Normality is similar to molarity, but it takes into account, for our purposes, acids with multiple hydrogens, such as Sulfuric or Phosphoric. I tossed them out there because I wasn’t quite sure what the OP wanted as far as ‘most powerful’.
I just looked this up, and it’s “Whink”. It does, indeed, contain hydrofluoric acid. Considering what HF can do, I have to confess thatb this freaks me out.
http://www.whink.com/rust_stain_remover.htm
It also freaks me out that Ammonium Bifluorite, used to etch window glass (and used by artists) is so easily available. It, too, contains lotsa fluoride ions.
First, some definitions (from 45th Edition of the Handbook of Chemistry and Physics and please no comments on how old the book is as newer editions dropped the Definitions and Formulas section):[ul]
[li]Normal - a one normal solution contains one gram molecular weight of the dissolved substance divided by the hydrogen equivalent of the substance (that is, one gram equivalent) per liter of solution.[/li][li]Molar - a one molar solution contains one mole or gram molecular weight of the solute in one liter of solution [/li][li]Molal - a one molal solution contains one mole per 1000 grams of solvent.[/li][/ul]
Thus for sulfuric acid (a diprotic acid - 2 moles of hydrogen ions per mole of acid) the normality equals twice the molarity. For phosphoric acid (a triprotic acid) the normality equals three times the molarity.
Further data on hydrogen chloride, hydrogen fluoride and sulfuric concerning their states at normal room temperatures:[ul]
[li]Hydrogen chloride exists as a gas at normal room temperature (20 degrees C or 68 degrees F). The boiling point of HCl is -84.9 degrees C (at atmospheric pressure). What is commonly called hydrochloric acid is a mixture of HCl dissolved in water. Normal commercial strength of hydrochloric (or muriatic acid) is approximately 36% by weight or 11.6 N solution[/li][li]Hydrogen fluoride is a colorless liquid or gas with a boiling point of 19.5 degrees C. If kept cool, it can exist at a pure liquid with a strong tendancy to vaporize.[/li][li]Sulfuric acid is a colorless liquid with a boiling point of 338 degrees C (for 98.3% and therefore can exist as a pure liquid at normal room temperatures with little associated vapor. Concentrated sulfuric acid (100% and not to be confused with “fuming sulfuric acid” or “oleum” which is a mixture of sulfur trioxide and sulfuric acid) has a normality of 37.3.[/li][/ul]
Further fire on the “strongest acid” argument (from the same 45th Handbook of Chemistry & Physics[ul]
[li]1 N HCl = 0.1[/li][li]1 N H2SO4 = 0.3[/li][li]1 N Acetic = 2.4[/li][li]0.1 N HCl = 1.1[/li][li]0.1 N H2SO4 = 1.2[/li][li]0.1 N Orthophosphoric = 1.5[/li][li]0.1 N Citric = 2.2[/li][li]0.1 N Lactic = 2.4[/li][li]0.1 N Acetic = 2.9[/li][/ul]
The pH of a completely dissociated acid at a 1 N concentration would be 0.0, with 0.1 N being a pH of 1.0. The reason that none of the above acids have a 1 N pH of 0.0 is because they are not completely dissociated which gets into the issue of activity coefficients and other considerations. So at 1 N concentration HCl is “stronger” than 1 N H2SO4. Acetic acid is “vinegar” and citric acid is what is in most citrus fruits. These latter two acids are said to be weak because they do not fully dissociate into hydrogen ions.
Hope this sheds some light on the subject.
There are different definitions of acidity, Jinx. This thread is largely about Arrhenius acids, which are defined as those substances which produce the hydrogen ion when dissolved in water (as has been pointed out by previous posters). As pH is related to the concentration of H+ in solution, it is not meaningful to talk about pH in the gas phase, as per your HF vapour question. (Ions do not form readily in the gas phase as they would represent very high energy species in this context).
I don’t think that pH is defined as having to be measured in water, you could measure the hydrogen ion concentration in any solution if you wanted to, but IME pH values are always discussed in aqueous solution.
If you’re interested in more definitions of acidity, a Bronsted acid is defined as something that donates a hydrogen ion. There is no reference to water here, so the definition is broader. Much broader still is the concept of Lewis acidity, defining an acid as a species that can accept a lone pair of electrons. Now you’re away from the hydrogen ion altogether, and this is the all-encompassing description that is probably used the most by chemists, at least IME.
people have died drinking it
"
A four-year-old boy drank several ounces of a laundry rust
remover containing 7-10% hydrogen fluoride. He was taken to an
emergency room where he was evaluated. No oral or pharyngeal
burns were noted. The skin was clear. The patient was sent to
the radiology suite for chest x-rays. During the hour that the
patient was in the radiology department, he rapidly developed
hypotension and arrhythmias. Attempts at resuscitation were
unsuccessful and the patient died. A serum calcium level was
4.3 mg per 100 ml.
"
I just want to say that making a paste of salt and lemon juice, putting it on any rust stain and giving it time to work is a better way to treat the things than a corrosive acid.
Dave Evans lists HBr as having a pKa of -10 in water (PDF). I didn’t see anything else with a lower pKa.
Btw, that link is a very nice reference for anyone for which pKas of organic compounds (and a few inorganic acids) are important!
Is this the reason I got sick to my stomach when I accidentally swallowed some of the fluoride treatment gel for my teeth?
Also re: the alkaloids, is that why when I clean my house with bleach/bleach products, my fingers feel slimy even after I wash them a couple times?
The only thing interesting thing that happened to me in Chemistry class were the nifty black pockmarks I got from spilling silver nitrate on my hand.
Dunno how you define “corrosive”, but all you’re really doing when you make that salt and lemon juice paste IS applying an acid. I seem to recall that lemon juice will dissolve some fairly unlikely things if given time to work.
Also dunno if I’ve just been wooshed.
OK, so it is my military bend of mind. Let me ask you all a dumb question. If I could deliver a liter or so of some sort of really nasty acid onto a tank, would it burn through (say 50cm) or armor?
How long would it take?
I was gonna say, “The brown acid at Woodstock.”
I think the point is that lemon juice won’t kill a person on contact with skin. Yeah, it’s corrosive, but it’s nowhere near in the same league as HF.
Corii: Is this the reason I got sick to my stomach when I accidentally swallowed some of the fluoride treatment gel for my teeth?
I don’t know.
Corii: Also re: the alkaloids, is that why when I clean my house with bleach/bleach products, my fingers feel slimy even after I wash them a couple times?
Bleach is sodium hypochlorite, a base. Your hands feel slimey because you are saponifying (turning to soap) the lipids in your hands. Has nothing to do with alkaloids AFAIK.
I checked. “MAY BE FATAL OR CAUSE PERMANENT DAMAGE. CAUSES SEVERE BURNS WHICH MAY NOT BE IMMEDIATELY PAINFUL OR VISIBLE. VAPOR HARMFUL. CONTAINS HYDROFLUORIC ACID. KEEP OUT OF REACH OF CHILDREN”
then the fine print begins.
It is called wHinK Rust Stain Remover (Not a general purpose rust remover)
It comes in a plastic bottle.
works for all colorfast fabrics white sinks and white toilet bowls.
As I said, I haven’t experiemented with it much. :eek:
That is a truly frightening idea. Selling that stuff to people who have no idea how dangerous it is.
He doesn’t list hydriodic acid, HI, which has the highest pKa of any acid and is generally considered to be the strongest of the strong acids. Not in terms of reactivity, just in terms of dissociation into H+ and I- in solution.
Exactly. You’d have to put your hand in a dish of lemon juice and keep it there for hours to do any damage. And it is not classified as an environmental toxin. Lemon juice and salt are also cheaper than commercial rust remover.
Most importantly, I’m sure you’d rather have your child accidently drink some lemon juice rather than any cleaner on the market.
Which alloys? I’ve used NaOH solution to etch 2024, 6061, and 6063. It seems to react very quickly with 2024, quite a bit slower with the 6000-series alloys, but eventually gets the job done without the need for fume hoods and major protective gear.