Heating baking soda

[Billionzz]

I was making a reference solution using di water and baking soda.

I found instructions on on the web to heat the baking soda in the oven at 400 degrees for 45 minutes to remove the moisture from it.

Then I also found this.
>>>""Sodium bicarbonate is even less stable with respect to heating. Solid NaHCO3 begins to lose carbon dioxide and water around 100°C, with complete conversion to sodium carbonate by 200°C: 2 NaHCO3(s) CO2(g) + H2O(g) + Na2CO3(s) ""<<<

All of the formulas I found for for calculating a determined dKH of di water uses baking soda instead of sodium bicarbonate.

Does anyone know what the formula would be when using sodium carbonate?

Doesn't it seem that heating the sodium bicarbonate and changing it to sodium carbonate would be the more accurate way to go?

Thanks,
Bill

[bertoni]

Baking soda is sodium bicarbonate, and the heating process converts it to sodium carbonate and drives off moisture. That process might make the weight more deterministic.

What does the recipe you're using say?

[JimW]

Originally posted by Billionzz
All of the formulas I found for for calculating a determined dKH of di water uses baking soda instead of sodium bicarbonate.

Trying to learn more about water chemistry, so forgive my for asking what might be a ridiculous question.
What is the purpose for calculating the dKH of di water? For the purpose of reefkeeping, wouldn't test kit provide sufficient results?

Jim

[Billionzz]

What I used was this calculator.

http://www.cnykoi.com/calculators/calckh.asp

I just thought that the amount of sodium bicarbonate and the amount of sodium carbonate would be different.

I thought someone might know how to figure out what the weight difference might be.

Thanks,
Bill

[Billionzz]

This would give you the ability to check your test kit and make sure it is correct.

[bertoni]

Well, sodium bicarbonate is NaHCO3 and sodium carbonate is Na2CO3, so you should be able to work from the atomic weights. I'd worry about the accuracy of the scale and the purity of the baking soda, but it might make for a reasonable sanity test.

[Randy Holmes-Farley]

Unless you need super high precision, there is not enough free water in commercial baking soda to make any heating a worthwhile process. The heating will make you much less able to predict the exact properties due to variable conversion of bicarbonate to carbonate.

This is not a process that I generally recommend as accurate alkalinity test kits are easy to make and so most should be OK, but if you want to, dissolve 252 milligrams (0.252 g) of baking soda in 1 L of pure fresh water to get a 3 meq/L standard. Do not bake it first.

[Billionzz]

Hi Randy,

Thanks for your help, I still have a few more questions I was hoping you could help me with.

I have found a few calculators on the web that tells how much baking soda to use but it seems everywhere I look I always get conflicting answers.

For example you said to use the following amount of baking soda.

>>>0.252 g of baking soda in 1 L of pure fresh water to get a 3 meq/L standard<<<

But here is link to a calculator that says to use a different amount

http://reef.diesyst.com/

0.180 g of baking soda in 1 L of pure fresh water to get a 3 meq/L standard

You say .252 g of baking soda and the calculator says .180 g of baking soda.

I’m assuming that your correct (very impressive resume) and the calculator is wrong but there must be some reason they think this is the correct amount of baking soda to use.

The same thing happens even at different web sites and calculators.

The weight that I’m trying to come up with is how many grams of baking soda it would take to make 1 liter of distilled water 5dKH.

On the following two links you can see that again they both give different amounts of baking soda to use.

Do you have any idea as to why it would be different?

http://reef.diesyst.com/

0.10 g of baking soda in 1 L of pure fresh water to get a 3 dKH/L standard

http://www.cnykoi.com/calculators/calckh.asp

0.125 g of baking soda in 1 L of pure fresh water to get a 3 dKH/L standard



In the previous post you stated the following.

>>>Unless you need super high precision, there is not enough free water in commercial baking soda to make any heating a worthwhile process. The heating will make you much less able to predict the exact properties due to variable conversion of bicarbonate to carbonate.<<<

So if I heated 10 grams of baking soda at 400 degrees F for 45 minutes wouldn’t all of it have changed to sodium carbonate and would there still be any free water left in that 10 grams?

If it’s not to much, how would you go about make a super high precision standard?

Thanks again for you help,
Bill

[Randy Holmes-Farley]

dKH and ppm kh are different than meq/L. Multiply 1 meq/L by 2.8 to get dKH.

I am not sure why Jose's calculator (the firs tone) does not get 0.252 mg of baking soda. I am certain that is correct. Perhaps Jose will pop in and comment on the math behind the calulator and point out what we are missing.

NaHCO3 mw = 84 g/mole

so 84 mg = 1 mmole
84 x 3 = 252 mg, so 252 mg in 1 L makes 3 mmole/L = 3 meq/L

If it’s not to much, how would you go about make a super high precision standard?

I would buy a liquid standard, or a purified chemical like very pure sodium carbonate. I cannot be sure how much heating makes pure sodium bicarbonate without making any sodium oxide (which is what happens if it is heated very hot).

[jdieck]

Originally posted by Randy Holmes-Farley
I am not sure why Jose's calculator (the firs tone) does not get 0.252 mg of baking soda. I am certain that is correct. Perhaps Jose will pop in and comment on the math behind the calculator and point out what we are missing.

NaHCO3 mw = 84 g/mole

so 84 mg = 1 mmole
84 x 3 = 252 mg, so 252 mg in 1 L makes 3 mmole/L = 3 meq/L

Sorry, could be my poor conversion to weight.
The original calculator was based on tests dissolving Baking Soda in teaspoons. The original series of tests resulted in a half a teaspoon increasing 10 gallons by 1 meq/lt.
In order to give an approximate weight I weighted one teaspoon of baking soda at 4.6 grams. This methodologies (backwards) could have built a lot of inaccuracies (the spoon size, the accuracy of my small scale etc.)
I will re-verify the numbers and update the calculator accordingly which could mean that an actual teaspoon shall weight 6.4 grams (not 4.6 grams)

Jose

[Billionzz]

Hi Randy,

>>>dKH and ppm kh are different than meq/L. Multiply 1 meq/L by 2.8 to get dKH. <<<

Can you tell me if I calculated this correct?

If I want to have 5 dKH in 1 liter of distilled water I would need to use 149.94 grams of sodium bicarbonate.

>>>I would buy a liquid standard, or a purified chemical like very pure sodium carbonate.<<<<

I saw two different forms of sodium carbonate for sale, Sodium Carbonate Monhydrate and Sodium Carbonate Anhydrous.

Which of these should I use?

How much many grams would I use to get a 5 dKH in 1 liter of water?

If it’s not to much can you tell me the formula to calculate this?


Thanks for all of the help,
Bill

[Chicago]

where can you buuy pure sodium carbonate?

[Billionzz]

I just did a search for lab grade or reagent grade sodium carbonate.

Bill

[jdieck]

Originally posted by Billionzz
Hi Randy,

>>>dKH and ppm kh are different than meq/L. Multiply 1 meq/L by 2.8 to get dKH. <<<

Can you tell me if I calculated this correct?

If I want to have 5 dKH in 1 liter of distilled water I would need to use 149.94 grams of sodium bicarbonate.

>>>I would buy a liquid standard, or a purified chemical like very pure sodium carbonate.<<<<

I saw two different forms of sodium carbonate for sale, Sodium Carbonate Monhydrate and Sodium Carbonate Anhydrous.

Which of these should I use?

How much many grams would I use to get a 5 dKH in 1 liter of water?

If it’s not to much can you tell me the formula to calculate this?


Thanks for all of the help,
Bill

Should be milligrams not grams.

[jdieck]

Originally posted by Chicago
where can you buuy pure sodium carbonate?

https://www1.fishersci.com/index.jsp

I would prefer to use Anhydrous 99.5% although there is a risk of being off. Because it is hygroscopic it can easily absorb water and if so, it might trow off your weight measurement.
I have had a lot of difficulty trying to get the proper bulk density of either the commercial powder or the baked baking soda to aproximate teaspoons for practical use in the calculator although I have found out that for use as Aquarium supplement the variation seems to be in the acceptable range.

[Billionzz]

>>>Should be milligrams not gram<<<

Thanks, that might have threw it off a little

I have a scale at home to weigh to .01 grams so hopefully this will help with the accuracy.

If it needs to be more accurate I have a scale a work that measures to .001 grams if needed.

Thanks,
Bill

[Randy Holmes-Farley]

Let us know how the standard works out.

[jdieck]

I already updated the calculators. Now weight measurement is the base and teaspoons are the approximation.

[Billionzz]

>>>If I want to have 5 dKH in 1 liter of distilled water I would need to use 149.94 mg of sodium bicarbonate.<<<

I guess I missed it, is this the correct amount of sodium bicarbonate to add ?

>>>I saw two different forms of sodium carbonate for sale, Sodium Carbonate Monhydrate and Sodium Carbonate Anhydrous.
Which of these should I use?<<<

Can someone tell me what the difference is between the two and why Anhydrous is better than Monhydrate?

>>>How many mg (of sodium carbonate) would I use to get a 5 dKH in 1 liter of distilled water?<<<

Again maybe I missed it could someone help me with this question?

Thanks for all of the help,
Bill

[jdieck]

The diference is basically the weight. The Monohydrate has one molecule of water so the formula is Na2CO3-H2O while the Anhydrous does not have it so the formula is NA2CO3

If you use Calcium Carbonate Anhydrous 99.5% you need 1,008 milligrams (about 1 gram)

[Randy Holmes-Farley]

I guess I missed it, is this the correct amount of sodium bicarbonate to add ?

Yes.

Can someone tell me what the difference is between the two and why Anhydrous is better than Monhydrate?

Either is OK, if it is exactly what it says.

[Billionzz]

I would like to thank everyone for their help I have been trying to find out the correct answers for this the last 3 weeks.

I have been on chemical forums, chemistry forums and a few freshwater forums trying to get answers and while sometimes I got some answers they all seem to come up with different weights.

Even now here are the weights of sodium bicarbonate to use in 1 liter of distilled water to get 5 dKH. I’m assuming that the calculators are just not as accurate.

149.9 mg from Randy
100 mg from Jose’s calculator / http://reef.diesyst.com/ .
125 mg from web calculator / http://www.cnykoi.com/calculators/calckh.asp

So just a few more questions if you don’t mind.

1) In 1 liter of distilled water how many mg of Sodium Carbonate Anhydrous would it take to get a dKH of 5?

2) Would using lab grade Sodium Carbonate Anhydrous help me to have a more accurate sample than using arm and hammer baking soda?

3) Should Sodium Carbonate Anhydrous be dried in the oven at all before the sample preparation?


Thanks,
Bill

[jdieck]

Originally posted by Billionzz

Even now here are the weights of sodium bicarbonate to use in 1 liter of distilled water to get 5 dKH. I’m assuming that the calculators are just not as accurate.

149.9 mg from Randy
100 mg from Jose’s calculator / http://reef.diesyst.com/ .
125 mg from web calculator / http://www.cnykoi.com/calculators/calckh.asp

So just a few more questions if you don’t mind.

1) In 1 liter of distilled water how many mg of Sodium Carbonate Anhydrous would it take to get a dKH of 5?

2) Would using lab grade Sodium Carbonate Anhydrous help me to have a more accurate sample than using arm and hammer baking soda?

3) Should Sodium Carbonate Anhydrous be dried in the oven at all before the sample preparation?


Thanks,
Bill

NOTE: I have updated the calculator, it will now calculate 149.9 (rounded at 150 mg) the 100 mg was not correct.

1) To have a solution with 5 dKH you need to add 95.11 milligrams of Sodium Carbonate Anhydrous 99.5% pure to 1000 ml of distilled or RO/DI water.

2) Given the accuracy of our test kits I would say you might not see a difference using either Arm and Hammer or the Calcium Carbonate Anhydrous. If Arm and Hammer is 97% pure that might generate a 3% margin of error which is below the typical 5 to 10% error of an Alkalinity tritration kit. I would try Arm and Hammer first and see how it goes. Use a new box.

3) No if it has been properly packaged. Yoiu will be running the risk of contaminating it specially if the oven uses gas rather than electricity. In addition overheating may partially create some Sodium Oxides thus changing the Carbonate concentration.

[Randy Holmes-Farley]

I agree. I'd just use baking soda for the standard for this purpose.

[Billionzz]

Randy and Jose,

Thanks for all of the help I really appreciate it.

Bill