THE BUBBLER 



17 



The Bubbler 



I next describe the most important part of the apparatus, 

 the Bubbler, by which successive quantities of gas of equal 

 volume are given off. The 

 Bubbler attached to the plant- 

 vessel consists of a thick- 

 walled tube with a relatively 

 small bore ; there is a stop- 

 cock, s, by the manipulation 

 of which the tube is put in 

 communication with the at- 

 mosphere, or cut off from it. 

 The thick tube has a lateral 

 branch, b, which is shaped as 

 shown in fig. 2. The end of 

 this branch is blown into the 

 form of a hollow cone. The 

 junction between the cone and 

 the b tube is closed with a 

 drop of non-adhesive oil, o, 

 which acts as a valve. 



One end of the Bubbler is 

 thrust through the india- 

 rubber cork closing the plant- 

 vessel which is nearly filled 

 with water. For final adjust- 

 ment, the stop-cock, s, is 

 opened and the cork pushed 

 in till the level of the water 

 reaches a definite mark in 

 the Bubbler. During this 



process air is expelled into the atmosphere. The stop-cock 

 is now closed, and we have a definite volume of air enclosed 

 in the Bubbler under atmospheric pressure. On exposure to 

 light, oxygen is evolved and an increase of pressure is pro- 

 duced ; this lifts the oil- valve and the volume in excess, V, 



Fig. 2. The Plant Vessel and the 

 Bubbler 



s, stop-cock ; b, Bubbler ; o, 

 oil-valve. 



