In the _lead chamber process_ the furnace gases pass through flues in which the flue dust and a portion of the arsenious acid are deposited into the Glover tower at a temperature of about 300° C., and from there into the lead chambers where oxidation of the sulphur dioxide into sulphuric acid takes place, in the presence of sufficient water, by transference of the oxygen of the air through the intervention of the oxides of nitrogen. The gases containing oxides of nitrogen, &c., which are drawn out of the lead chambers, have the nitrous fumes absorbed in the Gay-Lussac tower (of which there are one or two in series), by passage through sulphuric acid which is made to trickle down the tower. The sulphuric acid so obtained, rich in oxides of nitrogen, and the chamber acid are led to the Glover tower for the purpose of denitration and concentration, so that all the sulphuric acid leaves the Glover as Glover acid of about 136-144° Tw. Losses in nitrous fumes are best made up by addition of nitric acid at the Glover or introduction into the first chamber. The deficiency is also frequently made good from nitre-pots. The lead chambers (fig. 2) are usually constructed entirely—sides, roof, and floor—of lead sheets, which are joined together by means of a hydrogen blowpipe. The sheets forming the roof and walls are supported, independent of the bottom, on a framework of wood. The capacity varies from 35,000 to 80,000 cubic feet. The floor forms a flat collecting surface for the chamber acid which lutes the chamber from the outer air. The necessary water is introduced into the chamber as steam or fine water spray. The Glover and Gay-Lussac towers are lead towers. The Glover is lined with acid-proof bricks and filled with acid-proof packing to increase the amount of contact. The Gay-Lussac is filled with coke over which the concentrated sulphuric acid referred to above flows, forming, after absorption of the nitrous fumes, nitro-sulphuric acid. [Illustration: FIG. 2A.—Lead Chamber System—Section through X X (_after Ost_) FIG. 2B.—Lead Chamber System—Plan A Pyrites Burner B Glover Tower C Draft Regulator D, D´ Lead Chambers E Air Shaft F, F,´ F,´´ F´´´ Acid Reservoirs G Acid Egg H Cooler J Gay-Lussac Tower]