276 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



substance, since the globules " acted more or less upon 

 almost every body to which they were exposed." It could 

 be preserved in " recently distilled naphtha " ; but when 

 exposed to the atmosphere its metallic lustre was immediately 

 destroyed and a white crust formed upon it. 



"This crust I soon found to be pure potash, which 

 immediately deliquesced, and new quantities were formed, 

 which in their turn attracted moisture from the atmosphere 

 till the whole globule disappeared, and assumed the form of 

 a saturated solution of potash." 



When exposed to air or oxygen confined by mercury, 



" an absorption of oxygen took place ; a crust of alkali 

 instantly formed upon the globule ; but from the want of 

 moisture for its solution, the process stopped, the interior 

 being defended from the action of gas." 



The new metal was readily combustible ; when strongly 

 heated in oxygen " a rapid combustion with a brilliant white 

 flame was produced, and the metallic globules were found 

 converted into a white and solid mass," which Davy was not 

 able to distinguish from ordinary potash (A.C.R. VI. u). 



(b) Combination with Chlorine, Sulphur, Phosphorus and 

 the Metals. When introduced into chlorine gas, potassium 

 " burns spontaneously with a bright red light, and a white 

 salt, proving to be muriate of potash is formed " (A.C.R. 

 VI. 1 6). Muriate of potash is, therefore, a binary com- 

 pound of a metal with chlorine, of the same type as those 

 prepared from lead, silver, and iron ; this fact is expressed 

 in the name POTASSIUM CHLORIDE which is now given to 

 the salt. 



Potassium also resembles the other metals in that it 

 combines readily with sulphur and phosphorus. 



It possesses the property of forming alloys with other 

 metals. With mercury it forms an amalgam, " a substance 

 exactly like mercury in colour " ; " the compound is fluid at 

 the temperature of its formation ; but when cool it appears as 



