102 



JUNIOR GRADE SCIENCE 



The solubility at other temperatures should be found by different members 

 of the class, the results collected and a graph obtained. It is customary 

 to mark the horizontal (OY) line in degrees. If time permits a similar 

 set of results should be obtained for common salt, and plotted on the same 

 page. 



Solubility. From experiment it is found that as a general rule 

 the solubility of substances increases with a rise of temperature ; but 



Temperature 

 FiQ. 79. Solubility curves of common salt and nitre. 



each substance is not affected to the same extent. The solubility 

 curves for nitre and salt show that, while the solubility of nitre in- 

 creases very rapidly with rise of temperature, as the steepness of the 

 curve shows, the curve of salt is not greatly affected, being nearly a 

 horizontal line. 



45. CRYSTALLISATION. 



i. (a) Effect of cooling a hot saturated solution. Make a hot saturated 

 solution of alum, and divide it into two portions. Quickly cool one under 

 a tap, and place the other aside till next class day. Make observations. 



(6) Repeat the last experiment using (a) nitre, (6) blue vitrioL 



