ALKALIES. 255 



very vivid light, and much heat, and often explosion. The amalgam 

 of mercury and sodium seems to form triple compounds with other 

 metals; Sir H. Davy thought that the mercury remained in combina- 

 tion with iron and platinum, after the sodium was alkalized, and sep- 

 arated by deliquescence. The amalgam forms a triple compound 

 of a dark gray color with sulphur. 



(k.) Inflames on the strong acids, forming salts with soda for a 

 basis ; the nitric acid, as usual, acts with the most energy. 



4. OXIDES. 



(a.) Protoxide. Sodium combines spontaneously with oxygen re- 

 producing soda,* but its attraction for oxygen appears to be less en- 

 ergetic than that of potassium ; the process is slower, and the deli- 

 quescence of the alkali produced is not so rapid. The combination 

 is accelerated by heat, but combustion in oxygen gas does not take 

 place till near ignition ; it then burns beautifully with a white flame 

 and bright sparks, and, in common air, the flame is similar to that 

 from burning charcoal, but much brighter. Sodium heated with so- 

 da, is said to divide the oxygen between them, producing a deep 

 brown fluid, which, on cooling, becomes a dark gray solid, and at- 

 tracts oxygen again from air and water.f 



The protoxide is produced also by burning sodium in dry common 

 air, the sodium being in excess, or by the action of water. This 

 protoxide is caustic soda; its color is gray, fracture vitreous, does 

 not conduct electricity, fusible at a red heat, combines with water, 

 with great heat, and produces hydrate of soda, which is white, crys- 

 talline and more fusible and volatile than before. Its constitution is, 

 1 proportion of sodium, 24 



1 " oxygen, 8 



And the equivalent of anhydrous soda is 32 



It combines with water, as already remarked, with great energy, be- 

 coming a hydrate, and the water cannot be expelled by ignition. 

 The constitution of the hydrate, 



1 proportion of protoxide, 32 per cent. 22 J water. J 



1 " water, 9 



41 



(b.) Deutoxide of sodium. Burn sodium in an excess of oxygen 

 gas, or heat the protoxide in that gas ; the protoxide is always formed 



* This happens, of course, if it is not carefully kept; I have lost masses of sodium 

 in this manner; the metal turns into white caustic soda, and eventually effloresces 

 in the form of carbonate, at the same time enlarging its volume very much. 



t It is doubted whether it is not a mixture of the metal with soda. 



J See Mr. Dalton's table of the quantities of soda, in different solutions, Henry, 

 Vol. I, p. 558, 10th Lon. Ed. 



