Lately the news media have made much ado about so-called perchlorate in drinking water. I don't remember much of the chemistry class I took in high school some 42 years ago, but I remember enough to know that the "ate" suffix denotes a chemical compound, and not chlorine alone. So I wonder, WHAT perchlorate? I assume it's ammonium perchlorate that they're talking about, but I'm certainly not sure. Why do these so-called news reporters not find out what they're talking about before reporting it?
Asa, your last sentence is a rhetorical question, I trust?
On the other question, I have no definite answer, but the dictionary tells me that a perchlorate is 'a salt of perchloric acid', so I suspect that there are lots of perchlorates, not just one. Perhaps several perchlorates are in the water, all having similar effect? If so, the usage in the news reports would be understandable.
Hmmm, I am struggling here, but doesn't "per" in this situation mean something like an extra amount? I looked it up in some online chemistry dictionaries, and the synonym of "hyerchlorate" was given, which would seem to confirm that. Of course, I really don't know what "hyperchorate" means, either!
quote: Perhaps several perchlorates are in the water, all having similar effect? If so, the usage in the news reports would be understandable.
Then why wouldn't they make it plural? This is as assinine as people freaking out because "chemicals" are in our drinking water! Oh, heaven forbid that we should consume dihydrogen monoxide! And then there are the loonies claiming that they only buy "organic" food! Get a clue, folks, if it ain't organic, it ain't food! Orgainc chemistry is that branch that deals with carbon, hydrogen, and oxygen compounds, that is, the chemicals found in living organisms! But maybe the world is different since I was in school...
I forget what the per means, but since hydrogen peroxide is H2O2 it might mean an extra oxygen and perchlorate is ClO4 rather than ClO3... it could be looked up.
But in water it would exist as a dissociated ion, not a salt, wouldn't it? If you throw Na2ClO4 and K2ClO4 into water (and I'm making up these valencies instead of web-searching for the right answers) you get quantities of Na(2+), K(2+), and ClO4(2-). So it's right to talk of perchlorate regardless of its solid origin because that's now the stuff that's floating around in the water.
I thought that perchlorate (like oxide or sulphate or any other of these compound designators) couldn't exist on their own. Or as our old chemistry master said, "...You can't have a bucket of chlorate.."
So any perchlorates in drinking water will be linked to an element, such as sodium. So surely you wouldn't get "free" percholorate in water, would you?
And I agree with Asa about the spurious nonsense that's talked about "chemicals". Chemical-free food (or chemical-free anything) is a vacuum since everything is made up of chemicals (including ourselves).
Of course, the term is used to refer to chemicals that have been added to a foodstuff in which they weren't originally present which may, or may not, be a good thing. In the case of the chemicals added to many US beers to create sparkle and a frothing head they are probably not a good thing.
In the UK is is now illegal to produce any pre-packaged foodstuff (with the inexplicable and rather pointless exception of alcoholic drinks) that does not have a complete list of all its constituents shown, in order of their proportion, in a place where they are clearly visible to potential purchasers before purchase.
Sadly few people read them of they'd never drink Coca Cola ever again!
Richard English
Posts: 8038 | Location: Partridge Green, West Sussex, UK
Aput is right, Richard is wrong. There is nothing wrong with the language of the news reports.
Water will be full of all sorts of ions, some of them positive, some negative, all free to move around individually, and none of them likely to pair up with a partner of the opposite charge because their attractiveness is smothered by a thick blanket of water molecules.
Perchlorate is the chlorate (VII) ion. It is ClO4-. It comes from perchloric acid (chloric (VII) acid). The acid is very strong and also explosive. Don't try and open a bottle of perchloric acid if the stopper has jammed - the friction of freeing the stopper could cause you to lose an arm. Always delegate such a task. You get perchlorates in fireworks.
I would be worried with too much perchlorate in my drinking water. Thankfully, English tap water is excellent.
Well, chemistry wasn't my subject - but even so, perchloric acid isn't perchlorate, is it? And more than sulphuric acid is sulphate. It has to be linked with another element - in the case of the acid, that element is hydrogen.
Having said which, my learning didn't get as far as ions so that part of it is a blank to me. Indeed, when I was at school I don't know that the mechanism of valencies was even fully understood although the values of the various elements' valencies were know.
Richard English
Posts: 8038 | Location: Partridge Green, West Sussex, UK
Perchlorate molecules like potassium perchlorate, ammonium perchlorate and perchloric acid dissociate in water into a free potassium, ammonium or hydrogen ion and a free perchlorate ion. The free perchlorate ion interferes with iodine transport in the thyroid gland, in fact, in the past it was used to treat Grave's disease or hyperthyroidism: slow iodine intake and you slow hormone production. The fear is that people with iodine deficiency, particularly pregnant women, are at risk for things like cretinism. Perchlorates are used in explosives, so places with perchlorate contamination tend to be near military reservations and manufacturers of explosives.This message has been edited. Last edited by: neveu,
Thank you, Graham and neveu, for setting me straight! It appears that even if they didn't know what they were talking about, the reporters WERE correct! I guess it's time I find a chemistry book...
We have the same pluralization rule, RE, but for us the singular is valence. Apparently for you folks the prefered form is valency, so the plurals differ accordingly.
The free perchlorate ion interferes with iodine transport in the thyroid gland, in fact, in the past it was used to treat Grave's disease or hyperthyroidism: slow iodine intake and you slow hormone production.
Of course! That's where I had heard it. Because it is not used that often, I had to go to the gold standard of pharmacology, my "Goodman and Gilman." They call the classification of "perchlorate" an ionic inhibitor. These agents are anions that resemble iodide; they are monovalent, hydrated ions and similar to the size of iodide. Another is thiocyanate.
Among the other anions, "perchlorate" is 10 times as active. It is still used to treat hyperthyroidism, according to "Goodman and Gilman," though at high doses it has been thought to cause fatal aplastic anema. There are other good drugs to treat hyperthyroidism now, as well as radioactive iodide.
Great discussion, guys! And, Asa, you asked a good question, obviously. No crow for you!
When I first learned those words in chemistry class, valence and valency were synonyms for me and I remember being struck by their interchangeability. But somehow I settled on valency and have never used (or indeed seen) the other since.
That's as a name for the property: the valency of chlorine is 1. However, there's the expression 'valence electron', which I'd only ever say with valence. And this is odd: a noun form that's only used in a N N compound.
quote:Originally posted by aput: I forget what the per means, but since hydrogen peroxide is H2O2 it might mean an extra oxygen and perchlorate is ClO4 rather than ClO3... it could be looked up.
That's right, as I understand it. Since Lavoisier believed (incorrectly) that all acids and their salts contained oxygen, he used the prefixes hypo and per (from hyper) and the suffixes ite and ate to indicate the relative amounts of oxygen in them. There are a number of sites that explain it. Here's one from Purdue University. Click on Polyatomic, then scroll down to Naming Polyatomic Ions
quote:Naming Polyatomic Ions
At first glance, the nomenclature of the polyatomic negative ions in the table above seems hopeless. There are several general rules, however, that can bring some order out of this apparent chaos.
The name of the ion usually ends in either -ite or -ate. The -ite ending indicates a low oxidation state. Thus,the NO2- ion is the nitrite ion.
The -ate ending indicates a high oxidation state. The NO3- ion, for example, is the nitrate ion.
The prefix hypo- is used to indicate the very lowest oxidation state. The ClO- ion, for example, is the hypochlorite ion.
The prefix per- (as in hyper-) is used to indicate the very highest oxidation state. The ClO4- ion is therefore the perchlorate ion.
There are only a handful of exceptions to these generalizations. The names of the hydroxide (OH-), cyanide (CN-), and peroxide (O22-) ions, for example, have the -ide ending because they were once thought to be monatomic ions.
TinmanThis message has been edited. Last edited by: tinman,
Valency is also used as a linguistics term: it means the number of arguments a verb takes. For example: impersonal verbs have a valency of 0, intransitive 1, transitive 2, ditransitive 3. The arguments being nouns/NPs as subject, object, indirect object, etc.
Weather verbs are normally regarded as valency 0: it rains, it thunders. In English we need a surface subject, so if there isn't a real one we use 'it'. In languages that don't require subjects, like Italian or Spanish, a weather clause is just the verb.
Beyond 3: the apparently unique example of a higher-valency verb in English is 'bet', valency 4: A bet B (amount) C that D.This message has been edited. Last edited by: aput,
There's a discussion of valence here. You know about transitive and intransitive verbs because they exist in English. Transitive verbs take a required subject, and intransitive verbs take a required subject and direct object. Those verbs have a valence of 1 and 2. It's just a way to talk about verbs and their arguments cross-linguistically.
