Beneath this container is next stood another large flask filled with red litmus solution (A) and fitted with a stopper, through which pass two glass tubes (M and N, in [Fig. 13]). One of these (N) is bent outwards, and extends only just inside the flask’s neck, whilst the other is long enough to reach from the bottom of the lower flask almost to the top of that holding the ammonia. Instead of red litmus solution, a liquid made by boiling red cabbage leaves in water, and adding just enough vinegar to dispel entirely the bluish coloration, may be used with equal success.
The position then is that two flasks—of which the upper (B) holds ammonia gas, whilst the lower retains a pink solution—are supported one above the other, their necks approaching and joined by a glass tube (M). A second glass tube (N) also emerges from just above the surface of the pink liquid, and is bent outwards from the flask, so that it may be held in the mouth. When this is blown through, the pink water is forced up the connecting tube (M) and sprays out, fountain-like, within the upper flask. Moreover, as the ammonia is so rapidly absorbed by the incoming water, this continually ascends to fill the vacuum, which tends to form as the gas is dissolved. The fountain continues to play when the blowing has ceased, and further, although the spray presents a reddish tinge on entering the flask, it immediately turns blue as the ammonia dissolves (C, [Fig. 13]). This reaction indicates the alkalinity of ammonia, such substances being capable of neutralizing acids, which redden solutions of vegetable blues.
CHAPTER XXXVIII
ODD EXPERIMENTS
To While Away Winter Hours
The famous King Belshazzar was much dismayed to see the mysterious writing upon the wall of his palace. Without reducing your friends to a similar state of terror, a very easy experiment can be performed productive of the same effect, and if it does not exactly make their knees strike together, it will astonish them very much.
The appliances are such as can be found in any home, and the strange writing can be produced in the following way.
Fig. 1.—Showing relative positions of candle and mirror so that patch of light is thrown on the wall.
At one end of a dark room erect a screen that shall conceal you and your apparatus effectually from the spectators. Upon a table behind this screen place a large mirror, such as can be found upon any dressing-table. Put a lighted candle in front of this glass, placing the latter at such an angle that a large patch of light is thrown upon the wall before you, as in [Fig. 1].