xin THE DECOMPOSITION OF THE ALKALIS 277 



a solid metal, similar in colour to silver " even when con- 

 taining only one part of potassium to seventy parts of 

 mercury. When these amalgams are exposed to air, "they 

 rapidly absorb oxygen ; potash which deliquesces is formed ; 

 and in a few minutes the mercury is found pure and 

 unaltered." " When a globule of the amalgam is thrown into 

 water, it rapidly decomposes it with a hissing noise ; potash 

 is formed, pure hydrogen disengaged, and the mercury 

 remains free " (A.C.R. VI. 20).. 



(c) Decomposition of Water. The strong affinity of 

 potassium for oxygen was shown in a very striking manner 

 by its violent action upon water even when quite cold : 



" When it is thrown upon water, or when it is brought 

 into contact with a drop of water at common temperatures, it 

 decomposes it with great violence, an instantaneous explo- 

 sion is produced with brilliant flame, and a solution of pure 

 potash is the result." 



" When water is made to act upon the basis of potash 

 out of the contact of air and preserved by means of a glass 

 tube under naphtha, the decomposition is violent ; and there 

 is much heat and noise, but no luminous appearance, and 

 the gas evolved when examined in the mercurial or water 

 pneumatic apparatus is found to be pure hydrogen." 



" So strong is the attraction of the basis of potash for 

 oxygen, and so great the energy of its action upon water, 

 that it discovers and decomposes the small quantities of 

 water contained in alchol and ether, even when they are 

 carefully purified." 



" The basis of potash when thrown into solutions of the 

 mineral acids, inflames and burns on the surface" (A.C.R. 

 VI. 16, 17, 18). 



(d) Reduction of Oxides. Finally potassium was found to 

 be an active reducing agent, removing the oxygen from 

 metallic oxides and liberating the metal. 



" When a small quantity of the oxide of iron was heated 

 with it, to a temperature approaching its point of distillation, 



