These powerful chemicals are essential to obtain the minerals that build our world, the fertilisers that feed the planet, and the fuels that propel our vehicles - as presenter Laurence Knight discovers on a trip to the Ineos Grangemouth oil refinery in Scotland. But while most traditional acids are based on the power of hydrogen ions, Prof Andrea Sella of University College London explains that many modern industrial "acids" do not, and come in startlingly unexpected forms such as powders. Many of the most corrosive acids are very tricky to contain, resulting in the occasional nasty accident, as chemical engineer Keith Plumb explains. Also, Justin Rowlatt has a report on acid attacks in southern Asia in which he speaks to campaigner Selina Ahmed of the Acid Survivors Foundation on how Bangladesh has tackled the problem. (Picture: A team working with toxic acids and chemicals secures chemical cargo train tanks crashed near Sofia, Bulgaria; Credit: Cylonphoto/Thinkstock)