FREE ESSAY ON OXYGEN

OXYGEN

Oxygen is one of the 92 known elements. An element is a substance that cannot be
decomposed into a simpler substance by any simple means. Each of the 92 naturally
occurring elements are therefore one of the fundamental materials from which everything
in the Universe is made.
The History of Oxygen
On August 1,1774, Joseph Priestley examined the effect of intense heat on mercuric oxide.
He noted that an air or gas was readily expelled from the specimen. To his surprise a
candle burned in this with a remarkably vigorous flame. He called this new substance
dephlogisticated air, in terms of the current chemical theory of combustion. On a visit
to Paris in 1775 he related his discovery directly to Antoine Lavoisier. Immediately
Lavoisier checked the results by accurate experiments and found that Priestley's
dephlogisticated air actually combined with metals and other substances. Since some of
the compounds he formed produced acids he regarded the dephlogisticated air as a
acidifying principle and called it oxygen, derived from the Greek words for "sour" and "I
Produce". 
From his experiments Lavoisier recognized that air was composed of two main constituents:
vital air or oxygen and azote (Greek for lifeless-now called nitrogen) which would not
support life or combustion. From these facts Lavoisier developed the modern theory of
combustion, and thus laid the foundation of modern chemistry.
Forms of Oxygen
Oxygen comes in a variety of forms. One of the more deadly forms of Oxygen is Ozone, O3.
Ozone (O3), named for the Greek word for smell, is a poisonous, colorless and tasteless
gas with a distinctive strong smell. Molecules of ozone are probably the source of the
smell that can be detected close to working electrical equipment such as motors and TVs.
If a vehicle with a catalytic converter is started cold, ozone can be detected in the
exhaust fumes. Most ozone is found high in the atmosphere in a region of the stratosphere
called the ozone layer. Here ozone performs a vital life-protecting role, absorbing the
ultraviolet rays of the sun that would be harmful to both plant and animal life. 
Ozone is usually prepared by passing a silent electric discharge through oxygen. Because
of its powerful oxidizing properties ozone is widely used for sterilizing water and for
air purification. It also is applied in organic chemistry in ozonolysis, which is the
reaction of ozone with unsaturated compounds such as the hydrocarbon ethylene. 
Oxides are a large and important class of chemical compounds in which oxygen is combined
with another element. Nearly all the elements form oxides, which vary in properties
according to their composition. Metal oxides are crystalline solids that contain a metal
cation and the oxide anion, O-2. They typically react with water to form bases or with
acids to form salts. Calcium oxide (CaO), for example, reacts with water to form calcium
hydroxide [Ca(OH2)], a strong base, and with hydrochloric acid to form calcium carbonate
(CaCl2), a salt. 
Nonmetals oxides are volatile compounds in which the oxygen atoms are linked covalently
to the nonmetal atom. They react with water to form acids or with bases to form salts.
Thus, sulfur trioxide (SO3) reacts with water to form sulfuric acid (H2SO4), a strong
acid, and with sodium hydroxide to form sodium sulfate (Na2SO4), a salt. Amphoteric
oxides contain oxygen along with cations such as aluminum, tin, or zinc; they may combine
with either acids or bases to form salts. Aluminum oxide (Al2O3), for example, reacts
with hydrochloric acid to form aluminum chloride (AlCl3) and with sodium hydroxide to
form Sodium Aluminate (NaAlO2). 
Certain organic compounds react with oxygen or other oxidizing agents to produce
substances called oxides. Thus, amines, phosphines, and sulfides form amine oxides,
phosphine oxides, and sulfoxides, respectively, in which the oxygen atom is covalently
bonded to the nitrogen, phosphorus, or sulfur atom. The so-called olefin oxides are
cyclic ethers. 
Another place where oxygen is found is the atmosphere. The Atmosphere surrounding the
earth is a mechanical mixture of gases. The most important of these gases are oxygen,
nitrogen, and carbon dioxide. The relative proportions of these gases in the atmosphere
are found to be remarkably constant. 
Oxygen is essential to life. It is odorless, colorless, tasteless, and slightly heavier
than air. The chief commercial source of oxygen is the atmosphere. Oxygen may be
separated from the mixture of gases that make up the atmosphere. This is done by physical
means, by subjecting air to very high pressures and low temperatures until a point is
reached where it passes form the gaseous into the liquid state. The liquid air is then
allowed to warm slightly, so that nitrogen, which has a lower boiling point than oxygen,
evaporates off. At a slightly higher temperature, almost pure oxygen is reconverted into
gas, which is pumped into steel cylinders and thus stored in compressed form. 
It may be interesting to note that oxygen was first prepared by heating certain metal
oxides, including mercury oxide. Oxygen in the air is kept constant by the balance
between the actions of plants and animals. Oxygen also supports combustion.
Uses
In our busy world of today, we are using oxygen for many different things and in many
different ways.
One of the ways is oxygen therapy where oxygen is used to cure stress or to calm people
down. Oxygen Therapies have been around for many years, and range from the use of
hydrogen peroxide to Ozone Therapy. Ozone is by far the most aggressive of all the Oxygen
Therapies, and perhaps the most controversial. Accepted in 16 countries, Ozone Therapy
has met with much resistance in the United States. The FDA does everything in its power
to quell the acceptance of it, but it is slowly gaining acceptance. The FDA would like
people to believe that Ozone is a form of pollution found in the air, but Ozone in
relation to Oxygen Therapies is produced using high quality Ozone generators from Medical
Grade Oxygen. The main thrust behind the suppression of Ozone appears to be
pharmaceutical based. Only Ozone delivery methods are paten able, so there is not much
money to be gained by pursuing it clinically. On the other hand, the money that the
pharmaceutical companies stand to lose because of Ozone is where the problem begins. If
Ozone Therapy were to eliminate the use of even 50% of pharmaceutical drugs, billions of
dollars are at stake.
Another way is, of course, respiration. The term respiration refers to the gaseous
interchange between an organism and its environment, namely taking in oxygen and getting
rid of carbon dioxide. Inhalation (the breathing of air into the lungs and the diffusion
of oxygen form the inspired air across the pulmonary membrane in the blood stream),
together with exhalation (the passage of carbon dioxide from the blood into the lungs and
the breathing out of air), constitutes only one phase of respiration. A second phase of
it is the transportation of oxygen by the blood from the lungs to the tissues and of
carbon dioxide from the tissues to the lungs. A third phase is the absorption (passage by
diffusion) of oxygen into the tissue cells and tissue use of oxygen (the oxidative and
other respiratory processes with in the tissues cells whereby energy is liberated). 
External respiration involves the exchange of gases between the circulation blood and the
air. For this exchange to take place, a person needs a large moist surface where air and
blood can come in close contact. The lungs provide area for diffusion. And of course
there must be a passageway state air expelled from the lungs.
Internal respiration, on the other hand, involves the exchange of gases between the
circulating blood and the various tissue cells as they use oxygen and produce waste
carbon dioxide. When the blood reaches the capillaries, the oxygen molecules are forced
through the capillary wall because the tension outside the wall is lower, oxygen then
moves onto the tissue cells. The tension of oxygen in the plasma rapidly falls, and this
leads to a dissociation of oxygen from combination with hemoglobin diffuse out of the red
blood cells into the plasma, and hence through the capillary wall. The average amount of
oxygen gives up to the tissue cells all over the body from each 100cc. of blood is about
5cc. In other words, the tissue cells of an adult normally utilize 250cc. of oxygen per
minute. Even after the tissues have received all their requirements, the venous blood is
still 70-75% saturated with oxygen, under ordinary circumstances. The body needs oxygen
to release energy from food.
Through respiration, body cells take in oxygen and use it to turn the sugar in food into
energy which is involved in every activity that occurs within the body. For example, the
beating of the heart the building and repair of tissue and brain activity cannot occur
without energy. The energy needs of the body must take precedence over all others.
Without energy there is cell disorganization and death. Every person must be supplied
with oxygen continually, since oxygen cannot be stored in the body. What occurs when the
body does not get enough oxygen to supply its needs? Whatever the reasons may be, the
person usually has dyspnea (difficult breathing), rapid pulse, pallor, and hyperpnoea
(increase in breathing), often he also has cyanosis (bluish discoloration of the skin).
In hemorrhage, there is air hunger, a kind of gasping for breath. 
Yet another way is combustion, where oxygen can be used to fuel a flame and increase its
heat. Oxygen has two fundamentally important properties: it supports combustion and it
supports life. The first commercial use of oxygen was for limelight illumination in
theaters, but oxygen has been used in welding and medicine since the turn of the century
and in steel production since the 1950s. Iron and steel producers need oxygen to
accelerate melting and to remove impurities the refining process. Steel mills consume
oxygen on a massive scale. A modern plant can use in excess of 2,000 tons per day, and it
is for this reason that supplies to this market are usually piped directly form an air
separation unit (ASU)plant. 
Oxygen is also used by many other industries in a variety of oxidation processes. Mixed
with fuel gases, oxygen provides a heat source for many welding, cutting and metal
fabrication processes. Oxygen-fed furnaces and burners are also found in non-ferrous
metal plants, brick making kilns, pulp and paper mills and in glass manufacturing.
Oxygen-enhanced combustion increases productivity and help to reduce harmful combustion
by-products. Combustion is the process of burning. More specifically, it is a rapid
chemical reaction that releases energy. An example of a combustion reaction is the
burning of coal, where the main reaction involves converting carbon and oxygen to carbon
dioxide. For combustion to occur, fuel, and oxidizer, and an ignition stimulus are
required. Fuels can be divided into three categories, solid, liquid and gas. Examples of
solid fuels include filter paper, Plexiglas, wood, and coal. Liquid fuels include
materials like kerosene and gasoline, while materials such as methane and hydrogen
constitute gaseous fuels. Oxidizers can similarly be solid, liquid, or gaseous. Air,
which contains gaseous oxygen as one of its components, is a particularly common
oxidizer. An electrical spark is an example of a ignition stimulus. A vital process that
has been the subject of vigorous scientific research for over a century, combustion
accounts for approximately 85% of the world's energy production - and a significant
fraction of the world's atmospheric pollution as well. Combustion plays a key role in
ground transportation, spacecraft and aircraft propulsion, global environmental heating,
materials processing, hazardous waste disposal through incineration, as well as many
other areas. Despite this, there is limited understanding of many fundamental combustion
processes, for example how pollutants are formed during these processes?
The manufacture of oxygen
Originally oxygen was prepared on an industrial scale by the Brin process. Barium oxide
(BaO) is heated in compressed air to form barium peroxide (BaO*SUB2* sub*). The
temperature and pressure are reduced and the peroxide reverts to the monoxide. During the
process, oxygen is released. 
2BaO2 --* 2BaO --* O2 
barium peroxide--* barium oxide--* oxygen
Today a little oxygen is prepared by the electrolytic decomposition of water, but the
principal method, of production is the liquefaction and fractional distillation of air.
Name
Greek oxy genes meaning 'acid forming'
Name in OtherLanguages Croatian Kisik
Danish oxygen
Dutch zuurstof
Finnish happi
French oxygene
German Sauerstoff
Italian ossigeno
Norwegian oksygen
Portuguese oxigenio
Spanish oxigeno
Swedish syre
Data
8O15.9994 Atomic Number 8
Atomic Weight 15.9994
Electron Config. 2-2-4
Mechanical Properties Conditions
Phase Temp. (K) Pressure (Pa)
Density (O2) 1.429 kg/m3 Gas 293.15 101325 
Density (O2) 1141 kg/m3 Liquid 90.188 101325 
Thermal Properties Conditions
Temp. (K) Pressure (Pa)
Melting Temperature (O2) 54.36 K 101325 
Boiling Temperature (O2) 90.2 K 101325 
Critical Temperature (O2) 154.59 K 
Fusion Enthalpy (O2) 13.8 J/g 0 101325 
Vaporization Enthalpy (O2) 213.13 J/g 0 101325 
Heat Capacity (O2) 918 J/kg-K 298.15 100000 
Bibliography
Bibliography
van Vlack, L.H. (1985), Elements of Materials Science and Engineering, Addison-Wesley
(Reading, MA).
Brady, G.S., et al. (ed.) (1997), Materials Handbook, 14th ed., McGraw-Hill (New York).
Gere J.M., Timoshenko, S.P. (1984), Mechanics of Materials, 2nd ed., Brooks/Cole
(Monterey, CA).