In its action, of course, it is not unlike an ordinary mirror galvanometer, but its special feature is in the mechanical arrangement of its parts which enable it to move with sufficient rapidity to follow the rapidly succeeding changes which need to be investigated. It is far less sensitive than, say, a Thomson Galvanometer, but the latter could not respond quickly enough for this particular purpose.
CHAPTER III
THE FUEL OF THE FUTURE
We now enter for a while the realm of organic chemistry, a branch of knowledge which is of supreme interest, since it covers the matters of which our own bodies are constructed, the foods which we eat and the beverages which we drink, besides a host of other things of great value to us.
Although the old division of chemistry into inorganic and organic is still kept up as a matter of convenience, the old boundaries between the two have become largely obliterated. The distinction arose from the fact that there used to be (and are still to a very great extent) a number of highly complex substances the composition of which is known, for they can be a.n.a.lysed, or taken to pieces, but which the wit of man has failed to put together. Consequently these substances could only be obtained from organic bodies. The living trees, or animals, could in some mysterious way bring these combinations about, but man could not. The molecules of these substances are much more complicated than those with which the inorganic chemist deals. The important ingredient in them all is carbon, which with hydrogen, nitrogen and oxygen almost completes the list of the simple elements of which these marvellous substances are compounded. In some cases there appear to be hundreds of atoms in the molecule.
If one takes a glance at a text-book on organic chemistry the pages are seen to be sprinkled all over with C"s and O"s, N"s and H"s, with but an occasional symbol for some other element.
Another feature of this branch which cannot fail to strike the casual observer is the queer names which many of the substances possess.
Trimethylaniline, triphenylmethane and mononitrophenol are a few examples which happen to occur to the memory, and they are by no means the longest or queerest-sounding.
Another peculiarity about these organic substances is that a number of them, each quite different from the others, can be formed of the same atoms. Certain atoms of hydrogen, sulphur and oxygen form sulphuric acid, and under whatever conditions they combine they never form anything else. On the other hand, there are sixty-six different substances all formed of eight of carbon, twelve of hydrogen and four of oxygen. This can only mean that in such cases as the latter the atoms have different groupings and that when grouped in one way they form one thing, in another way some other thing, and so on. This explains the extreme difficulty which the chemist finds in building up some of these organic substances.
Every now and again we are startled by some eminent man stating that the time will come when we shall be able to make living things, when the laboratory will turn out living cows and sheep, birds and insects, even man with a mind and soul of his own. Yet one cannot but feel that such men, no matter how great their authority, are simply "pulling the public"s leg," to use a colloquial expression. For they hopelessly fail to make many of the commonest things. In many cases where they wish to produce an organic substance they have to call in the aid of some living thing to do it for them, even if it be but a humble microbe. For the microbes perform wonderful feats in chemistry, far surpa.s.sing those of the most eminent men. Hence the latter very sensibly use the microbe, employ it to work for them, just set things in order and then stand by while the microbe does the work.
Thus most things can be a.n.a.lysed--that is to say, taken to pieces--while many things can now be synthesised--that is to say, built up from their const.i.tuent atoms--but still a great many remain, and among them the most important, the synthesis of which completely baffles man. One of the most useful and widespread substances, for example, cellulose, is, at present at least, utterly beyond us. We do not even know how many atoms there are in the cellulose molecule. The molecules may, for all we know, contain thousands of atoms. Indeed many of these organic matters have very large molecules.
And even if the chemist were able to make all kinds of organic matter, he would still be as far off as ever from making _living_ matter. Indigo used to be derived entirely from plants of that name. One of the greatest triumphs of the organic chemist was when he produced artificial or synthetic indigo. But he is as far off as ever from making the indigo plant. It is claimed that "synthetic" rubber is exactly the same as natural rubber, although some users say it is not quite the same. Still, if it be so, it is dead rubber, not the living part of the plant. The time, then, is infinitely far distant when the chemist will be able to make anything with the characteristics of life--namely, to grow by accretion from within and to reproduce its kind. The most wonderful product of the laboratory is dead. At most it simply resembles something which _once_ was alive.
But that is somewhat of a digression. This dissertation on organic chemistry was simply intended to lead up to the question of liquid fuels, all of which are organic.
In the life of to-day one of the most important things is petroleum.
This is a kind of liquid coal. Just how it was formed down in the depths of the earth is not clear. One idea is that it is due to the decomposition of animal and vegetable matter. Another is that certain volcanic rocks which are known to contain carbide of iron might, under the influence of steam, have in bygone ages given off petroleum, or paraffin, to use the other name for the same thing.
In many parts of the world these deposits of oil are obtained by sinking wells and pumping up the oil. In others the liquid gushes out without the necessity of pumping at all. This is believed to be due to the fact that water pressure is at work. Artesian wells, from which the water rushes of its own accord, are quite familiar, and are due to the fact that some underground reservoir tapped by the well is fed through natural pipes, really fissures in the rock, from some point higher than the mouth of the well. Now supposing that a reservoir of oil were also in communication with the upper world in the same way, the descending water would go to the bottom, underneath the lighter oil, and would thus lift it up, so that on being tapped the oil would rush out.
Another source of mineral oil is shale, such as is to be found in vast deposits in the south-east of Scotland. This shale is mined much as coal is: it is then heated in retorts as coal is heated at the gas-works: and the vapour which is given off, on being condensed, forms a liquid like crude petroleum.
In all these cases the original oil is a mixture of a great number of grades differing from each other in various ways. They are all "hydro-carbons," which means compounds of carbon and hydrogen, and they extend from cymogene (the molecules of which contain four atoms of carbon and ten of hydrogen) to paraffin wax, which has somewhere about thirty-two of carbon to sixty-six of hydrogen. For practical purposes their most important difference is the temperature at which they boil, or turn quickly into vapour.
This forms the means by which they are sorted out. In a huge still, like a steam-boiler, the crude or mixed oil is gradually heated, and the gas given off is led to a cooling vessel where it is chilled back into liquid. The lightest of all, cymogene, is given off even at the freezing-point of water. That is led into one chamber and condensed there. Then, as the temperature rises to 18 C., rhigolene is given off: that is collected and condensed in another vessel. Between 70 and 120 petroleum ether and petroleum naphtha are produced, and they together const.i.tute what is commonly called petrol. Between 120 and 150 petroleum benzine arises. All the foregoing taken together const.i.tute about 8 to 10 per cent. of the whole crude oil. Then between 150 and 300 there comes off the great bulk of the oil, nearly 80 per cent., the kerosene or paraffin which we burn in lamps. Above 300 there is obtained another oil, which is used for lubrication, also the invaluable vaseline, and finally, when the still is allowed to cool, there remains a solid residuum known as paraffin wax. This process is known as fractional distillation, and it will be noticed that it consists essentially in collecting and liquefying separately those vapours which are given off at different ranges of temperature. For our purpose in this chapter we are mainly concerned with the petrol and the kerosene.
Many efforts have been made in times gone by to use kerosene for firing the boilers of steam-engines. In naval vessels a great deal is so used at the present time. But the chief method of employing oil for generating power is to use it in an internal combustion-engine. These machines have been dealt with at length in _Engineering of To-day_ and _Mechanical Inventions of To-day_ and so must be simply mentioned here.
They consist of two types. In one, which is exemplified by the ordinary car or bicycle motor, the oil is gasified in a vessel called a carburetter or vaporiser and then led into the cylinder of the engine, together with the necessary air to enable it to burn. At the right moment a spark ignites the mixture, which burns suddenly, causing a sudden expansion, in other words, an explosion. Thus the power of the engine is derived from a succession of explosions. If the fuel be petrol it vaporises at the ordinary temperature of the engine and needs no added heat. With kerosene, however, heat has to be employed in the vaporiser to make it turn readily into a gas.
The other method is employed in engines of the new "Diesel" type, in which the cylinder of the engine, being already filled with hot air, has a jet of oil sprayed into it. The heat of the air causes it to burst into flame, causing an expansion which drives the engine.
An important feature in the latter type of engine is that the oil is very completely burnt, so that very heavy oils can be used, oils which, if employed in an engine of the other kind, would choke up the cylinder with soot. In other words, the range of oils which can be used in this new kind of engine is much wider than is possible in the others. The latter may be likened to a fastidious man who is very particular about his food, while the former resembles the man of hearty appet.i.te who can eat anything. And just as a man of the latter sort is more easily provided for by the domestic authorities, so the Diesel engine makes the problem of the provision of liquid fuel much simpler.
For it must never be forgotten that the provision of liquid fuel for the world is by no means a simple matter, since the supply is by no means adequate. The output runs into thousands of millions of gallons, and the whole world is being searched for new fields of oil, and yet it is all swallowed up as fast as it can be produced, while the coal mines do not feel the compet.i.tion. A year or so ago the United States and Russia between them (and they are the greatest producers) obtained 5,000,000,000 gallons of oil, seemingly an enormous quant.i.ty. But, on the other hand, Great Britain alone produces over 250,000,000 _tons_ of coal per annum. If, therefore, liquid fuel is to displace coal, as some people lightly think it is going to do, the supply will have to be multiplied many times. In the amount of heat which it is capable of giving the coal of Great Britain alone beats the oil produced by the whole world.
And another thing to be borne in mind is that as the coal miner goes down to the seam and sees for himself what is there, while the oil producer simply stays at the surface and draws it up with a pump, the coal man knows far more as to how much there is still left than the oil man does. We know that the coal deposits will last for many years to come, even if the production go on increasing, whereas the oil supply may fall off in the near future instead of increasing.
And in both cases we are using up capital. Coal is not being made on the earth now, at any rate in any appreciable quant.i.ty. The stage of the earth"s history favourable to the formation of coal measures has long gone by. And the same probably applies to oil.
It is interesting in this connection to note that coal itself is to a certain extent, or can be at all events, a source of oil. When coal is heated in order to make it give up its gas, or to turn it into c.o.ke, vapours are given off which on cooling become coal-tar. At one time regarded only as a crude sort of paint, this is now the source from which many chemical substances are obtained, varying from photographic chemicals to saccharine, a subst.i.tute for sugar. So valuable are these products that there is a brisk demand for the tar, in other directions than the manufacture of oils, but oils of various kinds are also obtained from it.
The first step in the operations is fractional distillation, after the manner just described for petroleum. The first "fraction" is "coal-tar naphtha." Then follows "carbolic oil," after that "heavy" or "creosote oil," anthracene oil, and finally there remains in the still on cooling a solid residue known as coal-pitch. The naphtha, on being distilled again, gives, among other things, benzine, from which the famous aniline dyes are made, and which is useful in many industries. Creosote is largely employed as a preservative for wood, being forced into the timber under high pressure, so that it penetrates right into it and tends to prevent rotting, no matter how wet it may be. Railway sleepers are thus treated, small truck-loads of them being run into a cast-iron tunnel which is then sealed at both ends, while the creosote is forced in by powerful pumps. After such treatment they can lie nearly buried in the damp ballast for a long time without any deterioration.
These coal-tar substances are all very similar to petroleum and its products, hydro-carbons, compounds of hydrogen and carbon in various proportions. Many of them could be used for fuel.
[Ill.u.s.tration: _By permission of Dupont Powder Co._
APPLE TREE PLANTED WITH A SPADE
This apple tree was planted in the ordinary way with a spade. Compare its size with that in following ill.u.s.tration at p. 48.]
But since they are based upon the supply of coal, which is itself limited, they cannot, however they may be used, do more than stave off the evil day when the supply will be exhausted.
Quite different is it with alcohol, which it seems likely may be the fuel of the future. Some people will be inclined to exclaim "What a pity to burn it!" since to many the word conveys ideas of another sort altogether. There are many nowadays, however, who, like the writer, have none but a scientific interest in it. To such whisky, for example, is but "impure" alcohol, and it is without the "impurities" that it may become of vast use to the world, thereby possibly repaying man for some of the harm which in the past it has inflicted upon him.
Alcohol, again, is a hydrocarbon. It is really more correct to speak of it in the plural, as "alcohols," since there is a large group of substances all of the same name. Two of these are of the greatest importance, methyl alcohol and ethyl alcohol. The former is obtained from wood, hence it is sometimes called wood spirit. Wood is strongly heated in an iron still, and the methyl alcohol is given off in the form of vapour, which on being collected and cooled condenses into liquid. It is exceedingly unpleasant to the taste: if it were the only kind there would be no consumption of alcohol as a drink.
The second kind mentioned is obtained by the agency of germs or microbes, and the story of its production is so interesting as to demand a little s.p.a.ce.
We will commence with the maltster. He performs the first part of the operation. Starting with ordinary barley, by the action of heat, aided by natural growth, he produces the raw material on which the brewer may work. Now barley, like all grain, is largely made up of starch, and although starch will not make alcohol, it can be turned into sugar, which will. So the task of the maltster is to commence the change of the starch in the grain into sugar.
First of all it is soaked in water and spread upon floors and heated until it begins to sprout. There is a little part in each grain called the endosperm, which is the embryonic plant, and the starch is really the food provided by nature to nourish the growing endosperm until such time as it shall be strong enough to draw its nourishment from the soil.
In order that it may not be washed away prematurely, the starch is locked up by nature in closely fastened cells, and, moreover, it is insoluble, so that water cannot carry it away. The endosperm, however, has at its disposal certain substances known as enzymes (and it increases its store of these as it grows), one of which is able to dissolve away the walls of the cells, to unlock the treasures, as it were, while the other turns the insoluble starch into soluble matter, in which state the growing organism is able to make use of it as food.
So as the grain sprouts upon the maltster"s floor this process is going on--the cells are being opened and their contents converted from starch into soluble matters. Then, when the growth has gone far enough, the grain is transferred to a kiln, where it is subjected to heat, by which the growth is stopped. The living part of the grain is, in fact, killed.
That is mainly to stop the young plant from eating up the altered starch, which it would do if allowed time, but which the brewer wants to be kept for his own use.
The maltster"s task is now finished, and we come to the brewer"s. The first thing he does with the malt is to crush it between rolls, thereby liberating thoroughly those substances which have been formed from the starch and which he intends to turn into sugar. Having crushed it, he places it in the "mash tun," a large tank of wood or iron, in which it is mixed with water and subjected to heat. While in this vessel the enzymes become active again and turn the soluble starch, or a part of it, into a kind of sugar.
The liquid drawn off from the mash tun, containing, of course, the sugar, is subsequently boiled, numerous flavouring matters (including hops) are added, and then it is cooled again, ready for the final process--fermentation.
This takes place in a large vat or "tun" and is brought about by the agency of yeast which is added to the liquid.
Now yeast is a mult.i.tude of microscopic plants round in shape and about one three-thousandth of an inch in diameter. Though so small, this little organism is really quite complicated in its structure, and within its little body there are carried on complicated chemical changes which baffle entirely the most learned chemist to imitate. Further, he has yet to find out how the little yeast plant does it. He not only cannot imitate the process, he does not know what the process is. These little organisms multiply mainly by the process of "budding." A new one grows out of the side of each old one, rapidly reaches maturity, breaks away and commences an independent existence. No sooner is it free than it in turn gives birth to another. Indeed so great is its hurry to propagate itself that sometimes the new cell begins to throw out a bud before it has itself separated from its parent. It is therefore easy to see that yeast increases in quant.i.ty by what some call "leaps and bounds," but which the mathematically minded know as geometrical progression.
The particular form of sugar with which we are concerned here is known as "dextro-glucose." This the yeast splits up into alcohol and carbonic acid gas. The latter bubbles up to the surface, and escapes into the air, while the alcohol becomes dissolved in the watery liquid. It is believed that the yeast performs this operation not directly, but by the production of certain enzymes, which in their turn act upon the sugar.
The liquid so formed is beer. But since it is alcohol with which we are concerned, and not beer, many details connected with its manufacture have been omitted. Enough has been said, however, to show that by comparatively simple processes grain of all sorts, in fact, anything which contains starch, and such things are to be found in worldwide profusion, can be turned into alcohol. All the really intricate chemical functions are performed readily and cheaply by living organisms. All man has to do is to set up the conditions under which the organisms can work.
In the process just described only a portion of the starch in the grain is converted into sugar, hence the percentage of alcohol in beer is comparatively small. If all the starch be converted a liquid much stronger in alcohol is produced, and if that be distilled, so as to separate the spirit from the water with which it is mixed, there results whisky. Brandy, likewise, is the spirit distilled from wine, rum from mola.s.ses, and so on. In all these familiar beverages the essential feature is this same alcohol, of the variety known as ethyl alcohol.
It will be noticed that in the making of beer the alcohol is actually formed in water. There is a sugary water which under the action of the yeast becomes an alcoholic water. And this indicates a very useful feature about the liquid when used for industrial purposes. A tank full of petrol is extremely dangerous, so much so that the storage of petrol is hedged about by all manner of precautions. The danger is that it gives off an inflammable vapour and that if it once begin to burn there is practically no possibility of putting it out. Being lighter than water, it simply clothes with a layer of fire any water which may be thrown on to it. The water in such circ.u.mstances simply serves to spread the naming petrol about and so to make matters worse. Now alcohol, with its partiality for the companionship of water, behaves quite differently. True, it also may give off an inflammable vapour, but if a quant.i.ty of it catch fire it can be extinguished in the usual way by a fire-engine. The water and alcohol immediately combine--the alcohol becomes dissolved in the water just as sugar may do, and as soon as the percentage of water in the mixture becomes considerable the burning stops.
It may be that some readers will have discovered this fact for themselves without knowing precisely what it was. It is a common dodge with amateur photographers if they want to dry a negative quickly to immerse it in methylated spirit. The spirit seems to take the water out of the film and, itself drying quickly, leaves the negative in a perfectly dry condition in a few minutes. Now after using spirit in that way it is useless to put it in a spirit stove or lamp. It will not burn.
Methylated spirit is alcohol, and the reason why it has such a quick drying action is that it and the water in the wet film quickly mix.