I use this method also to make CuO for one of the chemicals used for
combustion analysis of organic compounds. What might interest others is how I dispose of the SO3. Using a fume hood is difficult when the fumes also violate the local clean air standards. A (costly) permit would be required. So instead I dispose of the SO3 by absorbing into concentrated H2SO4, obtaining "oleum", then add water to keep the solution at 100%. To MAKE the original concentrated H2SO4 I burned sulfur to obtain SO2, absorbed the SO2 in water to obtain H2SO3, then bubbled ozonized air through the solution to oxidize it to H2SO4. An ozonizer making 4% ozone in air is not a difficult project and can be built using an automotive coil and ignition control module with a pulse circuit to fire the control module. Running at 5000 hertz the coil produces a corona discharge in air between aluminum plates separated by 1/4 inch, and insulated from each other with bathtub caulking compound around the edges. The process apparatus all runs under negative pressure using a water aspirator to pull the SO2 fumes from the burning sulfur, and the ozone from the corona discharge, into a single flask of water with both entrant tubes under the surface. I use aquarium bubble blocks on the ends of the tubes to produce fine bubbles into the water. Ozone is a powerful oxidizer, and will oxidize the H2SO3 to H2SO4. The apparatus performs without problems, and can be used to make any volume of concentrated sulfuric acid without complications. If distilled water is used in the synthesis the acid will be laboratory grade. The sulfur starting material was purchased at a garden supply, and the automotive parts at an auto store. The pulse circuit is a simple relaxation oscillator. I realize if one is not familiar with electricity or electronics making ozone the way described might be difficult, but the point to understand is that ozone, O3, will oxidize H2SO3, made by dissolving SO2 into water, into H2SO4. The apparatus as described performs without problems, and enables making concentrated sulfuric acid without any of the contamination issues other methods posted in this forum thread have.
I understand the difficulty young people have doing chemical experiments at home. When I was younger I had a few mishaps due to lack of being able to obtain proper equipment and chemicals, but fortunately survived the poison gases and small explosions long enough to learn safety first.
I suggest unless one is completely familiar with safety issues do not try this at home without supervision. If possible always best to purchase laboratory grade chemicals to begin with. I had the ozone apparatus left over from a different project used to make concentrated nitric acid, HNO3, so used it in the combustion analysis project.
