following substances are also imparted to cotton fabrics by the operationsof spinning and weaving:—ist, starch and paste; 2nd, fatty matters ; 3rd, asoap of copper (due to the aftion of the fatty substances upon the copperteeth of the comb); and 4th, of dirt from the hands of the operatives. It isimpossible to aft upon the incrustating matters until after the removal of thelast-named impurities, for which purpose alkaline lyes are resorted to. These,besides eliminating grease and dirt, promote the removal of incrustatingmatters by predisposing them to oxidisation. Cotton is easier to bleach thanany other fibre, because it contains but few impurities and consists mainly ofcellulose, which resists uninjured the aftion of pretty strong chemicals, sothat energetic agents may be safely employed. Wool and silk cannot beso aftively treated. The theory of bleaching is that the greasy matters areremoved by caustic or carbonated alkaline lyes, while the incrustating sub-stances are destroyed by an oxidating process; its praftice consists of thefollowing operations :—“ Singeing,” “ rot steep ” or “ wetting-out steep,”“liming,” passing through a solution of chloride of lime, “bowking,” passingthrough weak acids, chiefly hydrochloric acid, washing, squeezing, and dyeing.The “ rot steep,” so called because the flour or size with which the goods wereimpregnated was formerly allowed to ferment and putrefy, is intended tothoroughly wet the cloth. This takes some time, as the fabric, on account ofthe greasy matters contained in it, throws off the water in places, and if it benot thoroughly wetted there is risk of irregularity in the after processes.“Liming” takes place in large kiers or kettles capable of holding from 500to 1500 pieces of cloth. The lime is carefully slaked some days previous touse, and sifted to prevent the introduftion of small lumps of quick-lime intothe kiers into which it is equally distributed : the stuff is then pressed downinto the kiers, and the boiling commenced and continued for a period of fromtwelve to sixteen hours. After this the liquor is drawn off and clear waterrun in to cool the pieces, which are then taken out and washed. Limingusually takes place at low pressure, but a patent process, which employs apressure of upwards of 40 lbs., appears to answer very well and saves time.It is very important that the goods remain entirely covered with liquid duringthis operation, since, according to Dr. E. Schwartz, the aftion of lime uponcloth is highly destruftive if it be at the same time exposed to the air. The latestof the methods of bleaching under pressure is that of Mr. Barlow. Of this methodand the machinery employed we give illustrations. In that of Mr. Barlow’s,Fig. 1 is an elevation showing a pair of kiers, fitted with distributers, &c.A and b are the kiers (which it is preferable to make of strong boiler-plateiron), the kier A being shown in seftion, and exhibiting the distributors, &c.

At the bottom of the kier is a plate of an umbrella shape, c. This platespreads over about three-fourths of the bottom of the kier; it is .perforatedwith holes all around its outer ridge, at d d, which rests upon the bottom ofthe kier ; all the rest of the plate being solid. This plate is fastened in thecentre to an iron block, e, which stands upon the bottom of the kier, in thecentre, over the outlet hole. The block e is pigeon-holed at the bottom, so asto allow the liquor to pass from the kier. A socket is left in the upper part ofthe block e, to admit the insertion of the distributor,/. This distributor ismade of dimensions corresponding to the size of the kier; it is solid for somedistance from the bottom, and above that is hollow and perforated as full as