ELEMENTS 



197 



Combination of P with O also takes place very easily. 

 Sometimes P will burn as soon as it is placed in the 

 air, especially if it be cut or rubbed a little. Owing to 

 the ease with which it kindles, P is commonly used in 

 making matches. The red tip contains some P mixed 

 with other substances. Simple rubbing heats this tip 

 enough to make the P burn, and this kindles the wood. 

 P gives out a faint glow in the dark; hence it is used 

 in luminous paint, etc. 



228. Chlorine. Chlorine is a greenish-yellow gas hav- 

 ing a disagreeable odor. It is not common in a free state, 



but occurs in a group of salts called chlorides. With 

 hydrogen Cl forms hydrochloric acid, HC1. The pure ele- 

 ment acts strongly upon the throat and lungs if inhaled. 

 It is used as a disinfectant and as a bleaching agent. 



Experiment 125. Arrange apparatus as in Fig. 133, passing 

 the tube to the bottom of a jar through a loosely fitting cover of 

 cardboard. Into the test tube put 5 g. of MnO 2 and 10 cc. of 



