What does the quote, "I want arsenic" mean in the short story "A Rose for Emily"?

This quote is a literal statement by Miss Emily to the
pharmacist in her hometown of Jefferson, but it is the implication and the
tone that aresignificant to the story.  Miss Emily has decided to buy poison and we
aren't sure exactly why but can certainly imagine the stoic and determined tone of voice
she uses when she asks for it.  The pharmacist asks her what she wants it for and she
refuses to answer the question; she just makes her demand.  It is a scene where the
reader can easily see the intimidating presence of Miss Emily -- no one wants to
challenge her too much, so the druggist just retreats, wraps up the arsenic, and has
another employee bring it to her.  The narrator then tells us the that the whole town
thought she would kill herself with it, but that doesn't actually happen and she goes on
to live a long life after that event.  What we don't learn until the last section of the
story is that she actually killed Homer Barron with the arsenic and then she kept his
dead body in an upper room of her home.  The reader gets to the end of the story and
says to himself, "so THAT'S what happened with the poison!"  Once the reader has the all
the pieces of the puzzle, the cold and commanding demand for the poison shows a
determination in Miss Emily to do whatever she needs to do to take control of her
situation -- she demands the poison and she kills Homer so that he can't leave her.  It
is a short line, but the whole story hinges on it.