Chemistry Question #1524

Amanda, a 16 year old female from Calgary asks on July 23, 2003,

I am interested in finding more information on how to detect the presence of arsenic in the foods we eat everyday. I know there are expensive lab methods for doing that, but is there a simpler or cheaper way of detecting arsenic.

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The answer

Barry Shell answered on July 23, 2003

In 1832 the English chemist James Marsh came up with a simple test for arsenic that essentially put an end to its rather common use as a poison. With the advent of the Marsh Test people could test their food and drink to determine if they were being poisoned. The food sample is mixed with zinc and sulphuric acid. Any arsenic present causes the production of arsine gas and hydrogen. When the gas impinges on a cold surface, a mirror-like deposit of arsenic forms.

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