wax partially purified by re-crystallization from benzine and pressure is selected. The same is gently heated to its melting point, when about five per cent. of sulphuric acid is gradually added while brisk agitation is sustained. The action of the acid upon the melted wax is even more violent than upon the paraffine oil, and some arrangement is necessary to carry off the abundant vapors of sulphurous acid which are disengaged. This can be accomplished by covering the agitator with a hood, which will conduct these suffocating vapors into a chimneystack. The same arrangements for keeping the contents of the vessel warm, which were needed in treating heavy oil, are required here. After half an hour's treatment, the heavy acid is drawn off at the bottom, a hot solution of soda-lye (five per cent. of a solution 120 B.) is added. The agitator is again put in motion, and the melted wax thoroughly treated, the sodawashing is withdrawn from the bottom of the tank, which is kept warm until it has completely settled, and the contents are bright and clear. The wax is run into large flat cakes, which when cool have a fine pearly lustre and are nearly colorless. Decolorization through this agency appears to offer the most perfect results. This process, however, is only employed upon paraffine which has been partially whitened either by repeated crystallization or by acid process, or by a combination of both processes. To accomplish this upon a manufacturing scale commensurate with the demand, a number of plans have been suggested. One of the most complete of these is Ramdohr's filtering apparatus, which is constructed to filter about 2,500 lbs. per day. The apparatus has the following peculiarities in its arrangement: 1. The mixing of the paraffine with bone black does not take place by the hand or through a mechanical stirring device, but through a warm current of air previously blown into the apparatus. 2. The paraffine treated with boneblack flows of itself into the filter paper placed in a glass funnel, and, after the influx has once been regulated, the operation proceeds without demanding special attention on the part of the workman. Even if, at times, less permeable paper should be accidentally placed in the filter, this, with some attention on the part of the workman, cannot easily cause an overflow of the paraffine, since the greater or less permeability of the paper is easily observable during the first half hour and the feed-cocks can be regulated accordingly by the workman. 3. The whole apparatus is heated by waste-steam. 4. The mixing and filtering apparatus occupy little space. The mixing apparatus A, Fig. 114, consists of a wrought iron chest, with cast iron lid secured by screws, and made tight with iron cement In this lid are three openings for the reception of FIG. 114. FILTERING APPARATUS—HORIZONTAL SECTION. A, Mixing Apparatus; B, Filtering Apparatus. three cast iron mixing kettles. These kettles are fastened to the lid of the steam-chest by a few screws in order to prevent any displacement which might cause the outflow tubes to become leaky. The connections of the kettles with the steam-chest are rendered steam-tight in the simplest manner by a band of rubber, placed beneath the rim of each kettle. About 3 inches above the deepest part of the bottom is cast a tube about 1 inch in diameter, of such a length that its forward end provided with screw threads projects about 1 inch through the side of the steam-chest. At this point the plate of the steam-chest, which is about 0.079 inch thick, is strengthened on the inside by a cast iron disk 0.59 inch thick, which is secured by means of sunken rivets, and provided with four holes for the reception of screw-bolts. From the outside a flange is screwed upon the end of the above-mentioned tube and solidly packed against the side of the steam-chest with chopped hemp intimately mixed with red lead cement, so that the four screw-holes in this flange exactly correspond to those of the inner disk. When the flange has been firmly secured, the end of the kettle, which is turned or planed level, should project about 0.079 to 0.118 inch above the flange. Four screw-bolts, each furnished in the centre with a six-cornered swelling, are now placed in the four holes provided for them and firmly and steam-tight drawn against the outer flange; each of the above-mentioned tubes is furnished with a cock for the passage of steam. A tight connection is effected here as well as on the pipe distributing the paraffine, and everywhere where finished paraffine has to pass, by several layers of soft, unsized paper, with the avoidance of all kinds of cement. It is advisable to provide the surfaces turned upon the lathe with fine circular grooves. In the lower portion of the steam-chest are placed six drawn copper pipes with thin sides, packed in the manner of the tubes of locomotive boilers, and connected by cast-iron joints outside the steamchest so that they form a coil, heated by steam in which the air for mixing the bone-black and paraffine is heated. The outlet of this coil is connected with a pipe running obliquely over the mixing kettle. From this pipe narrower blast pipes furnished with cocks run towards the centre of the kettle and extend nearly to the bottom. The principal pipe for the heated air, is, of course, to be protected from cooling by a jacket. The filtering apparatus B, Fig, 115, consists of two chests, one inserted partially into the other with a common front side. Hence the latter is not touched by the steam, this arrangement having been made to prevent having a stronglyheated surface on the side where the workman is mostly occupied, and to render access to the actual filtering apparatus as convenient as possible. If here were a double wall filled with steam it would absolutely have to be protected from too strong a radiation of heat by a brick wall in front of it, which would render attendance of the filtering apparatus more difficult. Besides, the arrangement chosen secures a cheaper and simpler construction, larger surfaces being made tight with difficulty Fig. 115. A B FILTERING APPARATUS-VERTICAL SECTION. against the action of melted and hot paraffine; and as any loss of paraffine should be avoided, the inner filtering chest serving for its reception is cast in one piece. The attachment of the steam jacket is simple and plainly shown in the illustration. The bottom of the cast iron filtering chest inclines towards the front and at the same time towards the centre from both sides. At the lowest point is an exit tube with stop-cock for the discharge of the filtered paraffine. The interior of the filtering chest is provided with an edge projecting about 2 inches, which on the rear wall and at the same time on both sides serves for the formation of a steam-space. Upon this edge rest 8 wrought-iron funnel supports, each of which is capable of holding two glass funnels; thus there are 16 filters arranged in two rows always in operation. The funnels are made of glass, this material securing better control over the absolutely necessary cleanliness than if they were made of tin. In the centre of the filtering chest, running along its entire length and about 2 to 21⁄2 inches above the glass funnels, is the paraffine distributing pipe. It is of wrought iron 11⁄2 inches in diameter, closed on both ends, connected by three tubes with the corresponding stop-cocks of the mixing kettles, and furnished on each side. with 8 cast iron cocks 0.15 inch in diameter. These small cocks are screwed in, small pieces of wrought iron being for this purpose fastened with hard solder in the proper places on the distributing pipe. The mouths of the small cocks do not lie perpendicularly over the centres of the filters, but are about in the middle of one of their side walls, to prefent perforation of the filter-points by droppings. The paper used for filtering is a thin, but tolerably firm, unsized printing paper. A sheet 1.57x1.57 inches gives one filter, and suffices for the passage of about 88 lbs. of paraffine; one filter is thus in use for 12 hours. But little paraffine remains in the filter and can be recovered by steam. It being well known that the fresher bone-black is, the more energetically it acts, it is recommended that large paraffine factories prepare their own bone-black. In a business of less extext, powdered bone-black has to be procured from factories. Ramdohr recommends to reduce freshly-prepared, granulated and dust-free bone-black to a fine powder in a simple pulverizing drum, shown in Fig. 116. It is of cast-iron, 291⁄2 inches long, 191⁄2 inches in diameter, and revolves with two wroughtiron arbors riveted to the front-plates in metallic bearings. |