Potassium sodium tartrate preparation and comparison with recipes

[latot]

TL;DR Summary

There is several sites that explain how to prepare this salt with bicarbonate and potassium bitartrate, but trying to match with the chemical reactions seems to not match, trying to do a better recipe.

Hi hi, here a question, how can we prepare Potassium sodium tartrate?, well, there is a lot of sites and videos, but in order to this right I'll write what have I done and checked, I'll try use the info I have, even if is not very dependable.

First, we need sodium carbonate, to do this, we can heat bicarbonate in a oven, it must be over 80C and less than 851C, with more heat will be faster, but over the 851C the sodium carbonate will descompose.

https://www.scientificamerican.com/article/vanishing-baking-soda/
https://www.thoughtco.com/decomposition-equation-for-baking-soda-604045

So, the reaction is
$$2 NaHCO_3(s) → Na_3CO_3(s) + CO_2(g) + H_2O(g)$$

Getting the proportion, for every 2 mol of bicarbonate we get 1 mol of carbonate, so
$$\frac {Na_3CO_3}{2 NaHCO_3} = \frac {105.9888}{2* 84.007} \sim 63\%$$

Now we know the % of mass we get from the bicarbonate.

The problem in this phase is that, is probable that even I put the bicarbonate a lot of time in the oven, there will be a % of bicarbonate, is there a way to separate them?

The next phase, mix sodium carbonate with potassium bitartrate:

$$2KC_4H_5O_6 + Na_2CO_3 → 2KNaC_4H_4O_6 + CO_2 + H_2O$$

From here, we can know the amount of carbonate we need in mass, for every:

potassium bitartrate 376,354 g + 105.9888g of sodium carbonate -> 420.318g of potassium sodium tartrate

So, where is the problem? here is a web with the same experiment:

http://materiability.com/portfolio/piezoelectric-crystals/

The experiment is empiric, so, it should works, but I can't avoid notice how doesn't match the balance with what I wrote above, in the experiment is used:

120g of bicarbonate or carbonate
200g of potassium bitartrate

well, the experiment don't says how much potassium sodium tartrate we get, but the initial proportions are weird, if we follow the actual procedure, if we use 200g of potassium bitartrate we need 56.32g of carbonate, in the worst case, let's say is bicarbonate, is 56.32/0.63 = 89.40...

Other differences that I don't write, in the experiment, when is mixed the carbonate and potassium bitartrate, is in water at 80C, I don't know how use dissolutions...

Maybe I do an error above, or something else is weird here, because a difference of 90g to 120g..., is like a lot for this reaction, or, there is more written just in case?.

Even if the last question is because the actual recipe don't match with the link, the idea is check this recipe, and do it better if there is the possibility.

I'm trying to do this with things that are easy to get, or make.

Thx.

 

[Borek]

Without trying to precisely analyze your calculations: it is not unusual for the practical recipes to not follow stoichiometry. Some excess of one of the reagents can be desired to get a better yield, to keep the pH right and so on.

I am not saying your thinking is flawed, there just can be more to that.