226 



APPARATUS FOR PREPARING HYDROGEN. 





which is generated in this apparatus, must never be checked b} 

 pressing the india-rubber tube with the fingers or closing it by j 

 pinch-cock ; for if not allowed to pass through the india-rubber tube 

 it will force the liquid in the bottle through the funnel tube. Instead 

 of the latter a glass tube connected with a funnel by means of a shori 

 piece of india-rubber tubing, as shown in fig. 155, may be used. 



A more perfect apparatus for preparing the gas is represented 

 in fig. 156. It is convenient for many purposes, and possesses th( 



FIG. 156 (an.proj. | real size}. 



advantage that the escape of the gas may be regulated and checker 

 by means of a stop-cock. Two bottles, a and , of equal size, an 

 each provided with a short tubule near the bottom, and maybe con- 

 nected by passing the ends of an india-rubber tube over the tubules ii 

 they are small enough, or over short pieces of glass tubing fitted intc 

 the tubules by perforated india-rubber corks. The bottle a is closec 

 by a funnel which is placed loosely in the neck so as to prevent the 

 liquid spirting out ; the bottle b is closed tightly by an india-rubbei 

 stopper, through which a short glass tube passes. The tube t which 

 serves as drying tube is filled with cotton ; it is fixed by thread to 

 the neck of the bottle &, and is closed at one end by an india-rubber i 

 stopper with a short glass tube through it, and may thus be con- 

 nected with the bottle by an india-rubber tube ; a stopcock /;, winch 

 has a short nozzle for attaching an india-rubber tube to it, is fixed tc 

 the other end. The drying tube has a bulb at one end not fillec 

 with cotton, in which the greater part of the moisture carried ovei 

 by the gas collects, so that the cotton in the tube does not require 

 frequent changing. A layer of small pebbles, sufficient to reach about 

 1 or 2 cm above the lateral orifice, is first placed at the bottom of 



