# Where does the sulfuric acid, used in Contact Process for manufacturing sulfuric acid, come from?

If Contact process is used for manufacturing sulfuric acid, then where does the sulfuric acid used in the process itself come from?

Hot sulfur trioxide passes through the heat exchanger and is dissolved in concentrated $\ce{H2SO4}$ in the absorption tower to form oleum:

$\ce{H2SO4(l) + SO3(g) → H2S2O7(l)}$

Hence, where does this sulfuric acid come from?

• Welcome to Chemistry.SE! Don't overdo the problem :) This is not a philosophical hen-or-egg dilemma. If you would have to build the plant, you would have to buy the a lot of parts from other suppliers, isn't it? Couldn't the same be true for the conc. sulfuric acid for the first runs? – Klaus-Dieter Warzecha Mar 8 '16 at 8:34
• maybe this will help- chemistry.stackexchange.com/questions/34138/… – Nilay Ghosh Mar 8 '16 at 12:57

• I thought $\ce{H2SO4}$ was used, because the reaction of $\ce{SO3}$ with $\ce{H2O}$ was too difficult to control. If that's not right it would be great if you could add some links and more details to your answer. – Curt F. Mar 9 '16 at 3:54
• Welcome to Chemistry.SE! Take the tour to get familiar with this site. Mathematical expressions and equations can be formatted using $\LaTeX$ syntax. For more information in general have a look at the help center. I think you are confusing the Contact process with the wet sulfuric acid process. – Martin - マーチン Mar 9 '16 at 4:24