But during the eighteenth century the balance was introduced as an instrument of chemical research.

Now, if the phlogistic hypothesis be true, it would follow that a metal should be the heavier, its oxide the lighter body, for the former contains something--phlogiston--that has been added to the latter.

But, on weighing a portion of any metal, and also the oxide producible from it, the latter proves to be the heavier, and here the phlogistic hypothesis fails.

Still further, on continuing the investigation, it may be shown that the oxide or calx, as it used to be called, has become heavier by combining with one of the ingredients of the air.
To Lavoisier is usually attributed this test experiment; but the fact that the weight of a metal increases by calcination was established by earlier European experimenters, and, indeed, was well known to the Arabian chemists.

Lavoisier, however, was the first to recognize its great importance.