CHLORINE. 99 



Phosphoretted hydrogen. "When phosphorus is heated with 

 solutions of potassium or calcium hydrate, a number of pro- 

 ducts, chiefly hypophosphites, and phosphoretted hydrogen are 

 formed. The latter compound has the composition PH 3 , and is 

 a colorless, badly smelling, poisonous gas, which, when generated 

 as directed above, is spontaneously inflammable. This last- 

 named property is most likely due to the presence of small 

 quantities of another compound of phosphorus and hydrogen 

 which has the composition P 4 H 2 . 



QUESTIONS. 



141. In what forms of combination is phosphorus found in nature? 



142. Give an outline of the process for manufacturing phosphorus. 



143. What are the symbol, valence, atomic and molecular weight of 

 phosphorus ? 



144. State chemical and physical properties both of common and red 

 phosphorus. 



145. By what methods may phosphorus be detected in cases of 

 poisoning ? 



146. What two oxides of phosphorus are known ; what is their com- 

 position, and what four acids do they form by combining with water? 



147. State the officinal process for making phosphoric acid, and what 

 are its properties? 



148. By what tests may the three phosphoric acids be recognized and 

 distinguished from phosphorous acid ? 



149. What is a phosphide, phosphite, phosphate, and hypophosphite ? 



150. What is glacial phosphoric acid, and in what respect does its 

 action upon the animal system differ from the action of common phos- 

 phoric acid ? 



16. CHLORINE. 



Cli = 35.4. 



Haloids or halogens. The four elements, fluorine, chlorine, 

 bromine, and iodine, which form a natural group of elements, 

 are known as haloids or halogens. The relation shown by the 

 atomic weights of these four elements has been mentioned in 

 connection with the consideration of natural groups of elements 

 generally (see page 59). In many other respects a resemblance 

 or relation can be discovered. For instance : All haloids are 



