Here ya go, this is my write up on the dry rock acid bathing process.
Well, it wasnt the most sceintific of approaches...lol we were shooting for a 10:1 water to acid ratio. We used muratic acid(31% hydrocloric acid) that you can get at the hardware store either in the tile section where it is used to clean up grout and to etch concrete prior to painting, or in the paint department. His rock looked freshly plucked from the ocean and only dried for a short time. Theres no way to know for sure but there was a lot of dead algae on it.
We scrubbed the loose stuff with a wire brush after soaking in freshwater overnight. After that, add your water(ro.di if you want, my water is rainwater from a cistern so its low in tds) using a gallon pitcher so you know how much you put in. We just covered the rock with water. It was 17gal. So to get a 10:1 we shouldve used 26 cups of acid. I only had a half gallon at my house so we just used that much on the first go. Make sure you always pour acid into water, not the other way around or you risk having it bubble out of control and splashing it on yourself. It was FILTHY on the first round(the pics are of the second bath). I put a powerhead in the bin with it and let it do its thing for around half hour.
We carefully, using chemical gloves and eye protection, emptied out the bin and dumped it in a flowerbed that Only contains weeds(project that got backburnered due to my tank build this summer). Then we filled the bin with new freswater after rinsing the rocks with a hose. We added a few tbsp of baking soda to nuetralize the acid and let it soak with the powerhead running while we went to the store to get more acid.
When we got home, we dumped the water out and filled it again with freshwater and started to add the acid. It was a different brand than the stuff I had and it said it was 90% less fumes plus didnt give a percentage of HCL. We assumed it was a weeker solution so we added the whole gallon. That was probably a mistake. We let it soak for another 20 mins then dumped and added new water with baking soda again and allowed that to soak for 20mins.
He then took the rock home where hes currently doing rodi soaks with baking soda for 24 hours. Once the ph of the water is above 7 the rock should be ready to go in the tank.
Now, he says the rock is really brittle. I think using the full gallon of acid was too much. Ill tell ya though, that rock was FULL of nasties. I would be leary as hell of using it in my own tank right out of the box so im glad we did it for him. However, if I were to do it again I would stick on the low side of the 10:1 ratio and make sure that whatever acid you get has a clear label of HCL concentration. Good luck!