Woodcut showing saltpetre (potasium nitrate) preparation. Saltpetre is used to make gunpowder and to preserve meat. Illustration from 'Beschreibung aller furnemisten mineralischen Ertzt vnnd Bergtwercks arten' ('Description of the Principle Mineral Ores and Methods of Mining') by Lazarus Ercker (d 1594) published in Frankfurt-am-Main in 1580. In 1554 Ercker was appointed asayer at Dresden and later became a control tester of coins. This book is a mine of information concerning sixteenth century metallurgy and asaying. It can be regarded as the first manual of analytical and metallurgical chemistry.
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