DETECTION OP ELEMENTS AND INORGANIC SALTS 253 



slum pyroantimonate solution. If sodium is present a fine white 

 granular precipitate will form in the course of a few minutes 

 and stick to the glass. This test must be made in neutral or 

 alkaline solution. If no precipitate is visible, observe carefully 

 in a good light. Rotate the watch glass carefully so that small 

 particles of precipitate will collect in the center. It often is pos- 

 sible to hasten the formation of a precipitate by rubbing the in- 

 side of the containing vessel with a glass rod. 



19. Potassium. From the portion of the liquid reserved in 16 

 for the potassium test, remove ammonia as in 18, but use sodium 

 hydrate instead of potassium hydrate. Add glacial acetic acid 

 until the liquid is acid to litmus. Now add 2-3 drops of sodium 

 cobaltinitrite solution. In the presence of potassium a yellow 

 crystalline precipitate forms at once. 



