42 



system of lead pipes leading from a divided tank, fed by a 

 reaction wheel distributor, through the upper lead plate of the 

 tower. 



The chambers, through which the mixed gases pass in sac- 

 cession, are each about 132 ft. long, 20 ft. 6 in. wide, and 

 16 ft. 6 in. high. 



They are formed of thin sheet lead supported on a stout 

 wooden framework ; the sheets of metal are united at the edges 

 by autogenous soldering, i.e., the overlapping edges of adjoining- 

 sheets are fused together by careful heating with the hydrogen- 

 air blowpipe. 



The chambers are each supplied with windows in the sides 

 and man-holes and gauging recesses at each end. Steam enters 

 each chamber by pipes from the boiler as shown in the model. 



The steam, sulphur dioxide, nitrogen oxides, and oxygen (from 

 excess of air admitted through the burners) react in the chambers 

 and produce sulphuric acid. 



The residual gases from the third chamber of the series pass 

 through the long leaden pipe into the square Gay-Lussac tower 

 (7 ft. by 7 ft., height 51 ft.). 



Here any nitrogen oxides remaining are absorbed by strong- 

 acid from the Glover tower distributed by similar apparatus to 

 that described above. 



The waste gases from the top of the Gay-Lussac tower pass 

 thence to the chimney, which also serves the boiler seen on the 

 left. 



Between the boiler and the burners are placed the pumping 

 engine and reservoirs for distributing the chamber acid, 

 Glover acid, and nitrous vitriol contained in the tanks beneath 

 the chambers. 



143. Specimens illustrating the manufacture of soda. 



1876. Exhibited by Sullivan fy Co. 



No. 1. Common salt. From the salt works of North wich, 

 Cheshire ; used in the manufacture of salt cake or sulphate of 

 soda. 



No. 2. Salt cake, or commercial sulphate of soda, containing 

 about 98 per cent, of real sulphate ; made by decomposing common 

 salt with vitriol in an iron pan heated externally. When about 

 three-fourths of the decomposition has been effected, the charge 

 is pushed upon the bed of a " muffle " furnace, maintained at a 

 bright red heat till the decomposition is completed. The gaseous 

 hydrochloric acid evolved during the process is conducted away 

 through pipes or flues to condensing towers, where, being absorbed 

 by water, it assumes the form of liquid acid, 



No. 3. Limestone, or native carbonate of lime from Derby- 

 shire ; used in combination with slack or small coal for converting 

 salt cake or sulphate of soda into carbonate of soda. 



