I want to lower my soil pH from 7 to 4.5 with dilute sulphuric acid. It's time to buy potted blueberry plants here in El Dorado County, CA (Zone 9A) so I would like to adjust the pH quickly rather than waiting for elemental sulphur to convert to sulphuric acid in the soil over several months. My soil is a 50-50 mix of clay soil and rich compost with perlite added, and no commercial potting soil. I will be growing my blueberries in 20 in dia containers shaped like half barrels. I would appreciate a recommendation on the level of dilution for 93% sulphuric acid (I'm thinking 3 tablespoons of acid to a gallon of distilled water) and the application rate. Should the application rate be based on the surface area or the volume of soil in the container? After obtaining the desired pH, perhaps after several applications as determined by monitor pH, how long should I wait before adding 2 potted blueberry plants to the container?
IMO the only place 93% sulphuric acid belongs is in a chemistry lab or an industrial plant. It is a very hazardous material.
Using sulphuric acid directly at any concentration is probably a bad idea, because it will react with organic materials (e.g. cellulose and carbohydrates) in the compost, and won't do anything good to the microorganisms in the soil either.
Two relatively safe ways to "instantly" decrease soil pH are aluminium sulphate (sold horticulturally for producing blue hydrangea flowers on alkaline soils) and ferrous sulphate. Both have the disadvantage of reducing the availability of phosphorous in the soil to plants, but that might not be an issue for blueberries which grow in impoverished soil in any case.
I asked about the compost and the clay soil for a reason, because you want to use it in containers. Your compost should be pathogen free because its been produced aerobically, but the soil from the garden is another matter. Garden soil may contain pathogens which, all the time they're in open ground are fine, but may not be fine if transferred into containers. That is why potting soils are sterilised, to prevent any such problems.
I wouldn't recommend using sulphuric acid for the various reasons mentioned by other people already - I would recommend buying ericaceous (acid) potting soil instead, which is formulated for acid loving plants. If you want to add some of your own compost to it, don't add too much because composted materials are usually more alkaline than acid.
Having done that , I would say you can't do it . That is , it is not reasonably possible to make that large a change in a natural soil pH. I had a clay , sand , gravel soil in IL and I wanted blue berries . I put in a lot of organic mulch, a lot of gypsum ( Ca SO4) , sulfur dust and I forget what else ( I worked in a lab so many things were available ) . After 2 years of marginal growth and marginal pH change , I decided to cure them or kill them. I got a bottle ( 3 L ? ) of concentrated sulfuric . I poured it on 6 in. snow depth in a circle around 6 blue berry plants. Immediate snow melt - I could see where I poured. Some brown foaming on the soil surface. Next spring the blueberries grew very well . But the following year it was back to poor growth . So I decided it was not worth the trouble. PS ; several miles away in a very sandy soil , commercial blueberry farm did fine , they had a pick-yourself deal so that is where I got blueberries. PS 2 : Pretty sure conc, sulfuric is 98% ; in a refinery alkylation unit they try to keep sulfuric at 95% + or it starts dissolving steel.
I was a molecular biologist for 20 years and I have had more years of botany labs than I care to remember.
dilute Sulfuric acid is the quickest and safest way to lower pH - elemental sulfur is great if you want to wait a year. Plants love sulfates. Vinegar used at around 1/4 dilution works but only for a couple weeks - due to acetate effect after soil transformations.
I am searching for the proper dilution as well...but I know 1/4 vinegar in water works great for about 1.5 pH decrease in my crappy calciferous clay soil full of ca carbonates.
So simply determine the Normality of 1/4 vinegar and replicate. Probably about 2 tablespoons per gallon of water.