10 



BULLETIN" 283, U. S. DEPARTMENT OF AGRICULTURE. 



tivity in the apparatus. Moreover, the constant impinging of the 

 gases on the walls of the spiral flue, which can be cooled either by 

 air or water, makes it practicable to maintain the gases at a temper- 

 ature most favorable for the efficient yield of sulphuric acid.. 



In the following laboratory experiments, however, the sulphur 

 dioxide (S0 2 ) used was not directly derived from burning pyrites or 

 sulphur, so it was necessary to heat the system artificially to at- 

 tain a temperature as high as that obtained under factory conditions. 



The sulphur dioxide was obtained from a small cylinder of the 

 liquefied gas, which was weighed both before and after each experi- 

 ment, and the S0 2 used thus determined. The oxides of nitrogen 

 (chiefly N 2 3 and N 2 4 ) were produced by the action of dilute nitric 

 acid on copper, and the rate at which they were used was roughly 



/l/ranc/Stea, 





Fig. 1. — Apparatus used in proposed new method for manufacture of sulphuric acid. 



determined by allowing the gases to bubble through dilute sulphuric 

 acid saturated with these gases. A mixture of air and water vapor 

 was obtained by drawing air through a flask of water heated to the 

 boiling point. 



The apparatus employed (fig. 1) consisted, first, of a large test 

 tube (A), having a capacity of 200 c.c, and containing a little water 

 heated to boiling. The oxides 'of nitrogen, sulphur dioxide, air, and 

 water vapor were led to the bottom of this vessel by separate tubes 

 and given a preliminary mixing. From the test tube the gases were 

 drawn into the lead or glass spiral (B), which was boated to about 

 90° C. in ordor to facilitate the reactions. In winding downward 

 through this spiral the warm gases were thoroughly mixed, with the 

 result that most of tho sulphuric acid produced in the system was 

 formed in this coil. The residual gases were then passed through 



