XXIT ACIDS, BASES, AND SALTS 309 



Acid Salts and Basic Salts. A cid .sv<//.s arc those which are formed 

 when the quantity of base is insufficient to completely neutralise the 

 whole of the acid on which it acts. Acid sodium sulphate, NaHS0 4 , 

 and those sodium phosphates containing hydrogen mentioned on p. 305 

 are examples. Basic salts are those which result by the action of a 

 greater quantity of base than is required for the complete neutralisa- 

 tion of the acid on which it acts. 



Ammonia. When the gas, ammonia, is dissolved in water, the 

 solution which results acts as a base of the kind described as an 

 alkali. The salts which it forms are known as ammonium salts, e.g., 

 ammonium . sulphate. When the solution of ammonia in water is 

 heated the dissolved gas is again driven off and can be dried and 

 collected. 



The composition of ammonia is shown by the symbol NH 3 . That 

 this is so can be proved by the experiment described in the chapter. 



Ammonium. The salts which a solution of ammonia in water 

 forms with acids are exactly analogous to those similarly formed from 

 sodium and potassium hydroxide. This leads to the name ammonium 

 hydroxide for the solution of ammonia in water. The group am- 

 monium, NH 4 , has no independent existence, but is only known in 

 combination. 



QUESTIONS ox CHAPTER XXII. 



1. Describe the terms acid, base, salt, and indicate how they are 

 mutually related. 



2. What are normal salts, acid salts, basic salts ? Give examples 

 of an acid salt. 



3. How would you obtain potassium nitrate and sodium chloride 

 from their respective acids and bases ? 



4. What is ammonia ? Give an account of its preparation and 

 more characteristic properties. 



5. In what respect does a solution of ammonia resemble a solution 

 of caustic soda or caustic potash ? 



6. What do you mean by " ammonium" and "ammonia " ? 



7. Draw the apparatus, and describe how you would prepare 

 ammonia gas from the ordinary solution of ammonia. 



8. What is the difference between the action of an acid, say 

 hydrochloric acid, upon iron and oxide of iron ? 



9. How would you obtain crystallised sal-ammoniac from a solution 

 of ammonia ? How would you also obtain the solution of ammonia 

 from this product ? 



10. What is meant by an alkali ? Compare the chemical behaviour 

 of an alkali with that of an acid. Describe the appearance of any 

 two alkalis. 



11. You are required to prove that with regard to its power in 

 neutralising acids fifty-six grams of caustic potash are equivalent to 

 forty grams of caustic soda. Describe exactly how you would per- 

 form the experiment. 



