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RETORTS.

carbonic acid, which is again taken up by the lime in the purifying process; the nitrogen, with thecarbon of the tar, forming cyanogen, whilst the hydrogen unites with another portion of carbon andforms carburetted hydrogen.

“ It will thus be seen that about 50 per cent, of the products of the distillation, which are con-densed in the hydraulic main and carried off with the gas to the condenser in the ordinary retorts,are by my patent retorts productive of 35 per cent, more gas, and having it entirely in your power inthe course of two hours to change the quantity and quality of the gas with the least possible trouble,which is an advantage that cannot be accomplished by the ordinary process in less than five timesthat period.”

Notwithstanding the important advantages which Mr. Brunton stated were derived fromthese retorts, they were, on his retirement from his position as engineer of the West Brom-w’ich Gas-works, discontinued, and they have not been tried elsewhere. One great drawbackfrom the increased yield of gas stated to have been produced, was the unsaleable conditionof the residual products; for as the coke fell into the tar, it was unfit for general fuel.

CLAY RETORTS.

The relative merits of iron and clay retorts has been for a long time a subject of conten-tion, but it may now be considered as established that clay retorts, whether made in onepiece or in sections, or of several pieces, jointed together so as to be perfectly tight, aremore economical than iron retorts.

When first set to work, clay retorts are porous, and the loss of gas is often very conside-rable. It has been suggested to charge them repeatedly with breeze and tar, to glaze theminternally, before using them for distillation ; and this may probably be advisable whenpracticable. After a week’s working, however, their pores are filled up with the carbona-ceous matter formed by the decomposition of the richest portions of the gas, which matter,as in iron retorts, accumulates afterwards, and forms in time a thick coating, especiallyunder careless management. Several attempts have been made to render earthenware retortsless porous and less liable to accumulate carbon, by glazing them, and a patent to effectthat object was obtained in 1854, by Mr. F. J. Evans. But most of these efforts to renderclay retorts smooth and impervious have failed, in consequence of the glaze itself fluxing ata lower heat than the retorts are usually subjected to. Mr. Cliff, of Wortley, near Leeds,has, he conceives, overcome that difficulty by working into the body of the retort a silicateof alumina which only fluxes at the highest working heats, and it then fixes itself on thesurface.

The deposition of carbon is greater in clay than in iron retorts, because they are workedat a higher heat, and the gas should be removed from them by an exhauster as fast as it ismade, to prevent the deposit from becoming excessive. It is also advisable, especially whenan exhauster is not used, to allow them to remain uncharged, with their lids off, for a dayor two every six days, that the admission of atmospheric air may break down the deposit.

Clay retorts, unless encircled by frequent thicknesses of brickwork, would crack, andprobably break down. In most gas-works, the fire-brick partitions or bonds are built com-