Notes on Limeing.—The chief point to be aimed at in limeing is to have the goods equally and thoroughly well saturated with the milk of lime ; any defect in this respect is sure to give rise to stains that will be noticeable in subsequent dyeing. With some bleachers, especially where open low-press kiers are employed, it is usual to occasionally throw scoops-full of milk of lime over the pieces while being admitted into the lime kier, more particularly if the first washing has been dispensed with. The lime may be slaked immediately before using ; the milk of lime as formed, and free from lumps, is gradually run into the limeing machine, during the passage of the pieces. The more preferable plan is to keep a stock of previously slaked lime in a stone cistern, from which the necessary quantity of pasty lime is ladled into a tub, there mixed with water, and run into the limeing machine. The quantity of lime used is variable according to quality of cloth. A good average amount is 5 lb. lime per 100 lb. cloth. The proportion of lime being absorbed by the cloth is readily ascertained by washing a yard or two of the limed cloth, and testing a given portion of the measured wash water with a solution of hydrochloric acid of known strength.
Notes on Lime Boil.—In filling the kier, the cloth should be evenly and well packed, especially at the sides, but not too tightly, so that the liquor may percolate as equally and easily as possible throughout the interior of the mass. During the boiling, the lime decomposes the greasy, resinous, and wax-like matters in the fabric, forming with them insoluble lime soaps ; it also attacks the alumina, and modifies the brown colouring matter of the fibre, yet preserves the latter in a good, strong condition. The insolubility of the lime soaps formed is peculiarly advantageous, since the fatty matters are fixed the moment they become decomposed, and are thus prevented from floating about and accumulating irregularly through the cloth, thereby producing stains. In consideration of this property, coupled with the facts that the resinous matters are more energetically attacked by lime than by the caustic alkalies potash and sods, and that its price is low, lime is to be preferred for the first boil. When using low-press kiers with central puffer pipe, and with an insufficiency of water in the lime boil, the pieces at the top are liable to become tendered by the continued notion of the heat and steam. In the same way, it may happen that the pieces lying at the bottom of the kier may be tendered, by the liquor having been forced up the puffer pipe to the top, and being so small in quantity as not to have time to circulate through the pieces to the bottom again. It is best to have the level of the liquor about I to 2 feet below the top of the pieces. With too much liquor, on the other band, there is the risk of the pieces floating, and becoming entangled and damaged by tremulous boiling. During the lengthened boiling, water condenses and accumulates ;
care must therefore be taken not to run off too much or too little liquor. With Barlow's kiers, and with the injector kier to be afterwards described, when care is taken to add the proper measure of liquor at the beginning, there is not the same risk in this respect. During the lime boiling and subsequent washing, the cloth loses most of the stare*, insoluble and soluble, iuorganio matters of the weaver's dressing. The resinous, fatty, and colouring matters still remain, but in 'an altered state, and the goods look even darker than before.
Notes on Souring.—The object of the souring after the lime boil is to decompose the insoluble lime soaps by removing the lime, besides dissolving out any excess of the latter adhering mechani cally to the cloth. The acid also dissolves iron, copper, and other metallic oxides which may be present, and loosens the brown colouring matter of the fibre. Hydrochloric acid is preferable to sulphuric acid for this purpose, on account of the greater solubility of its lime salt ; and oare should be taken to keep up the strength of the acid to about 2° Tw., by having a regular flow from tho cistern, siuce it is rapidly neutralized by the lime from the piecee. It is not advisable to add strong aeid to the machine, for fear of its getting on to the oloth in its undiluted state, when, being more difficult to wash out, it might cause tender plaees. The following is an excellent method of keeping the sour at a regular strength, the hydiometer being of no use. A I pint of the hydrochloric acid sour is taken from the maehine while the pieces are running, and put into a small pot ; a solution of caustic soda at 25i° Tw. is slowly added, from a graduated tube, with constant stirring, till a small pieee of turmeric-dyed cloth, dipped in the mixture, shows, by its becoming slightly brown, that the acid is fully neutralized. The number of divisions of caustic soda required to effect this, gives the strength of the acid. The graduated tube should be a thick glass bottle of tubular furm, each division showing oz. measure of water. Divided in this manner, eaeh oz. measure of the caustic soda required represents 1° Tw. of hydrochloric acid, and the marks I° Tw., 2° Tw., 3° Tw., &c., may be at once ffied on the glass, beginning at the top. This testing is sufficiently exact, and can be performed in a few minutes by an ordinary workman. Soured goods should never be left lying long enough in a pile for the exposed parts tu become dry, as the gradual concentratiou of the acid in sueh parts may tender them ; hence exposure of the goods in this state to air currents should be avoided.