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How much citric acid to add to a liquid to drop pH down 2 points
First, thanks to the administrators for allowing me access to this forum. My question is NOT about cosmetics, pretty far from it in fact, but I asked for access to the forum’s experts and the admin agreed to let me in. If no one wants to jump into my project I certainly understand. So here goes.
My company manufacturers organic fertilizer from poultry manure. I told you it wasn’t about cosmetics.
Anyway, I am now in the R&D phase of formulated a liquid product using CMS (concentrated molasses solubles) which is basically spent molasses with most of the sugar removed by yeast and a very fine dust that is collected from our dryer. The mixture is 1 gallon CMS plus 1# of manure dust along with a small amount of dry humate powder (pH around 9) and a liquid trace mineral extract (pH 1.
. The final pH of the mixture is 5.3 +/-. The specific gravity of the mixture is 1.35.I have located a source of citric acid but have never used dry acids to adjust pH of a liquid. The final product needs to be below 4 pH so as to stop microbial activity and give me some level of shelf stability.I am NOT an organic chemist, but have some (little) experience with inorganic just from my time spent formulated fertilizers.I have ordered a 50# bag of citric acid and will begin working on a trial and error basis to determine how much of the acid I will need to add, but was hoping to get SOME idea from the panel experts.That’s all I have. I look forward to your assistance.Thanks in advance. -
5 Replies
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Experimenting is the way to go - there is no way to calculate the amount of C.A. needed unless you know the exact composition of the soil, and even then you are faster just doing some tests.
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For best results make a 50% Solution of the Citric acid. It will be easier to add and it will adjust the pH slower. Anyone who has over shot a pH adjustment can understand.
As David rightfully pointed out, experimentation is key. You will want to slowly add the Citric acid Solution, mix thoroughly and then you will check the pH with a meter. Go slow. If you get heavu handed you will overshoot the pH.
Lastly, while it would be nice to be able to calculate this in the lab (you can roughly) and then simply include the needed quantity on the Batch instructions, the pH adjustment must also be added to the process instructions. Your batchmaster must slowly drop the pH to the desired level on the floor.
In both the lab and floor documetation be sure to record both initial and final pH results.
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The saturation point for citric acid and water not quite 50:50, so you’ll have an easier time making a 40% solution.It’s very important to remember that the pH scale is logarithmic, not linear. So, on the pH scale, a difference of 1 number/unit is a power of 10. This means that a pH of 5 is 10 times less acidic than a pH of 4, or you can look at it that a pH of 4 is 10 times more acidic than a pH of 5.It goes further - a pH of 3 is 100 times more acidic than a pH of 5, and a pH of 2 is 1,000 times more acidic than a pH of 5, and so on.If it were me, I wouldn’t even bother trying to calculate this, because it’s so quick to do the titration. Make a kilo of your solution, check the pH, add 10 grams of 40% Citric Acid, re-check the ph, increase or decrease your acid additions as needed.Also, be careful of citric acid + stainless steel, it’s a known passivator. -
If you’re comfortable with graphs, this might help:
This is the full article: -
Thanks so much for your assistance. Since I originally posted my question, things have changed a little bit. I am now simply breaking down a solid protein into a liquid. Now I need to adjust the pH below 4.0. The only acids that are allowed are citric, which is just too weak and strong acetic acid - pH 2.0. Right now I am looking at using a 70:30 mix of liquid fertilizer to acetic. That gives me a pH of around 4.0. I just don’t know of any other options. Thanks again for your assistance.
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