Muriatic acid vs acetic (Vinegar), and relative strength

badpacket

badpacket

Premium Member
Hi All,

Just wondering if any knows what the relative difference is between MA and Vinegar, at a 5% solution.

I know MA is normally ~28% strength, and vinegar is 5%. I am assuming that even if I dilute MA to 5%, it is still going to be stronger than the Vinegar as it is a much stronger acid.

I also assume that many people may be under the mistaken impression that when they've diluted their MA to approximately Vinegar strength, they are underestimating its actual true strength.

Would this be correct?

pH of 0.10 M Solutions of Common Acids and Bases
Compound pH
HCl (hydrochloric acid) 1.1
H2SO4 (sulfuric acid) 1.2
NaHSO4 (sodium hydrogen sulfate) 1.4
H2SO3 (sulfurous acid) 1.5
H3PO4 (phosphoric acid) 1.5
HF (hydrofluoric acid) 2.1
CH3CO2H (acetic acid) 2.9
H2CO3 (carbonic acid) 3.8 (saturated solution)
H2S (hydrogen sulfide) 4.1
NaH2PO4 (sodium dihydrogen phos) 4.4
NH4Cl (ammonium chloride) 4.6
HCN (hydrocyanic acid) 5.1
Na2SO4 (sodium sulfate) 6.1
NaCl (sodium chloride) 6.4
NaCH3CO2 (sodium acetate) 8.4
NaHCO3 (sodium bicarbonate) 8.4
Na2HPO4 (sodium hydrogen phos) 9.3
Na2SO3 (sodium sulfite) 9.8
NaCN (sodium cyanide) 11.0
NH3 (aqueous ammonia) 11.1
Na2CO3 (sodium carbonate) 11.6
Na3PO4 (sodium phosphate) 12.0
NaOH (sodium hydroxide, lye) 13.0​
 
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It is way stronger. :D

Muriatic acid at full strength is more than 10 M, pH below 0. At 5%, that is 50 g/L, which is more than 1 M, so pH is still close to and possibly below 0.
 
For comparison to the pH below 0 for 5% HCl that I mentioned above, 5% acetic acid (vinegar) has a pH of about 2.4.

That makes 5% HCl several hundred times stronger in terms of H+ concentration, which directly impacts such things as dissolving CaCO3 deposits on pumps, etc. :)
 
Thats what I thought.

So, if one buys the pool acid from HD or a pool store @28%, one would really need to dilute it down to ~ x% to get a solution that is similar in strength to vinegar.
Can someone tell me how many ml for gallon of tap water that would be? Or would RO be preferred, I think?
 
Well, lets say for cleaning pumps, or cleaning tanks of coraline. I'd like to be able to take a gallon of water, and mix some MA and end up with a gallon of diluted acid at a strength equal to vinegar.
 
I think it is potentially a bit hard to exactly equate them. If you dilute muriatic acid to the point where the pH is the same, giving the same initial speed of dissolving CaCO3, the pH will rise faster in the HCl solution than in the vinegar because the vinegar has more potency (buffering) to keep the pH from rising above 6. So the vinegar at the same initial pH may last longer and ultimately may dissolve more if you wait a long time, even if it is slower initially.

I personally use muriatic acid for such applications.
 
no harm in going stronger, right?

No, except it fumes at high strength and becomes more likely to cause burns to you if you spill it. Be very careful to protect your eyes.
 
yah, I've burnt my skin before. but don't have the time to sit and wait for vineger. quick and easy at 1/2 strength. only problem, I have to dump some baking soda in the solution before it goes down the drain at that strength.
 
I agree with Randy. Make sure you use eye protection--better safe than sorry. Try a 10x dilution, which should still work quickly. 2x dilution could also easily ruin metal impellar shafts, suction cups, etc.
 
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