Manufacture.—The apparatus employed in the manufacture of aerated water consists essentially of four parts : namely, the generator, a vessel in which the carbonic acid gas is generated by the action of an acid upon a carbonate ; the purifier, another vessel partially filled with water, through which the gas is made to pass for the purpose of removing impurities carried over ; the gas-holder, a reservoir in which the gas is expanded and stored ; the mixing machine, consisting of a cylinder containing an agitator, into which the water and gas are pumped, and stirred up to cause absorption of the latter by the former ; and the bottling machine, by means of which the aerated liquid may be transferred into bottles or siphons, and securely closed without allowing any of the contained gas to escape during the operation. In all large manufactories of aerated water, other auxiliary machines are used to cleanse the bottles returned from the consumer to be refilled. It now remains to describe in detail each of these several parts of the apparatus.
, The Generator.—This vessel, which is shown partly in section in Fig. 293, consists of a vertical cylinder, made either of lead, wood, or copper. The body is well and substantially supported, under its top flange, on a cast-iron ring attached to the framework, and also at the bottom part on four iron brackets, which are secured by bolts to the legs. The bottom part is joined to the body by a circle of bolts and nuts ; and these may be easily removed to give access to the agitator, which is the only part liable to derangement. The frictional or working part of the spindle which carries the fans, is a stout silver tube, worked in the stuffing boxes, so that it is not affected by the acid. The top of the cylinder is covered with a lid, which i, fastened down and made to fit tightly by means of asbestos jointing. At one side, and close to the top, is a curved leaden pipe, connected with an acid box, for supplying the acid. In the interior of the vessel, and at the bottom, is a metal agitator, or fan, worked by a handle, which is turned by hand from the outside. At the bottom of the vessel is an aperture through which the waste product, arc withdrawn when neces sary ; this aperture is securely closed by means of a tightly-Stting lid, working on a hinge. The carbonate, which is generally made into a semi-fluid state, in order to facilitate the action of tho acid, is introduced through the opening at the top of the vessel ; whiting, or any other cheap and perfectly pure form of carbonate of lime, may be used. With pure materials, 50 parts of whiting will neutralize 49 parts of oil of vitriol, liberating 22 parts of carbonic acid gas, and forming 77 parts of hydrated sulphate of lime ; from these figures may be calculated approximately the amount of both carbonate and vitriol required to produce a given quantity of gas. The vitriol is introduced
by means of the leaden pipe connected with the top of the vessel. The evolution of the gas may be regulated by the speed with which the agitator is made to revolve. Sometimes the vitriol chamber is connected by a swing joint, and, if fixed above, when working under pressure, has an equalizing pipe. The outlet is closed by a lever or screw, which is locked to prevent leakage, or automatically closed by the pressure of the gas. In some places, it is enclosed in the body of the generator, and manipulated from the outside ; in other places, the plan is reversed, and the acid solution is placed in the body of the generator, the carbonate, which is held on plates with revolving discs, being allowed to fall in as desired ; some carbonates, however, are apt to cake, and instead of a steady delivery, fall in in lumps; this arrangement is shown in Fig. 284. In other places, again, it is customary to suspend the carbonate above the acid, and to dip it in when required, but care must be taken to see that there is no waste by the formation of an insoluble crust. In many cases, the apparatus is self-acting, the carbonate being lowered into the acid as the pressure is lessened in the generator. In those systems in which the gas is retained under pressure, the gauge is usually fixed on the purifier, and the generator is provided with a safety-cap in which a disc is ruptured when the pressure becomes excessive. Some safety valves have an alarm whistle which can be set to blow off at various pressures.
The generator shown in Fig. 293 is made usually in two sizes, holding respectively 36 gallons and 26 gallons. The former kind is 3 ft. 6 in. long and 1 ft. 11 in. in diameter ; the latter is 2 ft. 2 in. long attd 1 ft. 6 in. in diameter.
The whole is placed on a strong iron stand, nt a con venient height for a pail or gutter to be placed directly under neath it.
As soon as the action of the acid has ceased, and the required quantity of the gas has been evolved, the aperture at the bottom of the generator is opened, and the waste sulphate of limo allowed to fall out into vessels placed beneath ; the generator must then be thoroughly cleansed by pouring iu water at the top and running it out from below. The sulphate of lime has hitherto been rejected as useless, and is often a source of much annoyance to manufacturers; there is, however, a possibility of its being utilized for the preparation of plaster of Paris, or as a manure.