BLEACHING 



379 



as often as b c and e d are in ono line. It is not shown by the drawing that tho cloth 

 passes eight times round these wheels. Thero is a constant stream of water from 

 the pipe/, which is flattened at the mouth about one and a half inch in one diameter, 



125 



and about 10 inches in the other. This machine can wash 900 pieces in an hour. It 

 requires about twice as much water as a dash-wheel, but washes seven and a half 

 times more pieces. Its length is 9 feet. 



Souring . After boiling in tho first kier and washing, the goods are soured in 

 muriatic acid of 1010- specific gravity, or 6 gallons of the usual acid, which contains 

 33 per cent, of real acid, mixed with 100 gallons of water. This is equal to 2 

 Twaddle. Muriatic acid may be replaced by sulphuric acid of 1024* specific gravity, 

 i.e. 3 gallons liquid acid to 100 of water ; or the amount of the acid may be doubled 

 in either case, and a shorter time allowed for the souring. The souring is performed 

 in wooden or stone cisterns, where the cloth is laid regularly as it falls over one of the 

 rollers of the calender ; or it is passed through the acid solution by the movement 

 of the calender in the same manner as described in the process of washing. If this 

 method is used, it is allowed to lie on the stillages from two to three hours to allow 

 the acid to act. The acid decomposes any lime-soap formed, and washes out tho lime. 

 Hydrochloric or muriatic acid has been preferred in the process described, as tho 

 chloride of calcium is so much more soluble than the sulphate. After souring, of 

 course the goods must be thoroughly washed as before. 



The sixth operation with soda removes the remaining fatty materials. If lime be 

 us:;d, it may be allowed to settle ; and it is better to allow it to do so, and thus to 

 use pure caustic soda, which will with the resin remove the impurities in a more 

 soluble form. If, instead of adding 170 Ibs. of soda crystals to 600 gallons of water, 

 4'6 Ibs. of liquid caustic soda of specific gravity 1320' were added, the effect would bo 

 tho same. 



The solution of rosin and carbonate of soda is a half-formed soap, which is con- 

 sidered to act beneficially in removing tho soluble matter. It would not appear, from 

 theory, to bo capable of doing so well as the soda which has its carbonic acid removed ; 

 but tender goods will not allow the action of caustic soda, and the carbonate is there- 

 fore safer. 



Powder-bleaching. Chloride of lime is added in stone vessels whore the goods are 

 allowed to lie. It is universally called chemick in tho manufactories. Tho strength 

 used at Brickacro is half a degree Twaddle, or 1002-5. This is sometimes* very much 

 increased, so as to be even 5 in some establishments, according to the goods 

 bleached ; but it is not safe to allow tho cloth to lio long in such strong solutions. In 

 such cases it is needful to pass them rapidly through with the calender, so as to soak 

 them thoroughly, and then to pass them on to the acid, and forward to be washed. 

 It may bo remarked that the use of the calender for those operations renders it pos- 

 sible to use strong solutions, even for tender goods, as there is no time given for 

 injurious action on the fibre. 



Great care is to be taken to make the solution of tho chloride of lime perfectly 

 clear. Tho powder does not readily wet with water, and it must therefore bo pressed 



