316 LECTURES TO SCIENCE TEACHERS. 



noxious and acrid red fumes into the air, and to enable the 

 manufacturer to use them again, the Gay-Lussac tower is 

 employed. This is built at the end of the third chamber, 

 and is placed in contact with this on the one hand and 

 with the chimney on the other, so that all acid fumes, before 

 they can be discharged into the air by the chimney, must 

 pass through the Gay-Lussac. It consists, like the Glover, 

 of a square tower, fifty feet high, made of strong lead, fixed 

 of course, on to a firm wooden frame, lined for thirty-five 

 feet with glazed fire tiles two inches thick, and filled with 

 hard coke. The exit gases from the third chamber are 

 drawn in at the bottom of this coke column, and escape 

 to the chimney by a flue at the top of the column. At the 

 top of this tower there is a reservoir filled with strong acid, 

 of specific gravity 1*75, obtained by concentrating the 

 chamber acid. By means of an arrangement identical to 

 that in the Glover's tower, a constant stream of this strong 

 acid is allowed to flow down the tower, and thus trickling 

 over the coke, meets the exhaust gases. The strong acid at 

 once absorbs the nitrous fumes, which would otherwise pass 

 up the chimney, and having become thus saturated with 

 nitrous fumes, runs away into a reservoir, whence this 

 nitrated acid is pumped up to the reservoir on the top of the 

 Glover's tower, for use, there, in the way I have already 

 described. The saving in nitre which this procedure enables 

 the manufacturer to make is very large. In works where 

 the Glover and Gay-Lussac towers are not used no less than 

 from twelve to fourteen parts of Chili saltpetre are needed 

 for every hundred parts of sulphur burnt, whereas when 

 these means are employed the percentage of nitre is reduced 

 to below five. Not only is this economy to the manufac- 

 turer, but it is a great benefit to his neighbour, for if 

 properly managed scarcely a trace of either nitrous or 

 sulphurous fumes ought to escape, and I shall be glad to see 

 the day arrive when sulphuric acid works, without exception, 

 are required to adopt these precautions. 



The question naturally suggests itself to our minds as 

 we study this subject, What do we know of the interior 

 working of the chambers 1 What size of chamber is most 

 efficacious 1 ? In what part of the chamber does most of 

 the acid condense 1 What is the temperature of the gases 

 which conduces to the largest yield ] To these and many 



