J. Energy Power Sources
Vol. 1, No. 1, 2014, pp. 1-8
Received: May 25, 2014, Published: July 31, 2014
Journal of Energy
and Power Sources
www.ethanpublishing.com
By the Combustion of Fossil-Fuels and that O2 Dropping
Faster than CO2 Rising is not Mystery
Reményi Károly
Hungarian Academy of Sciences, Budapest, 1014, Hungary
Corresponding author: Reményi Károly ([email protected])
Abstract: New research shows O2 dropping faster than CO2 rising. This is not mystery. When fossil fuels are burned, produced carbon
dioxide depends on the carbon content of the fuel. Oxygen need to the oxidation of elements other than carbon (dominately hydrogen)
in fossil fuels. Form a separate group of bio logical systems related fuels. In these fuels contain oxygen, which is a significant part of the
combustion process is used. Nature is trying to optimize its own system. The O2 and CO2 are exchanged in different processes in air.
Key words: Oxygen, carbon dioxide, fossil fuels, combustion, atmosphere.
1. Introduction
New research shows O2 dropping faster than CO2
rising [1]. Is that increasing levels of disturbance across
natural ecosystems in recent decades? This is one
aspect of the relationship between CO2 and O2. Fossil
fuels are made up of hydrogen and carbon. Fossil fuel
ranges from volatile materials with low-carbon and
almost pure carbon, like anthracite coal. When fossil
fuels are burned, produced carbon dioxide depends on
the carbon content of the fuel; for example, for each
unit of energy produced, natural gas emits about half
and petroleum fuels about three-quarters of the carbon
dioxide produced by coal. For the burning need oxygen
depending type of fuels.
There has been much focus on the negative impacts
of rising carbon dioxide (CO2) levels in the atmosphere
due to fossil fuel combustion in recent years. This is not
surprising, considering the large percentage of fossil
fuel CO2 that continues to accumulate in the
atmosphere since the industrial revolution. Because the
concentration of CO2 in the atmosphere is small
relative to other gases (only about 0.038%). The excess
CO2 generated from burning of fossil fuels creates an
impact not enough to affect global temperature, climate,
ocean chemistry and consequently, human and animal
health, welfare and the environment.
2. Earth’s Atmosphere
The Earth has over most of its 4.6 billion years long
history. The oceans, prairies, and mountain chains, air
we seem the norm and permanent things. But not so far
back in Earth’s history, perhaps only 5 million years
ago, oxygen levels were significantly higher than now,
while less than 100 million years ago, oxygen levels
were significantly lower than today. The atmosphere
has changed markedly over time. That is very interest
to look at how our current atmosphere came about and
how it was recently discovered that the air has
undergone relatively recent (compared to the age of
Earth) periods of hypoxia or low-oxygen.
There can be no discussion about the atmosphere
without including the global ocean.
The composition of Earth’s present-day atmosphere is
basically known. Essentially it is made up of two gases:
78 percent of its volume is nitrogen, and 21 percent is
oxygen. The remaining 1 percent is made up of trace
amounts of other gases for example CO2 and water
vapor. The atmosphere of our planet is as old as Earth
2
By the Combustion of Fossil-Fuels and that O2 Dropping Faster than CO2 Rising is not Mystery
itself. World oceans (since it is interconnected, even
though we give parts of it separate names) have also
changed its chemistry, mainly by changes in salinity
through time. The oceans of planet Earth were created as
part of the natural evolution of the cooling planet.
The most important gases to us are those in the
during photosynthesis, when carbon dioxide is
consumed. It is removed, when carbon dioxide is
produced. On average, it takes about a decade for
oxygen and carbon dioxide to cycle through living
plants. In the ocean, some of this organic detritus
escapes destruction and is deposited in the sediments.
atmosphere that surrounds the earth’s surface. The
In the oceans, phytoplankton produce oxygen as a
principal components are N2 and O2, but many other
result, oxygen is released to the atmosphere. The
important gases, such as H2O and CO2, are also present.
organic carbon not decayed by this oxygen If this
The average composition of the earth’s atmosphere
accumulation were not counteracted by other processes,
near sea level, with the water vapor removed, is shown
and no other factors were to intervene, all the carbon
in Table 1.
dioxide in the atmosphere would disappear in less than
The atmosphere is a highly complex and dynamic
10,000 years.
System. The chemistry occurring in the higher levels of
We can conclude that the carbon and oxygen
the atmosphere is mostly determined by the affects of
biogeochemical cycles have changed throughout
high-energy radiation from the sun and the particles. In
geologic time. These changes have led to changes in
particular, the ozone in the upper atmosphere helps
atmospheric
composition
prevent high-energy ultraviolet radiation.
composition
of
The scientists occurring in the troposphere, the earth’s
the
and
atmosphere
climate.
and
The
other
environmental conditions changed.
surface is influenced by human activities. Millions of
The CO2 has historically been much more in our
tons of gases were released into the troposphere by our
atmosphere than exists today. For example, during the
civilization. The combustion of fossil fuels produces CO,
Jurassic Period (200 mya), average CO2 concentrations
CO2, NO, NO2, N2O, SO2, SO3 etc.
were about 1800 ppm or about 4.7 times higher than
Energy point of view, the two main gases is oxygen
today. The highest concentrations of CO2 during all of
and carbon dioxide. Oxygen composes 20.9% of the
the Paleozoic Era occurred during the Cambrian Period,
gases of the atmosphere. The cycling of oxygen is
nearly 7000 ppm -- about 18 times higher than today
coupled to that of carbon. Oxygen is produced by plants
(see Fig. 1).
Table 1 Average composition of dry atmosphere (mole
fractions).
Gas
per NASA
Nitrogen
N2
78.084%
Oxygen
O2
20.946%
Argon
Ar
0.934%
Minor constituents (mole fractions in ppm)
Carbon dioxide
CO2
383
Neon
Ne
18.18
Helium
He
5.24
Methane
CH4
1.7
Krypton
Kr
1.14
Hydrogen
H2
0.55
Water: Water vapour Highly variable; typically makes up
about 1%
Notes: the concentration of CO2 and CH4 vary by season and
location. The mean molecular mass of air is 28.97 g/mol.
Fig. 1 The average CO2 concentrations in the last 600
million years of Earth’s history.
By the Combustion of Fossil-Fuels and that O2 Dropping Faster than CO2 Rising is not Mystery
3
In the last 600 million years of Earth’s history only
the Carboniferous Period and our present age, the
Quaternary Period, have witnessed CO2 levels less than
400 ppm. During late Miocene according to
greenhouse theory, Earth should have been no warmer
than today but were as exceedingly hot (5 - 8 degrees
Celsius warmer than today) when atmospheric CO2
were as low (200 - 350 ppm) as they are today. Late
Miocene atmospheric carbon influence decoupling of
earth temperatures [5, 8].
3. Coupling between Atmospheric Carbon
Dioxide and Oxygen
Atmospheric concentrations of carbon dioxide (CO2)
in the Early Carboniferous Period were approximately
1500 ppm (parts per million), but by the Middle
Carboniferous
declined
to
about
350
ppm—comparable to average CO2 concentrations
today. The Fig. 2 is a model calculation of atmospheric
oxygen concentration variations during the last 600
million years. During the Carboniferous and Permian,
large quantities of vascular plant organic matter were
buried in the vast coastal lowlands and swamps of the
time. This material became the coal deposits mined
from rocks of Carboniferous and Permian age today.
This large accumulation of organic matter gave rise to
the high atmospheric oxygen levels of the late
Paleozoic.
Coal deposits are also important in Cretaceous- and
early Cenozoic-age rocks, another time of high
atmospheric oxygen concentrations (see Fig. 2).
Two main process affect on ratio of O2 dropping to
CO2 rising:
•
First is the CO2 buffering affect of nature;
• Second is that by different fossil fuel types
combustion the rate of oxygen depends on the
hydrogen content of fossil-fuel.
By knowing the fossil fuel emissions and Earth’s
processes, we can separate the total CO2 uptake into
land
and
ocean
components.
Oceanic
and
photosynthesis uptake of atmospheric CO2 reduces the
Fig. 2 Model Calculation of Atmospheric Oxygen During
Past 600 Millions Years. (The dashed line across the figure
shows today’s atmospheric concentration O2. The left
vertical axis shows the atmospheric O2 as a percentage of the
atmospheric gases. The horizontal axis shows time in
millions of years before the present and geological time
period/after Berner and Canfield, 1989). Environmental
Conditions before Human Interference.
upward trend in atmospheric CO2 concentrations.
Over the long-term, we can represent the global
budget for atmospheric CO2 according to
ΔCO2 = C – N
(1)
where ΔCO2 is the annual averaged change in
atmospheric CO2, C is the source of CO2 from burning
fossil fuels, N is the nature CO2 sink (including
biological and chemical uptake). All except exchange
ratios are in units of moles per year (moles yi-1).
It can represent the global budget for atmospheric O2
according to
ΔO2 = -F + O
(2)
where ΔO2 is the change in atmospheric oxygen, F is
all of O2 sink owing to combustion of fossil fuels, O
show the oxygen is released to the atmosphere by the
oceans, all produced O2 by photosynthesis the net rate
4
By the Combustion of Fossil-Fuels and that O2 Dropping Faster than CO2 Rising is not Mystery
change in atmospheric oxygen and represents the
chemical processes
the atmosphere annually. This positive imbalance
It can represent the F according to
F=C+H
(3)
where C is the source of CO2 from carbon content of
fossil fuels (CO2 are directly comparable on a mole O2),
H is the source of O2 owing to the oxidation of
elements other than carbon (predominately hydrogen)
in fossil fuels.
Researches show any direct impact on oxygen levels.
The atmospheric oxygen levels have been declining
while CO2 levels are rising due to fossil fuel
combustion. The research confirmed the general
upward trend for atmospheric CO2 and a downward
trend in atmospheric O2. O2 is decreasing faster than
can be accounted for by the rise in CO2. Possibility is
that part of oxygen sink as the result of human
activities [1, 4, 7].
The movement of carbon between the atmosphere and
the land and oceans is dominated by natural processes,
such as plant photosynthesis. While these natural
processes can absorb some of the net 6.2 billion metric
tons (7.2 billion metric tons less 1 billion metric tons of
sinks) of anthropogenic carbon dioxide emissions
produced each year (measured in carbon equivalent
terms), an estimated 4.1 billion metric tons are added to
results in the continuing increase in atmospheric
between greenhouse gas emissions and absorption
concentrations of greenhouse gases (see Table 2).
Concentrations of carbon dioxide in the atmosphere
are naturally regulated by numerous processes
collectively known as the “carbon cycle”. Not all of the
carbon dioxide that has been emitted by human
activities remains in the atmosphere (see Fig. 3). At
beginning of industrialization the energy consumption
had no affect on the movements of carbon of the nature.
This shows that in the movements of carbon in the
nature the industrial carbon is not separate (physical,
chemical, biological process) [6].
Fig. 3 Measured CO2 concentration and calculated CO2
concentration based upon fossil fuels demand.
Table 2 The changes of fossil fuels consumption and total consumption in the last 150 years calculating with 20 years’
period (last period is 5 years).
1860
1880
1900
Energy consumption
0.2
0.6
1.0
109 Gtoe/yr
By 20 years’ period the total energy consumption and CO2 emission
1920
1940
1960
1980
2000
2005
1.5
2.5
6.0
9.13
11.43
14.0
Gtoe by 20 years
8
16
25
40
85
152
203
63.5
CO2 (Gt) by 20 years
24
48
75
120
255
456
609
190.5
3
In air CO2 total 10 Gt
2.21
2.234
2.282
2.357
2.477
2.732
3.188
3.797
3.391
Calculate concentration (ppm)
288
291.1
297.4
307.2
322.8
356
415.5
494.8
519.7
Measured CO2 concentration (ppm)
288
293.6
306
319
362
383
-80.6
23
73.4
69
Capture (%)
Total energy consumption
in years: 1860-2005
592.5 Gtoe
Total emission CO2
in years: 1860-2005
1777.5 Gt
Average capture
in years: 1860-2005
59%
Note: Gt-billion (Am) tons; Gtoe-billion (Am) metric tons of oil equivalent-42 billion (Am) Joule; BTU-1055.056 Joule;
ppm-parts per million.
5
By the Combustion of Fossil-Fuels and that O2 Dropping Faster than CO2 Rising is not Mystery
Some of the carbon dioxide produced has been
absorbed by the oceans. This process involves
inorganic chemical reactions. The ocean is acting as an
efficient carbon sink, nearly half of CO2 is absorbed by
the ocean waters.
Nature helps maintain its balance amidst the rising
CO2 levels, decreasing O2 levels. At the warmer
conditions and higher CO2 concentrations make plants
grow more rapidly.
4. Affect of Fossil-Fuels Combustion on
Oxygen Dropping
Oxygen is quite abundant in the atmosphere that
In fact, it seems to be the case of high organic carbon
burial in the past gave rise to high atmospheric oxygen
levels [8].
It is difficult to measure changes in O2 because there
is so much of it in the atmosphere compared with CO2.
Changes are measured as differences in O2/N2 ratios.
Atmospheric exchange of O2 with land ecosystems
is commonly expressed in terms of a net carbon flux
from the atmosphere to the ecosystem and the net
O2:CO2 exchange ratio.
The burning of fossil fuels may also potentially
cause a decline in atmospheric oxygen levels indirectly
by affecting oxygen-producing organisms such as
even when fossil fuel reserves (mostly coal) are
phytoplankton. We
exhausted, the maximum potential loss in oxygen is
molecules for each CO2 molecule that accumulates in
only small (the O2 concentration in air is 209460 ppm
the air.
are
losing
nearly
three
O2
and compared with around 390 ppm of CO2). It is
This mix of CO2 and H2O vapor are the primary
already known that atmospheric oxygen is declining.
gases which come out of your tailpipe and by the
The rate of oxygen decline is even expected to be
combustion of all fossil fuels.
greater, but it was not the case [2].
The previous articles [3-4] O2/CO2 flux rate was
Oxygen composes 20.9% of the gases of the
primarily interest in Table 3. This does not respond to
atmosphere. The cycling of oxygen is partly coupled to
changes in actual concentrations of the two gases in
that of carbon. Oxygen is produced by plants during
the atmosphere. The use of fuels for energy generation,
photosynthesis, when carbon dioxide is consumed. It is
so the human activity, the goal of the generation of
removed by respiration and decay, when carbon
heat. Taking into account the composition of the fuel
dioxide is produced. On average, it takes about a
(in power generation reaction) is essential to know the
decade for oxygen and carbon dioxide to cycle through
actual
living plants. In the ocean, some of organic detritus
characteristics can be O2/MJ. Oxygen consumption of
escapes destruction and is deposited in the sediments.
a high-energy flux of the process in terms of oxygen
amount
of
oxygen
consumed.
Typical
In the oceans, phytoplankton produces slightly more
demand may be more favorable than low-flux (see
oxygen than is consumed during the respiration and
Table 3). Dr. Keeling explained that the Oxygen:
decay of marine life. As a result, oxygen is released to
Carbon combustion ratio of a fossil fuel depends on its
the atmosphere. The organic carbon not decayed by
hydrogen content. He said it can vary from 1.2 for coal,
this oxygen, some of the terrestrial organic detritus is
1.45 for liquid fuels and 2.0 for natural gas. While
deposited on the seafloor and accumulates in the
considering these factors, Dr. Keeling came up with
sediments of the ocean. The oxygen content of the
the 3:1 ratio of oxygen lost per carbon dioxide
atmosphere would double in less than several million
produced.
years. The overproduction of oxygen in the oceans is
The H/C ratios will be useful for determining the
balanced by the weathering of fossil organic carbon
mechanism by which excess carbon dioxide produced
and other materials in rocks on land. During this
from fossil-fuels burning is removed from the
process, carbon dioxide is returned to the atmosphere.
atmosphere (see Table 4).
6
By the Combustion of Fossil-Fuels and that O2 Dropping Faster than CO2 Rising is not Mystery
Table 3 From the keeling article is the: Table of flux.
Process
Ratio of O2 flux to CO2 flux
Photosynthesis and respiration on land
-1.05a
CO2 + H2O = CH2O + O2
Burning fossil fuel
-1.42b
CHy + (1 + y/4)O2 = y/2H2O + CO2
Oceanic uptake of excess CO2
0
H2O + CO2 + CO → 2HCO
Ocean photosynthesis and respiration
-2 to -8c
106CO2 + 16NO + H2PO + 17H+ = C106H263O220N26P + 138O2
a
On average, the ratio for terrestrial organic matter is slightly more reduced than for carbohydrate, which yields a 02:C02
ratio slightly higher than 1.0.
b
This is the global average ratio estimated for the year 1989 based on fuel production data, and using O2:CO2 ratios of
different fuel types.
c
Ocean photosynthesis adds O2 to seawater and removes CO2 from seawater in proportions of approximately—1.3:1 as
determined by the composition of marine organic matter. The relative fluxes across the air-sea interface also depend on the
relative efficiencies of gas exchange and can vary depending on the time scale involved.
Table 4 Ratio of H/C and ratio of O2/CO2 flux for different Fuels.
Ratio of hydrogen H to carbon
C, H/C
Ratio of O2 flux to CO2 flux,
O2/CO2
Heat
MJ/mol
242
C + O2 = CO2
0
1.0
394
Fuels and reactions
2H2 + O2 = 2H2O
CH4 + 2O2 = 2H2O + CO2
4
2.0
878
C3H8 + 5O2 = 4H2O + 3CO2
2.7
1.7
2149
C4H10 + 6.5O2 = 5H2O + 4CO2
2.5
1.6
2785
C2H4 + 3O2 = 2H2O + 2CO2
2
1.5
1271
Anthracite: C—86%, H—3.7%
Lignite: C—19.7%, H—1.7%,
O—8.5%
Biological materials
C6H12O6 + 6O2 = 6H2O + 6CO2
(glucose)
C2H6O + 3O2 = 3H2O + 2CO2
(ethanol)
CH4O + 1.5O2 = 2H2O + CO2
(methanol)
Crusty tree: C—47%, H—6%,
O—43%
0.25
1.25
0.26
1.0
2
1
3814
3
1.5
1513
4
1.5
878
0.77
1.4
Combustion is a chemical reaction. Combustion fuel
(usually hydrocarbons), oxygen, and a spark. In
addition to producing carbon dioxide and water, the
combustion of hydrocarbons produces heat and light.
Furthermore, real fuels usually have other compounds
in them besides just carbon and hydrogen. Coal for
example, can include carbon, hydrogen, oxygen,
nitrogen, sulfur and even small amounts of lead and
mercury. The burning of fossil fuels such as gasoline,
coal, oil, natural gas in combustion reactions results in
the production of carbon dioxide and water.
released,
The following balanced equations represent the
burning of various pure fuels in pure oxygen. Real life
is more complicated, because most fuels are not pure
and the air is not 100% oxygen. Air is 78% nitrogen, 21%
oxygen and almost 1% argon.
The dates for calculation are:
C—32.808 MJ/kg; H—121.0 MJ/kg; CO—10.11
MJ/kg.
For example here’s an equation describing the
reaction of octane gas with oxygen:
2C8H18 + 25O2 →16CO2 + 18H2O
(4)
By the Combustion of Fossil-Fuels and that O2 Dropping Faster than CO2 Rising is not Mystery
Table 5
7
Specific oxygen demand for different fuels.
Specific oxygen demand (106.O2mol/MJ)
Fossil fuels
Heating value (MJ/kg)
H2
121.0
2066
C
32.808
2538
CH4
54.9
2279
C3H8
48.8
2326
C4H10
48.0
2334
C2H4
45.4
2360
Anthracite: C—86%, H—3.7%
35.3
2540
Lignite: C—19.7%, H—1.7%, O—8.5%
Biological materials
8.52
1813
C6H12O6 (glucose)
21.2
1573
CH4O (methanol)
27.4
1710
C2H6O (ethanol)
32.9
1980
Crusty tree: C—47%, H—6%, O—43%,
(Moisture and ash-free)
18.1
1492
Carbon has an atomic weight of 12 and carbon
dioxide has a molecular weight of 44 (1 carbon atom at
12 and 2 oxygen atoms at 16 each). If we want to know
how much carbon dioxide you will end up with for
every one part of carbon, simplify the ratio by dividing
44 by 12 and you will get 3.7 parts carbon dioxide for
every 1 part carbon. The flux ratios only provide
information on the nature of the processes and the
energy scenario is not enough to understand the affect
of fossil fuels combustion on oxygen concentration.
Necessary to know the specific mass of oxygen
needed to burn off the unit weight of fuel (O2/MJ).
Fig. 4 Function between ratio H/C and O2/CO2 for
different fuels.
These parameters can be calculated knowing the
reaction processes (see Table 5).
The analysis of the values in the table should be
pointed out that the analysis is very important to pre-set
goals. An important target for the combustion of fuels
gets to know the impact of atmospheric oxygen
concentration and thus rank them. The following
analysis is done on the basis of this target set.
5. The Impact of Different Fuel Types on
Oxygen Concentration
The fuel H/C ratio increases, the O2/CO2 flux ratio is
increased, of course, because oxygen is required for
combustion of the hydrogen (see Fig. 4). Increases the
Fig. 5 Function of specific oxygen demand from heating
value for different fuels.
ratio of the fact that the carbon dioxide 50% is
absorbed by the nature itself (see Fig. 3). Reduces the
8
By the Combustion of Fossil-Fuels and that O2 Dropping Faster than CO2 Rising is not Mystery
expected atmospheric carbon dioxide concentration
increase.
The fuels used for energy purpose: to heat generation.
In this respect, the fuel parameter evaluation is: for the
generation of unit of heat per mass of oxygen needed
(see Fig. 5). The data indicate if the H/C value
increases, reducing the amount of oxygen required per
unit of heat.
6. Conclusions
World air has changed its chemistry, mainly by
changes in composition through time. When fossil
fuels are burned, produced carbon dioxide depends on
the carbon and other elements content of the fuel. New
research shows O2 dropping faster than CO2 rising.
The main processes affect on ratio of O2 dropping to
CO2 rising: are the CO2 buffering affect of nature, and
that by different fossil fuel types combustion the rate
of oxygen depends on the hydrogen content of
fossil-fuel.
1. The fuel H/C ratio increases, the O2/CO2 flux ratio
is increased, of course, because oxygen is required for
combustion of the hydrogen. This is taken into account
in terms of the oxygen flux to the combustion of
methane (natural gas) is unfavorable. In the process the
oxygen-CO2 ratio is high. Increases the ratio of the fact
that the carbon dioxide 50% is absorbed by the nature
itself. Reduces the expected atmospheric carbon
dioxide concentration increase;
2. Energetically is favorable for methane combustion.
This is the inverse to the former opinion. The fuels used
for energy purpose: to heat generation. In this respect,
the fuel parameter evaluation is: for the generation of
unit of heat per mass of oxygen needed. The data
indicate if the H/C value increases, reducing the amount
of oxygen required per unit of heat Natural gas is the
most favorable among hydrocarbons;
3. With increase the degree of carbonization of fossil
fuels increases the specific oxygen needs. The low
value has the lignite. It has high hydrogen content,
specifically, significant the oxygen content (the woody
structure is significant);
4. Form a separate group of biological systems
related fuels. In the fuels contain oxygen, which is a
significant part of the combustion process is used.
Nature is trying to optimize its own system. The
bio-fuels, thus both carbon dioxide and the oxygen
management are the most favorable. Unfortunately,
other aspects for energy are unfavorable;
5. The specific oxygen consumption of hydrogen
combustion is better than the hydrocarbons, but worse
than the bio-fuels.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
O2 Dropping Faster than CO2 Rising, ISIS Report,
http://www.i-sis.org.uk/O2DroppingFasterThanCO2Risin
g.php (accessed August 19, 2009).
S. Ishidoya, S. Aoki, T. Nakazawa, A high precision
measurements of the atmospheric O2/N2 ratio on a mass
spectrometer, Journal of the Meteorological Society of
Japan 81 (1) (2003) 127-140.
R. Keeling, Atmospheric O2 concentration, reported as the
O2/N2 Ratio, University of California at San Diego
Institution of Oceanography (SIO), U.S., 2006.
R. Keeling, The atmospheric oxigen cycle: The oxygen
isotopes of atmospheric CO2 and O2 and the O2/CO2 ratio,
U.S. National Report to International Union Geodesy and
Geophisics, 1991-1994.
J.P. LaRiviere, A.C. Ravelo, A. Crimmins, P.S. Dekens,
H.L. Ford, M. Lyle, M.W. Wara, Late Miocene
decoupling of oceanic warmth and atmospheric carbon
dioxid forcing, Nature 486 (2012) 97-100.
E. Mészáros, Különleges egyensúly a levegőben, MTA,
Miskolci Akadémiai Bizottság, June 2, 2010.
H. Warwick, Something in the air we breathe, Research
School of Biological Sciences, Australian National
University Canberra ACT 0200 Australia, 2011.
S.S. Zumdahl, Chemical Principles, 5th ed., Houghton
Mifflin Company, 2005.