PURIFICATION.

20 L

contain three sieves, which would amount to about three square yards of surface to each tonof coal carbonized. The lid of the purifier is made of thin boiler-plate, and has a rim allround, which dips into an annular cell, filled with water to make a hydraulic joint. Thecover is lifted by handles when it is required to be removed.

Another plan of making purifiers, practised in Francefor the purpose of economizing iron, is to constructbrick vessels, and line them with cement in the mannerthat the tanks of gas-holders are often formed. Fig. 03shows a section of one of the side walls of these brickpurifiers. The brickwork, which is faced with cementthree-quarters of an inch thick, diminishes towards thesurface by steps which form projections for the supportof the sieves. The upper part of these ledges is co-vered with iron. The top of the wall is also capped withiron, the two vertical parts, a and b, forming the water-lute for the cover. These purifier tanks are easily con-structed, and for large works, where iron is dear, theyare found economical and effective. —

The following details of a dry-lime purifier, as given in the specification of the GreatCentral Gas Company’s Works at Bow Common, presented to the Parliamentary Committee,may be taken as a good illustration of the construction of such purifiers for works of thatmagnitude.

Bottom Plates .—Sixteen in number, so that when joined together they will be 12 feet square, 4thick, with flange all round, 2f inches broad, clear of the plate, all firmly bolted together, 5-J- boltssix inches apart, centre to centre, with strengthening brackets, one between every two holes. One ofthe bottom-plates to have a hole in it 14 inches in diameter, with a cover-plate standing 9 incheshigh, and 24 inches in diameter, made fast over the hole by six 15-inch bolts, with a collar threeinches from each end, the one to rest upon the bottom, the other to support the cover-plate, and madefast to each end of the cover-plate and bottom-plate by A-nuts screwed on each end of the bolt. Onebottom-plate to have a hole 12 inches in diameter, with ears, lid, and cross-bar, the same as a retortmouth-piece, for the purpose of opening from beneath as a discharge-hole.

Side Plates to bolt on the bottom-plates and stand, 4 feet 2 inches deep on the inside of the puri-fier : sixteen plates to form the sides, having a water-lute cast on 8 inches broad, 1 foot 6 inches deepinside all round these plates, to be f thick, with flanges 2 4 inches broad clear of the plate; the wholeto have fillets between every two holes, being six inches apart centre to centre. Two side plates ineach purifier to have a flange outlet, 14 inches diameter, cast on, standing out 9 inches ; the flange tobe 2| inches clear of the pipes ; the bottom of the pipe on the inside to be on a level with the bottomof the purifier. On the inside of this plate are to be cast two flanges, standing the whole height ofthe plate, 2£ inches broad, and 14 inches between them; these flanges to have 4-boles in them, every9 inches in height, for the purpose of receiving bolts to fasten them on the outlet-box.

Outlet box to be 4 feet deep by 12 inches square, with a 2^-flange at the bottom, for bolting it tothe bottom of the purifier; the bolts to be Aths, 6 inches apart centre to centre.

Snuggs to be cast upon the side plates at given heights, for the purpose of resting a tee-iron into,upon which the trays will rest, projecting 4 inches, and 6 inches deep; twenty bars of 4-inch tee-iron,

2 D

Fig. 63.