DECOMPOSITION OF WATER. 



679 



necessary to collect the gases separately, the cheaper apparatus, re- 

 presented in fig. 345 A, may be constructed. The platinum elec- 

 trodes are replaced by strips of very thin sheet iron, which are passed 

 through a cork, are bent as shown in the figure, and have short 

 pieces of copper wire or strips of copper soldered to them. A bent 

 glass tube is also inserted in the cork, which serves for conveying 

 the oxy-hydrogen gas into the solution of soap. The strips of iron 

 are cut in the form shown at B in the figure ; two slits are made 

 with the penknife through the cork, and also a hole for the glass 



FIG. 345 (A an. proj., real size; B'and C real size}. 



tube, as shown at C in the figure ; the strips of iron are pushed 

 through the cork from below, the copper wires or strips are soldered 

 to them with soft solder, the strips are then bent at right angles, 

 and finally the glass tube is set in. The little bottle (a small glass 

 pomatum jar) is filled with a strong solution of caustic potash. 

 This substance is sold in small sticks, which are very deliquescent 

 when exposed to the air, as they attract the moisture and also 

 the carbonic acid contained in the atmosphere : the sticks should 

 therefore be dissolved very soon after they are purchased. The 

 solution, which becomes hot at first, should contain about 10 

 grammes in'50 cc of water. It is poured into the jar by means of a 

 funnel, care being taken not to wet the neck of the jar. The cork 



