MATTER FORMED OF SMALL PARTICLES 



99 



After some time the clips are turned, and the vessels discon- 

 nected and opened under water. The water will be found to 

 rise about half-way inside each vessel, on account of the 

 solubility of a portion of the contents of each vessel. Thus it 

 is demonstrated that the ammonia which previously filled the 

 upper vessel has evenly distributed itself throughout both 

 vessels. The experiment also illustrates the fact that the 

 gases are soluble in liquids, for the water entering into the 

 vessels replaces the ammonia removed by solution. It is con- 

 venient to use, as the source of the ammonia for filling B, a 

 strong solution of the gas in water, placed in a flask, fitted with 

 a delivery tube which leads to the top of B, inverted over it. 

 On raising the temperature of this solution, ammonia will be 

 driven off and completely fill the vessel B, expelling the air 

 downwards. This depends upon the fact that the quantity of gas 

 dissolved by a liquid varies with the temperature. The higher 

 the temperature the smaller is the quantity held in solution. 



Table of Solubility of Air in Water. 

 Unit Volume of Water at 760 m.m. pressure dissolves at : 



67. Atmospheric Pressure and its Variations. An instru- 

 ment for indicating the pressure of the atmosphere is called a 

 barometer. A glass tube, of the form shown in fig. 33, closed at 

 the end A and open at the end B, is nearly filled with mercury 



H 2 



