{Sulphate of soda 3 parts.
{Dilute nitric acid 2 “
{Nitrate of ammonia 1 “
{Water 1 “
{Phosphate of soda 2 “
{Dilute nitric acid 1 “
{Sulphate of soda 2 “
{Muriatic acid 1 “
The effects of most of these mixtures may be considerably increased
by previously cooling the ingredients _separately_ in other freezing
mixtures.
In connection with this branch of science, and especially with
chemistry, the youthful philosopher should practice the art of
decanting air from one jar to another standing over water, beginning
by passing it from a small to a larger jar, then with two of equal
size; and when he can accomplish the transfer without permitting even
one bubble to escape, he may essay the much more difficult task of
transferring the air from a large to a smaller jar.
He should also practice using the blowpipe until he can keep up a
steady and uninterrupted flame for ten minutes or a quarter of an hour,
without stopping for breath. It is quite possible to replenish _wind_
in the mouth, which alone ought to be used, without interrupting the
breathing for an instant, but it requires some practice.