160 
NOTES FROM NEWCASTLE. 
who obtained it in the form of a grey powder, but in subsequent experiments 
he succeeded in getting malleable globules. It is however only within the last 
few years that the experiments of M. Deville have been successful in reducing 
the cost of manufacture to such an extent as to turn it to useful account. The 
sources of alumina, from which it is obtained, are abundant, but the difficulty 
has always been in finding a substance that would yield it pure. It was first 
extracted from ammonia alum of commerce, which, on heating, produces alu¬ 
mina, but the impurities in the shape of silica and iron, which could not be 
got rid of, contaminated the product. After this, cryolite (a double fluoride 
of aluminium and sodium) was tried and abandoned for the present mineral 
bauxite (an aluminate of iron with a little silica), from which all the aluminium 
is now made. 
The method adopted is to grind the bauxite to fine powder, mix it with car¬ 
bonate of soda, and heat it in a furnace ; by this means an aluminate of soda 
is formed ; this is treated with water, which dissolves out the aluminate of soda 
and leaves the oxide of iron behind. The solution is then treated with hydro¬ 
chloric acid, and the alumina is precipitated in a granular form, perfectly 
pure ; this is well washed and mixed into a stiff paste with charcoal and chlo¬ 
ride of sodium, afterwards made into pellets, and well dried. Then follows the 
next stage of the process ; these pellets containing alumina, charcoal, and salt, 
are placed in a tube in a furnace and brought up to a red-heat, at the same 
time a stream of chlorine is passed through the tube; thus effecting the re¬ 
duction of the alumina by the charcoal and forming a double chloride of 
aluminium and sodium, which sublimes as a yellow crystalline mass into an 
earthen pot placed to receive it. This double chloride is then intimately mixed 
with sodium and some cryolite, which is used as a flux, thus rendering the mass 
more fusible; this mixture is then placed in a furnace and strongly heated ; as 
the sodium has a stronger affinity for the chlorine than the aluminium, it takes 
the chlorine and leaves the aluminium free ; when heated sufficiently, the fur¬ 
nace is tapped and the silver-like metal flows out, and is carried away and run 
into bars each weighing about | lb. 
There are many purposes for which aluminium is desirable on account of its 
lightness, its specific gravity being 2-6. A bar of copper of equal size would 
weigh 2^ lb. It is largely used in making the alloy called aluminium bronze, 
which contains ten parts of aluminium to ninety parts of copper; this is likely to 
become popular in consequence of its colour, and its mechanical properties give 
it great value. 
Sodium .—As the commercial success of aluminium depends upon the cheap¬ 
ness with which sodium can be produced, it may be interesting to hear that the 
latter is made at these works at ten shillings the pound, and the stock is about 
half a ton. 
Sodium is obtained from carbonate of soda, and the process adopted is the 
following :—Dried carbonate of soda, powdered charcoal, and finely-powdered 
chalk are mixed intimately and kneaded into a stiff paste with oil, and calcined 
in a covered pot, the mass is then introduced into an iron retort and distilled ; 
the sodium is received into a vessel containing mineral oil. A man constantly 
watches to prevent any obstruction in the tube, which is cleared by passing in 
an iron rod ; the sodium is afterwards fused and run into bars. 
Carbonate of Soda .—A few steps brought us to the building where carbonate 
of soda w r as being made, and we saw all the processes for its manufacture in 
operation ; first, there was the common salt being acted on by oil of vitriol for 
the production of sulphate of soda, under the name of “salt-cake;” this is carried 
on in a reverberatory furnace connected with an apparatus for condensing the 
hydrochloric acid. This rough sulphate of soda is then mixed with chalk and 
powxlered coal and thrown into a reverberatory furnace, and frequently stirred 
