I think the pH is the combined result of acid and base ions. So the pH of 8 means alkaline. By adding acid the alkalinty is neutralize and further has become acidic.

No, but I think the release of hydrogen from the acid rips the alkaline molecules apart, so yes less of them.
M3 is a mystery to me? Carbonate is usually measured in mg/L. Meters cubed?
The reaction does take awhile btw, you may want to re-measure the PH, bet it is higher than 6.0 now...
People often confuse the terms alkaline and basic. They actually mean quite different things.

This post was edited by Drew51 on Mon, Dec 9, 13 at 11:54

People also wrongly assume a high water pH automatically assumes high alkalinity. You can have a pH of 8 and alkalinity below 50ppm. High alkalinity though always means an elevated pH.

Drew. "M3 is a mystery to me?"

Does 25 g CaCO3m3 shine more light on the subject?
My local counsel gave it to me without the 'g'. The correct way apparently is ...g CaCO3m3.
It makes sense to me that after I adjusted the pH, the alkalinity will also change. Is that correct? Any indication by how much maybe? A proper alkalinity/pH tester is maybe the way to go...?

Unless google or somebody can give you the conversion to a more common alkalinity measure, you're never going to know your starting alkalinity. You need to somehow get a sense if your starting alkalinity is "high", "acceptable" or "low."

This all said, you (or we) might be overthinking this. I am 95% certain that a pH of 6.0 indicates a low alkalinity, which will be fine for you, as 6.0 is very near the sweet spot in terms of nutrient availability range in solution and adding minimal bicarbs to your potting mix.

The 5% uncertainty comes from if the acid brought the alkalinity down to zero (like distilled water) and you add a very acidic liquid fert to the water. Repeat irrigating with this water may crash your medium pH down to below 4, which can be problematic.

At the end of the day, it's more important to know your medium pH than your irrigation water pH. Google the 'pour-thru' method and try it on your containers. You can indirectly back into whether your water is low/med/hi alkalinity. If your medium pH is between 5.5 and 6.0, you're in good shape for 90% of potted plants and your aim should be to keep it there stable.

Thanks for that Oxboy. I only use FP 9.3.6 and add ProTekt in flower/fruit time. I feed as they say "weakly". I am thinking the same thing about the "pour-thu". I've ordered some litmus paper, as my liquid pH tester will be influenced by the dirty water I think. Either way I am waiting in anticipation on the papers.
I know my media pH. Its 6.9 because I added to much dolomite with the 5.1.1.

probably "25 g CaCO3m3 " means (CaCO3 = 25g per cubic meter).

So that is the basis for alkalinity. Calcium is often co related to raising pH( hence alkalinity). Acids can counter balance it. But Calcium, as an element will be there in some form.

BACK TO TOPIC:
Your water is basic(pH>>7) because of CaCO3. And any time you water, you will be like adding calcium to the soil. Depending on the soil analysis this might be actually good. So before treating your water, perhaps it would be a good idea to find out the soil pH and the amount of calcium in it. JMO

I don't know if this will be helpful to any of you, but hopefully I can shed a little light on acidity/pH without getting into too much weird chemistry stuff.

pH=-log[HâÂÂOâº]
pOH=-log[OHâ»]
pH+pOH=14
[ ] denotes molarity (concentration of solute in one liter of solution)

HâÂÂOâº, the hydronium ion, is formed when acids dissociate in water and release hydrogen ions. Free hydrogen ions bond with water.

OHâ», the hydroxide ion, can form either from the dissolution of a substance that contains it, or the dissolution of a substance that can capture a hydrogen atom from water. Oòâ» is technically a stronger base, but reacts immediately with water to form hydroxide.

Pure water dissociates into both ions, but at an extremely low rate. The ions then quickly react and form water. The concentrations of these ions in pure water at standard temperature and pressure forms the basis of the pH and pOH scales.

How does this relate to something like dissolved minerals?

CaCOâ is a salt that can dissociate (though not very well) into two ions, Caò⺠and COâÂÂâ» (carbonate ion). Carbonate can react with water to form carbonic acid and hydroxide, which is a weak acid--it dissociates very slightly to form hydronium and bicarbonate. Even though the reaction formed an acid, the low solubility of the acid results in a net increase in OHâ» in the solution:

COâÂÂâ» + HâÂÂO-->HâÂÂCOâ + Oòâ»
Oòâ» + HâÂÂO--> 2OHâ»

On the other hand, calcium ions can react with water to form Ca(OH)â + HâÂÂOâº. Ca(OH)â is a weak base and does not dissolve completely either, so this reaction results in a net increase in HâÂÂO⺠in the solution:

Caò⺠+ 2HâÂÂO-->Ca(OH)â + 2Hâº
2H⺠+ 2HâÂÂO-->2HâÂÂOâº

Consider NaCl (you call it salt; geologists call it halite). It dissolves into two ions: Na⺠and Clâ». Both of those ions could potentially form a strong base and a strong acid (NaOH and HCl). Both will dissociate completely in water; hydroxide and hydronium will react and form water; there will be no net change in pH:

Na⺠+ 2HâÂÂO-->NaOH + HâÂÂOâº
NaOH-->Na⺠+ OHâ»
OHâ» + HâÂÂOâº-->2HâÂÂO

Back to CaCOâÂÂ. To increase the pH of the solution, the strength (which can be thought of as the potential for an acid or base to dissociate into its ions) of the base formed after dissolution of the salt needs to be higher than the strength of the acid formed. A stronger base will dissociate more, and its hydroxide ion will react with any hydronium present--this can come from the formation of the base or dissociation of the acid. Either way, there will be excess hydroxide in the solution, and little to no...

Well, if your media pH is 6.9, you'll want to get it down and the steps are very simple:
- flush flush flush with water, preferably low alkaline/distilled/rain water, but any water will end up working. This will dissolve and rinse the lime/bicarbs out the drainage holes.
- begin watering with low/zero alkalinity water. This of course is what you are trying to get at.
- keep using your FP. I use FP and it always drops my water pH about 1 or 2 notches (from say 6.5 to 6.3.6.4)
- test periodically. Once you get to 5.5-6.2 medium pH, work out what it takes to keep it there. Take notes and be detailed/precise until you get a feel for how much acid to add each watering.

Yeah that sounds like a good plan Oxboy. I have been flushing with rainwater but fast running out. Its kind of a natural response hey? I'm "creating" my own rainwater now by adding acid to the tap water. The sulphuric acid works very well for the pH but i'm concerned about the alkalinity.
Thank you ever so much for all your info. Much appreciated... :-)

CaCo3+H2SO4---CaSO4+H20+CO2

CASO4 is calcium sulfate otherwise known as gypsum, No more alkalinity. And it won't come back!
Gypsum is a precipatate, and is neutral.

This post was edited by Drew51 on Tue, Dec 10, 13 at 18:58

Vinegar turns calcium carbonate to calcium acetate. Many genera of bacteria can convert it back. Even higher organisms can do it. Citric acid makes calcium citrate, I don't know if any bacteria can convert it back?
One thing about vinegar though calcium acetate is soluable, and you could flush it out. But as you see in the previous post no worries with sulfur.

HUH... Why do I get the feeling that something just flew over my head Drew? Maybe its because it messed up my heardo... LOL. Will stick to the pH and Alkalinity strips and Suphuric Acid for now. Rome wasn't built in a day. Hopefully I will get to some scientific standard someday...:-)

CaCo3+H2SO4---CaSO4+H20+CO2

Sorry OK, first is the alkaline calcium carbonate in your water(CaCo3) plus sulfuric acid (H2SO4) makes water(H2O) carbon dioxide(CO2) and gypsum(CaSO4).
Remember you quoted that paragraph and the guy said first the acid will neutralize the alkaline, then the PH drops?
So your water now is completely free of any alkaline substances, as you did drop the PH.

If you used vinegar instead of sulfuric acid you would not get gypsum, you would get Calcium Acetate, which can be converted back to alkaline by bacteria. So temporary. If you tried citric acid you would get Calcium citrate.

Sorry I have had lot's of chemistry and I forgot most of it, but do remember it makes little sense at first. Plus I'm not a good teacher!
I just wanted to go over why sulfuric acid is superior to the other acids.

"My tap water had a pH of 8.0 and alkalinity of 25 CaCO3m3. I added 3mL Sulphuric acid to 60L and got the pH down to 6.0. Any guesses as to where the Alkalinity will be now? "

OK, now I can answer your question The alkalinity would be zero! If it wasn't the PH would be the same.
The alkalinity destroys the acid too, some was left to lower the PH. When this acid is put in the soil it will destroy itself if it finds any basic molecules (Like lime!). But eventually it will lower the PH of the soil, so you have to monitor PH of the soil after awhile. If it get's too low, just start using tap water till it raises itself. it's a balancing act!

Now that makes a lot of sense. Thanks for that. You say the Alkalinity is zero. Is that a good thing? Isn't there a sweet spot for Alkalinity to?

"You say the Alkalinity is zero. Is that a good thing? Isn't there a sweet spot for Alkalinity to?"

Depends what you are growing? For acid loving plants, no. They do need calcium, but getting it from calcium carbonate is not an option. It's unable to absorb it. They need acid to allow transfer of nutrients, they become chlorotic with alkalinity. Most plants do not care much about PH but azalea's and blueberries do. The 5-1-1 mix has a PH of 5 without lime. Why the lime is added to bring it up to neutral. So for most plants you need the lime. Foliage Pro fertilizer has all the trace minerals the plants need btw, so that will supply any minerals needed by your plants. Good stuff! I myself add trace minerals with kelp powder and Azomite which has 67 Trace Minerals.I don't use Foliage Pro. I prefer a more acidic fertilizer like cottonseed meal or amonium sulfate. With blueberries you have an added problem. Nitrate as a nitrogen source will harm plants. you must supply nitrogen in other forms. I know what i use is good, not sure about Foliage Pro? If it contains nitrates, i can't use it.

"My tap water had a pH of 8.0 and alkalinity of 25 CaCO3m3. I added 3mL Sulphuric acid to 60L and got the pH down to 6.0. Any guesses as to where the Alkalinity will be now? "

OK, now I can answer your question The alkalinity would be zero! If it wasn't the PH would be the same."

Huh? How do you know the acid ate up ALL the alkalis? You make it sound like if he added any amount of acid, whether a drop or a gallon, it would change the pH to 6.0 and remove all the minerals. I don't think that's the case unless I'm misunderstanding.

"Why the lime is added to bring it up to neutral."

-Not necessarily true. Neutral is 7.0 and the lime often leaves the pH well below that. It's not an automatic jump to neutral.

"Nitrate as a nitrogen source will harm plants. you must supply nitrogen in other forms."

-Where does this logic come from, Drew? Can you source an article? For containers, you want fertilizers that are predominantly nitrate based, as opposed to ammonium/urea.

"Huh? How do you know the acid ate up ALL the alkalis?"

Because the PH went down from 8.0 to 6.0 If the acid was unable to neutrilize calcium carbonate, none would be left to lower PH. If you add acid and all the carbonate is not removed the PH would not change. The carbonate would have destroyed all the acid. Remember PH is a measurement of free hydrogen ions, not how much acid or how much base is in the solution. The hydrogen from the acid would now be water (see the common acid and base to salt and water equation).
Sorry, I'm not the best teacher. The base and acid first neutrilize each other. They tend to react with each other.
Both are destroyed in the process, so if the base wins and not enough acid was added, it cannot lower the PH. No more is in the solution. The acid and base react with each other and form gypsum(salt) and water (H2O).
Acid +base = Salt + water (A very common reaction).
Notice the right side has no acid or base if excess acid the PH will be lower, if excess base, the PH will be higher.

Lime is added to raise the PH of the 5-1-1 medium closer to neutral, yeah it depends how much you use if you reach your goal or not.

I said:
Nitrate is harmful to plants
"Where does this logic come from, Drew? Can you source an article?"

Yes, I was talking about blueberries I should have used blueberries not plants, see sentence before that one. I meant blueberry plants, not all plants. I must admit my grammar is terrible. i should have made that statement one sentence, not two. See attached article.
Department of Horticulture
Purdue University Cooperative Extension Service ⢠West Lafayette, IN See start of page 2 for nitrate reference or search document with the word nitrate.

Here is a link that might be useful: Nitrate toxic to blueberries

This post was edited by Drew51 on Wed, Dec 11, 13 at 14:30

I'm reasonably sure that Drew's comment about nitrates was with regard to blueberries, not plants in general. That being said, nitrates aren't inherently harmful to blueberries, but they can be if applied in excess. That's hardly relevant to the current topic at hand, so I'll leave it there.

EDIT: I see that Drew posted a clarification while I was typing this post. Now my post is even more irrelevant.

This post was edited by shazaam on Wed, Dec 11, 13 at 14:25

And I'm evidently not the best chem student.

I can't get my head around the fact that you end up with distilled water (aka zero alkalinity) in either case of adding a drop of acid that moves you from pH 7.0 to 6.9 -OR- a gallon of acid that moves you from 7.0 to 4.0. is this what we're saying, Drew?

Yes, but I must admit even with ton's of chemistry credit, I have to take the word of others, as It is a difficult concept. I don't claim to understand it well at all. With sulfuric acid the salt is gypsum which is very stable, so the alkalinity is gone for good. Only with sulfuric acid we have different and unstable salts with other acids.

I guess once the alkalinity is gone, the hydrogen from the acid is considered free ions. That lowers the PH.
And this is really a guess in that the base ties up free hydrogen ions so the solution has a higher PH when base is only present.

So to sum up the water is going to have CaCo3 (calcium carbonate) and be alkaline OR have H2SO4 (sulfuric acid) and be acidic. The water cannot be alkaline and acidic, it's either one or the other. the substances are at war!
Fred turned the alkaline solution into an acidic one by adding enough acid to neutrilize the base.
If he added only enough to neutrilize the base, the PH would still be 8.0, he added more...
The alkalinity and the PH are different beasts.

When Fred uses this to water, many alkalines in the soil will react with the acid and turn it to gypsum. But if he keeps using it, you will eventually make the soil acidic too.
Depending on how alkaline the soil is in the first place.

Drew and Oxboy. Thanks for your engagement. I'm glad you two discussed it in more detail. Makes it easier for me to grasp. The more one learns about these things the more interesting the subject becomes. A whole new world has opened to me since I joined this forum. Happy faces from the plants to...:-)
Been away for a few days (with the irrigation system spraying tap water). Every time I sat down to eat I thought about my poor little plants back home, frowning at all those dreaded carbonates :-)
But they are back to a proper balanced and nutritional regime now...!
I noticed an interesting thing when I prepared my water and fertilizer tanks yesterday.
I filled a separate 60l tank and got the pH to 6.0. I added FP 9.3.6/ ProTekt to the tank and the pH went up to 6.4. I read somewhere here that after mixing in the fertilizer the pH will drop. I did not expect it to rise. Any ideas about the science behind that?

This post was edited by fredman on Sun, Dec 15, 13 at 21:13

I mentioned rebound somewhere? Unless you can confirm the PH was 6.0 right before you added the fertilizer, it could be rebound.
It has been observed when lowering PH of water, that the PH rebounds a bit, and the PH raises slightly. Not sure of the time frame on this? Time may vary depending on water chemistry.
This observation is unexplained. Noticed first by a cactus grower who has had his studies published in Cactus and Succulent magazine. He observed it happening but didn't analyze as to why? It probably is that the acid takes time to react to all bases.

I tested the ph after I added the acid and it was 6.0. I tested it again the next day and it was still 6.0. I added the acid and tested it about 5 min later after I thoroughly mixed it, and it was 6.4. I added another 0.5 ml acid and it went down to 6.0 again. That was after about 5 min. I will test again tomorrow...

Not sure what happened? Maybe the fert does not lower PH!?

Double post, deleted.

This post was edited by Drew51 on Mon, Dec 16, 13 at 10:42

Alkalinity is a measure of a waterâÂÂs capacity to neutralize acids. It is the concentration of soluble alkalis in a solution. It should not be confused with pH. If your water is high in alkalinity (usually measured in ppm of CaCO3), it will require more acid to lower the pH. I had to study up a lot on this during the growing season for my container pawpaw production. Pawpaws are much like blueberries--they like low pH--close to 5.0.

I am not a chemist--just a studious grower. Here are two websites you need. The first is a great article from NC State about alkalinity. The second is the ALKCALC, an invaluable calculator to help you determine how much acid you need to add to your water to bring down the pH.

NC State Alkalinity article

ALKCALC

As an example, my well water has high alkalinity (280 ppm CaCO3), and the pH is 7.5. To get the pH down to 5.5, I must add 2.055 ml of sulfuric acid (battery acid) to a gallon of water. My container blueberries also thrived on this solution. However, water that has been treated with acid may not be able to overcome the problems in the container mix. Most of my containers were made up with 5-1-1 or a mix of pine bark and compost. It worked great. In other containers I experimented with mixes containing sand. Here, the plants did poorly. I later did a pour-through test and learned that the pH of these containers was 7.0, despite the acidic irrigation water!

Have your water tested. Use test strips to confirm your pH changes.

Best of luck with your plants.

Marc

Thanks Marc that is a good read. In relation to the pH rising after adding fertilizer to acid water, this extract is of special interest....

Nutrients from acids..... "With the exception of citric acid,
the acids used for water acidification also supply a plant
nutrient in conjunction with supplying H+. The nutrient
supplied can be beneficial to plant growth (if not supplied in
excess), but it can also react with fertilizer salts in concentrated
stock solutions or with pesticides if mixed into spray solutions.
Growers who acidify their water should adjust their
fertilization program for the nutrient supplied by the acid used"

That is a very good point! You have to think about everything. Captan which is a fungicide used for scab on peaches, and also for Botrytis Fruit Rot on strawberries is ineffective if you mix it with our typical tap water. It is extremely important to acidify the water first. I know you're at present pointing out a different point. And to talk about that point sulfur is a trace mineral, so no adjusting is needed if using sulfuric acid. I don't think any negative reactions otherwise will occur. But I'm not positive? It's not like the fertilizer has a whopping dose of sulfur, it does not. Plus extra sulfur is great for azalea's anyway. That info is really a concern with nitric and phosphoric acid, which we are not using.

Yeah my thinking exactly. This has been a good thread. Learnt a lot. Thanks again Drew.

I learned a lot too!! Well relearned, i knew this stuff inside and out in the 1980's when in college. Biochemistry 401 at MSU was the hardest class I ever took. It made the 3 prerequiseate organc chemistry classes look easy. And these reactions are chemistry 101, long before organic.
And none of it stuck! :)
But I'm still a nerd as I was wondering how the bicarbonate looked, and that article shows the formula, with the molecule having two carbonate groups. So got it now!

"Huh? How do you know the acid ate up ALL the alkalis?"

Because the PH went down from 8.0 to 6.0 If the acid was unable to neutrilize calcium carbonate, none would be left to lower PH. If you add acid and all the carbonate is not removed the PH would not change. The carbonate would have destroyed all the acid. Remember PH is a measurement of free hydrogen ions, not how much acid or how much base is in the solution.

This isn't accurate. If you have a solution with a basic pH and add acid to it, the pH will decrease even if the acid can't neutralize all of the base. It still reacts with SOME of the base, lowering the concentration of hydroxide ions in the solution.

I disagree completely. If the acid can't neutrilize all of the base, no acid will be left to decrease PH. The hydrogen will be water, chem 101. A solution cannot be acidic and basic.
They have to react with each other. Unless they cannot find each other. I think it does take time.
If you can show a source where acid and base can coexist, well maybe I'll believe you. Or point out where the hydrogen is coming from to lower the PH. Acid plus base equals salt and water calls for no free hydrogen.

This post was edited by Drew51 on Wed, Dec 18, 13 at 14:41

OK, I looked at the chemistry a little deeper, and yeah I think you are right. Alkalinity makes it harder to decrease the PH, but removing some of it will decrease the PH. They can and do coexist. PH is a measure of the ionic potential.
No doubt adding more ions no matter what the alkalinity should decrease the PH. By how much is dependant on the amount of alkalinity. Got it, thanks for the clarification! My bad!

Most people think of acids and bases in terms of pH only, which I think can lead to some confusion when talking about bases. pH is definitely useful for talking about acidic solutions, which have excess HâÂÂO⺠ions and a negligible concentration of OHâ». But when you're talking about basic solutions, you're no longer speaking in terms of HâÂÂO⺠concentration, but OHâ» concentration, so pOH is, in my opinion, a more useful measurement for basic solutions.

You're right; the two ions can't coexist (at least in any amount that matters in most situations). That's why adding even a tiny amount of an acid to a strongly-basic solution will lower the pH and vice-versa. Even adding pure water to any acidic or basic solution will bring the pH and pOH closer to 7, because the concentration of the relevant ions will be lower.

Thanks for continuing this discussion. Playing around with the ALKCALC I referenced above can be educational. As an example:

Water before acid treatment (with 35% sulfuric acid, i.e. batter acid:

pH 7.5
Alkalinity 250 ppm CaCO3

After adding 1.4 ml of acid per gallon:

pH 6.0
Alkalinity 81 ppm CaCO3

The acid reduced the pH significantly, but there is still some alkalinity in the water.

Marc