1 18 Dr. Dana on the Manufacture of Sulphuric Acid, 



retained by the water. Hence in starting a new lead-house, or 

 whenever fresh water is used, there is withdrawn at once a 

 large portion of that element which is essential to the acidifi- 

 cation of the sulphurous gas; it is withdrawn either as nitric 

 acid, or as deutoxide of azote. As the water of the lead-house 

 becomes slightly acidulated by sulphuric acid, part of the ni- 

 trous acid is also retained by it (7) ; it undergoes no further 

 decomposition. As the chamber absorbs sulphurous acid gas, 

 this acts on the deutoxk\e of azote, and protoxide* is the result ; 

 it acts on the nitric acid, the usual decompositions occur, and 

 we have the nitric and nitrous acids and deutoxide of azote pro- 

 duced. As the acidulated waters of the lead-house increase in 

 density, less sulphurous acid is absorbed, and the nitrous acid is 

 retained, undergoing no further change. Hence we easily ac- 

 count for the fact, that little sulphuric acid can be obtained by 

 using fresh water in the chambers. The nitrous acid vapour 

 is withdrawn, being changed into nitric acid, deutoxide and 

 protoxide of azote, and being itself partly retained as such. 



The white solid, I suppose, is formed in every part of a lead- 

 house, and falls like hail into the water or acid on the floor. 

 Cold condenses the moisture of the lead-house ; and I have 

 generally observed the formation of this substance to take 

 place either at the escape valve, or on the sides of the house, 

 when the thermometer falls to 40°. When the thermometer 

 sinks to 0, its production is very rapid; and in long-continued 

 very cold weather it concretes on the walls of the lead-house 

 from 4 to 1 inch in thickness. The effervescence is not ob- 

 served at first in the vast body of water in the lead-house, 

 because, as the nitrous acid is decomposed, the deutoxide is 

 retained; as the density of the liquid increases, effervescence 

 begins. It is very perceptible at the sp. gr. 1*29; and at 1*33 

 it is in its greatest vigour. The acidulated water is then filled 

 with nitrous acid and deutoxide of azote. If it is poured from 

 one vessel into another it foams like beer. It hisses and boils 

 in the lead-house, and the surface of the liquid is covered with 

 froth, and fermentation seems to pervade the whole mass (as 

 in Experiment 8). But the manufacturer of oil of vitriol may 



* I have been led to the belief, from some results in the large way, that 

 such a change may occur. Some say it actually does, and attribute it " to 

 the too violent action of the water." Since I have been in London, I have 

 learned from Dr. Turner's Chemistry, 4th edition, that Gaultier de Clau- 

 bry has made experiments on this white solid, and observed that a little 

 nitrogen gas is always disengaged when the solid is produced: it is doubt- 

 less owing to the cause above stated. It deserves further investigation, 

 and its production is probably owing to peculiar circumstances, and is the 

 cause of the great variation of the products sometimes noticed by the ma- 

 nufacturers. 



