DISCOVERY 



83 



But this, we fear, is not " discovery " ; it is at best 

 but a reasonable anticipation. We trust that future 

 issues of this Journal may, as the horizons become 

 dearer and as opportunities offer, testify to the shaping 

 of the new literatures and to the spirit in which they 

 are facing the tasks that lie before them. 



The Source of Nitrogen, 



Old and New 



By Edward Cahen, A.R.C.Sc, F.I.C. 



All living plants and animals require nitrogen if they 

 are to exist, and in addition to this, man, the noblest 

 of all the animals, uses this element in huge quantities 

 for the purpose of putting an end to existence by means 

 of his great invention — firearms. 



The earth on which they have their being is a sphere 

 of some 8,000 mOes in diameter, around which there 

 is an envelope about twenty miles deep of air, four- 

 fifths of which is nitrogen, and yet these plants and 

 animals, with but few exceptions, are unable to make 

 use of all this good nourishment unless it is specially 

 prepared for them. As far as one can see, this enor- 

 mous quantitiy of nitrogen is merely mixed with the 

 oxygen to dilute the latter for our consumption. 

 Rutherford (1772) is usually credited with the discovery 

 of nitrogen. He burnt various elements, such as phos- 

 phorus and carbon, in air, and observed that what 

 was left had lost something; he therefore called the 

 residue " phlogisticated air." It was not till much later 

 that Chaptal (1823) gave it its present name Nitrogen, 

 from the Greek virpov (saltpetre) and ytwaiu (I produce), 

 in reference to its existence in this material. Nitrogen 

 is one of the most ubiquitous of elements ; not only is 

 it a constituent of all living plants and animals, and 

 supplies four-fifths of our atmosphere, but it is also 

 found in some nebulae in the heavens, and has been 

 discovered hidden away in many minerals. If agri- 

 culture is to be developed, a supply of suitable nitrogen 

 must be found. At first, of course, the manure from 

 stables and cowsheds was enough to meet the small 

 demands; but, when more and more land came under 

 cultivation in the course of the ages, more and more 

 fertihsers had to be found. A fruitful source of supply 

 in the past has been the saltpetre beds in the rainless 

 region on the West Coast of South America — in Peru, 

 Chili, and Bolivia ; but, large as this source is, it cannot 

 last for ever at the rate at which it is being used up. 

 Although in 1873 there existed some 550 square 

 miles of these beds in large flat basins between the 

 ridges of the Tarapueca plateau, every square mile 



of which was capable of producing about four million 

 tons of the precious material, it was estimated that 

 these beds could not last much more than a hundred 

 years. There is another disadvantage about a source 

 of nitrogen so far across the seas, and that is, it is 

 not always available. A war arises, a blockade is 

 declared, and the supply is cut off at just that time 

 when it is most needed for the making of munitions. 

 Not only during this war has the lack of nitrates made 

 itself felt, but even during the Napoleonic Wars, 

 France was in such desperate straits for the lack of them 

 for making gunpowder that she had to resort to what 

 were known as " nitre-plantations." These were 

 simply great heaps of manure protected from the rain 

 and allowed to rot ; in course of time several different 

 kinds of bacteria set to work and converted the nitrogen 

 into nitrates. This method of obtaining nitrates is 

 still resorted to in hot countries such as Bengal. In 

 this connection it is interesting to speculate how the 

 Chili deposits of nitrate got there ; the problem in 

 point of fact is a very difficult one, and has not yet 

 been solved in a satisfactory manner. It is thought 

 that the sodium nitrate might be of animal origin, 

 but in that case, where the phosphates which must at 

 one time have been associated with them have gone to, 

 is more than one can tell. 



In nature there is a complete cycle round which the 

 available nitrogen moves : the verdure covering the 

 surface of the world is consumed by the animals ; 

 these die and decay, part of the nitrogen going back 

 into the soil to nourish the vegetation, part returning 

 into the atmosphere, where a thunderstorm, with its 

 flashes of lightning, soon o.xidises it to nitric acid, 

 which dissolves in the rain and so is returned to earth. 

 This cycle is not quite so simple as I have described it, 

 but a glance at the diagram will at once make matters 



Action of 

 Ferments or 

 '' Bacteria. 



Living Plants. • -»- - - A 



Fixed by Electric 

 Discharge or 

 Symbiotic Bacteria. 



Death and Decay. 



Free 

 - Atmospheric 

 Nitrogen. 



clear. The symbiotic bacteria in the diagram are 

 rather interesting little bodies; they live in a sort of 

 partnership in nodules on the roots of plants, mostly 

 of the bean family (Leguminosa;), and in return for their 

 board and lodging they make the atmospheric nitrogen 

 palatable for the plants, their landlords. It was per- 

 haps to be expected that, when the natural sources 

 of nitrates began to get more scarce and more diffi- 

 cult to come by, the ingenuity of man should be 



