What are "negative ions"?

Hello, Cecil. I have read your below article (all I could find in your archives
after searching for ‘negative oinization’),

Do “corona discharge” devices alleviate asthma?

but a question remains; What IS a “negative ion”, and how do these silly machines
make them? The below article which I found here; http://www.skepdic.com/refuge/funk36.html
seems to make it obvious that they don’t exist. If this is so, what are manufacturers putting
inside these “negative ion generators”? Somebody must have ‘reverse-engineered’ some of
these things, surely.

Also, what about sites like this; http://www.ionic-hepa-air-purifier.com/negative-ions.htm
and http://gsearch.ars.usda.gov/search?q=negative+ionization&btnG=Go!&restrict=iapreview&filter=0&as_sitesearch=www.ars.usda.gov&site=iapreview&ie=&output=xml_no_dtd&client=iapreview&lr=&proxystylesheet=iapreview&oe=
who claim to have made and scientifically tested these things? How are they made? Are these
experiments peer-reviewed? How can ‘negative ions’ be ‘made’ if they don’t exist???

The straight dope, please!!! :slight_smile:

…> Start article>>>

I would appreciate being contacted by email rather than here… Thanks.

mj.wade@qut.edu.au

>but a question remains; What IS a “negative ion”

I’m surprised you couldn’t find anything on this on the web. It is simply an atom with extra electon(s), giving it a negative charge.

For example http://education.jlab.org/qa/pen_number.html :

"An atom can gain or lose electrons, becoming what is known as an ion. An ion is nothing more than an electrically charged atom. Adding or removing electrons from an atom does not change which element it is, just its net charge.

For example, removing an electron from an atom of krypton forms a krypton ion, which is usually written as Kr+. The plus sign means that this is a positively charged ion. It is positively charged because a negatively charged electron was removed from the atom. The 35 remaining electrons were outnumbered by the 36 positively charged protons, resulting in a charge of +1".
Or is your question more like: “air ionizers discharge negative ions of what atoms”?

The only atoms available to them are in the atmosphere, so it pretty much has to be nitrogen or oxygen. As that site you posted says, you really hope it isn’t oxygen as that would make a pretty fierce free radical, causing exactly the opposite effects to those claimed.

Note that site is NOT saying that negative ions don’t exist, just that they could not possibly accumulate on mountain tops or by the sea, and that there is no evidence they have the health benefits claimed.

Welcome wreckage. (I am not Cecil, so i’ll post here instead of emailing you at QUT.)

Negative ion generators produce a high voltage at the tips of needles, which in turn ionizes air near the tip of the needle. Needles are used because charge accumulates at points. The current produced is very low.

The negatively charged air is forced by self repulsion away from the tip of the needle. You can feel the ion wind if you hold the needles close to your top lip.

The idea is that the negatively charged air neatralises positively charges dust particles, thus preventing repulsion between the particles and allowing them to collide and precipitate out. Similar to adding Al3+ or Fe3+ to muddy water.

You can see a small collection of dust build up around the needles of one of these devices over a long period. The thing is - the amount of dust precipitated is negligible.

Another good negative ion generator is a CRT. You will notice around computer moniters and TV sets the build up of dust over time. In fact CRT’s are probably better than the new-age products.

Any ionised air is soon neutralised by coming into contact with a positive charge before it can do anything magical to you healthwise.

Biefeld-Brown effect

Note that not just atoms, but molecules can be ionized, and since the only noteworthy atom in air is Argon, and in very low quantities, ionizers are ionizing molecules: N2, O2, CO2.

As for Ozone, that is a very undesirable side effect of improperly built/maintained ionizers. If you smell “thunderstorm freshness”, shut it off and try to get a refund.

Since ionizers are frequently made by fly-by-night companies that don’t actually care about your health, the chances of getting an Ozone producer is much better than average. Consumer Reports routinely checks into these things and never has anything nice to say about them.

An ion is just an atom (or group of atoms) which has an electric charge. If it has more electrons than protons, it’s a negative ion, and if it has less electrons, it’s a positive ion (since electrons are negative and protons are positive). The way they’re most commonly encountered is dissolved in water: Salt or any other salty compound splits into ions in solution. In the case of ordinary table salt, for instance, sodium chloride, neutral sodium has one more electron than it’d “like”, and neutral chlorine has one less electron than it’d “like”, so the chlorine atoms take electrons from the sodium atoms. In a solid salt crystal, the sodium ions and chlorine ions are stuck together, because their opposite charges attract each other. Dissolved in water, the different kinds of ions are just sort of floating around.

Now for ion generators: You can make negative ions of anything (presumably nitrogen or oxygen molecules, if you’re in air) just by sticking extra electrons onto it. But those electrons have to come from somewhere, so whenever you create negative ions, you’ll also have to create the same number of positive ions. And unless you’re in a Hellaciously hot environment, those electrons are going to move right back to where they came from pretty quickly, leaving you with no ions at all. So even if those gadgets do produce ions, they probably don’t do any good.

Many years ago I helped a friend move out of a room in a share house right next to a main road. He had had a NIG running in the room continually for, oh, two years.

When we pulled his bookshelves and other furniture off the wall the place where every piece of furniture had been was outlined in deposited dirt/dust/crud/whatever. I mean really dramatically; the bit of wall directly behind each shelf was virtually clean, and a good centimetre around it quite black with quite a sharp line between.

Just a datapoint.

Welcome. For a newbie that’s quite a first post!

Welcome to the SDMB, wreckage.

I have edited your post to remove most of the text from the Skeptic’s Dictionary site. We are pretty strict about copyright concerns around here. Generally, quoting more than a couple of paragraphs is too much. The rest can be read at the link you provided.

Since this is a question about one of Cecil’s columns, I’ll move this thread to the Comments on Cecil’s Columns forum.

bibliophage
moderator GQ

Not all negative ions are stable - an unstable negative ion can just get rid of the extra electron (the technical term is “autodetach”) and become neutral. Many stable molecules (and some atoms) don’t have stable negative ions - these include argon, nitrogen (both N2 and N atom), water and carbon dioxide. So, for example, your negative ion generator won’t make (N2)-.

Negative ions you make from air are (O2)- predominately, with some O-, maybe a bit of ozone anion (O3)- and a little bit of hydroxyl anion (OH)-.

(This is not meant to imply that your negative ion generator will actually make any of these ions or do anything useful at all)

Not all negative ions are stable - an unstable negative ion can just get rid of the extra electron (the technical term is “autodetach”) and become neutral. Many stable molecules (and some atoms) don’t have stable negative ions - these include argon, nitrogen (both N2 and N atom), water and carbon dioxide. So, for example, your negative ion generator won’t make (N2)-.

Negative ions you make from air are (O2)- predominately, with some O-, maybe a bit of ozone anion (O3)- and a little bit of hydroxyl anion (OH)-.

(This is not meant to imply that your negative ion generator will actually make any of these ions or do anything useful at all)

Thank-you for your informative replies. I leave a wiser man. :slight_smile: