# How did chemists in the 18th century learn that magnesium gain mass when it's burned?

Crucial to disprove the phlogiston hypothesis was the observation that magnesium gains mass when burns.

But how was this observation made in the 18th century? Is there any way this property of magnesium would be obvious to a layman today?

• Presumably by weighing magnesium before and after it was burnt? It's not that difficult to do.
– bon
Mar 9 '16 at 14:17
• Per Wikipedia "The metal itself was first produced by Sir Humphry Davy in England in 1808." So burning the metal would have taken place in the early 19th century. en.wikipedia.org/wiki/Magnesium#History "Phlogiston remained the dominant theory until the 1780s when Antoine-Laurent Lavoisier showed that combustion requires a gas that has mass (oxygen) and could be measured by means of weighing closed vessels." en.wikipedia.org/wiki/Phlogiston_theory#Challenge_and_demise So by the time metallic magnesium was isolated the phlogiston hypothesis was dead.
– MaxW
Mar 10 '16 at 4:28