SPONTANEOUS COMBUSTION. 



363 



lower end of which is placed a small cylinder of zinc o p. 

 A brass tube a b c is fitted at a into the neck of the globe 

 C D, and through this tube, which is furnished with a 

 stop-cock d, the gas can escape at the small aperture c. 

 A brass pin c /, carrying a brass box P, is made to slide 

 through a hole h, so that the brass box P, in which the 

 spongy platinum is placed, can be set at any required 

 distance from the aperture c. If sulphuric acid diluted 



Fig. 73. 



with an equal quantity of water is now poured into the 

 vessel A B by its mouth at S, now closed with a stopper, 

 the fluid will descend through the tube m n o p, and if the 

 cock d is shut, it will compress the air contained in C D. 

 The dilute acid thus introduced into C D will act upon 

 the ring of zinc o p, and generate hydrogen gas, which 

 after the atmospheric air in C D is let off, will gradually 

 fill the vessel C D, the diluted acid being forced up the 

 tube o p m n, into the glass globe A B. The ring of zinc 

 o p floats on a piece of cork, so that when C D is full of 



