Formerly, stale urine was in muoh request for scouring purposes, for which it was found very suitable, owing to the presence therein of a considerable quantity of carbonate of ammonia, which is a weak alkali, whilst the aecompanying organic matters were also useful in proteetieg the fibre from the action of the stronger alkalies added to the bath. Its insufficient supply, combined with its offensive odour, has greatly diminished its use. Ammonia is also frequently used for the " scour," and that obtained from urine is the best for the purpose. Gas-liquor yields a considerable quantity of ammonia by distillation, hut when obtained from this source, it is apt to contain hydroearbons and sulphide of ammonium, the former of which are injurious to the hands and skin of the workpeople, and the latter damages the wool. Carbonate of soda is another scouring agent, and, in one form or another, is very extensively employed. It is an ingredient, and often the chief one in the special preparations or oompounds, retailed in the woollen districts as efficacious wool purifiers. (See pp. 1788-9). Soaps are the most generally accepted scouring agents. In order, however, to employ them so as to secure a satisfactory result, it is imperatively necessary to obtain them of uniform strength. Few articles are more liable to adulteration than soap, as few better hide the sophistication.
Silicate of soda, or soluble glass, has of late years been extensively introduced as a detergent for cleansing wool, and it is stated to have been found to possess valuable properties. Like soap, it holds its alkali in feeble combination. Its detergent power is considerable, and it may be employed alone or in combination with ordinary soap. When used alone for scouring wool, the latter should be well pressed to clear it thoroughly, otherwise the silicate is apt to coat the fibres with a thin film when it comes into contact with the cold water in which the rinsing is performed. Should this occur, dyeing or bleaching of the wool afterwards will be impeded, and the wool rendered more harsh than when properly cleared.
In using soap for scouring purposes, in conjunction with an alkali, soda crystals is the best form if a carbonated alkali is used. A small quantity of powdered double-refined caustic soda, however, can he substituted with advantage in most processes ; as compared with soda crystals, not exceeding .6—i part of the quantity of soda ash usually employed. It is absolutely necessary that the caustic soda should be free from iron, and that it should be moderately used.
Wool washing is performed by very different methods in different countries. In sonae, clear running streams are utilized ; in others, mill-streams for turning water-wheels, either before or after passing the latter. In other cases, tanks, tubs, or any vessel capable of holding water, are made to do duty for this purpose. A common way, and that perhaps most generally in vogue, is
to scour wool in a round tub provided with a false bottom of either wood or galvanized wire. This bottom is usually placed about 9-12 in. from the true bottom, so as to form a cavity for the recep tion of the sand, dirt, and other matter that the washing releases. The perforations of the wooden bottom or the spaces between the wires are so arranged that, whilst permitting the sediment to pass freely through, the wool is prevented from going at the same time. This bottom is supported upon vertical strips of wood, and is furnished with handles to facilitate lifting it out of tho tub when required, in order to cleanse the bottom. The tub is generally about 5 ft. deep and 4-5 ft. diam. The water is heated by means of steam, delivered by a pipe going dowu the inside of the tub to about 3 in. below the false bottom, and which is furnished with a tap to turn off the steam when a proper temperature has been attained. On the top, and projecting to the outer side so as to form a slope, is affixed a frame having vertical sides about 6 in. high, across which narrow strips of wood may be nailed, or a sheet of galvanized wire extended, to form a strainer or " scray; " upon this the wool is placed to drain after being lifted from the wash, and previously to rinsing in clear water. " Squeezers," or a pair of pressing-rollers usually intervene between the " scray " and the "rinsing-box," but not always. The latter vessel is mostly an oblong box about 5 ft. deep, having also a perforated copper bottom, the holes of which are about ylw in. diam., and as numerous as the strength of the sheet of copper will permit. A copious supply of clean water is required for this vessel, in which, having received its contents, the wool from the scray is immersed and agitated, or passed backwards and forwards by means of a wooden fork, until thoroughly cleansed flom the " scour " or suds of the previous bath, and the grease and suint that it has liberated.
The process is to carefully prepare the scouring bath, caution being observed to get it to the proper tetnperature, for ascertaining which a thermometer should be used. The wool is then placed in the bath in such quantity (but not more than that) as will allow it to be freely agitated, so that every fibre may be fully exposed to the action of the bath. The agitation must be per formed in such a manner as not to render the wool stringy, but to keep the mass light and open. The same procedure must be followed and the same care displayed in the rinsing process. If the operation has been properly performed, the wool will leave it in a soft and open condition. Tepid water is always best for the rinsing process, helping considerably to attain the desired ends. By this method, 500-1000 lb. can he washed per diem in one tub.