I cleaned my commercial water purification system with muriatic acid but I overdid it. Now there is excess muriatic acid residue. I used 6 liters of 29 % muriatic acid and further reduced with 33.6 gallons (134.4 liters) water as solvent at 1.2 % concentration of muriatic hcl.I believe the mole for the solution is 3.29 moles, is that right?

I have 99 % caustic soda flakes that I can use to neutralize muriatic acid residue. How do I go about it? How do I mix caustic soda at the right amount to neutralize the muriatic acid residue?

I'm not a chemist or a student so I would really, really appreciate your help guys. I'm on the verge of losing my small business if I don't fix this.

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    $\begingroup$ Better using backing soda and you just add it until gas evolution ceases. Don't forget standard safety behavior. $\endgroup$ – Alchimista Dec 20 '18 at 9:27
  • $\begingroup$ I can't. I have to mix this in the tank and run through the whole machine provided I allow the caustic soda to settle down a bit after a few minutes. Besides that baking soda leaves a residue. I tried it once, didn't like it. $\endgroup$ – rich33356 Dec 21 '18 at 2:41
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    $\begingroup$ Hi rich, I'm inclined to believe that the community closed this for the wrong reason (it does look like a homework question, funnily enough, but I'm sure that this is an actual problem you are facing). Your edit has put it into the reopen queue so that people can vote to reopen it. I'm not a chemist of any import, but I would say that the amount of flakes that you put in would depend on the amount of the residue, not necessarily the amount of solution that you originally put in. $\endgroup$ – jonsca Dec 21 '18 at 2:59
  • $\begingroup$ Thank you Jonsca for your reply. I measured the water. It measured 5.10 ph. Usually chlorinated water measures around 6.30 ph. And I could really taste the acidity of the water though it has lessened somewhat after a few days. The acidity even sticks to my gums when I taste it. Isn't there a way to calculate how much caustic soda I would need to adjust the ph judging from the measurement I took ? $\endgroup$ – rich33356 Dec 21 '18 at 5:07
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    $\begingroup$ I think it would be a bad idea to calculate a certain amount of caustic soda and then add this total calculated amount. Your assumptions for the calculation could easily be wrong. If replacing the water in the system is not an option, I would rather add small amounts of diluted NaOH and measure the pH after each step. Be sure that it has mixed with the water in the system properly to avoid false measurements. $\endgroup$ – aventurin Dec 21 '18 at 17:31

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