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Composition of air:
The air we breathe is not the air we think it is!
While air should ideally be a composition of different gases,
in reality it includes unwanted particles like dust, smoke,
transient micro-organisms (viruses, bacteria and fungi), and
water particles. This unwanted stuff affects our day to day
life, infecting us with different diseases, allergies and
an overall unpleasentness.
This text discusses air and its composition
from 'how it effects man' point of view. So the presence of
the various components must be in adequate ratios to have
no or positive effects on human health. Ideally, the amount
of dust, smoke and viruses/bacteria should be nill. Water
content is also important and for a comfortable living the
level must be around 50%. It is important to note that 50%
humidity level does not mean that half of the air is water.
Instead it means that the amount of water molecules present
in the air should be half of the maximum amount that can be
present without raining. At this point the air will be saturated
with water.
Another very important factor, in this context,
is the temperature of the air. The temperature of the air
that we live in matters for a comfortable living. We understand
this and that is why we use expensive air conditioning systems
in our homes and bear huge electricity bills.
However, this is still not all. There is
something our air misses. It misses the freshness that is
present around water falls, water resources like sea shores,
on mountain tops and after a lighting thunderstorm.
Ions and how they are produced:
Scientists have proven that electrically charged
particles present in the air are the reason for this. Charged
particles are scientifically termed as ions. Ions are of two
types, positive and negative.
Positive and negative Ions:
A molecule of any kind (gas, dust, smoke etc) is electrically
neutral. That is it contains no charge. However, as we know
from our basic science knowledge, every atom has equal number
of protons and electrons. Protons are positively charged while
electrons are negatively charged. However, if an atom (alone
or in a molecule) losses an electron, it will become positively
charged. Conversely if it gains an additional electron, it
will become negatively charged.
In 1775, C. A. Coulomb (French physicist
(1738-1806) who studied electricity and formulated the famous
Coulombs Law) showed that air is an electrical conductor;
104 years later, studies demonstrated that this property was
due to the presence of electrically charged particles, molecules
and sub-molecules which were called ions (Elster and Geital
1899).
Size of ions:
Ions are of different sizes from small to large.
1. Small ions are spatially charged and form part of the mixture
of gases making up the air;
2. Intermediate and large ions (Langevin's ions) are both
the result of the union of small ions with minute solid or
liquid particles called "Aitken's nuclei" (after
Aitken John, Scottish physicist (1839-1919)),
present in the atmosphere and mainly produced by human activity.
Large concentrations of Aitken's nuclei reduce the air's conductivity.
Generation of Ions:
In nature, the generation of small ions takes place in three
distinct, successive phases:
1. Ionisation
2. Attachment
3. Formation of clusters
During ionisation an external electron is
removed by a molecule or an atom of atmospheric gas. During
the ionisation process a free electron and a positive atom
or molecule are generated, resulting in N+, O+ and N2+, O2+
respectively.
Life of an ion:
As the electron extracted can only exist freely for an extremely
short time span (10.5 - 10.9 s) it tends to combine with oxygen
and nitrogen, which are both electronegative. However, as
the electronegativity of oxygen is greater, negative ions
are mainly formed of oxygen molecules.
Monomolecular positive and negative ions
are also only capable of existing freely in the atmosphere
for brief periods of time with normal pressure and temperature
values. Collisions and the electrostatic attraction of other
atmospheric components cause these ions to become surrounded
by neutral molecules forming clusters consisting of a charged
atomic or molecular "nucleus" surrounded by water
molecules, minor components of the air and polluting molecules.
The small hydrated ion will then be able
to:
1. Annihilate themselves with another oppositely charged ion
2. Form an intermediate or large ion (with a mass that is
2000 times greater)
3. Be removed through contact with solid or liquid surfaces.
Intermediate and large ions are charged aerosol
particles which are removed from the atmosphere by being transported
to the ground by rain or snow, or by sedimentation due to
the force of gravity or to the action of the wind. Artificially
produced negative ions are identical to natural ions and therefore
capable of eliminating toxic or allergenic particles.
Natural Sources of Ions:
The following are natural ionising agents:
a) Natural radioactivity given off by the ground and the air
in the form of electromagnetic radiation (rays) and corpuscular
emissions (protons)
b) Cosmic rays
c) Short-wave ultraviolet radiation produced by the sun
d) Chemical reactions like plant photosynthesis
e) The electric field produced by cloud formations, electromagnetic
storms due to the activity of sunspots and atmospheric electric
disturbance due to lightning (around 3500 storms are taking
place every second worldwide)
f) Interaction between solid particles (triboelectricity)
and between solid particles and air (charging through the
friction due to the wind).
Natural causes of ions elimination:
Among the causes for the reduction of ionic concentration
in the air are:
a) Industrial emissions
b) Car exhaust fumes
c) Conditioning plants
d) Synthetic materials (coatings and insulators in particular)
Household sources of postive ions:
a) Computer monitors
b) TV sets
c) Electric heaters
d) Dryers
e) Vacuum cleaners
f) Microwave ovens
g) Tobacco smoke
h) Fire (any process where combustion takes place)
Ratio of positive/negative ions:
It is important to note that in the presence of various positive
ions generators all around us, the negative ion generation
is insufficient, and therefore, should be artificially produced
to balance out the effect of positive ion concentrated air.
The air around us should be electrically neutral, that is
the ratio of the number of positive to negative ions should
be 1. It should be less than 1 rather than being greater than
it.
It is also pertinent to note that while temperature
and water presence is important for comfortable living, the
presence of correct ratio of positive to negative ions is
important for healthy living! So it is important for us to
give more consideration to ion-conditioning then to air-conditioning.
Ion-condition your living. Healthy livings
effect interpersonal relations.
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