[
So btw: this question is INSANELY over-precise for just making some noodles,
but I want to understand this chemistry stuff better anyway,
and I'm curious to be able to play around later with exact amounts and see if I can get significantly different effects in the finished products.
]
So I can't find pre-made kansui(かん水) / jiǎnshuǐ(碱水 (鹼水)) where I live
However, I of course have baking soda (sodium bicarbonate)
and I was able to get potassium carbonate from Amazon:
https://www.amazon.ca/gp/product/B074D9BXRT/
(
You can indeed decompose
"baking soda" aka sodium bicarbonate
into
"washing soda" aka sodium carbonate
just in the oven / a pan on the stovetop
[see this answer]
)
Since the sodium carbonate will be formed in the oven,
I think we can assume it's pretty much anhydrous, eh?
As for the potassium carbonate,
I didn't find anything on the wikipedia page for it about any heat decomposition it does
(I mean like, not counting anything that happens over 1000 C xD)
so I was planning to also heat it to drive off any moisture before weighing it for the ratios.
(No problem with that, right?)
Now I need to figure out what ratio to mix them...
Like, Wikipedia claims
More commonly a mixture of
20% sodium carbonate, which is also an anti-caking agent,
and 80% potassium carbonate in water is added directly.
but the source it gives is actually just this blog post
which says:
Kansui contains 80% potassium carbonate
and 20% sodium bicarbonate (or baking soda).
which apparently confuses baking soda and washing soda...
although it talks about converting sodium bicarbonate to sodium carbonate further down the page
(so I would guess the author understood but just wrote it ambiguously while trying to simplify things for a popular audience, maybe??).
So I dunno,
but I figure I may as well just take this ratio and use it as my starting point:
- 80% potassium carbonate
- 20% sodium carbonate
(I'll be taking that to mean ratio of weight, although of course my sources were technically ambiguous).
That make sense?
Anyway, I need to know the ratio of water to dissolve it in,
because I want to get the strongest solution possible at room temperature
(
in order to minimize the amount of hydration that the kansui adds to the final dough,
useful for making egg noodles etc
if you're trying to get as much of the hydration as possible to come from eggs rather than water
)
[
I'll be washing the glass bottle I store it in very thoroughly,
and using distilled water
-- because the last time I stored a concentrated sodium carbonate solution in a glass bottle,
this feathery black sediment formed at the bottom
]
So how do I find the solubility of potassium carbonate and sodium carbonate at like 21 C?
I mean, I've found some solubility tables by googling around
(although they're a bit inconsistent in a few little ways)
but like, my understanding of chemistry is pretty bad and I'm not sure what effect the mixing has on the total solubility?
So like, concretely, let's say I have 100 g of distilled water
What is the maximum amount of grams of potassium carbonate that I can add to the water,
such that when I add 1/4 that amount grams of sodium carbonate,
nothing precipitates out at 21 C?
(And like, how do I work that kind of question out in general myself?)
