The Effect

Show a dish of soap-suds and then blow bubbles with the apparatus described below.

When the bubbles take on a size of about 3 inches in diameter shake them off and they will rise slowly and gracefully in the air. Before they get out of reach touch them with a long lighted taper and they will explode viciously with a sharp report like that made by a revolver.

The Cause

The bubbles are filled with a mixture of hydrogen gas and oxygen gas and when these two gases are simply mixed they form a very explosive compound which is called detonating gas.

When the flame is brought close enough to the bubble it fires the gases in it, and they explode and combine chemically to form water. The apparatus necessary to do this experiment with is shown in Fig. 120.

It consists of (1) a hydrogen gas generator and (2) an oxygen gas generator.

The hydrogen bottle or flask is fitted with a two hole stopper through which runs a glass funnel and an L tube just as described in the fountain experiment and shown at B in Fig. 119. Connected to the L tube is a length of rubber tubing into the other end of which another L tube is fitted.

The oxygen bottle or flask is fitted with a single hole stopper which has an L tube running through it as shown at B in Fig. 119. Connected to the L tube is fixed another length of rubber tubing and in the free end of this is fixed another and shorter L tube. Now place the two short L tubes side by side and cement them together with sealing wax. A long length of rubber tube is forced on over the ends of the double tube and, finally, a clay pipe is fitted into the free end of the rubber tube, all of which is shown in Fig. 120. Set the bottles or flasks as far apart as possible and in the hydrogen bottle put a handful of granulated zinc. Dilute hydrochloric acid118 is poured down the funnel on the zinc when hydrogen will be set free, or generated as it is called.

Fig. 120. The Vicious Soap Bubbles

Put a small handful of a mixture of 2 parts of potassium chlorate and 1 part of manganese dioxide, finely powdered, in the oxygen bottle and then set a Bunsen burner under it when it will give off oxygen. When the two gases leave the short L tubes they mix in the long rubber tube and by the time they reach the clay pipe you will have detonating gas all right.

Caution

Do not bring a flame anywhere near the apparatus and as a further precaution wrap a thick towel around the hydrogen flask.

The bubbles that are blown rise in the air because both the hydrogen and the oxygen are lighter than the air.