234 



METALS. 



Explain the 578. COMBUSTION ON WATER. PotaS- 



actionofpo- gmm jf thrown UDOll 

 tassium on r 



water. water, is immediately 



ignited and burns with a beautiful 

 violet flame. Strictly speaking, it is not potassium 

 which burns, but the hydrogen which it sets at liberty, 

 Owing to its strong affinity for oxygen, it takes this 

 element from water, liberating, and at the same time 

 kindling, the hydrogen with which it was before 

 combined. The color of the flame is due to a small 

 portion of vaporized potassium which burns with 

 this gas, as it is evolved. The globule of metal used 

 in this experiment, gradually disappears, because the 

 potassa which it forms by uniting with oxygen, is 

 soluble in water. 



579. USES OF POTASSIUM. Potassium 

 State the uses 



of potassi- has not been applied to important uses in 

 the arts, but is a valuable agent in the 

 hands of the chemist. It is a key which unlocks 

 many substances from the prison in which nature has 

 confined them. Through its agency, brilliant metals 

 may be obtained from lime, magnesia, and common 

 clay. 



580. This effect depends on the supe- 



On what does 



its action dc- nor affinities of potassium, which enable 

 pcnd? - t to a pp r0 p r { a t e oxygen, chlorine, and 



other substances, with which the above, and several 

 other metals are combined in nature, and to isolate the 

 metals themselves. The potassium is, at the same 

 time, converted into oxide, or chloride of potassium, 



