Sciencemadness Discussion Board

Citric acid + Sodium bicarbonate

looren - 20-2-2016 at 07:43

Hello !

Not sure if this is actually the correct place to post this, but I hope so.

I am experimenting with producing co2 for my plants, using citric acid and sodium bicarbonate. But it kind of got me thinking how cost efficient this is compared to just getting a tube with co2. I have been trying to find out how many grams co2 is produced from a 50/50 of citric acid and sodium bicarbonate but can not really find anything on it.
Does anyone here perhaps know how to calculate this from say 100g citric acid and 100g sodium bicarbonate? It would be of great help!

Metacelsus - 20-2-2016 at 08:26

100 g of sodium bicarbonate is 1.19 mol. 100 g of citric acid is 0.52 mol; citric acid is a triprotic acid.

If all the bicarbonate is converted to carbon dioxide, there will be 1.19 mol produced, or 52.4 grams. However, I doubt all of it will react. The citric acid will definitely form disodium citrate, reacting with 1.04 moles of bicarbonate. After that, you'll end up with a complicated buffer (carbonic acid's first pKa is 6.35, and citric acid's third pKa is 6.4.)

On a cost efficiency basis, you should think about using a cheaper acid (perhaps hydrochloric). A strong acid will also ensure complete reaction. However, you'll want to make sure that none of this acid gets in your plants.



[Edited on 2-20-2016 by Cheddite Cheese]

Deathunter88 - 20-2-2016 at 08:46

Quote: Originally posted by looren  
Hello !

Not sure if this is actually the correct place to post this, but I hope so.

I am experimenting with producing co2 for my plants, using citric acid and sodium bicarbonate. But it kind of got me thinking how cost efficient this is compared to just getting a tube with co2. I have been trying to find out how many grams co2 is produced from a 50/50 of citric acid and sodium bicarbonate but can not really find anything on it.
Does anyone here perhaps know how to calculate this from say 100g citric acid and 100g sodium bicarbonate? It would be of great help!


You can get an actual CO2 cylinder that operates using citric acid and sodium bicarbonate. Basically its a tank made from very thick steel, and you fill it with water, citric acid and sodium bicarbonate. Then quickly you screw on the pressure regulator so you can control the outflow of gas. Very useful if you want a CO2 tank but do not want the hassle of going to a welding shop for refills. (There is also a type of hydrogen gas tank that works using aluminium and sodium hydroxide, saving you from needing to ever refill hydrogen when oxy-hydrogen welding) Another option would be to use one of those single use CO2 tanks meant for fish bubblers. They are cheap and you can just throw away the tank when finished. (Tank about the size of a 2L soda bottle)

looren - 20-2-2016 at 09:30

zts16; Thank you for the very detailed explanation.
Regarding hydrochloric acid, I see it is quite easy to obtain although it is 30%. Would it still work as well?
Currently I am using 100g citric acid+300g water. What would be the equivalent do you think if I were to use hydrochloric acid?
Also, is it okay to use hydrochloric acid with plastic soda bottles?

Deathunter88;
Do you have a link to a product like the tank you describe?
I am currently using something like this: https://www.youtube.com/watch?v=cla2q6D0nxs although mine is not plastic, its a solid block of aluminum.

Deathunter88 - 20-2-2016 at 10:43

Quote: Originally posted by looren  
er88;
Do you have a link to a product like the tank you describe?
I am currently using something like this: https://www.youtube.com/watch?v=cla2q6D0nxs although mine is not plastic, its a solid block of aluminum.


The tank that used citric acid and sodium bicarbonate is this: https://detail.tmall.com/item.htm?spm=a230r.1.14.16.shGN3J&id=43289665888&cm_id=140105335569ed55e27b&abbucket=12

The disposable tank is this: https://detail.tmall.com/item.htm?spm=a230r.1.14.9.lvRj0S&id=41746806104&cm_id=140105335569ed55e27b&abbucket=12

Unfortunately both of those are from a Chinese online shop similar to ebay called Taobao. But I'm sure that guided by the pictures you can find something similar where you live.

looren - 20-2-2016 at 10:47

Deathunter88; thanks for the links! I'll see what I can make of it, all in Chinese :)

Herr Haber - 22-2-2016 at 15:34

Chalk and vinegar would be even cheaper unless you have access to a lot of sodium bicarbonate.
Also, the fermentation of sugar does produce CO2 and I'm just guessing what kind of plant you are growing, but the temperature would ensure complete fermentation.

The Volatile Chemist - 22-2-2016 at 17:43

Quote: Originally posted by Herr Haber  
Chalk and vinegar would be even cheaper unless you have access to a lot of sodium bicarbonate.
Also, the fermentation of sugar does produce CO2 and I'm just guessing what kind of plant you are growing, but the temperature would ensure complete fermentation.


The problem with this is that vinegar is only ~5% acetic acid, so it takes up quite a bit of space for a small amount of CO2 produced. Since baking soda and citric acid are both solids, they give off a lot more CO2 per mass/volume.

deltaH - 22-2-2016 at 21:54

Quote: Originally posted by Metacelsus  

On a cost efficiency basis, you should think about using a cheaper acid (perhaps hydrochloric). A strong acid will also ensure complete reaction. However, you'll want to make sure that none of this acid gets in your plants.

[Edited on 2-20-2016 by Cheddite Cheese]


I must say that I think this is a bad idea IMHO. Aerosols of hydrochloric acid or at the very least, salt, will be ejected into the air that will rust everything in your green house to kingdom come and may even harm your plants' foliage long term, especially if it is acidic.

Citric acid and sodium bicarbonate is used because it's so benign, but yes, the cost is higher, but it's 'idiot proof', i.e. can be used as is and would be forgiving to wrong ratio's etc. Also aerosols of it are safe.

If you go down the cheap route, you must install some kind of scrubbing system to clean up the gas before ejecting it to the atmosphere, but this isn't trivial. Trace amounts of chlorides would probably still get through and rust up your room.

1.6180339 - 27-2-2016 at 18:19

Or you can use calcium diacetate.

1.6180339 - 27-2-2016 at 18:43

Quote: Originally posted by 1.6180339  
Or you can use calcium diacetate.
I mean calcium carbonate and double the acetic acid.

IrC - 27-2-2016 at 20:16

You could make a fitting and valve for a Sodastream cylinder available at local stores such as walmart. Do a cost analysis to see which route is best.

unionised - 28-2-2016 at 06:37

Assuming I have got the arithmetic right, 342 grams of sugar will cost about £0.20 and will ferment to produce 176 grams of CO2
That's 880 grams of CO2 per £
84 grams of NaHCO3 costs about £0.08 and produce 44 grams of CO2
About 550 grams of CO2 per £
And that's without paying for the acid.

Metacelsus - 28-2-2016 at 07:49

Burning the sugar would give more carbon dioxide (528 g vs. 176 g) than fermenting it. You could also burn a lot of different stuff.

unionised - 28-2-2016 at 10:26

True, but any unburned materials might mess up the plants. For example,ethylene is a trace component in smoke and it's also a plant pheromone.
On the other hand, if you are growing plants somewhere cold, burning some sort of fuel for bother heat and CO2 might work.

macckone - 28-2-2016 at 16:29

I think fermentation is a better solution as you can imbibe the remaining liquid if you do it right. We call that a win/win. Your plants get carbon dioxide and you get drunk.

TinSandwich - 1-3-2016 at 14:10

I always tought that the cheapest thing to do would be to use HCl, you can get the 10% concentrated one for about 0.50$ at any local supermarket, also depending on how much and how fast you have to produce it I would think of using calcium carbonate: it is found in most rocks so you might be able to get it for extremely cheap prices and it also reacts slower and may be better if you are looking for a small but steady flow of gas.

Metacelsus - 1-3-2016 at 18:04

Calcium carbonate is a good idea. Where I live the bedrock is limestone, so it's "dirt cheap."

Herr Haber - 2-3-2016 at 08:42

Quote: Originally posted by unionised  
Assuming I have got the arithmetic right, 342 grams of sugar will cost about £0.20 and will ferment to produce 176 grams of CO2
That's 880 grams of CO2 per £
84 grams of NaHCO3 costs about £0.08 and produce 44 grams of CO2
About 550 grams of CO2 per £
And that's without paying for the acid.


And the price of yeasts compared to acid is neglegible.
All the other alternatives are somehow too "chemical" for someone growing the kind of plants I Imagine he's growing.
And again, there's the speed at which CO2 will be formed: fermentation is the slowest. You dont need to "gas" your plants in finely powdered CaCO3 and HCL to do the trick.
And as previously said, the heat generated by the lamps will ensure that the plants get more CO2 during "daylight".

There must be a reason why bucket based kits based on this principle are sold to homegrowers guys :)

The Volatile Chemist - 13-3-2016 at 15:38

Fermentation is a pain in the butt to maintain properly - been finding that out recently - everything gets messy, and the CO2 output is not steady but variable.

chemrox - 14-3-2016 at 14:34

@deathhunter88:
" Another option would be to use one of those single use CO2 tanks meant for fish bubblers. They are cheap and you can just throw away the tank when finished. (Tank about the size of a 2L soda bottle)"
Fish bubblers? which fish breathe CO2?

Deathunter88 - 14-3-2016 at 16:15

Quote: Originally posted by chemrox  
@deathhunter88:
" Another option would be to use one of those single use CO2 tanks meant for fish bubblers. They are cheap and you can just throw away the tank when finished. (Tank about the size of a 2L soda bottle)"
Fish bubblers? which fish breathe CO2?


They are used for the underwater decoration effects such as a fake clam opening and closing. I wasn't sure what to call it in english so I just called it a "fish bubbler". Sorry about any possible confusion.

Herr Haber - 14-3-2016 at 16:41

Quote: Originally posted by Deathunter88  

They are used for the underwater decoration effects such as a fake clam opening and closing. I wasn't sure what to call it in english so I just called it a "fish bubbler". Sorry about any possible confusion.


For that you'd use an air pump. Air is generally cheaper than CO2.
But PLANTS use CO2. Even if they live underwater. And yeah, they release oxygen too!
That's what these kits are for...