414 



REGENT PROGRESS IN PHYSICS. 



wire upon the different gases. After many unsuccessful experiments 

 this decomposition was effected by means of the following apparatus : 



A bent glass tube, 

 Fig- 53- open at one end, (fig. 



53) was connected at 

 its other end by a nar- 

 row neck, with a bulb 

 into which the plati- 

 num wire passed, as 

 represented in the fig- 

 ure. The whole tube 

 was filled with water 

 previously freed from 

 air, and its open end 

 immersed in a vessel of water. On applying a battery of two zinc-plati- 

 num cells, the air in the bulb was expanded and expelled so that the 

 water entered it and then soon boiled, and at a certain period the wire 

 became ignited in the vapor. "At this instant a tremulous motion 

 was perceptible, and separate bubbles of the size of pin-heads ascended 

 and collected in the bend of the tube. It was not a continuous evolu- 

 tion of gas as in electrolysis, but appeared to be a series of jerks; the 

 water in returning through the narrow neck formed a natural valve, 

 which cut off by an intermitting action portions of the atmosphere 

 surrounding the wire." The collected gas was detonating gas. 



That this evolution of detonating gas can certainly not be attributed 

 to electrolysis has been satisfactorily demonstrated by G-rove. I give 

 below the most important of his arguments. 



1. A battery of two cups produces in distilled water, even under 

 the most favorable conditions, a scarcely perceptible electrolysis. 



2. The decomposition did not commence until the wire became 

 ignited. 



3. When the wire was divided no gas was evolved. 



Grove now endeavored to produce the decomposition of aqueous 

 vapor in such a manner that the red hot platinum wire could only 

 come in contact with the vapor. A glass tube, as in fig. 54, which 



at its closed end had a curved platinum 

 F's- ^'*- wire melted in, was filled with water 



which had been carefully freed from air 

 by long boiling and the air pump; it was 

 then inverted in a vessel of the same 

 water, and a spirit lamp applied to its 

 closed extremity until the upper half was 

 filled with vapor, which therefore sur- 

 rounded the platinum wire. The wire 

 ,„ was then brought to full ignition. After 



M.W'i^df0&>^' . the connexion was broken and the lamp 



removed, the water gradually ascended 

 again, but a bubble of the size of a mustard seed remained in the 

 tube, and detonated when touched by a lighted match at the surface 

 of the water trough. The experiment was repeated, the wire being 



