Proper use of muriatic acid to clean calcium deposit

[fsn77]

Oh gosh - i would never use 45 gallons of muriatic acid and soak things in it

Oh, I wasn't implying that you'd use 45 gallons of acid. I was using the words "acid solution" to refer to the furtherly diluted acid, not what's coming straight out of the bottle.

Good luck with the cleaning!

 

[nsamuel]

OK - today i took a ph check on the 40 gallons of tap water that i filled up into the tank. It was about 8.0 to 8.1 according to API test kit, and i know the local tap water has KH around 150 average. Hardness was around 160. To this i added 1 gallon of 5% vinegar i got from grocery store. I measured ph again and found that it was close in color to 6.0 of the API test kit. I do not trust the result because its so close to the low extreme that API test kit can measure and i suspected that the ph was much lower. So i looked up wikipedia and found "The pH of vinegar is typically in the range of 2.5 to 3, depending on the concentration of acetic acid. Commercially available vinegar usually has a pH of about 2.4" So i assume the resulting 41 or 42 gallons i had was much lower than 6.0. I dumped all my filters and other stuff into this diluted acid, and plan to leave it there for couple of days. I am hoping all the calcium deposits and fish waste that are in filter tubes would sort of melt away in the couple of days. I will keep this thread updated, so there is a place holder for cleaning efforts. By the way, simply soaking calcium deposits in tap water and leaving it for a few days softens them up and scrubbing becomes easy with a stiff bristled brush.

 

[Amphiprion]

I can tell you that the pH of the resulting solution is nowhere near 2.4. Somewhere around 6.0 sounds accurate, actually.

 

[nsamuel]

Thanks amphiprion. Can you explain to me why the resulting solution should be around 6.0 ? I understand it wont be 2.4 since its diluted. How do u arrive at the 6 ? just curious. Today i tested this tank water again and the ph has climbed to 6.3 and i think it might be due to the calcium deposits dissolving. The equipment is cleaning out very easily when i rub it with hand today. All the calcium is just dissloving with my hand rubbing. So, i guess 24 hrs of soaking is enough to disslove all deposits. After that just cleaning with a brush works great.

BTW, i also noticed that the RO water i buy from the local drinking water outlet has a ph of about 6.4 and i was wondering about that too. Any ideas why ? Has anyone tested their RO water ?

 

[Amphiprion]

I just ballparked it from intuition and experience. IF you are interested in a more precise answer, just use the Ka value for acetic acid and setup an equilibrium equation. Just convert your percent acetic acid in solution to Molar units (moles/L of solution) and plug the values in and solve for the H+ concentration. Take the -log of that and you'll get your (expected, not empirical) pH value.