The Dyeing of Woollen Fabrics | Page 9

these in a continuous stream, entering in at the delivery end of the second soaper and passing out at the entering end of the first soaper. The wool as it first enters the machine comes into contact with rather dirty soap liquor, but this suffices to rid it of a good deal of loose dirt; as it passes along the machine it comes in contact with cleaner and fresher soap liquor, which gradually takes all grease and dirt out of it, and, finally, when it passes out it comes in contact with fresh liquor, which removes out the last traces of dirt and grease. In the same way it passes through the washers, being treated at the last with clean water. By this plan the scouring is better done, while there is some saving of soap liquor and wash water, for of these rather less is required than by the usual system. These are matters of consideration for wool scourers. The wool-washing liquors after using should be stored in tanks to be treated for recovery of the grease which they contain.
The temperature of the scouring liquors should be about 100��?F., certainly not more than 120��?F., high temperatures are very liable to bring about felting, while tending to increase the harshness of the wool, particularly when soda is the agent used. By this method all the wool fat, suint, etc., of the wool find their way into the soap liquors. These were formerly thrown away, but they are generally treated with acid and the fat of the soap and wool recovered, under the name of wool grease or Yorkshire grease. (Vide G. H. Hurst, (p. 023) "Yorkshire Grease," Jour. Soc. Chem. Ind., February, 1889.)
The wool fat consists largely of a peculiar fat-like body known as cholesterine. This, however, is unsaponifiable, and cannot be made into soap; at the same time when it gets into, as it does, the recovered wool grease it spoils the latter for soap-making purposes.
Cholesterine has some properties which make it valuable for other purposes; it is a stable body not prone to decomposition, it is capable of absorbing a large quantity of water, and it is on these accounts useful for medicinal purposes in the production of ointments, and it might be useful in candle-making. When it gets into recovered grease it cannot be extracted from it in an economical manner. The wool suint consists largely of the potash soaps of oleic and stearic acids. These two fatty acids find their way into the recovered wool grease but the potash salts are lost, while they would be valuable for various purposes if they could be recovered.
Another form of wool-washing machine has a frame carrying a number of forks arranged transversely to the machine. The forks are by suitable gearing given a motion which consists of the following cycle of movements. The forks are driven forwards in the trough of the machine, carrying the wool along with them, they are then lifted out, carried back, and again allowed to drop into the machine, when they are ready to go forward again. Thus the forks continually push the wool from one end of the machine to the other.
It is a common plan to have three machines placed end to end, so that the wool passes from one to the other; in a set of this kind the first machine should have a capacity of 1,500 gallons or thereabouts, the second 1,000 gallons, and the third 750 gallons.
#Wool Scouring by Solvents.#--Of late years processes have been (p. 024) invented for the scouring of wool, either raw or spun by means of solvents, like carbon bisulphide, benzol, petroleum spirit, etc. Such processes are in a sense rather more scientific than the alkali processes, for whereas in the latter the grease, etc., of the wool and the oil used in batching it are practically lost for further use, and therefore wasted, being thrown away very often, although they may be partially recovered from the used scouring liquors, in the solvent processes the grease and oil may be recovered for future use for some purpose or other.
The great objection to these processes is the danger that attends their use, owing to the inflammable character of the solvents. Several other objections may be raised, some of which are mechanical, and due to the want of proper machinery for carrying out the processes. There are many ways in which solvents may be applied, some are the subject of patents. It is not possible to describe the details of all these, but two of the most recent will be mentioned.
In Singer's process, which was described in detail by Mr. Watson Smith some time ago before the Society of Dyers and Colourists, carbon bisulphide is used. The raw wool is placed between two endless bands of wire,