How you make battery acid?

Answer 1

"Battery Acid" nearly always refers to Sulfuric Acid.

Most sulfuric acid is made either by way of the Contact Process or (in much smaller quantities) the Wet Sulfuric Acid process.

In the Contact Process sulfur is first burned burned to produce sulfur dioxide. The sulfur dioxide is then oxidized to sulfur trioxide using oxygen in the presence of a vanadium(V) oxide catalyst. The sulfur trioxide is absorbed into 97-98% sulfuric acid to form oleum (also known as fuming sulfuric acid). The oleum is then diluted with water to form concentrated sulfuric acid. Dissolving the sulfur trioxide into sulfuric acid and then diluting to GET sulfuric acid sounds strange but directly dissolving the sulfur trioxide into liquid water is so exothermic that it creates boils the water and creates an extremely corrosive aerosol that is difficult to collect rather than a liquid.

In the Wet Sulfuric Acid process, sulfur contained in a fuel or hydrogen sulfide contained in the fuel is burned with the fuel creating sulfur dioxide gas. As with the Contact Process, the sulfur dioxide is reacted with oxygen over vanadium(V) oxide catalyst to produce sulfur trioxide. The next couple of steps differ from the contact process. The sulfur trioxide is hydrated with water in the gas phase to form sulfuric acid gas. This gas is then condensed to form highly concentrated sulfuric acid. One of the benefits of this is that clearing the sulfur from the exhaust gases of the burning fuel reduces air pollution while simultaneously producing a product that can be sold to offset the cost of the air pollution control measures.