text: Joseph Black was a chemist who took interest in the pneumatic field after studying under William Cullen. He was first interested in the topic of magnesia alba, or magnesium carbonate (MgCO), and limestone, or calcium carbonate (CaCO), and wrote a dissertation called "De humore acido a cibis orto, et magnesia alba" on the properties of both. His experiments on magnesium carbonate led him to discover that fixed air, or carbon dioxide (CO), was being given off during reactions with various chemicals, including breathing. Despite him never using the pneumatic trough or other instrumentation invented to collect and analyze the airs, his inferences led to more research into fixed air instead of common air, with the trough actually being used.
  Gaseous ammonia was first isolated by Joseph Black in 1756 by reacting sal ammoniac (ammonium chloride) with calcined magnesia (magnesium oxide). It was isolated again by Peter Woulfe in 1767, by Carl Wilhelm Scheele in 1770