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The law was introduced to keep undesirable and unhealthy additives out of beer. The brewers at the time added contaminants such as soot, sawdust, and even poisonous henbane in an effort to preserve the beer.

• 500 Years of Reinheitsgebot,
  ChemistryViews.org 2016.
  German beer purity law was adopted in 1516 and limited ingredients to barley, hops, and water

• Chemistry Advent Calendar 2016,
  ChemViews Mag. 2016.
  DOI: 10.1002/chemv.201600101