Sciencemadness Discussion Board - bicarbonate to carbonate

bicarbonate to carbonate

jamit - 24-6-2014 at 22:40

I am currently converting food grade sodium bicarbonate to sodium carbonate by heating it in the oven at boil for about 3 hrs. Is that long enough?

How can you tell when all the bicarbonate has been converted to carbonate?

And what is the chemical grade of the sodium carbonate after conversion from bicarbonate? Is it reagent grade, lab grade, or what?

I want to use sodium carbonate as a primary standard to standardize other acids and bases.

Also, is there a way to test for the presence of bicarbonate or carbonate? I tried adding pottery grade sodium carbonate to HCL and it fizzed alot and the same thing happened with a solution of bicarbonate, so adding acids doesn't help to distinguish the two chemicals. There's got to be another way. Any suggestions? thanks.

arkoma - 24-6-2014 at 23:05

suggest mebbe weighing before and after? your losing an atom of hydrogen. bicarb is supposed to change to carbonate at 50c

woelen - 24-6-2014 at 23:05

Heating at boil? You mean 100 C? That is not enough, decomposition then is slow and incomplete. I would heat it to at least 200 C for a few hours. At 200 C I expect you to get a decently pure product (assuming that your starting product is pure). If you want to use the material for standardizing other acids, then store it in a very well sealed bottle to assure that it does not absorb water from the air. The latter would cause weighing errors which cannot be corrected for if you do not know the precise amount of absorbed water.

The only practical way I can think of for testing maxes of Na2CO3 and NaHCO3 is to measure the amount of CO2 formed from a known amount of solid and excess acid. This, however, is not an accurate measurement. It can give you a rough indication of the ratio of NaHCO3 to Na2CO3, but when the chemical is quite pure already (e.g. at the order of 95% of one of them, then it will be hard to determine the precise amount of the other).

I expect that with your home made Na2CO3 you will get an accuracy not better than a few percent uncertainty, but I think that for most of your applications that will be sufficient. Keep in mind that this only works accurately with strong acids. Standardizing weak acids like acetic acid with sodium carbonate will be very inaccurate, due to the lack of sharp transition points.

jamit - 24-6-2014 at 23:22

Thank you guys for such a quick reply, much to think about.

I will try weighing before and after...and thanks Woelen... you're always reliable and helpful in your replies. I'm so glad there's guys like you around this forum.

Again, thanks.

violet sin - 24-6-2014 at 23:40

@ woelen, I think perhaps jamit meant broil, as "in the oven" was used. regardless the lowest temp on a lot of ovens is like 150'F on the "warm" setting. real cooking starts at 200'F on mine, but it also has the warm setting as stated. I do as arkoma said and weigh it before and after. done on steady weight even after more heating.

jamit - 25-6-2014 at 00:13

thanks "violet sin", that's exactly what I meant to say, "broil" not "boil". At broil its 400F.

prof_genius - 25-6-2014 at 00:40

You can find Sodium Carbonate in stores sold as Washing Soda. I found that the brand in the Netherlands is quite pure.

woelen - 25-6-2014 at 01:47

Quote: Originally posted by jamit

thanks "violet sin", that's exactly what I meant to say, "broil" not "boil". At broil its 400F.

I also learnt something new. English is not my native language and I did not know the term "at broil". Usually, ovens over here do not have such indications, we have a dial on them with temperatures in degrees Centigrade (e.g. from 80 C to 250 C or so).

jamit - 25-6-2014 at 01:48

here's in the US, you can buy it from pottery stores, but I'm sure it not reagent grade... maybe at most lab grade.
I thought I try another route, so I decided on making sodium carbonate from sodium bicarbonate which I believe is food grade and therefore quite pure.

aga - 25-6-2014 at 03:22

Quote: Originally posted by woelen

English is not my native language and I did not know the term "at broil".

Your English is better than many English people i have met !

To Broil = To Grill / cook under a Grill
It is an old term and is not used in modern spoken English.
Perhaps it is still in use in US English.

hyfalcon - 25-6-2014 at 03:34

http://householdproducts.nlm.nih.gov/cgi-bin/household/brand...

This is what I use.

sasan - 25-6-2014 at 03:48

I think it is very easy and safe to make sodium carbonate if you use sodium hydrogen carbonate and sodium hydroxide:NaHCO3(aq) + NaOH(aq) <---> Na2CO3(aq) + H2O(aq)

Any ideas and questions? :cool:

Pyro - 25-6-2014 at 05:50

you can buy it in europe for about 3eur/kg. it must be close to pharma grade as it suggests soaking your feet in it

arkoma - 25-6-2014 at 07:00

Quote: Originally posted by aga

Quote: Originally posted by woelen

English is not my native language and I did not know the term "at broil".

Yes, it is. Every oven I've ever seen has a "Broil" setting. Electric ones have an element in the very top that only comes on at broil, and gas ones have a pull out drawer in bottom.

I ALSO learned something about my native tongue LOL

Typical US oven knob:

125.jpg - 19kB

aga - 25-6-2014 at 08:09

It may be a sign of a decline in literacy in the UK that most ovens i have seen recently have Pictures instead of words ...

http://www.shutterstock.com/pic-87168826/stock-photo-oven-pr...

Texium - 25-6-2014 at 08:26

Wow, that's very cryptic! Not sure what the ones with the spikes on the oven ceiling are supposed to represent. And yeah, my oven has a broil setting on the knob, and the toaster oven has a broil button. I've never really thought of it as being an odd thing. Little oddities of culture are everywhere!
Also, I found my sodium carbonate at the hardware store as pool pH booster. It claims 99% purity (doubtful) and seems to be anhydrous. If I remember correctly it was $6 for a 2lb container.

[Edited on 6-25-2014 by zts16]

aga - 25-6-2014 at 08:30

the Spikes are the Grill (Broiler)
One row of spikes = half power
Spikes with a line = full power
With a propeller = fan assisted
The temperature is usually a second digital control knob/buttons.
The Icons on the right are for the top and bottom oven elements

Edit:
The light bulb icon is to get the oven to give you an Idea.
The snowflake icon is what you use for attempting to dehydrate aluminium sulphate.

[Edited on 25-6-2014 by aga]

DraconicAcid - 25-6-2014 at 08:42

Quote: Originally posted by aga

It may be a sign of a decline in literacy in the UK that most ovens i have seen recently have Pictures instead of words ...

http://www.shutterstock.com/pic-87168826/stock-photo-oven-pr...

It's probably not literacy so much as small market- the company making the knobs also wants to be able to sell them to France, Poland, Sweden, the Netherlands, Germany...

Texium - 25-6-2014 at 08:52

Quote: Originally posted by aga

The light bulb icon is to get the oven to give you an Idea.

Wish mine had a setting like that. Must come in handy sometimes on long boring afternoons. Well, if the oven has any good ideas that is!

unionised - 25-6-2014 at 10:15

I love the idea that there's someone named Aga talking about ovens.
http://en.wikipedia.org/wiki/AGA_cooker

Pyro - 25-6-2014 at 11:19

the pictograms are simple, the more expensive ovens put pictograms on the dial to make the whole thing look more simple and less cluttery

valeg96 - 28-6-2014 at 09:36

Quote: Originally posted by prof_genius

You can find Sodium Carbonate in stores sold as Washing Soda. I found that the brand in the Netherlands is quite pure.

In Italy is sold as "SODA SOLVAY" by Solvay, and is 99.8%, costs 2.8€/kg in supermarkets and 1.8€/kg in bulk. I may be repetitive but you should definitely buy it. Heating NaHCO₃ is way more expensive.

Zyklon-A - 28-6-2014 at 14:40

I decompose sodium bicarbonate in a stainless steel pan on the stove. I can convert 500 grams to carbonate in just 15 minutes, I think you'll find this to be a much easier, and faster method.
[EDIT] Just remember to stir often.

[Edited on 28-6-2014 by Zyklon-A]

Amos - 28-6-2014 at 16:23

For all of you that are more interested in the definition of the term broil, it is important to note that it differs from other cooking methods in an oven by the fact that broiling is done by bombarding food with infrared rays rather than surrounding the food with hot air. This makes whatever is being cooked more likely to cook on the top and develop a char, and to be less cooked on the inside. As a sidenote, broiling is probably much less effective than baking in order to convert baking soda to sodium carbonate, as all parts are not receiving the same amount of heat. The steel pan sounds the best to me, as you're treating the sodium bicarbonate with much higher temperatures, and also driving off more of the ambient water as a result.

Ascaridole - 7-7-2014 at 13:49

To be used as a primary standard you need to heat your sodium carbonate to 270ºC (518ºF) and cool in a desiccator. The decomposition of bicarbonate to carbonate is also not 100% efficient at lower temperatures.

Also carbonate needs boiling near the end point and can be fussy if your not careful with indicator choice and solution concentration.