How to Do Chemical Tricks — Noiseless Bell, The Bursting Bladder, Weight of the Air

Noiseless Bell.

We know that sound is a succession of vibrations which must be transmitted in a medium with weight, as air or water; in other words, in a vacuum there can be no sound at all.

To prove this, introduce into the receiver a small bell, and as the air is extracted the sounds become weaker and weaker, and cease altogether when the air is completely rarified.

[Illustration] The Bursting Bladder.

Tie a thin piece of light indiarubber round the top of the bottle, and you will notice that as the air is withdrawn, the indiarubber will stretch, and at length form a round small balloon in the interior of the bottle.

(Fig. 1).

[Illustration: FIG. 1. ] [Illustration: FIG. 2. ] If a piece of bladder is tightly stretched and tied round the vessel (fig. 2. ) it will burst under the force of the atmospheric pressure which acts upon it, through a vacuum having been made underneath.

This is another case of the first experiment with the air pump described above.

Weight of the Air.

Another experiment will still better make you appreciate the value of this factor: the weight of the air.

Put a piece of supple leather in which a ring is attached under the bottle; pump the air out of the latter and you will be astonished at the weight you may hang on this leather without dragging it off.

[Illustration] Should you not have at hand a glass receiver, a wooden reel may serve instead (see fig. ).

On one of its faces place a piece of strong cardboard, in the middle of which a hook has been fastened; when the rarefaction is made, rather heavy weights must be hooked on before the cardboard is detached from the face of the rest.