In order to test the strength of the chomick liquor of the machine, 100 grain measures of either of the test solutions is put into the graduated phial, and some of tho chemick liquor is added hy degrees (Shaking the mixture after each slight addition), till the test aolution is exactly decolorized. The number of the division at which the chemick liquor stands in the graduated phial gives the strength of the liquor in tenths of a degree Twaddle. The whole operation is extremely simple, and can be performed in half a minute or so, by the workman or boy attending the machine.
The most usual and rapid plan of applying the chemick is by means of the chemicking machine, as already deacribed. Another method also adopted, principally by market bleachers and for fine cloths, muslins, &o., is to pile down the pieces in large stone cisterns provided with false bottoms. The cbcmick is pumped up by a lifting or a centrifugal pump from a well below, it flows into wooden perforated troughs or trays (drainers) placed above the cisterns, and is allowed thus to circulate through the cloth down into the well below, to be again pumped up, and so on during two to four hours.
Notes ou White Sour.—For the " white sour," either hydrochloric or sulphuric acid may be used. Some bleachers prefer the latter, from its being less liable to contain iron. If this white souring is omitted and the goods are only washed after chcmicking, they seem still to retain somewhat of a colourable substance, since such goods, when stored in the warehouse for some time, acquire gradually a yellowish or creamy tinge. To avoid this as much as possible, the last passage in weak acid is given, to dissolve the colouring substance which the chemicking has merely destroyed, together with any traces of iron which may etill remain. It is needless to remark that the final washing must be thorough ; here, as in all washing, a rapid change of water is more essential than volume.
Referring to the boiling with lime, resin soap, &c., the great object sought after is to have every portion of the goods well boiled, and subjected to the action of the liquors ; to effect this purpose, many varieties of boiler or kier have from time to time been invented. Besides Barlow's kier, already described, there is also Pen dlebury's kier, identical in principle with Barlow's, and well adapted for bleachers on a smaller scale. The only difference is
that one of the pair of kiers is smaller, so that a smaller quantity of cloth can be bleached at once ; only the larger kier is filled with goods, the smaller one being required to contain the liquor between its passages through the goods. Still in use, especially for mualins, is the ordinary low press kicr, for worldng with steam at 3 to 10 lb. pressure. Fig. 348 represents this kier. A is the boiler, the lower part of which is given in section ; B is the vomiting or puffer pipe, with " bonnet " at the top; C is the perforated false bottom ; D is the lid working on the hinge E and lifted up by attached chains, not shown in the figure; F is an air-valve ; L is a steam-pressure gauge; H and I are the steam and liquor pipes, connected by a two-way valve K vrith the pipe J, leading to the bottom of the puffer-pipe; G is the draw-off valve. The usual method of working this apparatus is to blow steam through the goods for one and a half to two hours, then to enter the liquor and boil for ten to twelve hours. During this boiling, the liquor which collects below the false bottom is forced by the steam up to the top of the vomiting pipe and is there spread by the bonnet over the pieces. This action is of an intermittent character, since, after each ejection of the liquor, the force of the steam must accumulate till it is able to overcome the weight of the column of water in the puffer pipe. The most recently introduced is the injector kier of Messrs. Mather and Platt, Man chester, which bids fair to displace those mentioned. Fig. 849 gives a section of it ; A is the boiler or kier, filled with cloth to G ; H H is liquor collected on the top of the pieces ; B B are the steam pipes, F the liquor pipe, D the circulating pipe; C is the injector ; and E E the draw-off valve and waste pipe.
In the sense of there being a rapid continual circulaticm of goods through the bleach-house, without any long period of exposure on the grass, as was formerly the case, it may perhaps be con sidered that the bleaching process of to-day is ccrntinuous, thcrugh the term is not strictly correct, the operations being still intermittent. Attempts have been made in this direction; but with little or no commercial success.