The cooling apparatus consists of about eighteen cylindrical vessels of sheet-iron or zinc, com municating with each other. Each of these is about 264 in. diameter, bottomless, a.nd with slotted sides, whicb plunge into a larger saucer containing water a little deeper than the opening,s, so as to form a water-lute, permitting the passage of condensed liquids while closing the exit against gases or vapours. The false bottom of these vessels has two openings, which receive the bent siphon tubes forming the connection between the jars themselves, and between them and the cylinders. The sides of these vesseLs lise about 4 in. higher than the false bottom, forming a saucer, which is filled with cold water to assist in the c,00ling. Each group of four vessels 113 sup plied with a cylindrical cavity at it lower level, to admit of a receptacle being placed in position for siphoning off the liquid bisulphide as it accumulates. The gases escaping frorn the four cylinders circulate, by rncans of tubes, into the eighteen coolers, and from the last of these, are carried directly into the chimney of the works, or better, are first made to traverse " scrubbers" of pulverized lime in layers, for the purpose of retaining the hydrosulphuric acid gas, which would otherwise create a nuisance to the neighbourhood.
The mode of operation is as follows :—The four cylinders dre filled with charcoal and properly closed ; a fire is then made, and by it, the cylinders, and the charcoal contained in them, are rendered of a clear red heat. Then, but not before, the introduction of the sulphur commences, it having been previously wrapped up in little cartridges. Two cartridges, forming a charge, are introduced into the tube conducting to the false bottom of each cylinder ; the upper end of the tube is then closed with a bung of clay enveloped in a covering of linen. The charges of sulphur are made every three minutes ; at the end of seven or eight hours, the charcoal, partially consumed by the sulphur vapour, must be renewed. The introduction of sulphur is suspended, and each cylinder in turn is filled with charcoal, by means of an iron funnel placed in the opening. This is then closed, and the firing is commenced and continued for about one and three-quarter hours, to reach the temperature required. The charge of charcoal is thus renewed three times in twenty four hours. The liquefied sulphide may be drawn off at any time without suspending operations ; but advantage should be taken of each monthly stoppage to remove the sulphur which has formed crystals in the first four coolers.
Sometimes the cylinders are made of the same material as glass-house pots. These are glazed inside, by a mixture composed of 20 parts soda and 12 parts boracic acid. They last about six months, with care.
At Swoszowice, in Galicia, the apparatus used for making bisulphide of carbon consists of perpendicular retorts walled into a furnace, provided at top with a cover pierced by two openings. Through one of the openings, a pipe, open at both ends, descends almost to the bottom of the retort, while ihe second opening communicates with a cooler. The retort, which is lined with fire lumps, inside and out, is of cast iron, about 11 in. thick, and of an elliptical form, measuring about 39 in. x 16 in. and about 6 ft. 6 in. high, Cast on the retort at the bottom, is an arm, provided with flanges, to which a tube is riveted, for the purpose of charging in the sulphur at the proper time, without any serious loss. A similar projection on the top of the retort is surmounted by another cast-iron tube, closed with a bung. From this, proceeds an inclined tube, for the passage of the vapours, fixed to an intermediate vessel of sheet iron, whose lower part, being supported by screw rods, may be removed and replaced at will. At the end of the inclined tube, is au opening, closed by a stopper, which may be made to intercept communication between the retort and a reaeiver. The cooler or condenser is composed of three intercommunicating cylindrical zinc vessels. The topmost carries an escape pipe. The condensed bisulpbide is drawn off at pleasure by a tap. The three cylindrical vessels, as well as the tubes connecting them, are immersed in a water bath, capable of constantly receiving fresh supplies of water. The operations are conducted practically in the same way as with the apparatus previously described. The hisulploide formed always con tains a certain quantity of sulphur, which has escaped the action of the carbon, and this sulphur, being less volatile than the bisulphide, condenses with a part of the solvent, and crystallizes in the receiver, which is specially intended to catch it, and from which it can be easily removed when the distillation is interrupted.
The charges of sulphur are introduced during ten hours, from morning till evening ; the fire is fed during the night, in order to achieve the volatilization of the sulphur, and to leave the excess of charcoal bare towards the morning, when the communication with the cooler may be interrupted. The retort is now refine I with charcoal, the receiver is emptied of the sulphur which has collected, and is then replaced ; and, when the temperature has again reached a bright red, the sulphur is added little by little at the lateral opening, The product of hisulphide, per twenty-four hours, will be about 5 cwt., from the conversion of 477 lb. sull,hur (605 lb. total charged, of which 77 lb. recovered), and 90 lb. charcoal (out of a total of 242 lb. used).