212 



SCIENTIFIC AMUSEMENTS. 



commences, and consequently will not decompose liquid water, 



but will act more or less readily on steam. 



Wrap up in a bit of wire gauze a fragment of sodium the size 



of a small pea, and hold it by means of tongs under cold water 



(fig. 92) ; owing to the interstices in the gauze the water will not 



be prevented from com- 

 ing in contact with the 

 sodium ; displacement 

 of hydrogen by sodium 

 will rapidly take place, 

 the hydrogen thus 

 evolved bubbling up 

 through the water ; so 

 that by placing a small 

 jar filled with water 

 over the wire gauze the 

 hydrogen evolved can 

 be collected. Caustic 

 soda is the complemen- 

 tary product formed by 

 the action; this dis- 

 solves in the water, so 

 that on dipping therein 

 a red litmus test paper 

 it will be turned blue 

 owing to the alkaline ac- 

 tion of the caustic soda. 



Fig. 92. Hydrogen from Water and Sodium. 



In Expt. 168 the chemical action taking place was the same as in 

 this case, the mercury in the amalgam used serving to dilute the 

 sodium and render its action less violent. 



Caution. When making experiments with sodium, be careful 

 how water is brought in contact with the metal in a glass, porce- 

 lain, stoneware, or other glazed vessel ; if a fragment of sodium 

 be thrown into water in such a vessel without the protecting 

 wrapping of wire gauze, the sodium will float up and become 

 melted by the heat produced by the chemical action; and if 

 the globule of fused metal come in contact with the smooth 

 glazed surface, the action becomes very vigorous and explo- 

 sive, so that splashes of sodium are thrown about in a burning 

 state, the metal and the hydrogen evolved being kindled through 

 the violence of the action. If the water be warm, the evolved 

 hydrogen is lighted and burns steadily even though no explo- 

 sive projection of burning particles take place ; this is most simply 

 effected by putting a small fragment of sodium on a wooden 



