96 JUNIOR GRADE SCIENCE 



So far as can be seen heat has no effect on it, but this action also will 

 be more fully investigated at a later stage. When first examined 

 chalk appears to be a perfectly uniform (homogeneous) solid, but 

 when examined suitably under a microscope it is found to contain a 

 number of shell like particles (Fig. 73). 



FIG. 73A. Chalk seen under a micro- FIG. 73B. Deposit obtained from the 



scope. bottom of the Atlantic, and viewed 



under a microscope. 



(From photographs by Mr. J. E. Barnard.) 



These particles, as a matter of fact, are the remains of tiny animals 

 such as are still to be found in sea-water. When the animal dies its 

 shell remains on the sea bottom. The shells of multitudes of similar 

 creatures, accumulating on the ocean floor, in the course of many ages, 

 build up a deposit of chalk. 



37. EXAMINATION OF LIME. 



i. Examine as described in Chapter XVII. 



ii. Slaking of lime. Add a few drops of water to quicklime. Note 

 the effect. 



iii. Solubility. Examine its solubility as described under chalk (p. 95). 



Lime. Lime is a white amorphous solid and is prepared by strongly 

 heating limestone. When water is added to freshly made lime, quick- 

 lime, it gets very hot and steam is given off ; the lime crumbles into 

 powder and is said to be slaked. If left exposed to air, lime takes up 

 moisture out of the atmosphere and becomes slaked. On account of 

 this property it is said to be hygroscopic. It is slightly soluble in water; 

 the solution, known as limewater, turns litmus blue. 



Large quantities of lime are used along with sand for making mortar. 



