Today, my dad told me about a cleaning product for membranes he bought a while ago. He told me he put his finger in it and it didn't hurt him at all, nor did it seem to damage any tissues.

But later that day, he brought the substance and checked it's pH with a digital pH tester. It showed that it was pH 0. after diluting it to a concentration of around 20%, he said the pH meter reads 0.68.

I googled "strong acid non corrosive" and it came up with carborane superacid ($\ce{H(CHB11Cl11)}$) as an answer.

Is there a specific answer or is there a number of possible answers?
And what tests can we carry out to identify this acid?

Edit: My dad kept the acid for 15 seconds before rinsing

  • 8
    $\begingroup$ Acids (with few nasty exceptions) are not immediately corrosive to human skin. $\endgroup$ Jan 31 '18 at 12:16
  • $\begingroup$ my dad kept the acid on his skin 15 seconds before rinsing it with water $\endgroup$
    – Rickson
    Jan 31 '18 at 12:31
  • 2
    $\begingroup$ So what? I did the same on more than one occasion (not that I recommend it, but there were no consequences). Strong acids are very much not like what you think they are. $\endgroup$ Jan 31 '18 at 12:42
  • $\begingroup$ Suggested: youtube.com/watch?v=XeVZQoJ5FdE $\endgroup$ Jan 31 '18 at 15:52
  • 1
    $\begingroup$ Superacids like the one mentioned in the question are not for sale in stores etc. $\endgroup$
    – TAR86
    Jan 31 '18 at 16:52

This acid is actually not that concentrated. Suppose it were $\ce{HCl}$, then:

$\frac{10^{-0.68}\cdot 36.45}{0.20}\frac{100}{1000}=4\%\ \ce{HCl}$

I am not going to try on my skin but it is not like the 37% which we have in the bottle.

I guess that since it is for cleaning membranes, it is some chelant for the calcium with a bit of acid for the carbonate.


I could not resist...

I had some 5% $\ce{H2SO4}$ prepared for adjusting pH so I have tried it after all. So, no more speculation.

  • 20 seconds with the tip of the finger in it, does not itch;
  • 20 seconds on the hand, does not itch either;
  • on the tongue, it has definitively an acid taste, but it does not burn. It is, however, too acidic to take it.


Do never ever touch chemicals, nor taste them. Always work with proper attire, lab coat, gloves, goggles, etc.

  • $\begingroup$ I up voted but probably you should change into that concentrated.... I should change my answer as well as for I am not so sure that my finger started hitching in seconds with just 4% HCl. $\endgroup$
    – Alchimista
    Jan 31 '18 at 15:40
  • $\begingroup$ @Alchimista I have edited ;-) $\endgroup$ Jan 31 '18 at 16:06
  • $\begingroup$ Funny ediing :)) But I referred to your incipit . As for you use a strong acid for your demonstration ;) $\endgroup$
    – Alchimista
    Jan 31 '18 at 16:13
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    $\begingroup$ Don't try this at home kids! :D $\endgroup$
    – Mithoron
    Jan 31 '18 at 16:15
  • $\begingroup$ @Alchimista Ohh, right. Now I get. I will edit again. Thank you. $\endgroup$ Jan 31 '18 at 16:15

I cannot tell you what acid is in the product.

However burning and corrosion of skin and living tissues is not necessarily and directly due to fast acid/base reactions.

It involves reaction such as oxidation, nitration, dehydration, etc. or denaturing proteins.

For instance the damaging power of concentrated sulphuric acid resides mostly in its dehydrating and oxidizing power.

As such, the skin can get in touch with very acidic media without suffering immediate and permanent damage - and particularly so if the area is immediately and throughly rinsed.

This stated, I am not sure if such a low pH should cause an immediate hitching sensation. In my direct experience less than 15 seconds were enough to always start feeling hitches, independent of the nature and concentration of the acid handled.

On the other hand, we can exclude acid such as HCl, sulphuric acid, nitric acid, phosphoric acid. Plugging a finger on their solutions for 15 seconds will definitively be felt by the operator, unless very diluted, and burn its skin if conversely they are concentrated enough.

Final note. It is not a good idea to stick a finger in unknown chemicals as for some of them are very nasty, being them acid or alkali or none of the two.

  • 1
    $\begingroup$ "exclude acid such as HCl, sulphuric acid, nitric acid, phosphoric acid" - not really. pH = 0 is mentioned and it's quite diluted - around 1M. $\endgroup$
    – Mithoron
    Jan 31 '18 at 15:43
  • $\begingroup$ @Mithiron. I edited it upon reading the answer of R. Kessels. It is because I think to have felt hitching with all of them, including the about HCl 4 % we have in the bench. Then is matter of seconds 5 , 10, 15 etc. More diluted means no idea as for I am a chemist not an homeopath :)) $\endgroup$
    – Alchimista
    Jan 31 '18 at 15:50
  • $\begingroup$ I think the main danger from sulfuric acid isn't its oxidizing power, it is its dehydrating power. The reaction of water and concentrated sulfuric acid is extremely exothermic. Thus, sugar mixed with concentrated sulfuric acid results in decomposition of the sugar into water and carbon, with the water dissolved in the sulfuric acid. The reaction is pretty spectacular. $\endgroup$
    – AlaskaRon
    Feb 2 '18 at 7:24
  • $\begingroup$ @AlaskaRon. Yes, a spectacular example of oxidation as you can see from gas and water evolution plus the formation of tar. However I will edit for clarity, even more as for conc. Sulph. Ac. can suck out water even without reacting. $\endgroup$
    – Alchimista
    Feb 2 '18 at 8:36
  • $\begingroup$ @AlaskaRon you had me searching for p-nitroaniline videos. Quantity or quality? $\endgroup$ Feb 3 '18 at 3:17

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