: STORIES FROM PHYSICS
: Fables For Children, Stories For Children, Natural Science Stori
If you pour salt into water and stir it, the salt will begin to melt and
will entirely disappear; but if you pour more and still more salt into
it, the salt will in the end not dissolve, and no matter how much you
may stir after that, the salt will remain as a white powder. The water
is saturated with the salt and cannot receive any more. But heat the
water and it will receive more; and the salt which did not dissolve in
the cold water, will melt in hot water. But pour in more salt, even the
hot water will not receive it. And if you heat the water still more, the
water will pass away in steam, and more of the salt will be left.
Thus, for everything which dissolves in the water there is a measure
after which the water will not dissolve any more. Of anything, more will
be dissolved in hot than in cold water, and in each case, when it is
saturated, it will not receive any more. The thing will be left, but the
water will go away in steam.
If the water is saturated with saltpetre powder, and then more saltpetre
is added, and all is heated and is allowed to cool off without being
stirred, the superfluous saltpetre will not settle as a powder at the
bottom of the water, but will all gather in little six-edged columns,
and will settle at the bottom and at the sides, one column near another.
If the water is saturated with saltpetre powder and is put in a warm
place, the water will go away in vapours, and the superfluous saltpetre
will again gather in six-edged columns.
If water is saturated with simple salt and heated, and is allowed to
pass away in vapour, the superfluous salt will not settle as powder, but
as little cubes. If the water is saturated both with salt and saltpetre,
the superfluous salt and saltpetre will not mix, but will settle each in
its own way: the saltpetre in columns, and the salt in cubes.
If water is saturated with lime, or with some other salt, and anything
else, each thing will settle in its own way, when the water passes away
in vapour: one in three-edged columns, another in eight-edged columns, a
third in bricks, a fourth in little stars,--each in its own way. These
figures are different in each solid thing. At times these forms are as
large as a hand,--such stones are found in the ground. At times these
forms are so small that they cannot be made out with the naked eye; but
in each thing there is its own form.
If, when the water is saturated with saltpetre, and little figures are
forming in it, a corner be broken off one of these little figures with a
needle, new pieces of saltpetre will come up and will fix the broken end
as it ought to be,--into a six-edged column. The same will happen to
salt and to any other thing. All the tiny particles turn around and
attach themselves with the right side to each other.
When ice freezes, the same takes place.
A snowflake flies, and no figure is seen in it; but the moment it
settles on anything dark and cold, on cloth, on fur,--you can make out
its figure; you will see a little star, or a six-cornered little board.
On the windows the steam does not freeze in any form whatever, but
always as a star.
What is ice? It is cold, solid water. When liquid water becomes solid,
it forms itself into figures and the heat leaves it. The same takes
place with saltpetre: when it changes from a liquid into solid figures,
the heat leaves it. The same is true of salt, of melted cast-iron, when
it changes from a liquid into a solid. Whenever a thing changes from a
liquid into a solid, heat leaves it, and it forms figures. And when it
changes from a solid to a liquid it takes up heat, and the cold leaves
it, and its figures are dissolved.
Bring in melted iron and let it cool off; bring in hot dough and let it
cool off; bring in slacked lime and let it cool off,--and it will be
warm. Bring in ice and let it melt,--and it will grow cold. Bring in
saltpetre, salt, or any other thing that dissolves in the water, and
melt it in the water, and it will grow cold. In order to freeze
ice-cream, they put salt in the water.