In order more fully to expose the gas to the tic• tion of the lime cream, a variation from fig. S has been effected, and is used in some of the gas-light ing establishments in London and elsewhere. Fig. 5, a a a a is a flat cylindrical vessel, having tubes c and d for the entrance and exit of the gas; 6, a bent tube communicating with the vessel a, and through which the lime cream is introduced ; e, a pipe and valve to draw off the same when requisite; if; an inner cylindrical vessel, having a broad flanch or plate, g g, attached ; h h, a vertical axle, working through a stuffing box, and carrying an agitator near its lower end. Lime-cream is introduced to the level shown ; the gas, on being forced in, fills the interior cylinderff, and escapes along the under side of the broad flanch g g, and is there greatly exposed to the action of the liquid, and which action is increased by the motion of the agitator. After passing the flanch g, the gas escapes into the upper part of the outer cylinder, and is conveyed away by the pipe d. In order to render the purification more effectual, two or three of these vessels are connected together, so that the gas passes through the whole of them ; and by discharging the liquid from one at a time, the irregular action, which would otherwise be ex perienced, is in some measure done away.
In fig. 6 is shown a different construction of pu rifier; a a a a, a close vessel, and containing an in ternal one b b, open at the bottom, and furnished with a number of notches along each of its sides; the pipe c, which brings in the gas, communicates with the inner vessel, the discharging pipe, d, with the outer one. Lime-cream is admitted from a pro per vessel, e, through the pipe f, until the notches, above mentioned, are covered ; g g, an axle passing through air-tight collars at one end of the inner and outer vessels, and furnished with a handle or winch to turn it round by ; this axle carries a number of short arms, or levers, corresponding to the notches of the inner vessel, each of which passes through two of them during every revolution of the axle the use of these arms is partly to agitate the lime cream, and partly to keep the notches clear from the incrustation of the lime. This contrivance forms a part of one of Mr Clegg's patent inventions, the other parts of which, as they relate to a complex apparatus for discharging the lime after using, are here omitted. The lime-cream may be taken off by a pipe similar to e, fig. 5, attached to the lower part of the vessel.
From the principle on which all these purifiers are constructed, it is obvious, that where only one is used, the process must be carried on with extreme irregularity; for if when each charge of lime-cream is first admitted, a proper degree of purification is effected, the same cannot continue with any degree of uniformity, but must gradually become less per fect till the lime is discharged ; and though this de feet may be in some measure remedied by using two or more purifiers, even then the action cannot be very uniform. Fig. 7 represents a purifying appa ratus, which, though it obviates the want of regula rity above mentioned, has been found somewhat troublesome to keep clean, from the difficulty of getting into the inside to remove the lime which ad heres internally : a a a a, is a close vessel with pipes, communicating at c and d, to take the gas in and out ; ff, a cistern surmounting the vessel a, and this is surrounded by another cistern g g, somewhat deep er than the former ; h h are partitions, or shelves, placed nearly horizontal within the vessel a, and fit ting to its internal cavity, except at one edge, as re presented ; lime being put into the external cistern, and water admitted by means of a cock, or pipe, the mixture overflows into the inner cistern, and, passing through the tube 6, traverses gradually to the hot torn of the machine, forming thin sheets of liquid as it descends from shelf to shelf, and through which the gas has to make its way in passing upwards.
The lime-cream is thus constantly supplied from the outer cistern, and as constantly running out by the pipe e, after it has performed its office. The effect which such a purifier can produce, must, un less made of very large dimensions, be somewhat li mited, and without a construction to which mecha nical force can be effectually applied, the process will be accomplished but in an imperfect manner.
A purifier where the lime can be regularly ad mitted and discharged, is mentioned in a late publica tion (Peckston on Gas-Lights, p. 408) as of vety re cent invention; its particular construction, however, is not manifest from the description there given.
In fig. 8 is represented the vertical section of a purifying machine, which, while it has the property of regularity of action, also admits of a very effec tual application of its powers : a a, b b, is a cylindri. cal vessel placed an oblique direction, and having a number of internal partitions, 14 h, standing up nearly to its axis, in which is placed a spindle, k k, carrying a number of arms, 1 1; these act as agita tors, and also are capable of scooping up portions of the lime-cream, which is represented as contained in the different cells formed by the partitions h h ; a a,ff, a vessel forming an addition to the upper end of the cylinder and closed on all sides except where it joins to the cylinder, and where the exit gas pipe, d, and the lime admitting tube, e, are in serted ; it is surmounted with a cistern, g g. Through the aperture e, a vertical axis descends, giving mo tion to the inclined one k, by means of two conical wheels : m, an inverted cup, and n, an agitator, both fixed upon the vertical spindle. The lower end of the cylinder is united to a vessel p p, closed like the upper one, except where it joins at b b, and having an admission pipe, c, for the gas, and a pipe, q, to take off the impure lime-cream. The cistern, g, is supplied with water by means of a pipe, or other wise, and the axle being kept in motion, lime is put into the cistern; g, and there mixed and stirred about by means of the agitator, n ; from this it descends into the cylindrical vessel, and is collected in the , uppermost cell, from which situation it is scooped up and dashed about by means of the arms, 1, and a part of it constantly dropping down past the upper most partition, is then received into the next cell, and the same process is regularly going forward the whole length of the cylinder, the lime-cream finally escaping at the pipe, q, in an impure state. The gas, in its ascent upwards in this machine, has to pass among all the arms upon the inclined axis, and to encounter perpetual spray, and showers of the lime cream, which are constantly renewed, the supply be ing regulated by the quantity of lime and water in troduced into the upper cistern.