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I'd like to make sodium carbonate for ramen noodles. The instructions on the web however vary greatly. One source says to bake baking soda at 350 degrees for 2-5 hours. Others say 250 degrees for an hour. Another says just 200 degrees for an hour.

Does the temperature even matter at all?

How about if I use a higher temperature like 450 degrees? This would be preferable for me as I only need a small amount and I can probably bake it at the same time I'm baking bread.

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    Just to confirm: degrees Fahrenheit? The question is interesting but I was really confused until I got to the 450 degrees (no domestic oven goes that high in Celsius) – Juliana Karasawa Souza Sep 24 at 8:38
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    The quoted 200 is probably C. I used less than 200C for this answer. The 250 is likely to be also C (that's about as high as most domestic ovens go) – Chris H Sep 24 at 9:42
  • Yes, Fahrenheit. This is the one that says 200 degrees: thoughtco.com/… – aris Sep 24 at 17:27
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    200F seems low, but I couldn't get that link to work. It tried to load so many tracking and other unwanted scripts from all over the web that I gave up – Chris H Sep 26 at 16:22
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160 °C (320 °F) for 1-2 h worked for me once, but higher temperatures should not hurt the process.

If you are starting with dry sodium hydrogen carbonate, the mass should reduce to 63 % of the starting mass (more reduction in case of wet starting material).

Explanation for the mass loss number: You are converting two equivalents of sodium hydrogen carbonate with a molar mass of 84.01 g/mol to one equivalent of sodium carbonate with a molar mass of 105.99 g/mol. 105.99/(2*84.01) = 63 %

  • Is it close enough to be at 70%? – aris Oct 2 at 0:58
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    Depends on what you want to do with it. An "incomplete" product will be less alkaline, although I would wager it will still be absolutely fine for most culinary purposes. But there's also no harm in just baking it more at a later time. – Matthias Brandl Oct 2 at 7:07
  • By the way, I started with baking soda that had been in the fridge for probably a long time. Is it possible that the decomposition process had already started before I baked it and so the reduction in mass would be less than expected? – aris Oct 2 at 16:23
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    At low temperatures, the decomposition should be so slow as not to be noticeable by weight (except maybe on geological time scales). But possibly it was not pure sodium hydrogen carbonate to begin with (either already sodium carbonate or an inert filler as a contaminant). – Matthias Brandl Oct 7 at 9:04
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The temperature needs to be high enough, that's all. 450°F should work fine. (2-5 hours is a little silly, since the reaction is pretty quick once the baking soda itself is up to temperature.)

If you want to check that everything's gone okay, you can weigh the powder before and after. If it's converted properly, its mass should decrease to 63% (EDIT: fixed miscalculation, Matthias' number is the correct one) of the original. (Possibly a little further if there was some moisture in it.)

  • you should also add temperature units, I'd like to be sure you're talking F not C. – Luciano Sep 27 at 8:52
  • @Luciano fair enough, though I doubt the OP is cooking bread at 450°C. – Sneftel Sep 27 at 9:00

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