16 CHEMISTRY. 
The latter has so great an afhnity for oxygen as to take it from almost any 
combination possible to be formed. Thus, if sodium be thrown on water, a 
part of the latter will immediately be decomposed, its oxygen uniting with 
the metal to form the alkali soda, and the hydrogen escaping in the form of 
a gas. The combination, however, of sodium with water, is attended by 
the development of so much heat, as to inflame the liberated hydrogen, 
which immediately unites with the oxygen of the atmosphere. In the 
fabrication of hydrochloric acid from common salt, the base of the latter is 
finally obtained in the form of an oxyde, or as the alkali soda, known as 
caustic soda. This is, however, not obtained in its separate form without 
further manipulation, being exhibited as a carbonate. It is from this 
carbonate of soda that the metal may be obtained by means of the furnace 
DD (pl 31, fig. 9). The wrought iron vessel, A, is to be laid on the 
furnace on the two cross-bars, f, f. One of the iron bottles used to contain 
the mercury of commerce may be used as the vessel in question. Into the 
opening of this bottle, a gun-barrel, about six inches long, must be firmly 
fixed, and the bottle partially filled with a mixture of dry carbonate of soda 
and charcoal, and placed in the furnace, which must have a very powerful 
draught. The opening, CC, through which the bottle is introduced into the 
furnace, is closed tight by a piece of fire-brick, any interstices being luted 
or cemented. The short iron gun-barrel, a, passes through the brick. 
When the vessel has been brought to a red heat, the copper vessel, B, is 
joined to the gun-barrel, a, by a short neck in the upper portion, and 
partly covered by a wire frame. Opposite to the neck just referred to, is a 
short copper cylinder at e, extending to the wire frame, the object of which 
is to permit the introduction of an iron rod through B into the tube a, for 
the purpose of freeing it from any obstruction. The tube, d, is attached to 
the side of B, near its upper part. This copper vessel, B, consists of two 
portions which can be lifted apart. The lower part embraces the upper as far 
as the roof, ec, which is soldered nearly in the middle of the upper part of 
the vessel. The lower part of the vessel is now to be filled about two 
thirds with petroleum or naphtha, the upper part slipped in, and the vessel 
thus adjusted, brought into communication with the iron tube a. The wire 
frame must be kept constantly cold by means of snow or ice, and the heat 
of the furnace raised to a great intensity. Atastrong red heat the carbonate 
of soda is decomposed into carbonic acid and oxyde of sodium, and the carbon 
of the charcoal combines with the oxygen of the oxyde, forming carbonic 
oxyde and carbonic acid, leaving the metal free. The gases pass over 
through the tube into the cold copper vessel; the metal in the form of 
vapor also passes over, and is condensed into small globules, which fall to 
the bottom of the naphtha. The naphtha being a hydrogen compound, free 
from oxygen, prevents the access of the latter gas to the metallic sodium. 
A nearly similar process may be used to obtain some other metals, as 
potassium, from their combinations. 
Method of obtaining Metallic Iron. Our object in this place is not to 
treat of the reduction of iron on the large scale from its ores, but simply to 
mention the chemical process by which we are enabled to ascertain the 
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