By Ian Darwin on 2017-03-18 14:25On clarity: I've had this discussion with several people, so I'm posting it here: Please don't tell me you "don't work with chemicals" or "don't use chemicals"! If you mean "hazardous substances" or "toxic substances" then for clarity's sake please say so. You cannot live without chemicals. Two in particular: air and water. Air is a mixture of many chemicals in gaseous form. Water is "dihydrogen oxide" or as everybody learns in school H20. These are but two chemicals you can neither work nor live without - there are of course many others. A chemical is, by a rough definition, a substance that can't be decomposed by physical separation (like filtration). Milk, for example, is not a single chemical: you can separate milk into cream and buttermilk using a centrifuge (or a hand-cranked cream separator on a small farm; I used one of those at one point in my youth). But if you centrifuge pure water you will get... drumroll please... water. It's a chemical. So please, don't disparage all "chemicals", any more than you would disparage all people when you mean a particular group, such as criminals, politicians, or whomever.