COMPOUNDS OF SODIUM AND POTASSIUM 373 



Gunpowder is still used in mining, and for detonating charges 

 of smokeless powder. 



Other Compounds of Potassium. Potassium bromide KBr 

 (p. 202), used in medicine. to relieve nervousness and to produce 

 sleep, potassium iodide KI (p. 206), used also in medicine, 

 potassium chlorate KC10 3 , employed in making matches and 

 works (p. 321), have already been mentioned. Potassium 

 phate K 2 S0 4 , made by the action of sulphuric acid upon potassium 

 chloride at a red heat, is employed in making alum (p. 469). 



Exercises. 1. In the Solvay process why is the ammonia 

 dissolved in the salt solution, and not separately in water? Make 

 the equation for the action of heat on limestone. 



2. What is the exact percentage of water in washing soda? 



3. What will be the reactions to litmus of aqueous solutions of: 

 (a) sodium phosphate, (b) sodium bromide, (c) sodium silicate, 

 (d) sodium peroxide, (e) sodium nitrate? 



4. Write full ionic equations to show why cupric sulphate solu- 

 tion reacts acid to litmus. 



5. How will a solution of ammonium acetate react towards 

 litmus? 



6. Write full ionic equations for the Solvay process (p. 366). 



7. Why does a piece of glass, when strongly heated, confer a 

 yellow color on the Bunsen flame? 



