Vol. XXIV. No. lo.] 
POPULAR SCIENCE NEWS. 
149 
Pnictical Cljcuiistry aqil tlje '/Iits. 
THE MANUFACTURE OF SODIC 
CARBONATE. 
The history of the manufacture of sodic 
carbonate, or sal soda, is an interesting one, 
as it was a direct result of a chemical research, 
and has been an important factor in the com- 
mercial prosperity of France and other coim- 
tries. Carbonate of soda is used in immense 
((uantities in the arts, especially in soap and 
(jjlass making, and its cheap production is a 
matter of great importance. 
Carbonate of soda occurs but very spar- 
ingly in nature ; the vatron of Egypt and the 
troiia of Africa and South America are 
examples. Up to the latter part of the last 
century the principle source of supply Ivas 
obtained by burning the ashes of a marine 
plant growing on the coast of Spain. This 
ash contained about one-fourth its weight 
of sodic carbonate, and the cost of its pro- 
duction was necessarily large. But even this 
limited source of supply was curtailed during 
the wars of the French Revolution, and 
Napoleon, realizing the importance of a 
supply of the substance, otTered a premium 
for tlie discovery of a process by which it 
could be cheaply manufactured at home ; and 
this led to the discovery of the LeBlanc 
process, by which sodic carbonate can be 
abundantly produced from sodic chloride, or 
common salt, at a cost far less than that 
of the old-fashioned way of burning sea- 
weed. 
The first step in the process is the trans- 
formation of the sodic chloride into sodic 
sulphate, which is accomplished by heating 
it in a reverberatory furnace with sidphuric 
acid, the reaction being as follows : 
2(NaCl)+H2S04=2(H CI)+NasS04. 
The hydrochloric acid gas (H CI) is absorbed 
by water to form the commercial muriatic 
acid, which commands a ready market, and 
is an important factor in the economy of the 
■ process. 
' After the sodic sulphate — or "salt-cake," 
as it is called — has become thoroughly dry, it 
is mixed with fragments of limestone and 
coal, and again strongly heated, when it 
fuses to a dark-colored mass, known as 
"black-ash," composed of sodic carbonate, 
lime, and calcic sulphide. The chemical 
reactions which take place are rather com- 
plicated, but we give them below, as they 
may be of interest to students of chemistry. 
First, when the sodic sulphate is heated 
with the coal, or carbon, it is changed to 
sodic sulphide, while carbonic oxide gas is 
evolved, thus: Na^ S04 + C4 = Na.i S + 4CO. 
Again, when calcic carbonate is heated with 
carbon, carbonic oxide is given off, and calcic 
oxide, or lime, remains: Ca C03+C=2CO+ 
CaO. Finally, when sodic sulphide and 
lime are heated together in the presence 
of carbonic aciil gas, sodic carbonate and 
calcic sulphide are produced : Na-i S+Ca 0+ 
C0.2=Na2C03+CaS. 
The soda-ash produced by treating the 
black-ash with water and evaporating the 
solution to dryness, is not pure, but contains 
a certain amount of caustic soda, formed by 
the action of the excess of lime upon the 
sodic carbonate. So the crude soda-ash is 
mixed again with powdered coal, and heated, 
when the carbonic acid gas formed converts 
the caustic soda once more into carbonate, 
and it is only necessary to dissolve the mass 
in water and crystallize out the pure sodic 
carbonate. 
Later, the Solvay, or ammonia-soda, pro- 
cess for the manufacture of the carbonate 
was introduced, and would have entirely 
superseded the LeBlanc process if it were 
not for the fact that the latter produces, as a 
by-product, a large amount of hydrochloric 
acid, which finds a ready sale, thereby ren- 
dering it slightly more economical than the 
Solvay method. The latter process depends 
upon a curious reaction between sodic chlo- 
ride and hydro-ammonic carbonate, as follows : 
Na CI+NH4 H C03=NH4 Cl+Na H COs. 
In practice the solution of sodic chloride is 
mixed with about one-fifth its volume of am- 
monia, and carbonic acid gas passed into it, 
when the sodic bicarbonate is precipitated. 
The bicarbonate is converted into carbonate 
by simple heating, while the ammonic chloride 
is decomposed by lime, and the resulting 
ammonia gas used over again. Several meth- 
ods have been proposed by which the chlorine 
at present lost in this process may be recov- 
ered, but until this can be profitably accom- 
plished, the rivalry between the LeBlanc and 
Solvay systems will probably continue. 
Another by-product of the LeBlanc process 
is the sulphur, from the sulphide of calcium. 
This was formerly thrown away, thereby 
creating a nuisance, but the sulphur is now 
recovered in its elementary form and sold at 
a profit. 
Ilydrosodic carbonate, or saleratus, (HNa 
CO3) , is formed directly in the Solvay process, 
but is usually made by exposing the moist car- 
bonate to an atmosphere of carbonic acid gas, 
thus : Na.jC08-FCO.,+ H,0 = 2(Na H COa). 
It is principally used in the manufacture 
of baking-powder. 
The interdependence of the arts is well 
illustrated by the history of tlie LeBlanc 
process. The cheaper production of the 
soda-ash led to its increased use in glass and 
soap making, and the consequent cheapening 
of those articles led to an increased demand, 
which, in turn, created a still larger demand 
for soda-ash. The extension of the soda-ash 
manufacture led to a demand for larger quan- 
tities of tlie sulphuric acid used in the process, 
whicli gave rise to so many improvements in 
its manufacture that its previous high price 
was gradually reduced to the present nominal 
cost, allowing it also to be used freely in 
many other arts and manufactures. The 
increased production of hydrochloric acid as 
a by-product, cheapened the cost of bleaching- 
powder and greatly benefitted the cotton- 
bleaching and calico-printing industries. In 
short, it may be said that the indirect result 
of the French wars which led to LeBlanc's 
discovery, was of more benefit to mankind 
than the direct benefit of all the wars and 
battles that have occurred since tlie dawn 
of civilization. 
[Original in Popular Science ^ews-i 
THE ORES OF IRON. 
BY W. J. CHASE. 
Pure metallic iron is only to be found in the 
chemical laboratory, and, on account of the difficulty 
of its preparation, lias no commercial value. In 
color, the chemically pure metal varies from a bluish 
gray to a silvery white, according to the method 
of its preparation, and has a specific gravity of about 
7.85. Compaqntively pure iron, however, is some- 
times found in nature in the form of meteoric iron, 
but the supply from this source is extremely small. 
When thus found, it is almost invariably accom- 
panied by nickel. 
The sources from which the great iron supply 
of the world is derived, are those ores in which the 
iron exists in combination with non- metallic 
substances. These may be divided into three classes, 
viz., the sulphides, the carbonates, and the oxides, 
according to the proportion of sulphur, carbon, or 
oxygen present in the ore. Other substances also 
exist in these compounds, and on the varying 
proportions of this accompanying foreign matter 
depends the ore's value, which is by no means 
necessarily commensurate with the amount of actual 
iron present in them. The presence of certain 
impurities, notably phosphorus, in other than most 
minute quantities, greatly lessens the value of the 
ores, and in like manner the admixture of other 
gangues by increasing the difficulty of working the 
ores decreases their value. 
The sulphides, notably the pyrites, while an 
important source of oil of vitriol and sulphuric 
acid, furnish but little iron. The residue, however, 
left in the process of making this vitriol is an 
important aid in the working of iron in the pud- 
dling furnaces. 
Of the carbonates, the only two forms of value to 
the iron smelter are the spathic ores and the clay 
iron stones or argillaceous iron ores. The spathic 
ores, so called from their foliated structure, contain 
the carbonate of iron in a crystallized form, and are 
comparitively free from earthy matters. They gen- 
erally contain magnesium and manganese, but, being 
usually very free from sulphur and phosphorus, are 
very valuable ores for smelting purposes. Their 
yield of metal is usually about 40 per cent. In the 
argillaceous ores the crystalline structure is not 
usually apparent, and a more or less large amount 
of clayey matter is present. Usually, too, the 
ferrous carbonate is accompanied by a large amount 
of calcium carbonate, rendering the ores " lean,"' 
but, on account of their self-fluxing property, 
valuable for mixing with other richer ores. Large 
deposits of clay iron stones are found in the coal 
measures in layers alternating with strata of coal, 
and on this account, as well as because of the black 
color given them by the excess of carbonaceous 
