216 PHYSIOLOGICAL CHEMISTRY 



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. 



9. Potassium. From the portion of the liquid reserved in 6 for 

 the potassium test, remove ammonia as in 8, 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. 



