From Trevor Campbell, Berrima, New South Wales, Australia
I enjoyed Shannon Fischer's article about the price of a life (22 October, p 28). But I'm not sure in what form you buy carbon and sodium. I get carbon for A$100 a tonne in the form of coal, and sodium for A$500 a tonne when bought as salt for my pool.
The editor writes:
• These prices – supplied by the UK's Royal Society of Chemistry – were for elements in their purest available form. Some refining might be required.
