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Sulphuric: how do you do it



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Test Monkey (Moderator)
Mar 30, 2006
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Dude, if none of us know would you rather us tell you something that wasn't right? This isn't an instant question answering service. Give it more than a few hours.


Apr 18, 2006
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If you note your 'sulphuric ph hydroponics' google, on the first page of hits, is a tutorial on how to dilute battery acid for home hydroponics. The author describes a mixture of 950 ml. of water, to 50 ml. of battery acid.
The ratio of 950 to 50 isn't 9.5 to one. it's 19 to one. That gives you 20 parts in your solution, 19 of them being water, one being battery acid.

Well, that's to make one full liter.

a gallon is 128 ounces. At 8 ounces per cup, that's 16 cups per gallon. If you then did as the author of the site above and cut the acid with water, you could easily do a 15 cups of water, to 1 cup of battery acid, giving yourself a 15/1 ratio, instead of a 19/1 ratio. A little stronger, but, still quite within the same general range, of concentration when it is over.

Sulphuric will dissolve some plastics. Not all by any means and one that it won't dissolve, is the type you see on the bottom of plastic jugs denoted in the 'recyclable' triangle of the three arrows with a number inside, #2. It often says "h.d.p.e." under the universal 'recyclable' triangle with that 2 in it. The hdpe letters stand for "high density poly ethylene". A very common plastic for all sorts of plastic jugs.

Find one that is a gallon in size.

Go buy a gallon of some relatively pure water. Distilled is i guess technically the abso-*******-lutely purest in the land, de-ionized, or reverse osmosis, is a VERY close second, and tap water will work in a pinch.

Fetch a measuring cup. Make sure, please, that you don't fetch one that sulphuric will dissolve, by somehow or other doing a little test before hand, with a couple of drops of acid on the handle of it and a short wait, rinse, and examination, or get a glass one. Don't use a metal one. it'll corrode i'm pretty sure





If you drop the water into concentrated acid, the resultant steam droplet, surrounded by WAY enough acid to boil that little drop, will result in an expanding steam droplet so quick and severe, that acid will spash all over your ass.

The acid, dropped into the water, will be cooled by the vast quantity of water, and no such 'explosive expansion' will occur.

Clean out your plastic jug. Fill it, with exactly 15 cups of water. There will be some space left over, right? a gallon is 16 cups.

Then, having returned from auto zone with your new quart of SevenDollar and Fifty Cent battery electrolyte - acid-

Find a way to carefully open that acid, letting your freedom loving and responsible grown man make the smallest hole possible, so that when you store the acid later, it can't possibly spill everywhere.

The stuff is sold in a black and white generic box that says "DANGER: YOU CAN BE BURNED BADLY BY F*****G UP" on the side.

Inside will be either a clear plastic bag, with a spout for you to somehow clip, snip, poke, open; or a plastic box, with a spout for you to somehow clip, snip, poke, open;

Mine came in a plastic box with a screw off lid on one end, a little spout to cut off with a knife on the other.

I grabbed a drywall screw, and used it to screw into the top of that little spout, making a really, tiny hole, so it will be quite difficult to spill it later.

DRY OUT YOUR MEASURING CUP for um... good.... Measure. Don't let Murphy's law splash acid in your eyes by wearing some sunglasses. or some safety glasses. Or, do this near a faucet and if you get any in your eyes, wash it out immediatly, and for a prolonged time. If you get it in your eyes, try to save one eye so you can finish this project before time for bed and work in the morning.

pour exactly one cup into the measuring cup.

Now; slowly pour the acid, into the gallon jug you have, that's already got the previous 15 cups of water in it. When you're done, wash out the measuring cup with tap water. Use soap or your wife'll be pissed.

You now have, a 15 to 1 ratio, of battery acid, to purified water. here is how this breaks down:

15 cups is 120 ounces. The cup of acid you poured in was 38%. 38% of a cup, is 3.04 ounces. Lets call it 3 ounces. The other 5 ounces, was distilled water. Surprise.

So in effect, you have poured together, 3 ounces of pure sulphuric acid, and 125 ounces of water..
In order to find what percentage a little number is, of a larger number, you divide, the little number, by the bigger number, with a calculater: 3/125 = .024
(divide the little number by the big number. the answer comes out: .whatever - in this case .024

you move your . over, 2 places, to the right: it becomes wh.atever - and this is the percentage that your small number comprises of the larger one. In this case, .024, is 2.4 percent.

So, your new ph down solution is a 2.4 percent solution of sulphuric acid. At this point, if you dip your finger in it and touch it to your tongue, it will feel about as strong as a really cold coke on a real hot day. Don't drink it; i was just showing you that you don't have to be scared.

You can now put the stuff into your tap water, or your nutrient solution at oh, about.... the same amount as it would take if you used General Hydroponics ph down.

The difference? Well, it works just as well. It just doesn't add any phosphorus ppms.

The main difference is that you didn't have to drive to TimBukTu to go to the Hydro store; you don't have a big jug of "HEY I GROW POT HYDROPONICALLY LOOK AT ME" Sitting around, and the cost. Here's about how that breaks down.

1 Qt General Hydroponics ph down: give or take -15 bucks.
1Qt of your approved ph down: give or take - 72 Cents. if you used your own R.O. water or tap - 46 cents.

((7.50 for a quart of acid is 1.88 for a cup of it, (4 cups in a quart by the way) that makes a gallon of your ph down.)) a gallon has 4 quarts. That 1.88 divided by 4 is 47 cents. It costs 47 cents worth of acid to make your quart of ph down; a gallon of distilled water from a store is about 99 cents.. let's call it a buck; a quart of that water, is then, 25 Cents.

25 cents for a quart of distilled water from the store, plus 47 cents for the acid to make that quart of your ph down, 25 + 47 = 72 cents, more or less.


Apr 18, 2006
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No, it's not poisonous to the plants. If you do some creative googling, such as "Sulphuric ph down hydroponics" or "Sulphur toxicity roots" or Sulphuric toxicity or whatever,

You'll notice there isn't much said about sulphur toxicity. That's because it takes a lot of sulphur to hurt a plant. Not as much to hurt an animal. But plants do ok with quite a bit of it around.

However if you do some googling such as "Phosphorus toxicity roots" or 'Phosphoric acid precipitate' you will see where phosphoric acid is remarked about; sometimes they say, it will combine with calcium in water and precipitate out. I think this occurs when the ph is already climbing up into the sixes.

One thing that's interesting to note is that if the site isn't a hemp site, most of them suggest sulphuric as the recommended ph down. I guess it's because sulphuric is often cheaper, more easy to find anywhere, and is also a mild anti fungal agent, and doesnt have the problem of precipitating out when the ph starts to rise, although i'm certainly no expert on it.

You'll have to do your own google searches for all that. I can tell you a little bit; i can't make you free. Knowlege is power. Proper use of power is wisdom. and only wise men can be free for very long so you'll have to take care of the freedom loving wisdom accumulating part, yourself.

Good luck all. OverGrow the World.

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