On Sunday, February 11, 2018 at 10:23:41 AM UTC-5, Ralph Mowery wrote:

As most of the batteries used in portable devices are some type of
alkaline the baking soda is the opposit of what should be used. White
vinegar is what you should be using to neutralize it.

I am not sure what the very old carbon zinc batteries used, it may have
been a from of acid. I know the car batteries use acid and the baking
soda is good for that. Just not good for the newer smaller AA,C,D type
batteries.

LeClanche cells are acid-based (Ammonium CLoride) with an acidic pH (depending on the age of the cell) from about 6 (nearly dead) to about 4.6 (fresh). Hence the pointer to baking soda.

Baking Soda (Sodium Bicarbonate) is about pH 8.4 when dissolved in water. Household vinegar is pH 2.4, and will tear copper apart.

The neutralizing agent wants to be slow and mild. Vinegar (acetic acid) is pretty strong.

Peter Wieck
Melrose Park, PA