xin THE DECOMPOSITION OF THE ALKALIS 279 



nearly as nine to ten, or more accurately as 0-9348 to i " 

 (A.C.R. VI. 2324). 



Gay-Lussac and Thenard found the density at 15 to be 

 0-972 relatively to water at the same temperature. 



" The basis of soda has a much higher point of fusion 

 than the basis of potash." Davy gave the melting point as 

 120 to i8oF., but the value now accepted is higher, viz. 

 98 C. He was not " able to ascertain at what degree of 

 heat it is volatile ; but it remains fixed in a state of ignition 

 at the point of fusion of plate glass" (A.C.R. VI. 24). 



Chemical properties of sodium. In its chemical properties 

 sodium resembled potassium, but was much less vigorous in 

 its action on air, oxygen and water. 



" When the basis of soda is exposed to the atmosphere, 

 it immediately tarnishes, and by degress becomes covered 

 with a white crust, which deliquesces much more slowly 

 than the substance which forms on the basis of potash. It 

 proves, on minute examination, to be pure soda. 



"The basis of soda combines with oxygen slowly, and 

 without luminous appearance at all common temperatures ; 

 and when heated, this combination becomes more rapid ; 

 but no light is emitted till it has acquired a temperature 

 nearly that of ignition. 



" The flame that it produces in oxygen gas is white, and 

 it sends forth bright sparks, occasioning a very beautiful 

 effect ; in common air, it burns with light of the colour of 

 that produced during the combustion of charcoal, but much 

 brighter. 



" Its operation upon water offers most satisfactory evidence 

 of its nature. When thrown upon this fluid, it produces a 

 violent effervescence, with a loud hissing noise ; it combines 

 with the oxygen of the water to form soda, which is dissolved, 

 and its hydrogen is disengaged. In this operation there is 

 no luminous appearance" (A.C.R. VI. 24 25). 



" When introduced into [chlorine], it burnt vividly with 

 numerous scintillations of a bright red colour. Saline 

 matter was formed in this combustion, which, as might have 



