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Answer:
Annotation from editors:
"Negative ions" have become recently trendy in Japan
(2001, Reference) because negative ions seem to be good for our health. For example, there is a report which shows that more negative ions exist in forests than in urban areas. So some companies are selling products which produce negative ions. However, there is an argument about whether negative ions are good for our health or not, and even about whether negative ions really exist in air or not. We created
the following article based on the advice of an anonymous professor.
Please let us know if you have any
comments.
Many people in Japan are interested in and wondering about
"negative ions" There is an advertisement where negative ions are flying in the sky. We often hear that many negative ions exist near waterfalls.
However, according to the law of charge neutrality, it would be a bit strange that only negative ions exist. Actually, enormous amounts of energy would be required to bring two
1 g samples of imaginary salts containing only negative ions to within 1 cm of each other. First of all, let’s think about it.
Is there really a space where excessive negative ions exist?
In fact, it is a common phenomena that charge can be unequal, i.e. excessive negative or positive ions can exist. Metal wire will be highly charged if it is stretched in air. This implies that charge in air is not neutralized perfectly. Thunder is generated because
one type of charge is pooled on the bottom of some clouds, and the voltage between the cloud and the ground becomes so high that it finally
discharges.
Charge phenomena also occur when a bottle with liquid inside is twirled. If the liquid is water, the bottle is not charged because water is
a conductive liquid and the charges are neutralized by the current between the bottle and the water. However, if the liquid is not conductive (e.g. oil), then the bottle is charged. This sometimes causes oil tankers to explode. Thus, it is important to prevent oil tanks from becoming charged. Charge phenomena tend to occur whenever substances are
rubbed against one another.
The claim that "there are many negative ions near
waterfalls" is possibly connected to the phenomena of friction. Suppose that micro-drops of water are charged by
an excess of hydroxyl ions. As a drop of even a few
mm in size possesses an enormous number of water molecules, it would take a very small amount of energy to hold a few extra
H+ or OH-. Therefore, I think that the occurrence of charge phenomena is possible. The reported concentration of negative ions near waterfalls is extremely low (~ 8500 negative ions /
cm3). Therefore, the effect of this range of excess ions existing in air is negligible.
Although high-density charges, e.g. a 1 g sample of negative ions, do not occur, it is possible for excess negative ions to
exist in air to the extent just mentioned above.
Effects of negative ions on the human body
We could not find out how an extremely small amount of negative ions effect the human body. If it is statistically correct that negative ions tend to exist more in spaces where people feel comfortable, negative ions might influence something on the human body. This would be a very interesting subject for research. On the other hand, it would be difficult to study this causal relationship accurately. We will feel fantastic if we spend our time on the coast or in the
forest. However, it may be due to colors such as blue and green, or to proper moisture and temperature, rather than to negative ions. It would not be easy to
separate out the factor of negative ions from many other factors, and explain how it works scientifically. I think that we need to patiently wait for future research findings and then examine them carefully in order to conclude this issue.
Acknowledgement
We would like to thank an anonymous professor for his careful teaching and kind support for this answer.
This article is translated by Chemistryquestion.com from the original article in Chemistryquestion.jp. Please let us know if you find any errors.
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