MATTER FORMED OF SMALL PARTICLES 



97 



reached by Different Quantities at Different Temperatures. It 

 will be convenient to take water as the solvent, and potassium 

 nitrate as the solid. It will be found that water at about 55 C. 

 will hold in solution three times as much potassium nitrate 

 as the same quantity of water at 15 C. This may be shown 

 by allowing water to remain in contact with excess of the solid 

 (i.e. more than can be dissolved by the water) for several 



Fig. 31. 



hours. A known quantity of the solution, which will then be 

 at the temperature of the room, is then removed by a gradu- 

 ated pipette, placed in a crucible which has been previously 

 weighed, and kept at a moderate temperature until all the 

 water is gasified. Care must be taken that none of the solid 

 is lost in the process. The crucible, with the solid, is then 

 weighed, and the quantity held in solution thus determined. 

 The quantity dissolved at a higher temperature may be ascer- 

 tained by keeping the water, which is in contact with excess 



