POTASSIUM, SODIUM, ETC. 



133 



pounds are among the most useful and important com- 

 pounds found in nature. 



Experiment 27. Fill a cylinder about two-thirds full of water, 

 and place upon the surface of the water a piece of Na about half as 

 large as a pea, using forceps for the 

 purpose. If there is no small piece 

 of Na in the bottle, one may be cut 

 by means of a knife without re- 

 moving the Na from the naphtha 

 which surrounds it. Observe the 

 result when the Na is placed upon 

 the water. The apparatus can be 

 arranged and the escaping hydro- 

 gen collected as shown in Fig. 55. 

 (The test-tube should be filled with 

 water and the Na wrapped in a 

 piece of filter-paper. ) 



Questions, (i) Give the reaction 

 which takes place between the Na 

 and the H 2 O. ( 2 ) What gas is lib- 

 erated? (3) What becomes of the 

 Na in the experiment? (4) Is this 

 product soluble or insoluble? (5) 

 Test the liquid in the cylinder with 

 litmus paper and observe the result. 

 (6) Is Na a light or heavy metal l 

 Why? (7) Is it active or inert? (8) Fi g- 55- Decomposition of water 

 Why is Na always kept in a bottle 



containing naphtha or kerosene ? (9) Since Na is found in nature 

 and its compounds are present largely in sea-water, why does not 

 this element, Na, decompose sea-water as it did the water in this 

 experiment. 



