Sulphuric Acid-manufacture. 27 





Acid produced, cal- 





culated to percentage. 



Exp. IV. . 



. 66 per cent. 



Exp. V. . . 



. . 93 „ 



a certain amount of nitric acid still remaining untouched. In 

 both cases, however, the result, in appearance, was a complete 

 combination. Still, on examination, a large amount of nitric 

 acid was found in solution in water in No. 1 (Exp. IV) . 



Exp. VI. Equal volumes of steam and mixed gases were then 

 tried, and the result on examination gave — 



Acid produced, cal- 

 culated to percentage. 



Exp. VI. . . . 74 per cent. 



From these experiments, then, I considered myself justified 

 in adopting the theory of the leavening nature of the action 

 taking place. 



It is also evident that the volume of steam introduced should 

 be less than the combined volumes of the two gases. But let 

 us take another case. Suppose the temperature of the vessel in 

 which the experiment is to take place be raised to 100° C, or 

 kept in boiling water, the results are found to differ in every 

 case. 



Exp. VII., VIII., IX. Taking the same volumes as above, 

 I find the different yields of acid to be thus : — 



Acid produced, calcu- 

 Exp. lated to percentage. Exp. above. 



VII 86*7 corresponding to IV. 



VIII. . . . 24-5 „ „ V. 



IX. . . . . 80-2 „ „ VI. 



Here, then, is quite another phase opened up to us : tempera- 

 ture has a great deal to do with the action taking place ; and, 

 as the result of many experiments, I find that its influence may 

 be embodied in the general rule, that " The higher the tempera- 

 ture the more steam required." 



The foregoing results thus show the action occurring when 

 nitric acid gas is brought into contact with sulphurous acid gas, 

 both with and without the presence of steam. The next question 

 to be solved is, In what part of the vessel does most action 

 take place ? 



Most persons who have attended chemical lectures are familiar 

 with the method employed to illustrate the formation of sul- 

 phuric acid. The mixed gases of sulphurous and nitric acids 



