40 Chemistry. [Lecture 25, 



As it is possible I may not have explained 

 myself with sufficient clearness in describing 

 these experiments, and as some may be desirous 

 of a more perfect apparatus, I shall beg leave 

 to refer to Plate VI. fig. 19, where A repre- 

 sents the vessel or tub (sometimes filled with 

 water, and sometimes with mercury) ; K K K 

 the wooden shelf; B, G, F, are glass jars or re- 

 ceivers, inverted with their mouths downwards, 

 and resting on the shelf. C is a glass bottle, 

 which is supposed to contain the ingredients for 

 furnishing the gas, and to the bottom of which 

 heat is applied. D is a glass tube, generally 

 fitted by grinding to the neck of the bottle, and 

 curved so as to enter conveniently below the 

 shelf, and communicate with the jar or receiver. 

 E is a glass retort, which may be applied to the 

 same purpose. 



Since oxygen is one of the component parts 

 of water, any process that will decompose water 

 will furnish it in the form of gas. Pump water, 

 when exposed to the sun, will emit it in small 

 quantities ; and as all vegetables in a growing 

 state decompose water, when there is a green 

 slime (which is a vegetable matter) formed hi 

 water, in a bottle, &c. a quantity of oxygen gas 

 will be separated when the water is exposed to 

 the sun. Raw silk, and even very fine glass 

 tubes, immersed in water, will also decompose 

 it by means of the sun's heat, and produce oxy- 

 gen gas. 



