SCIENCE AND PRACTICE. 



233 



A wide-mouthed bottle (Fig. 120) is three-quarters filled 

 with sulphuric acid (sp. gr. 1'3). The mouth is filled up 

 by a leaden stopper, A A, through which, in small glass 

 tubes, two well-insulated copper wires, c and d, are led, 

 their ends being soldered below to two plates of platinum 

 foil, and protected by a coating of varnish or resin against 



Fig. 120. 



Ffc. 121. 



the corrosive action of the acid. The upper ends of the 

 wires c and d are furnished with binding screws, by which 

 they may be brought into contact with the poles of the 

 galvanic battery. On a glass tube, b, also cemented into 

 the cover A A, an S-shaped glass tube of the same diameter 

 is attached by means of a short piece of india-rubber pipe. 

 The lower curve of this S-shaped tube is placed in a 

 pneumatic trough underneath the opening of a glass mea- 

 sure, graduated in cubic centimeters (Fig. 121). The poles of 

 a battery being connected to c and d respectively, the current 

 passes from one of the platinum plates to the acidulated 

 water, and from the latter to the other platinum plate. In 



