What links soap, paper, heart disease and murder? Sodium. In the latest in our series of programmes looking at the world economy from the perspective of the elements of the periodic table, Justin Rowlatt returns to the chlor-alkali plant of Industrial Chemicals Ltd to discover from chemistry professor Andrea Sella how sodium is ripped from common table salt, and how it provides the grist for the global chemicals industry. One of its biggest uses is in the Kraft process, the most common way of pulping wood to make paper. Malcolm Brabant travels to a remote corner of Sweden, where the Munksjo paper company first put the technique into practice over a century ago. But sodium does not only digest wood - we hear the first-hand account of serial killer Leonarda Cianciulli on how she used caustic soda to dispose of her victims. Plus, Justin explores sodium's controversial role in our diet, and in regulating blood pressure. We pit Morton Satin, the self-styled 'Salt Guru' and spokesman for the US salt industry, against Graham MacGregor, a professor of cardiovascular medicine leading the drive to cut the salt content in food.