Discovery of Hydrogen
Cavendish was the first to recognize "inflammable air" (hydrogen) as a
distinct substance, and "fixed air" (carbon dioxide). In 1766,
Cavendish presented "Three papers containing experiments on Factitious
Air" to the Royal Society. By combining strong acids with metals, he
was able to produce hydrogen gas. Cavendish illustrates how he was able
to
determine the specific gravity of these gases by referencing them to
common air. He continued to investigate their properties on how well
they were absorbed by various liquids. From this he concluded that
common air containing one part in nine by volume of fixed air was no
longer able to support combustion.
Cavendish's Apparatus for Making
and Collecting Hydrogen
Properties of Water & Nitric Acid
Later in 1784 & 1785 Cavendish published a paper on "Experiments
with Air." In this research, Cavendish discovered that water (H2O)
acted
as
compound,
while
also
discovering
the
compound
nitric
acid (HNO3).
Cavendish's
paper
started
on
an
experiment in which John Warltire
applied electricity to a mixture of common air and hydrogen, concluding
that there was a reduction of volume and a deposit of moisture. When
Cavendish burnt about two parts of hydrogen with five parts common air,
he noticed they were condensed to a dew which lined the inside of the
container. Cavendish considered the dew to be pure water. In another
experiment, he applied an electric spark to a mixture of hydrogen and
oxygen and found that the resulting water contained nitric acid. He
supported this conclusion, by recognizing the nitrogen present as an
impurity in the oxygen. In his 1785 paper he concluded that when
electric sparks are passed through common air there is a shrinkage of
volume, which explains the nitrogen bonding with the oxygen to form
nitric acid.
