pancakes or muffins. The soda is a weak base. The sour milk is a weak
acid. The soda neutralizes the acid, changing it into a kind of salt
and plain water. Therefore the sour milk pancakes or muffins do not
taste sour.

In the same way a little soda keeps tomatoes from curdling the milk
when it is added to make cream of tomato soup. It is the acid in the
tomatoes that curdles milk. If you neutralize the acid by adding a
base, there is no acid left to curdle the milk; the acid and base turn
to water and a kind of salt.

When you did an experiment with strong acid, you were advised to have
some ammonia at hand to wash off any acid that might get on your skin
or clothes. The ammonia, being a base, would immediately neutralize
the acid and therefore keep it from doing any damage. Lye also would
neutralize the acid, but if you used the least bit too much, the lye
would do as much harm as the acid. That is why you should use a weak
base, like ammonia or baking soda or washing soda, to neutralize any
acid that spills on you. Then if you get too much on, it will not do
any harm.

In the same way you were warned to have vinegar near at hand while you
worked with lye. Strong nitric acid also would neutralize the lye, but
if you happened to use a drop too much, the acid would be worse than
the lye. Vinegar, of course, would not hurt you, no matter how much
you put on.

_Any_ acid will neutralize _any_ base. But it would take a great deal
of a weak acid to neutralize a strong base or alkali; you would have
to use a great deal of vinegar to neutralize concentrated lye. In the
same way it would take a great deal of a weak base to neutralize a
strong acid; you would have to use a large amount of baking soda or
ammonia to neutralize concentrated nitric acid.

_APPLICATION 83._ A woman was cleaning kettles with lye. Her
little boy was playing near, and some lye splashed on his
hand. She looked swiftly around and saw the following things:
soap, oil, lemon, flour, peroxide, ammonia, iodine, baking
soda, essence of peppermint. Which should she have put on the
boy's hand?

_APPLICATION 84._ A teacher spilled some nitric acid on her
apron. On the shelf there were: hydrochloric acid, vinegar,
lye, caustic soda, baking soda, ammonia, salt, alcohol,
kerosene, salad oil. Which should she have put on her apron?

_APPLICATION 85._ A boy had "sour stomach." His sister said,
"Chew some gum."