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7056THANKS: Aargh, chemistry!

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  • Simon Vollam
    Jul 2, 2001
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      Morning List,

      Thanks for all your helpful comments and suggestions.

      It turns out - as I expected - that the author was referring to the
      mass of a particular gas produced by burning a known amount of
      material (for example, mg of HCN per g of polyurethane foam). This is
      commonly referred to in combustion science as the yield. I agree that
      it is not a yield in the normal chemistry context, i.e. the amount of
      a substance actually produced in a chemical reaction relative to the
      amount predicted theoretically from the reaction stoichiometry. But
      it's a similar concept.

      The author tells me that he wished to stress the fact that it was a
      mass of gas, and not the volume concentration in air. However, I
      wonder whether "vytezek" has a narrower scientific meaning in Czech
      than "yield" does in English. BTW I agree that "amount" is more
      appropriate than "quantity" in this context.

      To answer the mass-vs-weight query, I was always taught that,
      strictly speaking, mass is measured in grammes whereas weight (being
      a force) is measured in Newtons. A man on the moon, for example,
      weighs much less than on earth, but his mass is the same regardless
      of location (relativistic considerations aside).

      On the other hand, strictly speaking one should say "ethanol", not
      "ethyl alcohol", but who cares? Not many chemists do their
      experiments extraterrestrially, and one often sees "weight" used in
      scientific papers as a synonym for mass, especially outside physics.

      Enough, enough. I'm an economist now.

      Thanks again,

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