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. 



