THE ELEMENTS OF PLANT FOOD 25 



ture is obtained that has no effect on the blue litmus. 

 The acid is then said to be neutralized. It is also true 

 that the alkali has been neutralized by the acid. The 

 reaction may be expressed : 



Acid + Base = Salt + Water 



HN0 3 + NH 4 OH = NH 4 N0 3 + H 2 O 



If, now, the water is evaporated, the salt, ammonium 

 nitrate, (NH 4 NO 3 ), will remain as white crystals. 



Note- If by accident acid of any kind gets on the clothes and 

 turns them red in spots, the color may sometimes be restored by 

 touching the spots with ammonia. 



Nature of Salts. Salts affect neither blue nor red 

 litmus; they are produced when acids and bases are 

 combined. 



Sodium chloride (NaCl), or common salt, is the salt 

 with which we are most acquainted. 



By combining the bases listed above with nitric 

 acid the following salts are formed : ammonium 

 nitrate (NH 4 NO 3 ) ; potassium nitrate (KNO 3 ) ; sodium 

 nitrate (NaNO 3 ) ; calcium nitrate (Ca(NO 3 ) 2 ). Write 

 all the reactions for the above. 



Note. It may be thought peculiar that NH 4 OH is not written 

 NH 5 O. NH 4 is called a radical. OH is also a radical. A radical is 

 a combination of elements that hang together so that they act as a single 

 element. Although it would not be wrong to write it NH 5 O, it is easier 

 in writing reactions to keep it in the form given. NH 4 unites with 

 OH just as K unites with OH. Other important radicals are : 



The nitrate radical, NO 3 , as in potassium nitrate, KNO 3 . 

 The sulphate radical, SO 4 , as in sulphuric acid, H 2 SO 4 . 

 The phosphate radical, PO 4 , as in phosphoric acid, H 3 PO 4 . 

 The silicate radical, SiO 3 , as in silicic acid, H 2 SiO 3 . 

 The chlorate radical, C1O 3 , as in potassium chlorate, KC1O 8 . 



