

SMITH'S 



INTERMEDIATE CHEMISTRY 



CHAPTER I 

 SUBSTANCES AND PROPERTIES 



WHEN exact information in regard to any sort of material is 

 required, we hand the material to a chemist. To learn something 

 about the nature of chemistry, let us watch the chemist at work 

 on a typical problem. 



Properties. Suppose that the material is a piece of cloth, 

 and we desire to know whether it is all wool, or partly cotton. 

 The chemist places a piece of the cloth in a test-tube (Fig. 1), 

 and pours in an amount of lye sufficient to cover 

 it. Lye is a solution in water of a white solid, 

 named by chemists, commonly, " caustic soda " 

 and, more formally, sodium hydroxide. The con- 

 tents of the test-tube are then heated over a flame 

 and are kept at the boiling point for ten minutes. 

 If the cloth dissolves entirely, leaving a liquid, 

 clear like water, then it was composed of nothing 

 but wool. The chemist draws this conclusion 

 because wool, although not affected by the boiling 

 water, has the property of turning into a soluble 

 substance when caustic soda is heated with it. If, on the other 

 hand, the piece of cloth becomes thinner, obviously losing a part 

 of its material, but leaving a part undissolved, then it contained 

 cotton. This conclusion depends on the fact that cotton has 

 the property of not being dissolved by caustic soda solution. 



1 



FIG. 1. 



