Basics and Discovery of Atmospheric Chemicals - Air Pollution and Global Warming: History, Science, and Solutions - page 13

acid was poured over the metals iron (Fe), zinc (Zn), or
tin (Sn), it gave off a highly flammable vapor. In 1766,
Henry Cavendish, who is more well known for the dis-
covery of molecular hydrogen, also made this determi-
nation and isolated the vapor's properties. Molecular
hydrogen is a well-mixed gas in today's lower atmo-
sphere. It is produced naturally by ocean and soil bac-
teria and anthropogenically by fossil fuel combustion.
It is removed from the air primarily by soil bacteria.

terra lapidia (“strong or vitrifiable earth,” believed to be
common salt), and terra pinguis (“fatty earth,” believed
to be sulfur). He claimed that, during combustion, terra
pinguis was expelled to the air. The principle that every
combustible material releases its “source” of combus-
tion, albeit incorrect, was not new, but it was more
specific than were previous theories.
One of Becher's followers was Georg Ernst Stahl
(1660-1734). In 1702, Stahl published Specimen
Becherianum ,inwhich he restated that every material
contains a special combustible substance that escapes
to the air when the material is burned. Stahl called
the combustible substance, previously named terra
pinguis by Becher, phlogiston after the Greek word
phlogizein ,“tosetonfire.”Stahl believed that phlogis-
ton escaped primarily as either fire or soot ,which he
believed was the purest form of phlogiston. According
to phlogiston theory, the following processes produced
phlogiston:

1.2.2.3. Ammonia and Carbon Dioxide (Gases)
John Baptist Van Helmont (1577-1644), born in
Belgium, introduced the term gas into the chemical
vocabulary. He produced what he called gas silvestre
(“gas that is wild and dwells in out-of-the-way places”)
by fermenting alcoholic liquor, burning charcoal, and
acidifying marble and chalk. The gas he discovered in
all three cases, but did not know at the time, was car-
bon dioxide [CO 2 (g)]. Another gas he produced was
an inflammable vapor evolved from dung. He called
this gas pingue ,which was probably impure ammonia
[NH 3 (g)]. Today, carbon dioxide is known to be the
main cause of global warming. Ammonia, produced
naturally and anthropogenically, dissolves and reacts in
aerosol particles.

Metal + fire → phlogiston + “calx” (residue)

Sulfur + fire → pure phlogiston

Phosphorus + fire → phlogiston + powder

Animal respiration → pure phlogiston

As demonstrated by the French chemist Antoine Lau-
rent de Lavoisier (1743-1794), more than 100 years
after Becher's first suggestion of the phlogiston theory,
the real processes are as follows:

1.2.2.4. Fire-Air
In 1676, John Mayow (1643-1679), an English physi-
cian, advanced the study of the composition of the air
slightly by suggesting that air appeared to contain two
components, one that allowed fire to burn and animals to
breathe (which Mayow called nitro-aereo or “ fire-air ”),
and another that did not. When he placed a lighted can-
dle and a small animal in a closed vessel, the lighted
candle went out before the animal died. When he placed
only the animal in the vessel, the animal took twice as
long to die. Thus, Mayow hypothesized that air was
diminished by combustion and breathing. Fire-air later
turned out to be molecular oxygen [O 2 (g)].

Metal + fire + O 2 (g) → metal oxide (residue)

Sulfur + fire + O 2 (g) → sulfur dioxide gas [SO 2 (g)]

4P(s) + fire + 5O 2 (g) → P 4 O 10 (s)

Animal respiration :
C 6 H 12 O 6 (s) + 6O 2 (g) → 6CO 2 (g) + 6H 2 O(g)

In other words, when a substance is burned, it combines
with oxygen to form an oxide of the substance that either
remains as a solid or is released to the air as a gas. In
both cases, the oxide of the substance weighs more than
the original substance. In the case of respiration, the
reaction is effectively the slow combustion of organic
material by inhaled oxygen. Thus, Becher and Stahl's
theories of terra pinguis and phlogiston turned out to
be incorrect.
To his credit, Stahl, in Specimen Becherianum ,was
the first to point out that sulfurous acid is more
volatile (evaporates more readily) than is sulfuric acid.

1.2.2.5. Phlogisticated Air
In 1669, Johann Joachim Becher (1635-1682), a
German physician, took what proved to be a step back-
ward in the understanding of the composition of air.
That year, he completed a topic, Physica Subterranea ,
in which he introduced an incorrect concept that dom-
inated the chemical world for the next 100 years. He
suggested that every combustible material contains dif-
ferent amounts of three components, terra mercurialis
(“fluid” or “mercurial earth,” believed to be mercury),