200 METALLOIDS. 



application of a taper. To secure against accident, the 

 precaution should invariably be observed, of winding 

 the vial with a towel, before the discharge. 



495. EXPLANATION. The explosion re- 



Why does this 



mixture ex- suits from the fact that all of the hydrogen 



plode? ^ n t j ie v - a j k urns at oncej causing great 



heat, and sudden expansion of vapor. The combus- 

 tion is thus simultaneous, because oxygen, the sup- 

 porter of combustion, is present at every point. When, 

 on the other hand, a jet of hydrogen is kindled, no 

 explosion occurs, because the combination is gradual. 

 Combustible hydrogen meets with oxygen in this case, 

 only on the surface of the jet. 



n , -i th 496. THE HYDROGEN GUN. The expe- 



hydrogen gun, riment for the explosion of mixed hydro- 



and the me- -, . -, -, 



thodofcharg- gen and oxygen gases, may be made in a 

 ing it. strong tin tube, provided with a vent near 



the closed end. Such a tube, about an inch in diame 

 ter, and eight inches in length, is called the hydrogen 

 gun. In loading it, the vent is stopped with wax, 

 the tube filled with water, and the gases, previ- 

 ously mixed in the right proportion, poured upward 

 into it, as indicated in the figure. The 

 gun, being thus loaded, is tightly 

 corked, under water, and afterward 

 fired at the vent. The explosion is 

 sufficient to expel the cork with vio- 

 lence, accompanied by a loud report. 

 The vial from which the tube is loaded 

 must not be too large, or it will not be practicable to 

 turn it and pour upward, as desired. This difficulty 



