The Pamphlet Collection of Sir Robert Stout: Volume 33
Nitrogen: its Economy in Nature
Nitrogen: its Economy in Nature.
The world around us has been ascertained to be built up of certain materials of diverse character called elements. Modern chemistry has increased the number of these bodies, from the comparatively few known to the ancients, to some 66 or 67 contained in the list before you. There are probably many more, but up to this time no further increase has been recorded. Of these substances the greatest number are metallic, generally found in combination with one or more of the other elements, and, with the exception of gold and platinum, rarely found free; and the same may be said of the other elements, for if we except oxygen, nitrogen, sulphur, and carbon, none of the rest are found uncombined in nature. Thus the great receptacle of chlorine is the sea, where it exists united to sodium to form common salt; hydrogen is associated principally with oxygen to form water; phosphorus with oxygen and lime to form bone earth; and so on with the rest, it being very rare to find any of these bodies free. There are, however, two very notable exceptions, nitrogen and oxygen; these two bodies, when simply mixed together in a free state in the proportion of about four to one, forming the great bulk of the air we breathe.
Nitrogen, the element we are called upon to study this evening, is under all ordinary circumstances a gas more remarkable when in a free state for its negative properties than for any other characteristic. It forms about four-fifths page 64 of ordinary air, the remainder being oxygen; At one time it was considered that nitrogen acted more as a diluent of oxygen than anything else in the atmosphere, and it was said that if it were not for the presence of this substance every combustible on the face of the earth would be consumed, and all life perish; for when oxygen gas in an unmixed state was examined, it was found to accelerate combustion to a most extraordinary extent, and bodies that burnt in air only slowly, or perhaps not at all, when placed in oxygen gas were found to do so with great rapidity.
There is no doubt that in the atmosphere nitrogen does act as a diluent of oxygen, but then this is only a part of its uses. Nitrogen may be prepared moderately pure by burning some substance in a confined space of atmospheric air that shall thus absorb the oxygen, such as a piece of phosphorus.
I before mentioned that we were conscious of the existence of some 66 elementary bodies; but though we call them simple substances and speak of them as elements, yet the truth must be confessed that not one of the so-called elements has been or can be shown to exist in an entirely independent state, or unassociated with an unknown principle which we term "force," a principle with which it enters into intimate union, and cannot be separated from except by substituting something else for it. For example, take the metal iron, one of the names on the list of elements: we find by experiment that it will unite with oxygen, that in fact it will rust by exposure; we also find that it may in pure oxygen be made to combine so rapidly as to ignite and give off heat and light. Now, the question suggests itself, whence came the heat and light? obviously they must have come from either the iron or the oxygen, or both; and this is exactly the point I want to press upon your attention. Heat and light exist in combination with all the known elementary bodies in certain fixed definite quantities that may be calculated. It has thus come to be understood that the quantity of heat given off by an elementary body in the act of combustion will be in exact proportion to the number of atoms burnt, without any reference to their weight. Thus, for example, an atom of iron is 28 times as heavy as an atom of hydrogen; but, as an atom of one body always contains the same amount of heat as an atom of another, be the weight what it may, it follows that 28 lbs. of iron will give off in burning no more heat than 1 lb. of hydrogen. The page 65 product of the combustion of iron will now be a compound of iron and oxygen, both of which elements have been deprived of the heat contained in each previous to their union with one another.
The notion that what are called elementary bodies are simple substances is therefore obviously incorrect; they are, in fact, definite compounds of some unknown substances with a force, the existence of which we recognise as heat and light, and which can only be separated from them by substituting some other combination, when the character of the substance becomes altered, nor can they ever be restored to their original condition unless this lost force is again given back to them. This may, however, be done in a variety of ways, of which the principal consists in directly mixing them with some other compound containing heat or "force," usually some of the compounds of carbon, as coal or charcoal, when the metal may have restored to it the forces it has lost, and made to reassume its original appearance. The following diagram illustrates this :—
The diagram explains generally what occurs in ordinary cases of union between elementary bodies, such union being usually accompanied by the elimination of force in some form or other, either as light, or heat, or electricity. That such forces do not necessarily depend upon a supply of oxygen, but may be equally produced by substituting other elements, can be shown by the energetic action of some of them, such as chlorine, which, when mixed with some of the metals, produce a sort of combustion. With antimony this is very marked.
Again, amongst the elements is phosphorus. By suitable contrivances this substance may be made to combine with chlorine and oxygen under water, and even under these page 66 circumstances we shall have heat and light given off, which the water is unable to quench.
I have here tubes containing metallic lead in a minute state of division, prepared by a chemical process. When the contents are allowed to come in contact with the oxygen of the air, the two enter into such rapid union that again we have heat and light expelled, and inert oxide of lead formed.
When oxygen and hydrogen unite, a great deal of force is disturbed, and water is generated. Water, then, is a compound of oxygen and hydrogen that have both been deprived of the latent forces existing in them when in a free state. I have here a flame of hydrogen; by its union with the oxygen of the air steam is produced, and when this is condensed, water.
As the equivalent or atomic value of hydrogen is only 1, and oxygen only 8, we might expect a great deal of force to be eliminated by the union of these gases, the two atoms, together weighing 9, containing previous to combination as much latent force as two equivalents of any other elements, in the case of iron weighing 56. I have here a mixture of oxygen and hydrogen, which I will cause to unite, and I will then show you what a deal of force, in this case eliminated in the form of heat, is evolved.
Water, the final result of the union of oxygen and hydrogen, is of course destitute of force. Nevertheless, these elements may again be separated from each other by restoring to one or both the forces originally contained in each before combustion. A piece of an oxidisable metal, such as iron, will slowly effect this; but with some of the alkaline metals, such as sodium and potassium, both of which contain force, the restoration of the hydrogen is effected with great violence, and even ignition, the hydrogen, as it is expelled again, taking fire in the air.
By substituting a current of electricity for the metals in this case, the forces may be restored to both, the oxygen and hydrogen being in this case obtained from the oxidation of certain plates of zinc contained in a galvanic battery.
It is useless to further multiply illustrations; enough has been shown to enable you to understand that what we call elements are in reality compounds of some unknown base (never yet in a single instance isolated) with a certain force, the effects of which are familiar to us under the forms of heat and light, or electricity, as the case may be. The combination of any of the elements is usually then accompanied page 67 by the evolution of the forces previously combined with them whilst in a free state. Usually, I say, for this is not always the case; for the element "nitrogen," which we have adopted for our lecture this evening, is a notable exception.
This body appears to have the power of uniting with and absorbing other elements, without causing the disengagement of their combined forces. In this respect no other body can compare with it, and on this account nitrogen becomes in nature one of the most important elements.
How nitrogen in the state in which it exists in the atmosphere first becomes united with other elements is not well understood, but it is known that when vegetable matters decay, nitrogen from the atmosphere is absorbed and ammonia formed, ammonia being a compound of nitrogen and hydrogen; and as ammonia is also the ultimate form that nitrogen in-variably assumes in the natural decomposition of any bodies containing it—such as animal matters—there can be no doubt that the affinity of nitrogen and hydrogen must be very great.
Ammonia, then, is a substance constantly being generated around us, composed of fourteen parts of nitrogen to three parts of hydrogen; it is a gas having very remarkable properties; it is peculiarly pungent to the smell; maybe readily detected in vessels containing it by the white cloud it produces with some acids. It is also a most powerful alkali, exceeding in neutralising power most other bases. It is also remarkable as assuming, under some circumstances, the properties of a true elementary body; and when united to one more atom of hydrogen, can even be made to amalgamate with mercury, exactly like a metallic body.
Ammonia is also remarkable as forming the type of a whole series of ammonias that are found in nature, and which have the same relation to each other, or family likeness, as the ethers and sugars I have referred to in my last lecture on "Fermentation." The substances known as "vegetable alkaloids," to which quinine, morphia, and strychnine belong, and which comprise such a vast body of interesting substances, are all "ammonias," brothers and sisters of the original ammonia we have been speaking of, and formed in vegetables by some mysterious process not understood.
Vegetable alkaloids appear to be ordinary ammonia, with one or more of the hydrogen elements replaced by groups of elements acting as only a single element, a circumstance very page 68 common in organic chemistry; hence the variety of such bodies is almost endless.
I just now remarked that under certain circumstances nitrogen had the power of absorbing other elements without necessarily expelling the latent forces contained. Thus, in the formation of nitrates, this takes place—nitrates are formed during the gradual decay of nitrogenised matters, such as animal refuse, under such circumstances that free access of air is admitted, and an admixture of lime or some other basic substance allowed to be present; under these conditions oxygen is absorbed by the nitrogen contained, and a nitrate of the base produced; this substance, when mixed with solution of carbonate potassium and filtered, gives on evaporation saltpetre or nitrate of potassium.
Nitrogen combines with oxygen in five different proportions—
NO1 NO2 NO3 NO4 NO2
The first of these, or nitrous oxide—or laughing gas, as it has been called—is sometimes used as a mild anæsthetic in place of the more dangerous chloroform, chiefly by dentists. The second is produced by the action of nitric acid upon some metallic substance, or upon starch. The third, fourth, and fifth are formed from the second by spontaneous absorption of oxygen. But the most remarkable circumstance connected with this absorption of oxygen by nitrogen consists in the fact that no force, such as heat or light, are given off during the operation. The nitrogen has absorbed not only the oxygen, but all the forces existing in it when in a gaseous form. These forces it not only absorbs and retains, but even transfers to any salt into the constitution of which it may enter—for example, saltpetre. We can now, therefore, understand what it is that makes nitre or saltpetre so destructive. By way of contrast, let us take phosphorus: this substance also combines with oxygen, absorbing a similar amount of that element that nitrogen does; during the process, however, much light and heat are given off, and the final result is a comparatively inert substance—phosphoric acid, utterly destitute of all the properties that nitric acid is remarkable for, and forming a class of salts, "the phosphates," of very fixed nature, difficult to decompose, and resisting the highest temperatures, no latent force being in point of fact left in them. If I mix nitrate of potass with charcoal and sulphur, it gives me gunpowder; with page 69 phosphate of potass in place of nitrate, no effect whatever is produced; and yet the oxygen, the element admitted to be the active ingredient in gunpowder, is present in nearly equal quantity in both. It is obvious, therefore, that the condition of the oxygen must be widely different in the two cases. Here then is the explanation. The phosphorus and oxygen when they became united lost the whole of the latent forces contained in them, the resulting phosphoric acid being a substance, in consequence, absolutely destitute of contained force, therefore quite incapable of indicating any under any circumstances whatever. The nitrogen, on the other hand, not only absorbs the same quantity of oxygen that phosphorus does, but it does it quietly, without allowing any of the forces contained in it to escape or be lost. These forces exist in nitric acid and nitrates, much in the condition of a compressed spring, ready to leap out with destructive violence and suddenness when the balance of conditions by which they are held is disturbed. Hence, in gunpowder the force is to be referred to that original wondrous absorptive power of nitrogen of forces eventually transferred to the carbon and sulphur contained in gunpowder, and, finally, economically applied for propelling shot or blasting rock.
This property of nitrogen to absorb and retain force is very marked in many other instances besides gunpowder; thus, in gun-cotton—a substance that has of late years been used as a substitute for gunpowder, over which it has some advantages principally relating to weight and smoke produced in its use—it is the part played by the nitrogen present that gives it its character. As in gunpowder, here the nitrogen has imprisoned a large amount of oxygen, and all the forces originally held by both when in a gaseous form, and when from any cause the integrity of the compound is interfered with, their forces become released, and away they go. When gun-cotton is ignited in the air, very little light is given off on account of the gaseous nature of the products, and no ashes; but if some solid substances be mixed with it, so as to present a fixed residue for the heat produced to ignite, much light is formed. I have here gun-cotton, mixed with an earthy salt baryta, to supply a solid material that will not be dispersed as a gas. When this substance is ignited, so sudden and brilliant is the effect that I, some years ago, tried to get it introduced to some of our theatres, for the purpose of producing artificial lightning in place of page 70 the miserable failures at present made use of, but without success; for, though I succeeded in astonishing many theatrical managers by its marvellous effects, so conservative did I find them, and difficult to move from the old grooves they had been accustomed to, that I at length gave up the task.
There are many explosive compounds into which nitrogen enters and to which they owe their properties, but it will be sufficient simply to mention their names. Glonoine, or nitro-glycerine, is one of these; then we have fulminating silver and mercury, the latter being the material used for priming caps for guns; then come iodide and chloride of nitrogen, the most violently-dangerous substance known.
Professor Fownes thus describes this body:—"It is a yellow, oily-looking substance, that may be distilled at 160° Fahr., although the experiment is attended with great danger. Between 200° and 212° it explodes with the most fearful violence. Contact with almost any combustible matter, as oil or fat of any kind, determines the explosion at common temperature; a vessel of porcelain, glass, or even cast-iron, is broken to pieces, and a leaden cup receives a deep indentation. With phosphorus the explosion is peculiarly violent even under ordinary circumstances; a grain of the substance produces when exploded a report as loud as a gun. In making these experiments great caution is required, the operator covering his face with a strong wire-gauze mask. Dulong lost an eye and the use of a finger, and Sir H. Davy was wounded in the face, by the effects of its detonation." I am sure, under these circumstances, you will excuse me for not introducing this substance personally to your notice this evening, but will leave it to be sought out by the private student in places remote from danger.
Nitrogen combines with carbon, producing a very remarkable substance called cyanogen, which, under ordinary circumstances, is a gas that burns with a peach-coloured flame.
Cyanogen has all the properties of an element, and is capable of entering directly into combination with other elements, or of replacing them in compounds. With hydrogen it produces an acid substance, long well known under the name of prussic acid, the most sudden and deadly poison known. Fatal as an overdose of this substance always is, yet it exists in many fruits—such as almonds, peaches, apple pips, and the kernels of cherries and plums. Of course page 71 the quantity contained in these fruits is very small; but the fact is nevertheless very interesting, as showing that the most deadly poisons, if sufficiently diluted, may become harmless, and often indeed supply most valuable medicines. Thus, in small closes, prussic acid is one of the most powerful remedies for allaying excessive irritation of the stomach, as during incessant vomiting; also for relieving palpitation of the heart; indeed, its action is specifically directed to the heart in preference to other organs, and I may observe that it is by no means an uncommon circumstance for medicines or poisons to select some organ in preference. Thus, whilst prussic acid and digitalis affect the heart, strychnine takes the spine and nerves, arsenic the stomach and skin, morphia and alcohol the brain, belladonna the eye, and so on with others. Hence the poisons, when properly administered, become ofttimes most valuable medicines.
Cyanogen has a great affinity for iron, with which it combines in several distinct ways; that beautiful-looking yellow crystal now present upon the table is a compound of cyanogen, iron, and potassium. In this case the iron appears to have assumed a character altogether foreign to its nature; usually playing in compounds the part of a base, it in this instance plays the part of an acid, and in conjunction with the cyanogen can combine with other bases. With copper, for instance, ferrocyanide produces a deep red-brown precipitate of ferrocyanide of copper; with iron salts, an equally deep and beautiful blue, manufactured on a large scale under the name of Prussian blue. Amongst other uses to which this substance is applied is that of painting tea, of giving that beautiful bloom so pleasing to the eye, at one time thought (erroneously) to be communicated by drying the tea-leaves upon copper plates.
A good many years ago a large trade was done with China in Prussian blue, all of which found its way back amongst the tea imported from there. But at length the Chinese succeeded in finding out the process by which Prussian blue is made, having sent a countryman to Europe for that purpose, since which time they have made their own.
Prussian blue may be easily detected in tea, by simply washing with cold water, when it is removed.
It has long been a matter of wonder how steel was produced. Bars of iron, laid in charcoal and exposed to a red page 72 heat, gradually became impregnated with a certain amount of carbon, which somehow penetrated through them during the process of cremation, but how it was enabled to travel through a solid bar of iron could not be explained. Of late years, however, it has been pretty satisfactorily proved that cyanogen is the carbon-carrying agent concerned in the production of steel; hence to nitrogen we are again indebted for all our best articles of cutlery, springs, and steelware generally.
Cyanogen, combined with potassium, produces a salt very much used, on account of its solvent power of silver and gold salts, in electro-plating and gilding; a solution of silver in cyanide of potassium being always used for plating. Indeed so easy is the process, that if a copper coin, or old worn plated spoon or fork, be simply rubbed with a solution so prepared and a little chalk, it will become immediately coated with silver and made to look quite new again. Even brass may be, by similar means, plated upon iron; and in Birmingham it is said that thousands of tons of buttons and similar articles are now regularly coated with brass upon iron bases, thus proving very economical.
On the large scale cyanogen is produced by boiling down together, in large iron pans, a mixture of animal matter, such as the refuse from slaughter-houses and tanneries, with potass and scraps of iron, to dryness and low ignition; the charred mass being then washed with water yields a solution of yellow prussiate of potash, from which salt all the other cyanides are directly or indirectly formed. A patent was some time ago taken out for the manufacture of cyanide by the direct union of carbon and nitrogen, produced by passing air through ignited charcoal, but I am not aware whether that process is now carried on. This country presents very favourable opportunities for making cyanide, from the immense quantities of animal refuse obtainable from our boiling-down establishments and meat-preserving companies, and it has often been a matter of surprise that no enterprising individual has started the new industry.
Nitrogen is intimately associated with life, and is never absent from living vegetable or animal tissues; indeed the degree of vitality in a vegetable or animal substance may be approximately estimated, by the nitrogen contained in it. In the lowest class of vegetables, such as the cryptogamia or sea-weeds, but little nitrogen is found, the quantity increasing as we progress upwards, being abundant in leaves page 73 and greatest of all in flowers and seeds; indeed, so general is this the case, that during fruition almost the whole of the nitrogen and vital force associated with it is not uncommonly removed from every other part of a plant and concentrated in the seeds, the stem then withering and drying up, as in wheat, and the agave Americana, or aloe tree, so common in this colony, and which, after growing a somewhat imposing and pretentious plant for seven years, then for the first time flowers, produces numerous seeds, and perishes.
Whilst wheat, oats, or barley are green, every part of the plant teems with nutriment, and if cut down in this state and dried, makes excellent hay; if, however, they be suffered to ripen, all this nutriment is withdrawn, the leaf and stem wither and grow yellow, a little straw being finally left, almost destitute of any nutritive properties whatever, all these having been removed to the ripening grain, destined as seed to produce new plants, or to be consumed as food by animals and man.
Vital force seems in all cases to be derived from the sun by vegetable aid, and to be stored by the latter in nitrogen compounds only, being afterwards transferred to the bodies of animals consuming them as food, and eventually becoming developed in the thousand different forms that constitute life. In the body these principles become gradually divested of the forces within them, becoming more and more reduced to substances of a simpler constitution. Hence it is that the much-used limb becomes harder than the part which has had rest, every motion being an act of life so far reducing the part where it is made. Hence beef from the leg of a cow will not be so tender as that removed from the rump or loin, because of the weight it has had to sustain, and the consequent loss of vital force and change into something inferior, and there can be no doubt that, weight for weight, such meat is really less nutritious than that cut from the best parts; it is therefore very doubtful whether such parts, unless very greatly cheaper, are really economical to use. One cause of the stringiness so general in Australian meat is the travelling the animals have undergone in search of water and food, incidental to a dry climate, every string thus produced representing original good meat, of much greater weight, that has lost its vital power in the process of exercise; indeed, much exercise of any kind is always injurious to meat, and tends to harden it and spoil it. For this reason it is not to be expected that meat produced in a page 74 dry climate will ever equal that supplied by well-watered plains, where cattle can eat and drink their fill with the least possible exertion to themselves, and where they may lay down and chew their cud, and rest in peace.
It is on account of the continued exercise that the legs of walking fowls are harder than their wings, whilst with birds that fly, as wild-fowl, the wings are harder than their legs. Even pigs that roam about, and for the most part find their own living, do not make good bacon, and most of our colonial hams are on this account very stringy and hard, and not to be for a moment compared with the delicious sty-fed pork of Cumberland or Yorkshire.
Nitrogen is the principal life-supporting element in the food of all animals. Food that is destitute of nitrogen—as starch, sugar, gum, and alcohol—are utterly unable to contribute anything towards the repair of that continual waste going on in every part of the body. True, these substances may contribute, and doubtless do, to the performance of many animal functions, such as sustaining temperature, and as nervous stimulants; but, inasmuch as they are destitute of nitrogen, they cannot increase muscle, or add anything to the tissues of the body; these are all nearly entirely made up from albuminous materials, originally derived from the vegetable world under the influence of sunshine and suitable other conditions. All plants are laboratories actively engaged in absorbing ammonia, carbonic acid, and water, and by the additional aid of a few mineral substances—as potash, phosphorus, sulphur, lime, magnesia, and iron, with a little silica—breaking them up into their constituents, and re-forming them into the most complex of all known compounds. A vegetable, therefore, may be viewed as containing the very highest and most complex principles of organic life. True, in animals very highly-organised principles are found, but these have in every instance been derived originally from the vegetable kingdom, and during the process of assimilation have suffered a diminution of elevation, being gradually reduced to a somewhat lower level. Gluten, the essential constituent of wheat, during the process of digestion and assimilation becomes modified into albumen and fibrin; no instance is known of albumen or fibrin producing gluten. Again, starch, the next important constituent of wheat, is easily converted into gum and sugar; no instance is known of gum or sugar being converted into starch. So it is in the animal economy: numbers of principles originally derived page 75 from the vegetable world are modified and altered into new ones, but the process is always one of destruction—a downward one, tending to reduce the substance to further and still greater simplicity, until it gets finally expelled from the body, expended and useless, and even reduced almost to the condition of a mineral substance.
I think gluten must be considered the highest and most complex form of organic creation; from the downward changes this substance undergoes when taken as food we successively obtain albumen and fibrin of blood, muscular fibre, chondrin (the cartilaginous principle of bones), gelatine, uric acid, and urea; every one of these changes being a downward one—the last, indeed, only half a stage removed from the mineral kingdom.
When an organic body has once been reduced to its primitive elements, there is only one way that it can be restored, viz., by vegetable life. It is not indeed possible to explain how this is by such means effected, but the result is palpable. Principles containing carbon, hydrogen, and oxygen are formed, and others again containing nitrogen; all vital power being contained in the latter. What this vital power is in the abstract we know not; it would, however, seem to be some higher force than heat, light, or electricity, though capable of being converted into any one of these at will. Thus by rapid exercise vital force is converted into heat; by the glow-worm, firefly, and sea animalculæ, into light; by the torpedo and gymnotus, into electricity, all at will; but whilst vital force may produce or be converted into any other force, there is no instance known of heat, light, or electricity producing vital force.
But it is necessary to draw to a close, not that the subject is in any way exhausted, but that the time is, and perhaps your patience also. I hope, however, I have been moderately successful in engaging your attention, whilst I have endeavoured, in a plain and simple manner, to bring before your notice a few of the important parts played by nitrogen in the economy of nature.