AMMONIA QI 



N 2 O 3 nitrogen trioxid or nitrous anhydrid. 



N 2 O 4 nitrogen tetroxid. 



N 2 O 5 nitrogen pentoxid or nitric anhydrid. 



While the oxids of nitrogen do not serve as either plant 

 or animal food, they are nevertheless important, and a 

 study of these compounds is necessary in order to under- 

 stand the subject of nitrogen. 



101. Anhydrids. An anhydrid is an oxid of an acid 

 element, or the product which is left after the elements 

 which form water are abstracted from an acid. SO 3 is 

 sulfuric anhydrid, and is the product formed by ab- 

 stracting H 2 O from H 2 SO 4 . H 2 SO 4 = H 2 O + SO 3 . N 2 O 5 

 is nitric anhydrid, derived from two molecules of HNO 3 . 

 2 HN0 3 = H 2 O + N 2 O 5 . 



Derive and name the anhydrids of the following acids: 

 2 H 3 PO 4 , H 2 CO 3 , H 2 SiO 3 , 2HNO 2 , H 2 SO 8 . 



102. Law of riultiple Proportion. When nitrogen 

 and oxygen combine, the number of parts of nitrogen in 

 the various compounds is constant, namely : 2, or 28 

 parts by weight in each compound. The number of 

 parts of O is always a multiple of the first combination, 

 N 2 O ; that is, it is either 2, 3, 4, or 5 times as much in 

 the other compounds as in the first one. This is an ex- 

 ample of the law of multiple proportion. When two 

 elements combine in more than one way, the amount by 

 weight of one of the elements remains constant in all the 

 combinations, while the amount of the other element is 

 always a multiple of the first combination. 



The law of definite proportion holds true for each in- 

 dividual compound, while the law of multiple proportion 



