8 BULLETIN 283, U. S. DEPARTMENT OF AGRICULTURE. 
horizontally. Each layer of plates is supported at some distance 
above the other by bearers in such a way that every plate is inde- 
pendent of the others. The plates are so constructed and placed 
that the holes in those of one layer do not come directly above the 
holes in the next layer below. 
Dilute sulphuric acid is allowed to trickle down the tower, splash- 
ing from one layer of plates to another and meeting the hot-chamber 
gases as they wind upward through the tower. The film of dilute 
acid over the plates presents an immense cooling surface to the 
gases and at the same time furnishes the water necessary for the 
decomposition of the nitrosulphuric acid. The formation of this 
latter compound is, according to Lunge, a necessary link in the 
chamber process. | 
Gilchrist’s pipe-column spaten! consists of lead towers (8 or 4° 
feet across and 15 feet high) having corrugated lead tubes, open at 
both ends, running through them Pomona Tike a steam boiler. 
The sides of the towers are boxed in with boards so as to form an air 
shaft which terminates in a flue at the top. 
The chamber gases, together with water vapor, enter the pipe 
columns at the sides near the bottom and work their way upward 
through the towers. Contact with the air-cooled corrugated tubes 
condenses the sulphuric acid, which then drips in showers from one 
series of pipes to another and frees the oxides of nitrogen, restoring 
them to the system. The gases issue from the top of the towers 
and enter the next chamber, from which they are drawn into another 
series of pipe columns, and so on through the system till their oxida- 
tion is practically complete. 
While some of the methods just described are designed to cut 
down the amount of chamber space required, none of them, with 
the exception of Falding’s process, reduces the initial cost of erecting 
an acid plant; for, while less lead may be employed in constructing 
the chambers, the expense of the cooling and mixing towers more 
than offsets the saving in chamber material. 
Another objection to most of the accelerating devices discussed 
above is that in order to mix the gases thoroughly they must be 
drawn or forced through small openings or made to pursue a mean- 
dering course by means of baffles or some acid-proof packing material 
in the towers. Under such conditions dust or impurities may clog 
the apparatus, choking off the draft and making it necessary to 
clean out the tower or chamber before operations can be resumed, 
Moreover, the collapse or disarrangement of the packmg material 
within the tower may cause even more serious trouble. 
Nearly all modifications of the chamber process complicate some- 
what the running of an acid plant, and should therefore be constantly 
under the supervision of a competent chemical engineer. 
1 Jour. Soc. Chem, In2., 18, 459-462 (1899). 
