MODEKN HIGH FAKMING. 79 



This acid runs through the coke, and without chemical action, 

 absorbs the peroxide of nitrogen and carries it downwards, allowing 

 any other gases to pass on to the flue whence they escape into 

 the air. 



The concentrated nitro-sulphuric acid is weakened during its on- 

 ward course by the introduction of newly made acid from the 

 chambers, and in this state passes into the " Glover's towers " and 

 meets upon its entry the vapors proceeding from the kiln at a 

 temperature of about 700 Fahrenheit. 



The immediate effect resulting from this encounter is the 

 following : 



The sudden contact with such intense heat, at once concentrates 

 the acid to a density of 150 Twaddle, with a great evolution of 

 steam. 



The peroxide of nitrogen is seized upon with avidity by the sul- 

 phurous acid vapors and carried with the steam into the leaden 

 chambers. 



The concentrated acid falls into a reservoir below, whence it is 

 returned by the forcing pump to the Gay-Lussac towers to serve 

 over again. 



It will be seen that if this process be thoroughly carried out, not 

 only must there be a vast economy of nitre, but all the necessary 

 strong acid for the Gay-Lussac towers is produced without the 

 slightest expenditure of fuel for its concentration. 



The cost of building leaden chambers being very considerable, 

 it is only natural that many attempts should have been made to con- 

 struct them from cheaper materials ; we have therefore witnessed 

 many trials of earthenware, stone, slate, glass and gutta percha, all 

 of which have failed, owing to the rapid manner in which the acid 

 has destroyed them. 



It is estimated that there are now consumed in this country 

 about 450 tons of pyrites every day, and that the total yearly pro- 

 duction of sulphuric acid is about 600,000 tons, of which about 350,000 

 are made from sulphur. 



