14 BULLETIN 283, U. S. DEPARTMENT OF AGRICULTURE. 
The amount of lead required per cubic foot of chamber space is 
considerably greater for a long spiral tube as herein suggested than 
for a cylindrical chamber in which the height and diameter are more 
nearly equal, but the great reduction in the chamber space required 
to produce sulphuric acid in the spiral should make it possible to 
build a plant with considerably less lead than is required in an ordi- 
nary chamber system. Moreover, the facts that the new type of 
plant requires no other device to accelerate the reactions and occu- 
pies much less ground space than the present type of factory, and 
therefore would not need large buildings, should decrease the initial 
cost of construction. 
The cooling of the lead spiral would be accomplished largely by 
the air, but if necessary in hot weather streams of water could be 
played upon its upper portion. The water thus warmed by the heat 
of the reaction of the upper part of the spiral would tend to raise the 
temperature of the lower portion of the spiral where the reactions are © 
not so vigorous. The immense amount of cooling surface contained 
in such a spiral, together with the constant movement of the acting 
gases, should also prevent excessive corrosion of the lead walls. 
While it is not fair, and hardly practicable, to predict how efficient 
a plant built along the lines of the apparatus just described would 
prove, all the indications are that such a scheme, worked on a fac- 
tory scale, would be economically successful. 
In the following tables the author has attempted to classify all the 
American patents on the manufacture of sulphuric acid, both by the 
contact and chamber processes. While these classifications are by 
no means drawn along sharp and distinct lines, still they should be 
of considerable assistance in enabling one to pick out the particular 
phase of acid manufacture which interests him most. 
In tabulating and abstracting these patents it is probable that 
numerous important points have been omitted, but in many cases 
this was unavoidable because of the limited space available in tables 
of this character. It is thought, however, that the information given 
will enable those interested in the subject to judge fairly well whether 
or not any particular patent is of sufficient value to him to warrant 
further investigation. 
Note.—Application has been made for a patent covering the process here 
described; if patent is allowed, it will be donated to the people of the United States. 
" “= | 
