Baking Soda in the Aquarium

[Angelscrx]

MIkeS, as usual thanks for answering my questions.

 

[WaterDogs]

Well since so many are using baking soda and washing soda as a buffer that I am trying it now, so bought the Arm & Hammer brand of both and mixed it up 6:1 as suggested I put 1/2 teaspoon mixed in RO/DI water and put it in my 75 gallon reef and nothing scatter chunks so will continue to dose and monitor to see how well it stacks up against the store bought name brand buffers; don't know how critical it is to bake the CO2 out but skipped that step; any comments on not baking the mix?

 

[mojoreef]

I believe the baking gets rid of a hydrogen mole and allows for a more concentrated mix

Mike

 

[uwscotch]

Excellent article by Farley on how to make your own two-part and push away the fears of making your own and using everyday material.

http://www.advancedaquarist.com/issues/april2004/chem.htm

The baking affects the solubility as follows

2 NaHCO3(baking soda) = Na2CO3 + H2O + CO2

If you bake the baking soda, you drive off the CO2 and H20. Therefore you drive the equilibrium to the right once you finally add it to the water resulting in more Na2CO3 being soluble. Otherwise you are waiting for all of the CO2 present in the mixture of NaHCO3 which is in its own equilibrium as well as the CO2 released from the reaction to come out of the solution. The gas exchange after the NaHCO3 is added to the water will take a while as the CO2 leaves the solution therby allowing "room" for the CO2 that will be given off during the chemical reaction. As Mike mentioned, you are also loosing any loose Hydrogen floating around as water, a molecule associated with most chemical right off the shelf and is sometimes factored into the chemical composition. Again, another equilibrium.

Hope this helps.

aaron

 

[cwcross]

Helpful posts. Sorry I couldn't get to this earlier. I think the homeade 2 part is a very good option. Otherwise just use baking soda or washing soda. The same thing will happen in either case. Same with heating it. These things will affect the intitial change in pH. However, if adding the correctly adjusted volumes of any of the options, you will reach the ultimately same point. The question is how much time it will take. Basically though if the gas exchange in your aquarium is sufficient, withing about 24 hours, everything will equilibrate. The rate limiting step is how quickly CO2 can enter your water column or leave it. Aaron hit the nail on the head here.

Regards...Collin

 

[Boomer]

Water so it doesn't really mater which one you use, excepting you have to use more of one than the other and the initial pH effects are different

There is more to it than that, as 1 meq of HCO3- will raise the Alk 1 meq and the Sigma CO2 1 meq, whereas 1 meq of CO3-- will raise the Alk 2 meq and the Sigma CO2 1 equivalent. Don't forget CO3-- is a double negated ion so it is twice as powerful

 

[WaterDogs]

Water so it doesn't really mater which one you use, excepting you have to use more of one than the other and the initial pH effects are different

There is more to it than that, as 1 meq of HCO3- will raise the Alk 1 meq and the Sigma CO2 1 meq, whereas 1 meq of CO3-- will raise the Alk 2 meq and the Sigma CO2 1 equivalent. Don't forget CO3-- is a double negated ion so it is twice as powerful

Can you say that in english for some of us.

 

[NaH2O]

BOOOOMMMMEEERRRR!!!!! I am so thrilled to see you've joined us!! Welcome!!!

 

[cwcross]

Can you say that in english for some of us.

A meq stand for milli-equivalent. An equivalent is a chemical term used to relate how much of an acid or base it takes to neutralize the other. This also happens to be a unit that Alk is often quoted in as this is at the heart of the basic definition of Alk.

If you consider a strong acid like HCL. HCL dissociates in water 100% effectively to yield one proton (H+) and one chloride ion (Cl-). If we also consider a strong base such as sodium hydroxide or NaOH, this dissociates in water to yield a hydroxide ion (OH-) and a sodium ion (Na+). These will neutralize each other because the proton and hydroxide will combine to form water:

H+ + OH- = H20

while the Sodium and Chloride will combine to form sodium chloride.

Na+ + Cl- = NaCl.

If we have a given number of HCl, say 1 mole (which is 6.02 x ten to the 23rd power (6.02x10^23)). We can call this an equivalent which is approximately 36 grams. Now if we ask how much NaOH does it take to neutralize the HCl, we know that one HCL reacts with one NaOH so we automatically know that it takes one equivalent weight of sodium hydroxide to neutralize one mole of HCL. A mole of NaOH weighs around 39 grams or so I think. (Please note the weights are not the same. In this case they are close but this is just coincidence. Acids and bases react on a molar basis. That is molecule to molecule. However, different molecules have different weights so molecule to molecule is not the same as weight to weight.)

Now to go a step forward. We'll keep the NaOH but change to sulfuric acid which is H2SO4. This dissociates in water to yield 2H(+) and 1 SO4(-2). So now the neutralization reaction with NaOH can be written

2*NaOH + H2SO4 = 2*H2O + Na2SO4

This is called stoichiometry. This says that it takes two equivalent weights of sodium hydroxide to neutralize one mole of H2SO4 which weighs about 96 grams or so (give or take a few grams if I am recalling Sulfurs MW correctly).

Anyway equivalents is a quick way of understanding how much of an acid or base it takes to neutralize another acid or base when considering the number of protons or hydroxide ions available in the molecule.

Now relating this to baking soda and ((edited) Washing Soda). Baking soda is NaHCO3 or sodium bi-carbonate while ((edited) Washing Soda) is Na2CO3. If we strip off the sodiums we have HCO3(-) and CO3(2-). Thus you can see that Baking soda will neutralize only 1 equivelant of acid while ((edited) Washing Soda) will neutralize 2 equivalents of acid. Thus, ((edited) Washing Soda) is twice as strong a base as is baking soda on a molar basis. The tricky thing is that one mole of BS weighs less than one mole of ((edited) WS). Thus weight for weight one is not quite twice as strong as the other.

So to go further and pulling out the periodic table, pencil and calculator.

WS = Na2CO3 = 105.97 grams/mole
which equals 0.00944 mole/gm or 9.44 mmol/gm. Since there are 2 meq/mmol then this equals 2*9.44=18.9 meq/gm

Similarly

BS = NaHCO3 = 83.97 grams/mol = 11.91 mmol/gm. Now there is only 1 eq/mol so this also equals 11.91 meq/gm.

Thus BS is a more than 1/2 as strong as WS on a meq/gm basis. Now if you want to dilute this into 100 gallons of water this shows that:

1 gram of BS will raise 50 gallons water 11.91 meq /50 gallon = 0.238 meq/gallon or 0.063 meq/L. So to raise 50 gallons by 1 meq/L you need 15.89 grams (this matches Farleys Value quite nicely if you bother to check)

1 gram of WS will raise 50 gallons water 18.9 meq/50 gall =0.378 meq/gallon or 0.0999 meq/L (1G=3.875L). So to raise 50 gallons by 1 meq/L you need 10.01 grams WS (this also matches Farleys value nicely but with a few more decimals).

Anyway... I'm not sure this english is any plainer but at least there is some more detail. I hope this helps. I would be happy to answer any specific questions on the above if there is interest...Sincerely...C

 

[Boomer]

Gald that you cleared all that up C , now I don't have to do all that typing

Thus, baking powder

Washing Soda C , Washing Soda or Soda Ash

Baking Powder is a composite of Sodium Bicarbonate (baking soda), one or more acid salts such as Cream of Tartar (Tartaric Acid), Sodium Aluminium Sulphate, Calcium Acid Phosphate plus a drying agent such as cornflour.

 

[Boomer]

Hi Nikki

 

[cwcross]

Thus, baking powder

Washing Soda C , Washing Soda or Soda Ash

Baking Powder is a composite of Sodium Bicarbonate (baking soda), one or more acid salts such as Cream of Tartar (Tartaric Acid), Sodium Aluminium Sulphate, Calcium Acid Phosphate plus a drying agent such as cornflour.

Ooops...Sorry,,my mistake. Washing Soda, not Baking Powder. I got crosswired there.


Interestingly enough, about 2 years ago I was up at American Soda in Colorado..near Grand Junction. They mine Soda Ash there. It is one of the largest Soda Mines in the world. Only a couple large deposits exist globally that are suitable for mining, if I remember right. They inject majorly hot water into deep wells that dissolves the Soda into a saturated mixture with water that then pours out the holes to bring up the Soda. Thier de-carbonation tower had fouled with Bitumen and the excess CO2 was running down the top of thier 40 mile multi-million dollar stainless steel pipe and corroding the beejeezus out of it. You could see a ditch in the top of the pipe where the CO2 bubbles were running. It had eaten nearly though the top of the pipe. Needless to say they were very upset.

They mined about 85% Soda Ash and 15% bicarbonate out of there. Only less than 5% gets sold for household use. The rest is industrial.

I ate lunch with the soon to be owner, who had launched a leveraged buyout with 51% stock from the people who had bought it from him originally and run it into the ground with the pipe and bitument problem among other things. He had hired us to fix the problems for him.

He was about 78 years old and did not look like someone with over 50 million in liquid assets in his pocket. He looked like a kind of dumpy old man with a timex watch and wrinkled clothes. He told me his story about how he had started as a young draftsman out of college working for a survey company. He somehow came across the location of a copper deposit that the company he worked for was not interested in. In those days you could get mineral rights from the government much easier somehow he said. Anyway, he aquired the mineral rights to the copper deposit for basically next to nothing and then exchanged them for capital to make build the mine and substantial equity. After than he had a very succesful career as a mining mogul in commodities like copper, Soda, Iron, etc. An amazing man with an interesting story of a self made american dream.

Oh well, enough rambling...Collin

 

[cwcross]

PS, I edited my original post to strike Baking Powder and replace with Washing Soda to clean up the bungle. Also added some detailed calculations regarding the two into an aquarium and the expected effect for any that are interested.

Please note that even if adding the APPROPRIATE amount of either WS or BS to provide the same theoretical change in meq/L Alk, the initial pH changes and initial Alk will be different because no matter whether you add BS or WS the equilibrium relating these two compounds will cause one to convert to the other by either expelling or drawing in CO2 from the air. Thus to see the true effect of either one, you must wait about 24 hours until the true Alk is established which will be somewhat different than the theoretical values. However, they are good ballparks.

Does anybody value this info?

Sincerley...C

 

[Boomer]

Oh well, enough rambling...

Yes, rambling and just like me But still a nice story

you must wait about 24 hours

Yes, for example the pH will fall with BS until the CO2 is "blown off"

initial Alk will be different because no matter whether you add BS or WS the equilibrium relating these two compounds will cause one to convert to the other by either expelling or drawing in CO2 from the air.

The initial pH will shift but not the Alk, CO2 has no effect on Alk and Alk has no effect on CO2. The only shift other than pH will be Sigma CO2, which is the sum total of the all CO2 and all the carbonate and bicarbonate that can/could be be converted into CO2. CO2 is a molecule, thus it is not part of the Alk equation as it has no charge.

Does anybody value this info?

They better C

 

[NaH2O]

Collin - I value the information, for sure. I'm always trying to get a better understanding of chemistry and every little bit helps.

If you make up a BS+WS solution (thinking of a 6 part BS to 1 part WS in RO/DI) to add to your system, is there a length of time that it holds it's buffering ability/does it reduce in strength over time? For instance, when you first mix it up as opposed to a couple of weeks or so down the road?

 

[cwcross]

Collin - I value the information, for sure. I'm always trying to get a better understanding of chemistry and every little bit helps.

If you make up a BS+WS solution (thinking of a 6 part BS to 1 part WS in RO/DI) to add to your system, is there a length of time that it holds it's buffering ability/does it reduce in strength over time? For instance, when you first mix it up as opposed to a couple of weeks or so down the road?

Do you mean in the aquarium or in a storage container. If you mean storage container and it is sealed, I would expect it to stay just fine for a couple weeks or longer. I would suggest to let the mixture sit on the counter for overnight and then seal it and keep it in refrigerator.

These measures are only precautionary though. The mixed solution should be stable after it equilibrates. I don't think you would want flies falling into it or so forth or onion fumes adsorbing into it but generally, the buffer solution should be stable as long as it is not contaminated.

Sincerely...Collin

 

[NaH2O]

Thanks, Collin. I felt like that was an odd/dumb question, but I wondered if it would be better to make small amounts rather than a larger batch. I keep a gallon jug mixed up at a time, but it takes awhile to go through.

 

[cwcross]

The initial pH will shift but not the Alk, CO2 has no effect on Alk and Alk has no effect on CO2. The only shift other than pH will be Sigma CO2, which is the sum total of the all CO2 and all the carbonate and bicarbonate that can/could be be converted into CO2. CO2 is a molecule, thus it is not part of the Alk equation as it has no charge.

I can see you are going to keep me on my toes here!

However, I'm not sure you are correct. I will think more on it. However, I am thinking that in the case of CO2 entering the system that it will react with H2O and form more -HCO3 which will affect alk in addition to whatever is added via the powder. In any case I see I need to strive to be more precise in my use of language.

I would also argue that as the solution reaches the carbonate/bicarbonate equilibrium, the buffering capacity of the water would change slightly in addition to pH and sigma CO2. I'm not sure of this though and will think about it tonight.

I'll address this more later. I've got to leave town tonight for a Christmas party.

Happy Holidays...Collin

 

[Boomer]

However, I'm not sure you are correct

Oh, I know I'm correct Randy and I have explained it many times on our chem forum. You will also find a review by Randy in his article on understanding Alk. There is also a extensive review in Pankow, Aquatic Chemistry Concepts, not to mention my talks my with Dr. Frank M. Millero. Buch-Park equations will also show this. The there is the old "Boomer Glass Trick

Take a sample of tap water and measure the pH and Alk, then fill two glasses with the same amount in each. In glass # 1 add some pH indicator, you will see the water change color to the pH of the sample. Now, take a straw and blow in the glass and watch before your eyes as the color changes to a lower pH. In glass #2 just blow in it with the straw, we already know the pH is going to go down due to the CO2, so no need for an indicator. Now in the second glass measure the Alk, it will not have changed at all. The ratio of Alk to CO2 dictates the pH, thus if you know the Alk and pH you can calculate, very accurately the CO2, buy using the std equation Buch-Park equation. If CO2 and Alk increase or decrease proportionally there will be no shift in pH at all. Meaning you can have a pH of 8.1 with a low CO2 & Alk or a pH of 8.1 with a high CO2 & Alk.

I am thinking that in the case of CO2 entering the system that it will react with H2O and form more -HCO3 which will affect alk

If that was the case, think about it, we would never have to add a buffer. You are saying, in so many words, bubble in CO2 and it will make HCO3- and if we continue this it will make H + CO3--

buffering capacity

Which buffering capacity, the one hobbyist use, which is really Alk or the real one chemists use ? The maximum BC, Buffering capacity of a solution is when the pH =pKa, for seawater that is at pH of 6 & 9, so if the pH was 8.1 and it dropped to 7.8 you have just increased your Buffering capacity. BC is the ability of a solution to with stand upward and downward trends in pH. It is a function of Alk, Acy and Ion Pairs (mostly Mg). Seawater has very little Bc if any at all.

I'll address this more later. I've got to leave town tonight for a Christmas party.

Well, have fun C

 

[wrightme43]

Ok I sorta maybe follow what you all are saying. I am glad your here to explain it. For me all I really want is to make sure that I am doing this right. I bought arm hammer washing soda, I bought A+H baking soda. My understanding is that I should mix these two in 6 parts Baking soda, to 1 part washing soda and bake it in the oven for 1 hr at 350 degrees F. I would at the end of this process have a dry carbonate hardness buffer compound that I can use just like the kent marines reef builder. I can if I wish mix it up with rodi water and have a liquid buffer compound. Is this correct? If not will you straighten me out? Steve