THE CHEMISTRY OF WATER. HYDROGEN. 



Ill 



from the combination of three volumes of the component 

 gases. 



141. Decomposition of Water. Water may be decom- 

 posedthat is, resolved into the two gases of which it is 

 made in a variety of ways, both physical and chemical. 

 We will first describe a method in which electricity is used, 

 and then give you some chemical methods. 



A current of electricity from a galvanic battery, gener- 

 ated as explained in Part I, decomposes water very readily. 

 By employing the apparatus, Fig. 35, the gases may be col- 



rig. 35. 



lected separately. Through the bottom of a glass dish are 

 introduced, water-tight, two platinum wires, a c and a b. 

 Over each of these wires a tube, with its upper end closed, 

 is placed. The tubes and the dish are filled with water, 

 which is slightly acidulated in order to make it a bet- 

 ter conductor. If now the wire a c be connected with 

 the positive pole of a battery, and the wire a b with its 

 negative pole, some of the water will be decomposed, and 

 the resulting gases, oxygen and hydrogen, will collect in 

 the tubes e and / respectively, driving the water down 



