APRIL 25, 1907] 
NATURE 
619 
obtains in the United States, where we find the greatest 
coalfields combined with the greatest amount of water- 
power existing in any civilised country. The day will 
inevitably come when the coalfields will be so far 
exhausted that all those industries which consume large 
amounts of mechanical energy will be forced to emigrate 
to countries where water-power is abundant. 
No other substitute has, as yet, been found for generating 
foree, and, indirectly, electricity. 
Even in those countries which are more favoured, the 
amount of water-power is by no means infinite; and, if 
it had to be drawn upon, not merely for motive purposes, 
but for the production of electricity for heating purposes, 
it would be found insufficient in most places. Here we 
are faced by one of the greatest problems of applied 
science, both in chemistry and in physics, a problem which 
will give plenty of occupation to generations of future 
inventors. At present we can only surmise that some 
solution will present itself in the shape of a direct con- 
version of the sun’s rays into other forms of energy; but 
the means by which this would be practically accomplished 
are at present quite uncertain. 
Seeing that the stock of mineral fuel upon this earth 
is so very limited, cannot we find means of husbanding 
it more than this has been done hitherto? Of the energy 
residing in coal, most ordinary steam-engines utilise less 
than ro per cent., and even the most perfect steam- 
engines hardly more than 15 per cent. The conversion 
of pig-iron into steel, the manufacture of glass, and many 
other industries consume from four to twenty times, and 
even more, the quantity of coal required by theory. 
Moreover, in burning our fuel, whether it be for industrial 
or for technical purposes, we invariably send its nitrogen 
into the atmosphere, which surely contains quite enough 
of that commodity, the only exception being the manu- 
facture of coal-gas. Here some of the grandest problems 
of applied chemistry present themselves to us—how to 
stop that fearful waste of fuel, and how to recover the 
nitrogen of the coal, if that be possible. 
It is certain that we must look for the solution of these 
questions in the direction of converting coal into gaseous 
fuel. Another great stride ahead lies in the better “utilisa- 
tion of the waste gases from blast furnaces, in which 
respect the last few years have witnessed some very 
important improvements. All this refers merely to a 
better utilisation of the heating power of coal, but not to 
that other great task, the recovery of its nitrogen in a 
useful shape. 
The immense importance of the problem lies in the fact 
that it touches our most urgent want, our supply of food. 
For agricultural purposes it ‘does not make much difference 
whether we apply the nitrogen in the form of ammonia or 
of nitrates. The ammonia, apart from insignificant quanti- 
ties otherwise obtained, all comes from the” nitrogen of the 
coal, but up to about twenty years ago only that coal which 
was used in the manufacture of gas was made to yield 
ammonia, and only one-sixth of its nitrogen was obtained 
in this form. In the manufacture of coke, which is also 
a process of destructive distillation, and entirely analogous 
to gas making, very much larger quantities of coal are 
consumed. Up to about twenty years ago all the volatile 
by-products in the manufacture of coke were lost—that is 
to say, tar, gas, and ammonia. Even now, both in France 
and England, as well as in America, the recovery coke- 
ovens have found only a very limited adoption ; in England 
perhaps 5 per cent. of the coke is made in this way, 
against upwards of 50 per cent. in Germany. 
“But that reserve is, after all, nothing like sufficient to 
cover the requirements of agriculture in the future, and it 
is quite likely that in the long run all the really available 
nitrogen of the coal would not suffice for the wants of 
man. And what about the time when coal itself will be 
exhausted? Well, there is an eternal and inexhaustible 
source of nitrogen in the atmospheric air. Four-fifths of 
this consists of nitrogen, calculated to amount to 4000 
billions of tons. But until a very few years ago the 
problem of turning the atmospheric nitrogen into ammonia 
or nitric acid, although frequently approached in a purely 
scientific or, experimentally, in a technical way, had not 
been solved. Our days have seen the realisation of that 
most important taslkx. 
NO. 1956, VOL. 75] 
Let us first spealk of ammonia. We must start from 
calcium carbide. Prof. Adolf Frank and Dr. Caro, of 
Berlin, found that when nitrogen is passed over red-hot 
calcium carbide it is absorbed with formation of calcium 
cyanamide. This latter, when treated with water under 
high pressure, is made to yield ammonia; but it is not 
necessary to do this, since the crude product, which they 
have called “ lime-nitrogen,’’ can serve directly as nitro- 
genous fertiliser, and is in that respect equivalent to its 
own weight of ammonium sulphate. The works already 
in operation, or in course of construction, will by the end 
of this year utilise water-power to the extent of some 
55,000 horse-power, and will produce lime-nitrogen 
equivalent to 100,000 tons of nitrate of soda. 
Important as ammonia is as a fertiliser, 
the nitrates in that respect, and, unlike ammonia, the 
nitrogen of the nitrates is of immense importance for 
other purposes as well, viz. the manufacture of nitric acid 
and of explosives. These have, up to the present, been 
prepared almost exclusively from Chilian saltpetre. What, 
then, shall we do when the nitre beds of Chili are ex- 
hausted? an event which, according to most estimates, 
is bound to take place within thirty or forty years from 
now. Unfortunately, there is no tangible hope of similar 
beds being found in any other localities, certainly not to 
any great extent. The solution of this problem, if not 
altogether settled in its final shape, has now been found 
by means of that well-nigh omnipotent agent, electricity. 
At Notodden, in the Norwegian Hitterdal, a factory has 
been established to carry out the process of Birkeland and 
Eyde, who, by an ingenious application of the extreme 
heat produced by the electric current, make the nitrogen 
and oxygen of air combine to form nitric oxide, which at a 
lower temperature is spontaneously oxidised into nitrous 
it ranks after 
vapours, with the ultimate production of nitrites or 
nitrates. This time there is really no doubt that a 
practicable and economical process has been discovered 
for which it is intended to employ, by the end of this 
year, water-power to the extent of 30,000 horse-power. 
The Notodden process bids fair to be followed by other 
even more efficient processes. The most important of these 
is that of the Badische Anilin- und Soda-Fabrik, for which 
an experimental factory is in course of construction, and 
for which 50,000 horse-power are to be employed. 
Electricity has often been invoked to produce the most 
important of all inorganic products, iron. If this problem 
could ever be solved in an economical way, it would bring 
about a perfect revolution in the position of the leading 
nations. On the one hand, the enormous quantity of coal 
now consumed in the production of iron and steel (which 
is probably at least a quarter of the entire output of coal) 
would be set free for other uses, and the exhaustion of 
the coal-fields would be put off to a corresponding extent. 
On the other hand, the production of iron would pass 
over into the hands of those nations which command the 
largest amount of water-power, and which, therefore, can 
produce electricity most cheaply. Of the three countries 
which now produce between them the bulk, that is, seven- 
eighths, of the world’s iron, Great Britain and Germany 
would go to the wall, and the United States, which already 
produce more iron than these two countries. put together, 
would become omnipotent in that field. 
One of the problems belonging to the domain of organic 
chemistry is the substitution of artificial for natural colour- 
ing matters. This, indeed, has now been carried out 
almost to the bitter end. Long ago, one of the oldest and 
most widely used colouring matters, that contained in 
madder, succumbed to the attacks of the chemists, among 
whom the names of Edward Schunck and William Henry 
Perkin testify to the glorious share taken by Englishmen 
in that victory. The colouring substance of madder— 
alizarin—is now made from English coal-tar, and has 
altogether taken the place of the impure form in which if 
occurs in the madder plant. The growers of this plant 
in the south of France and elsewhere have had to abandon 
its culture altogether, to their great sorrow. 
A similar fate has already partly overtaken, and may, in 
the end, destroy entirely, the culture of indigo. Synthetic 
indigotin is now manufactured at such a low price that 
its competition has proved a severe blow to the indigo- 
planting interests. ‘Thus the triumph of scientific investi- 
