248 ALKALIES. 



her of oxygen, 40 becomes that of potassium, and therefore the num- 

 ber for protoxide of potassium is 48. 



(6.) Properties of the protoxide, free from water ; this is its con- 

 dition when it is formed in dry air or in dry oxygen gas. It is white, 

 very caustic, and fusible a little above a red heat, but it requires a 

 very high heat to volatilize it. 



Dissolved in water and obtained again, it becomes even after igni- 

 tion, a hydrate, containing protoxide of potassium, 84, water, 16 = 100. 



Potassium being represented by 40, oxygen by 8, and water by 

 9, it follows that the equivalent of hydrate of potassa is 57. This is 

 the substance described under potassa. We know riot whether the 

 solid anhydrous protoxide is caustic or not, because its properties 

 cannot be examined in this particular, without admitting water to it, 

 when it becomes a hydrate. It has already been observed, that the 

 hydrate melts at a low heat, (360,) and is easily volatilized. The 

 protoxide is formed also by acting on potassium with a small quantity 

 of water, or by heating potassium with common caustic potassa, and 

 by igniting potash in a crucible of gold. 



(C.) PEROXIDE. 



(a.) The white dry protoxide heated in oxygen gas, absorbs two 

 additional proportions, and becomes of an orange color. It may be 

 formed also by heating and burning potassium in oxygen gas, or in 

 common air. 



(b.) Its properties. Color yellow ; fusible with less heat than hy- 

 drate of potassa, and crystallizes in laminae by cooling. When plunged 

 into water, the two additional proportions of oxygen are evolved, and 

 it becomes hydrate of potassa. Heat greater than that at which it 

 was formed, expels the excess of oxygen, and brings it to the state of 

 protoxide or true anhydrous potash.* The heating must be per- 

 formed in a platinum tray, and the oxide covered with muriate of pot- 

 ash. When mixed with combustible bodies, and heated, it acts vig- 

 orously upon them in consequence of the two additional proportions 

 of oxygen which it contains, and it thus becomes potassa. The com- 

 position of the peroxide is potassium, one proportion 40, and oxygen 

 3=24, and its equivalent number is 64. 



Nitrogen and potassium have no action upon each other, but if 

 potassium be heated in ammoniacal gas, a fusible olive colored com- 

 pound is formed, which consists of nitrogen and potassium, and of 

 this compound and ammonia, and at the same time, hydrogen gas is 

 liberated. As it appears not to be particularly important, we refer 



* This is said to be so fixed as to sustain the heat of a wind furnace without being 

 volatilized ; it attracts water very powerfully, and generates intense heat during its 

 solution. The hydrate of the protoxide is easily volatilized by heat. 



