New Methods of Rendering.—D'Arcet's Apparatus. This consists in conducting the rising vapours, consisting chiefly of hydrogen and carbon, through channels under the grate of the rendering pan, and using them as fuel. The pan is also covered with a strong iron plate, the front third of which can be lifted by means of a knuckle whenever it is necessary for stirring, filling, or emptying the kettle. D'Arcet was the first who employed chemicals for the purpose of neutralizing or destroying the noisome effluvia arising from the pans.

they acquire a darkish tint, and hence | be introduced with decided advantage are said to be browning. They are for keeping up the necessary motion, to then pressed, and the fat thus obtained prevent adhesions to the sides or bottom possesses somewhat of the brown colour of the vessel, and consequent scorching. of the cracklings, but not so much as Wilson's Process.-The chief feature to render it unfit for use as soap stock; of this process is to steam the rough it may, consequently, be mixed with suet for ten or fifteen hours in a perthat which has spontaneously separated fectly tight tank, under a pressure of while heating. 50 lbs. to the square inch, or more when lard is being rendered. A higher pressure is not profitable, for, though expediting the process, it produces an inferior quality of fat. No chemicals are used. The apparatus consists of an upright cylindrical vessel, made of strong boiler - plates, tightly riveted together. Its diameter is about two and a half times less than its height, and its capacity amounts to 1200 to 1500 gallons. It has a false bottom or diaphragm; below this a pipe enters, which is connected with an ordinary steam-boiler. There is a manhole at the top, through which the vessel is filled with the rough suet or lard to within about 2 ft. of the top. By a safety-valve the pressure can be regulated. There are also some try-cocks, by which the state of the contents can be examined; if the quantity of condensed steam in the tank be too great, it will be indicated by the ejection of the fatty contents at the top one. There is a regulating cock at the bottom for drawing off the condensed steam, as well as cocks in the side of the digester, by which the fatty materials can be drawn off. Through a hole made in the diaphragm, which can be shut and opened at will, the residual matters can be let out.

To Neutralize Effluvia from Tallow Pans.-Take 50 parts, by weight, of diluted oil of vitriol, put into the kettle, then 1000 parts, in weight, of chopped fat are gradually added in four equal portions; and lastly, 150 parts of water, to which 5 parts, in weight, of sulphuric acid of 66° B. have been previously added. The whole is then heated. Under the influence of the acid, which partly destroys, partly solves the membranes, the rendering of even greater amounts of fat is effected in 1 to 2 hours; 2 hours, however, are seldom required. The inventor's proposition of using acids was made when pans were heated by the direct action of the fire; but now steam is more generally employed. This, however, does not prevent the gases arising from the pans being thrown into the furnace and thereby aiding combustion. It is obvious that in the boiler of d'Arcet, stirring, as well as filling or emptying the contents of the pan cannot be accomplished so readily as in an open pan; nor can these processes be performed without opening the covers. To obviate this, a contrivance similar to that used by distillers in the mashing process could

Stein's Process.-A mixture of slacked lime and small pieces of fresh-burnt charcoal is prepared, and spread upon a coarse cloth stretched over a hoop, of 2 in. in depth, and the circumference corresponding with the size of the pan. During the process of rendering, it is securely adjusted by suitable catches above the pan. The rising vapours from the latter, in necessarily passing this chemico-mechanical arrangement, are said to be entirely absorbed, so that thus all cause of complaint against tallow factories as health-destroying nuisances would be effectually removed.

or, when not condensed, for escaping | left in the tank is again boiled with through X. F is a worm, which, successive portions of fresh water, for fastened to the stays G, Fig. 60, lies the better separation of which this on the bottom of the vessel. Through compound is left for 24 hours in a L L steam is introduced from a boiler, warm liquid state before being drawn and through M passes back into the off into the coolers. same boiler. HH is a small pipe entering into the vessel A, through which steam also passes into the vessel, mainly for the purpose of keeping the melted fat in agitation. J is a tube, having a sieve at its upper end, and a movable crank below, by which it is fastened to the faucet Y. If the vessel is being emptied, the tube J is gradually let down until its upper part, with the sieve, reaches the bottom. The fat is then passed through J and Y, and through a fine sieve outside the vessel, which acts as a filter. In this, 1000 lbs. are first introduced with 80 lbs. of water; 2 lbs. of sulphuric acid of 66°, previously mixed with 16 lbs. of water, are then added. Steam is next turned on, which, as described, passes from the generator through the worm, and must have a tension of three atmospheres, or a temperature of 255° F. In the vessel, however, a tension of 1 atmosphere is sufficient, and when this is reached, the safety-valve is no longer charged with weights. The vapours formed in the vessel are conducted through X into the hearth of the steam-boiler furnace, so that all the noxious odours which, by the action of the sulphuric acid, are diminished, but not destroyed, are thus conveyed from the working rooms.

Evrard's Process.-The apparatus used very much resembles that of Wilson. The process is based on the application of caustic ley, in the proportion of 25 gallons, each containing tolo. of solid caustic soda, to every 250 to 350 lbs. of rough tallow. It is the object of the application of the iey to dissolve the membranous parts, so that no preliminary mincing is necessary. For boiling the fat, steam is employed. As the alkaline ley is heavier than water, it will, after the boiling is completed, more easily subside. It is then drawn off, and the fat

Clarifying Tallow.-By mere melting and straining we do not obtain a fat entirely free from admixture of fine, undissolved substances. For separating these substances, it must be clarified, by remelting it in water, either on free fire or by steam. Generally, no more water than 5 per cent. is taken, and stirred well with the fat till the mixture becomes emulsive. The whole is then allowed to rest, without further heating, till the water has separated, when the fat may be drawn off, or dipped off. Sometimes, to conceal the yellowish tint, a very little blue colour is added, consisting of indigo rubbed finely with some oil, of which a few drops are sufficient for large quantities of tallow. The process of clarifying is occasionally repeated. At the line of demarcation between the water and fat, a grey slimy substance is often perceptible, and the liquid itself is turbid. Instead of pure water, some tallowmelters take brine or solutions of alum, saltpetre, chloride of ammonium, or other salts. These agents have no chemical action upon the fats, but simply induce a more rapid settling of the impurities and water, principally when strong agitation is used.

Ozokerit. This mineral is used in the production of illuminating oils of a

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high firing point, and of solid hydro- Stakes or posts are driven into the ground, carbons, more particularly adapted to and 2 ft. from the ground bag-clothes the manufacture of candles of a high are stretched over them, or table-like melting point; the inventors distil the frames are made from strips of cloth raw material by heat, thereby obtaining stretched over the frames in the same an oily distillate, the solid and liquid manner as a sacking-bottom is stretched constituent parts of which are then over a bedstead, care being taken to separated by pressure. The pressed fasten the ends of the cords to the posts solid material is purified by mixing and sufficiently firm to prevent them loosenstirring with sulphuric acid when ing by the wind. This done, the wax melted. After standing for some time, ribbons are spread upon the cloth in a in order to effect the complete separa- | thin layer. It is important that the place tion from the acid, the supernatant selected for this process should be so melted material is carefully decanted arranged that the sun's rays may have off, and thoroughly washed with hot full play upon the exposed wax, but at water. The water having been re- the same time protected from the prevamoved, the material is repeatedly fil- lent winds. The ribboned wax is daily tered through animal charcoal until the turned over, in order that fresh porrequisite degree of whiteness is attained. tions of it may be affected by the sun; Hardening of Tallow by Capaccioni's and should it not be sufficiently moistProcess. In 1000 parts of melted ened by the dew or rain, soft water is tallow, 7 parts of sugar lead, previously poured over it. When it is not dissolved in water, are stirred, during gradually becoming whiter, but still which process the mass must be con- continues yellow upon the fracture, it is stantly agitated. After a few minutes remelted, ribboned, and again bleached. the heat is diminished, and 15 parts of The continuance of the bleaching propowdered incense, with one part of cess varies, depending upon the weather; turpentine added, under constant stir- often one exposure to the sun and air ring of the mixture. It is then left suffices to bleach it, and no remelting is warm for several hours, or until the requisite. Four weeks are generally insoluble substances of the incense sufficient. The bleached wax is finally settle to the bottom. The hardening is fused into cakes or square blocks, preproduced by the sugar of lead, yielding viously moistening the moulds. As fast a material similar to the stearic acid, as the wax congeals, the cakes are while the incense is improving its thrown into a tub of clean, cold water, odour; it is said that by this treatment and then taken out and spread upon a the guttering of the candles is entirely pack-thread sieve for draining. Eventprevented. ually, they are dried and packed in boxes for the market, the loss being from 2 to 8 per cent.

Cassgrand's Process for Bleaching Wax.-First melt the wax with steam, which pass together through long pipes, so that a large surface becomes exposed to the steam. After traversing the pipes, it is received into a pan with a double bottom, heated by steam; it therein treated by water, left quiet for some time until its impurities are settled. It is then forced anew through the pipe together with the steam, washed a second time, and, if necessary, this process is repeated a third time. Probably water is absorbed by the wax, thus rendering it more easily bleached.

Arrangement of a Bleaching-house.

Wicks.-Wicks are twisted or plaited; the former, loosely twisted, present the appearance of a spiral similar to the separate strands of a rope; the latter, now generally adopted for most kinds of candles, is made by interlacing and crossing the strands of the wicks n the same manner as plaiting straw of bonnets. Common wicks are simply an aggregation of several loosely-twisted threads forming one general cord of many fibres. This is effected by the ball winding machine, a very simple apparatus. For cutting wicks, Sykes's apparatus is in

FIG. 62.

FIG. 63.

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general use, especially for tallow-candle | the side. It consists of two wooden wicks, which must be soaked with tallow frames, which are made tapering from at one end. Fig. 62 represents a vertical, the middle towards the end. On each and Fig. 63 a horizontal view of it. side there is a feather of steel attached, for the purpose of holding the frames, with a space between them, which may be diminished by sliding the feathered clamps e e towards the middle, or increased by drawing them towards the end. Immediately behind the clamp there is a cutting apparatus, consisting of an immovable f' and a movable blade f, with a handle. g is a small vessel filled with liquid fat, which may be kept from solidifying by steam, and a board i lying on the lathe h. The use of the apparatus is as follows;-The ends of the wicks, wound upon the spools c c c, are passed through the frame d, properly tightened by the clamps e e, so that all the wicks are kept firm. The knife f of the cutting apparatus is then lifted out of the way; the frame, with the wicks enclosed, is drawn backwards to the vessel g, and the ends of the wicks dipped in the melted fat; this done, the fat-soaked ends are drawn farther back and placed under the weight I, which holds them firmly while the clamps are loosened on the frame, and this returned to its first-described position and again tightened. The knife is next used, cutting all the wicks off at a stroke, then elevated, and the process repeated till a sufficient number of wicks are cut. The thickness of the wicks varies according to the diameter of the candles and the material of which they are made. The number of the cotton threads requisite to form a wick also varies according to their firmness. The yarn is composed of a slack-twisted cotton thread; No. 16 generally for plaited,

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