Basics and Discovery of Atmospheric Chemicals - Air Pollution and Global Warming: History, Science, and Solutions - page 7

Figure 1.3. Shiny mercury beads. C Ventin/ Figure 1.4. Pigments due to iron and manganese

oxides in fine-grained rock layers in the Painted
Desert, Arizona. C

Dreamstime.com.

Maniscalco/Dreamstime.com.

in Almaden, Spain. The heating of cinnabar produces
gas-phase mercury by the reaction HgS(s) + O 2 (g) →

Hg(g) SO 2 (g). Upon cooling, gas-phase mercury con-

denses to a liquid. The ancient Greeks used mercury
in ointments, and the ancient Egyptians and Romans
used it in cosmetics. Mercury has been found in Egyp-
tian tombs dating back to 1500 BC. Mercury enters the
atmosphere primarily as particulate matter. Today, most
mercury emissions occur during stationary power plant
combustion (primarily from coal-fired power plants),
gold production, metal production in smelters, cement
production, waste disposal, sodium hydroxide produc-
tion, and iron and steel production.

+ by first heating iron ore to high temperature for sev-

eral hours, then cooling, pounding, and reheating the
compound to release oxygen and brittle impurities to
produce shiny, pure iron. This technology transferred
slowly, making its way to Scandinavia only by 50 BC.
Today, iron is the element emitted in the greatest abun-
dance in aerosol particles from industrial processes
worldwide. Iron is also emitted naturally when the
wind lifts iron-containing desert soil dust particles into
the air.

1.2.1.4. Sulfur
Elemental sulfur ( sulvere in Sanskrit; sulphurium in
Latin) is a nonmetallic, pale yellow, crystalline min-
eral found in volcanic and hot spring deposits (e.g.,
Figure 1.5), sedimentary beds, and salt domes. Sulfur
burns with a weak blue flame, and burning continues
for a long time before the sulfur is consumed. Ancient
Egyptian alchemists were well aware of sulfur (Brown,
1913). The word brimstone (or “burn-stone,” referring
to its combustibility) is an Old English word for sul-
fur. In the Book of Genesis, “brimstone and fire” were
said to have rained down on the cities of Sodom and
Gomorrah, located near the southern end of the Dead
Sea, destroying them. The destruction of the cities, esti-
mated to have occurred c. 1900 BC, may have been due
to a volcanic eruption in which various forms of sulfur
emanated. Sulfur in the air is primarily in the form of
sulfur dioxide gas [SO 2 (g)] and aqueous sulfuric acid
[H 2 SO 4 (aq)].

1.2.1.3. Iron
Iron ( ferrum in Latin; iarn in Scandinavian) is a dense
metal element that is the primary component of the
Earth's core and the fourth most abundant element in the
Earth's crust. In pure form, it appears lustrous silvery
gray. However, in the form of iron ore [iron oxide,
Fe 2 O 3 (s)], it is reddish (e.g., Figure 1.4).
Meteorites consisting primarily of iron-nickel alloys,
called iron meteorites ,werethe only source of iron
before the discovery of iron ore. However, iron mete-
orites were rare, so only specialized meteoritic iron
swords were forged from them, usually for ritual.
Meteoric iron beads were also crafted, as evidenced
by an archeological find dating to 3500 BC, in Gerzah,
Egypt.
Between 3000 and 2700 BC, iron was purified
from iron ore in Asmar, Mesopotamia, and Tall Cha-
garBazaar, northern Syria. Pure iron was obtained