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OZONE
Do you know 'hole of Ozone layer' is? I'm so sure. Without any doubt you know that ozone is a substance with a huge importance for the Earth life. In fact, we know that we and organisms which are surrounded us couldn't live without this fantastic and famous gas.
That's why; we are going to study this substance. Ozone is an oxygen molecule; it is different to oxygen common because the oxygen common is formed by two oxygen atoms and ozone by three. It is formed when there is enough energy to break an oxygen molecule, each oxygen atom which is formed will be joined to another oxygen molecule, and so two ozone molecules are formed.
Ozone was discovered in 1.785 by Bon Marum who appreciated their characteristic scent. It spent a lot of time until this gas was classified, so it was in 1.840 when Shümbein called it 'OZONE', a name that comes from the Greek which means 'scent'. But in spite of this, it was not until 1.863 its true nature was discovered, since it was thought it was a hydrogen peroxide. That year, Soret confirmed that it was a compound formed by three oxygen atoms.
The properties of ozone are the following ones:
Molecular Weight (PM) ...................................................................... 48 g/mol
Temperature of condensation ......................................................... - 112 º C
Temperature of fusion ................................................................. -192, 5 º C
Critical Temperature ........................................................................... 54 atm
Density ......................................................................................... 1, 32 g/cm 3
Density (liquid to -182 º C) ........................................................ 1.572 g/cm 3
Weight of litre of gas (a 0º y 1 atm) ...............................................1,144 g
In normal conditions of pressure and temperature, OZONE is unstable; its instability increases in proportion to the temperature and humidity increasing and it arrives to be total over 200º C.
Its degree of greater stability reaches to - 50º C and equal pressure to 38 mm Hg.
To room temperature, it attacks to saturated organic compounds and it increases this attack to temperatures of 78 ºC and even lower.
Opposite to not saturated organic compounds, it forms ozonides (very unstable compounds) and it gives rise to aldehydes, acetones, carboxilics acids, etc
After we have previously shown, we can say that OZONE is:
In equal conditions, in addition, it is more stable in the water that in the air.• After the fluorine, ozone is the most oxidating compound, due to its facility to catch electrons.
• Of easy decomposition.
• In gaseous state it is slightly blue, blue dark in liquid phase and dark red in solid phase.
• It displays angular molecular structure between the three oxygen atoms which compose their molecule.
This ozone is usually in the stratosphere layer, between 10 and 50 kilometers of height, where is the famous ozone layer. This layer protects us against the ultraviolet radiation of the sun that produces very dangerous genetic damages. The ozone layer is charged to absorb a huge amount (from 97% to 99%) of the total UV radiation that arrives at the Earth. We are going to see this process:
The energy absorbed by an oxygen molecule break it in two oxygen atoms.
O2 + hv O + O
Each one of these atoms, as we had commented, is joined to an oxygen molecule to give another one of ozone.
O + O2 Finally the ozone molecule, which was formed, is destroyed again absorbing more ultraviolet radiation:
O3 + hv In this way, ultraviolet energy is being absorbed in a closed cycle of formation and destruction of the ozone.
However, in the 80 decade the ozone began to diminish in stratospheric layers of the Antarctica . The cause of this hole in the ozone layer is the Bromine and Chlorine molecules, which are originated by human race. These molecules cause a great destruction of ozone molecule, so the ozone is not able to absorb the ultraviolet radiation:Cl + O3
Br + O3
An atom of chlorine or bromine by itself can destroy many ozone molecules since the ClO and the BrO are broke down again according to following reaction
ClO + BrO
It causes a closed cycle of ozone elimination which is disastrous for the human race.
However, ozone is not only present in stratosphere layer; if not there is a troposphere one that we can sometimes find around us. It has the highest oxidation value, higher than the oxygen one, the well-known chlorine or other oxidants; in fact, according to the conditions, ozone can get a power disinfectant of 300 to 3000 times higher than chlorine.
It can be formed in a natural way that takes place in isolated processes, as the fall of a ray or in certain conditions of urban contamination associated to photoelectric effects.
Due to the high oxidation and disinfectant power, it began to be used for a great amount of applications focused to water treatment, air and elimination of odours. It has a disadvantage respect to other disinfectants like chlorine, because it must be formed "in situ". Besides the fact if you dissolve it in water, it has a short life period, so it looses its power disinfectant in the long term.
The advantages of the ozone use are innumerable:
- Ozone has a high efficiency in the disinfection in relation to other species disinfectants causing the elimination and inactivation of virus and others microorganisms which are immune to chlorine.
- It eliminates a great amount of injurious substances, like iron or manganese.
- It eliminates all type of odours and colours in the water.
- It causes an increase in the clarity of the water and the efficiency of filters , since it acts like flocculent.
- It produces a great and better ventilation of the places due to oxygen gas formation on the surface of the water.
- It avoids the use and handling of chemical substances that can be dangerous like chlorine.
- But, mainly, the absence of chloramines and all type of compounds of chlorine that are highly annoying and injurious for the health.
- For the treatment of swimming pools, ozone is the most effective compound known. Besides the fact of improving the quality of disinfection of a swimming pool treated with chlorine, it avoids many of problems that this traditional treatment entails. We are talking about typical odour of swimming pool produced by the formation of chloramines, irritations, malaises, asthma, etc.
- The use of chlorine has also consequences of structural wearing in the facilities due to the corrosion which produces. Its storage usually originates problems in corrosion and security by the manipulation of this substance. In addition to this, the flocculante effect of ozone as well as its capacity of destruction of the organic matter, allows an increase in the effectiveness of the filters, and therefore a transparency of the water without precedents in other types of treatment.
- On the other hand, the ozone use for swimming of high level allows a greater yield in the swimmers, since the high concentration of chlorine gas on the surface of the swimming pool is avoided and this is replaced by an elevated oxygen concentration like consequence of the decomposition of ozone in the water. This allows an improvement in the marks of the sportsman and it contributes in the long term to the health of him avoiding the pernicious effects of chlorine.
