Even more important, from an econoroical point of view, are the services rendered by this sub atance in the recovery of valuable ingredients from what would otherwise be waste products. Thus, in the manufacture of fatty acids, brown compact deposits are produced ; these, mixed with sawdust, and treated with bisulplaide, yield up to 20 per cent. of the acids, which would in another case be lost. Again, the dirty mass of metal dust, grease, &c., from car and waggon axles, is first treated with warm dilute sulphuric acid, then with bisulphide, and then washed and dried, which isolates the grease in a saponified state. The cotton waste used in machinery is easily freed from grease, leaving both in a fit condition for re-use. The residues from beeswax manufacture, which formerly were only worth about Si. per ton as manure, are now made to yield an excellent yellow wax by treat ment with bisulphide. It is used for recovering oil from the refuse of cocoa manufacture. Bones treated with it at 40° (104° F.) yield 12 per cent. of grease, and are still fit for making animal eharcoal. The cleanings of wool-cards, when acted upon by bisulphide, give about 30 per cent. of fatty substances, ueeful for the production of soap.
In Fig. 473, is seen a simple and inexpensive apparatus, in which bisulphide of carbon is used for dissolving out and extracting fatty matters from various waste substances ; its con,truction and arrangement are such that the escape of the bisulphide is rendered practically impossible, and when the solvent has been separated, by distillation or otherwise, it can be used over again. The liquid bisulphide is placed in a strong closed tank, a, situated above and connecting with the vessel b, where the greasy substance to he operated upon is placed, and held at a short distance off the bottom, by a perforated false bottom, b*. When the tank a is charged with bisulphide, and the close vessel b is filled with the greasy substance to be treated, the opening b' in the fixed cover must be secured, and it will only be necessary to open the tap c' on the pipe c, connecting the two vessels a and b, and the tap c2 on the cover of b (for the escape of the atmospheric air), when this latter vessel will become filled with the liquid bisulphide. It is found desirable to leave the two bodies in contact for about twenty minutes, so as to ensure the perfect extraction of the grease. A further quantity of the bisulphide is then run from a into b under the false bottom. The greasy bisulphide is then dis charged at the top through the pipe d, provided with a tap d*, into another close vessel e, whose tap e' is first opened to allow the air to escape. When this vessel is nearly filled with the greasy bisulphide, the taps e' and d* are closed, and the tap d* opened. Steam is then admitted from the steam pipe f' , by opening the tap f2, into the closed coil of pipe f*, with which the interior of the vessel e is fitted. The heat of this steam will volatilize the bisulphide, and when this operation has
been continued for a sufficient time, it may be desirable to finish the distilling by means of the coil of perforated pipe f, eituated near the bottom of the vessel e, into which steam is admitted by the tap 1-8, and allowed to bubble up through the greasy liquid. By this means, the whole of the vola tile bisulphide is driven off from the fixed greasy matters, and the vapour, being conducted by the pipe d' to a condenser g above, is then reduced to a liquid state. It can then be run from the worm g' back again iuto the tank a for re-use. The greasy matters remaining at the bottom of the evapo rating vessel e are then drawn off through a suitable pipe h for use. Taps, as at i, are for the purpose of drawing off and testing the liquid at various stages. All the vessels a, b, e, are provided with vertical glass gauges j, for the purpose of indicating the height of the liquid. Taps a' and e' allow of the escape of air, with which the vessels become filled during the operations, and which, if not liberated, would materially interfere with the efficient working of the apparatus. These several escape taps may be in connection with pipes, carried up through the building, for the purpose of leading away any noxioua vapours. The vessels b and e are also provided with tin nnotneters k, and pressure gauges /. In b, also, is a manhole b', through which it is charged, and another manhole V at the lower part, through which the fibrous matters, when the grease has been extracted from them, are removed from the vessel. Similar manholet are likewise provided in e.
When the fibrous substances in b are freed from grease, the remaining bisulphide is driven off, by allowing steam from the steana pipe f to be conducted by the branch steam-pipe 7n into the upper part of b, us shown. If sufficient prebaure be used, the steam will force all the liquid bisul phide through the fibrous mass in the vessel, and up a vertical pipe n4, the tap 777.5 being opened for that purpose, and the two-way tap 778 being turned so as to direct the liquid bisulphide by the horizontal pipe n3 to the still g', or, if desired, to the tank a through the two-way tap 773, By this mode of working, the steaming may be finished at one operation, with great economy of time and material. In some cases, however, it will he found convenient to use a pump n, which will draw the liquid through the pipe n1 from the space below the perforated plate b* (the tap 776 being opened and the taps n5, n7, closed), and will furce it up the pipe n2 into the tank a above. The steam admitted to the upper part of the vessel b through the pipe m will percolate through the fibrous mass, and drive the liquid bisulphide into the space below the perforated plate b*.