I’m assuming that the more intense an acid is, the sourer it tastes, such that lemon juice doesn’t burn our mouths but already registers as pretty strong on the sour-o-meter. What would things like nitric acid, sulfuric acid, hydrofluoric acid taste like if injury weren’t an issue?
Hydrochloric is comparable in strength to sulfuric and nitric, and much stronger than hydrofluoric, and you’ve probably tasted it. Yes, it’s sour.
Calling an acid super-strong isn’t likely the best metric.
The term strong acid is an important thing however.
So asking about sulphuric, nitric and hydrochloric makes sense. These are strong acids.
A strong acid becomes fully dissociated in solution. The converse, a weak acid doesn’t not fully dissociate and forms an equilibrium with water and whatever else is in solution. Since it isn’t fully dissociated it is not fully contributing to acid properties of the solution.
Where it becomes nuanced is that hydrofluoric is not a strong acid. It gets its particularly nasty corrosive properties from the oxidative capabilities of the fluorine it contains. Nitric is similar in this regard, the nitrogen in it adds to its evil properties.
An acidity is usually measured by its pH - potential hydrogen-aka its propensity to donate protons. Acids have a low pH. Strong acids get to a lower pH at lower concentrations. And get to very low pH at higher concentrations. In dilute form any acid can have have an arbitrarily mundane pH.
Tasting nitric or hydrofluoric acid would be a bad idea under any circumstances. The oxidative properties would likely swing the apparent taste away from pure sour.
Hydrochloric and sulphuric do taste sour. I once managed to vague out when drawing a pipette of dilute hydrochloric and was shocked into the present by the sudden taste of - well - a very lemony sour.
Sulphuric brings to mind a story from a century ago. I found this idly browsing books in the library. There was a series on annual reports from the Royal Navy. There was a report investigating an incident of lead poisoning aboard a navy ship. Suspicion fell on the “lemonade” issued to the crew in hot climates. This drink was nothing other than dilute sulphuric acid. The question was whether it had been contaminated with acid drawn from l ad acid batteries. But I was struck by the remarkable cheapness of the drink and what it was. A different time to be sure.
Ugh, obvious typo above. For “l ad” read “lead”.
Spurious “not” in there earlier as well.
Doing this on my phone is always painful.
Reminds me of one of the apocryphal stories about the origin of pink lemonade;
Do you have any more information about this? The only major case of lead poisoning I can find relates to the [now disproved] case of Sir John Franklin’s last expedition in HMS Terror and HMS Erebus. It was widely accepted that the crew perished partly through lead poisoning from the large amount of canned food they were eating (there was lead in the seals).
Modern analysis does not support this theory and concludes "Taken all together and within the context of previously published data, we conclude that the skeletal microstructural Pb distribution data do not support the conclusion that Pb played a pivotal role in the loss of Franklin and his crew."
Only very hazy memories I’m afraid. It was the early to mid 80’s when I was literally just killing some time in the depths of my university’s library, and ran across a series of volumes, and idly flicked through one. I’m pretty sure it was the British Royal Navy, and it was an event aboard a single ship, sometime in the early 1900s. The incident was investigated internally by the navy, but didn’t come to a useful conclusion. The trail to possible contaminated sulphuric acid from lead acid batteries didn’t hold up, and nothing else did either. Nobody died (I think), so I suspect it never escalated to greater prominence.
Having eaten these and burned my throat (mildly) doing so, I can say that yes, acid is sour.
Citric and malic acid are the relevant ingredients here.
pH describes the acidity of the solution, not the acid itself (e.g., HCl). Hydrogen chloride has a low pKa in water, meaning it dissociates easily. At a first order, sour taste is correlated with hydrogen ion concentration. But sour taste perception is more complicated than that:
For convenience, pH (–log [H+]) is generally used to indicate hydrogen ion concentration in acid solutions and foods. All acids partially or fully dissociated into anions and protons ([H+]) when they are dissolved in water. Thus one might expect a direct relationship between sour taste and pH. However, human psychophysical and animal physiological studies have shown that organic acids such as acetic and citric acids are more sour than hydrochloric acid at the same pH (Pfaffmann 1959; Koyama and Kurihara 1972; Ganzevles and Kroeze 1987a; Richards 1898; Ugawa and others 1998; Ogiso and others 2000; Lyall and others 2001; Richter and others 2003; Lugaz and others 2005). Beidler (1967) showed that solutions of 20 organic and inorganic acids that produced an equivalent neural response to 5 mM HCl in rats had pH values ranging from 2.11 to 3.14. Likewise, Makhlouf and Blum (1972) found a poor correlation between sour taste of organic acids and stimulus pH using acid-induced salivary secretion as an index of response. Moreover, the pH of various organic acid solutions is considerably different at their observed threshold concentrations (Berg and others 1955; Amerine and others 1965). Altogether, these results indicate that in addition to hydrogen ions, anions and/or protonated (undissociated) acid species play a role in determining sour taste intensity of organic acids.
https://ift.onlinelibrary.wiley.com/doi/10.1111/j.1750-3841.2007.00282.x
Obligatory safety warning to readers to never mouth pipette. This used to be common practice.
Gastric acid is pretty strong, with a pH value that is normally between 1 and 2. Its active component is hydrochloric acid. If you’ve ever thrown up and felt the taste of vomit in your mouth (I know, it’s not a pleasant topic to talk about, and probably not suitable for dinner table conversation, but it does happen), then you’ve had a taste of a strong acid (mixed, of course, with whatever partially digested food was included in the vomit).
I’m just old enough that in my freshman chemistry classes we had big NO MOUTH PIPETTING signs in the labs. Because this has just stopped being a thing.
And yes, I saw some of the old-timers do it.
The signs stopped being a thing? So, pipetting by mouth is totally OK now? Thanks for the tip! 
I once tried to use an old recipe for tanning hides. It called for the addition of vitriol (sulfuric acid) until it tasted as strong as a good vinegar. I declined to try it.
There’s also the issue that, like any sensor, human taste buds have some maximum response range. There’s some level of sourness that would just register as “that’s the sourest thing I ever tasted”, and beyond that, it wouldn’t matter how acidic it was; it’d all taste the same. I would imagine that all of the truly strong acids would be well beyond that limit.
When I was a kid, I had The Golden Book of Chemistry Experiments, a volume that taught me more basic chemistry than I got from my college textbooks. It had some pretty exotic (and sometimes dangerous) experiments. You wouldn’t be able to get away with publishing this today. But, fortunately, it’s up on the web at several sites. Here’s one – https://www.dancrean.com/BookChemistry.pdf
On page 42 it tells you how to dilute hydrochloric acid so you can taste that it, like other acids, is sour. On the next page it tells you how to taste dilute sodium hydroxide, which, like all bases, tastes “brackish”.
I’ve tasted sulphuric acid (accidentally*). It did taste acidic in a sort of lemony way, and of course, sulphurous.
*Years ago - as a forklift driver; we used to put the trucks on charge over night and during lunch break; you’re supposed to turn off the charger before unplugging the charging cables, but nobody did, and it was fine, right up to the time it wasn’t; an arc ignited hydrogen coming off the charging battery and there was an explosion which created a cloud of vapour from the battery liquid; some of it (not much) went in my face. It tasted sort of harshly lemony.
After a rinse down, I was taken to the hospital for a checkup - no lasting harm was done, but turn off the charger before detaching the cables, folks.
(blink)
Well, now I know to stop ignoring that handwritten post-it that suddenly appeared on our forklift charger in 2021.
Well, yeah, but we don’t need basic chemistry, here. We need acidic chemistry.
Same thing is true abut jump-starting cars. You can ignore the anti-arcing precautions a lot of times. Maybe even an entire lifetime’s-worth of times. But somebody somewhere blows up a battery in their face every day. Sucks to be them.
Do ya feel lucky? … Well … Do ya?