There is a shrub called manioc, or manihot, or cassava, which grows in
South America, the West Indies, and Africa. It has a great bulbous root,
and it is this root which is interesting. In that species of the plant
which is most used the root has a bitter, acrid juice, which is deadly
poisonous. The strange part of the matter is that both the root and the
poisonous juice are used for food, and probably every boy or girl who
reads this has eaten both.
The natives of hot countries dry the root, and make good wholesome bread
out of it. It is only the juice which is poisonous or disagreeable in
taste. But the juice itself contains a kind of starch, and when the
liquid parts of it are evaporated, there remains--what do you think?
Why, the tapioca of which your mother makes puddings.
But why isn't tapioca poisonous? Why is Brazilian arrowroot--which is
only the manioc root dried and powdered--harmless and nutritive? What
becomes of the poison, and how can we be sure that none of it remains in
the tapioca or the arrowroot?
Pour a spoonful of alcohol on a plate, and set it in the air or
sunshine. Then look for it half an hour afterward. The plate will be
dry, and not even a smell of the alcohol will remain. Liquids which
evaporate easily and completely in this way are called volatile, and the
acid which renders manioc root poisonous is extremely volatile. When the
least heat is applied to any mixture containing it, the acid quickly and
completely evaporates, and that is the way in which it disappears in the
process of making tapioca, or drying the root to make arrowroot of it.
There is a small quantity of bitter material in the manioc juice which
is removed by washing the tapioca as soon as it is made.