How to make baking soda

Sodium bicarbonate, the chemical name of baking soda, has always been manufactured using industrial processes at an industrial scale. I can't see how it could be practical to make at home. You'd need specialized equipment and you might well find that the materials you need aren't any easier to acquire.

Baking soda is known by different names, in addition to sodium bicarbonate according to Wikipedia it's also known as bread soda, cooking soda, and bicarbonate of soda. So it's possible it's available in your area on under one of these other names. If you live in area where a language other than English is used then you might find other alternative names in that language's version of the Wikipedia page. If you still can't find any you'll either have to pay to have it shipped to you or find a substitute recipe that uses some other leavening agent.

If you really want to do some chemistry, the next questions are:

1. What can you get?
2. Do you know how to handle these safely?

If you have a solution of carbonic acid (H2CO3) you can slowly mix in sodium hydroxide (NaOH - in a solution, not a powder!) until the pH is around 10.3, then you'll have a solution of NaHCO3. Or you could do the same thing by bubbling CO2 through a solution of NaOH.

You'll then need to dry or concentrate it without heating, or the NaHCO3 will break down (just like it would when baking).

Or you could start with sodium carbonate and add hydrochloric acid, but that would give you equal parts of baking soda and table salt in water, not sure how easy they would be to separate.

Keep in mind that sodium hydroxide will dissolve any flesh that it touches, and hydrochloric acid will do the same, plus it evaporates.

If you can get sodium hydroxide, you can make baking soda. The stuff absorbs CO2 from the air along with water to produce NaHCO3, baking soda. I've had batches of commercial NaOH that were in fact up to 40% NaHCO3.

Best way to do it is to dissolve your NaOH in water, and just let it stir a few weeks. It'll suck CO2 out of the air. When the pH gets down to 6.5 or 7, you'll have reasonably pure baking soda. Evaporate the water and you're done. Be aware that heating baking soda in an oven at over 200°F will give you sodium carbonate rather than baking soda, so evaporate gently.

If I'm understanding this right, lye dissolved in water and let sit to absorb carbon dioxide from the air will turn into sodium hydroxide. If you then gently evaporate the water (at low temperatures) the residue left will be baking soda.

My understanding is that back when everything (more or less) was made at home, lye was made from wood ash, so if my understanding is correct, this should be a way to make baking soda without resort to a pharmacist.