Elements of chemistry, in two volumes / by John Murray.

  • Murray, John.
Date:
1828
Catalogue details

Licence: Public Domain Mark

Credit: Elements of chemistry, in two volumes / by John Murray. Source: Wellcome Collection.

    64/768 (page 52)
    The process of Gay-Lussac and Thenard, of decompo- sing the alkali by iron, does not succeed so easily with soda as with potash : the easiest process for obtaining sodium is to decompose soda, by heating pure and dry sea-salt (chloride of sodium) with potassium : the potassium at- tracts the chlorine, and the sodium is sublimed. Sodium is white and opaque, with metallic lustre, having the ge- neral appearance of silver ; it is very malleable, and is so soft, that with a slight force it can be extended in thin leaves,—a softness which it retains even when cooled to 32° : several globules may by pressure be forced into one, a property analogous to the welding of iron and of pla- tina. Though lighter than water, its density is greater than that of potassium ; Mr Davy estimates its specific gravity at .9348, Gay-Lussac at .97223. It requires a higher heat to melt it than potassium does : at 120° it be- gins to lose its cohesion ; at 180° it is fused : it is also less volatile, as it remains fixed even at ignition. When exposed to the atmosphere it is oxidated, soda be- ing formed on its surface, which deliquesces slowly. When heated nearly to ignition in atmospheric air, the combina- tion is attended with combustion; and when heated in oxy- gen gas it burns with a vivid white light, emitting bright sparks. Like potassium it combines with oxygen in dif- ferent proportions. The protoxide is soda, which con- sists of one atom of sodium, 24, and one of oxygen, 8, its equivalent being therefore 32. There is another com- pound, the peroxide of sodium, which is formed when the metal is burnt in oxygen gas: it contains one-halt more oxygen than soda, or it is a compound of one equivalent of sodium, 24, and one equivalent and a half of oxygen, 12, or its atomiq weight is 36. To avoid the supposition of half an atom, this peroxide is regarded by some as a compound of two atoms of sodium and three of oxygen,