From: sbhattac@rnd.GBA.NYU.EDU (Shankar Bhattacharyya)
Newsgroups: rec.food.cooking
Subject: Re: Baking Soda/Powder
Date: 13 Jan 93 04:07:20 GMT
Organization: NYU Stern School of Business

In article <C0nrM4.207@usenet.ucs.indiana.edu> bondc@silver.ucs.indiana.edu (Clay M. Bond) writes:
>In article <34967@rnd.GBA.NYU.EDU> sbhattac@rnd.GBA.NYU.EDU (Shankar Bhattacharyya) writes:

>>I would argue that there is no real chemical basis for this. Indeed, the
>>facts would argue for the opposite. Baking soda, by itself, will not give
>>up its carbon dioxide until it is heated, 

>You are quite mistaken--and easily proved so.
>
>Take cold, very cold, buttermilk and add baking soda, then stir.
>The liquid will immediately foam to nearly twice its original
>volume, and will continue to do so until the reaction is complete.
>
>Ice cold buttermilk.  Baking soda.  Your "facts" are not facts,
>merely confusion.

Clay, I am often confused, and gladly so. I consider myself underemployed
if I'm not confused a lot of the time. In fact, I spent almost all day today
in a very confused state indeed. However, in this instance, not only am
I not confused, I haven't been confused about this since my early teens.
The chemistry of carbonates and bicarbonates with respect to baking
powder is really rather simple.

Mike Edelman has already responded to your post in clear and admirably
concise fashion. I will take the liberty of using rather more bandwidth.

You are entirely correct in your observation that carbon dioxide is
released when you add bicarbonate to buttermilk. However, the conclusions
you reach from that observation are exactly wrong.

Buttermilk is acidic, typically to the extent of about 1 to 1.5 % lactic
acid. That means that buttermilk is somewhere between 0.1 N and 0.15 N,
which means that 10 ml of buttermilk will neutralize something in the
neighbourhood of 75 to 125 mg of sodium bicarbonate. What your experiment
almost establishes is that the reaction of bicarbonate with acid is quite
rapid at low temperatures. You might find it difficult to find a chemist
who is surprised by that.

Now all you need to do is try the same experiment with cold, neutral
water, and you will have almost enough information to reach some more or
less reliable judgments about what is going on.

Your explanation as to how double acting baking powder works is precisely
backwards as to the facts, and incomprehensible as to the theory. Your
initial statements on the subject had me quite bemused. You said:

>>>There is another difference.  When using (all or predominantly)
>>>soda, you must get the pan in the oven as soon as possible,
>>>because the reaction is purely chemical.  Baking powder contains
>>>cream of tartar, recall, and the heat of the oven is the catalyst
>>>for the reaction (this is why it's called "double-acting": the
>>>soda reacts immediately, and the acid when heat is applied).

I'm afraid I had absolutely no idea whatsoever what that paragraph means,
starting with the "because" in the third line. Nor did a couple of
chemists with whom I work. We eventually reached a tentative explanation
as to what you might mean, and how you might have got there, but since it
is your explanation, and I cannot possibly really know how you got there,
it would be presumptious of me to try to explain your thoughts. So I will
hold my peace.

- Shankar
Newsgroups: rec.food.cooking