Читать книгу The Romance of War Inventions - Thomas W. Corbin - Страница 7

Table of Contents

One morning during the war the whole British nation was startled to learn that Mr. Lloyd George, then the Minister of Munitions, had taken over a large number of distilleries. Could it be that he, a teetotaller and temperance advocate, was going to supply all his workers with whiskey? Or was he going to close the places so as to stop the supply of that tempting drink?

Neither of these suggestions was his real reason. What he wanted the distilleries for was to make alcohol for the war, not for drinking purposes but for the very many uses which only alcohol can fulfil in most important manufactures.

Probably alcohol is the next important liquid to water. For example, certain parts of shells have to be varnished and the only satisfactory way to make varnish is to dissolve certain gums in alcohol. The spirit makes the solid gum for the time being into a liquid which we can spread with a brush, yet, after being spread, it evaporates and passes off into the air, leaving behind a beautiful coating of gum. That is how all varnishing is done, the alcohol forming the vehicle in which the solid gum is for the moment carried and by which it is applied. It is far and away the most suitable liquid for the purpose, and without it varnishing would be very difficult and unsatisfactory. Hence one need for alcohol, to carry on the war.

Then again some of the most important explosives are solid or semi-solid, and yet they require to be mixed in order to form the various "powders" in use by our gunners. The best way to bring about this mixture is to dissolve the two components in alcohol, thereby forming them both into liquids which can be readily mixed. Afterwards the alcohol evaporates; indeed, one of its great virtues for this and similar purposes is that it quietly takes itself off when it has done its work like a very well-drilled servant.

What then is this precious liquid and how is it produced? In order to answer that question it is necessary first to state that there are a whole family of substances called "alcohols," all of which are composed of carbon, hydrogen and oxygen in certain proportions. There are also a number of kindred substances also, not exactly brothers but first cousins, so to speak, which because of their resemblance to this important family have names terminating in "ol."

They owe their existence to the wonderful behaviour of the atoms of carbon. In order to obtain some sort of system whereby the various combinations of carbon can be simply explained chemists picture each carbon atom as being armed with four little links or hooks with which it is able to grapple, as it were, and hold on to other atoms. Each hydrogen atom, likewise, has its hook, but only one instead of four.

Now it is easy to picture to ourselves an atom of carbon in the middle with its hooks pointing out north, south, east and west with a hydrogen atom linked on to each. That gives us a picture of the molecule of Methane, the gas which forms the chief constituent of coal gas such as we burn in our homes. Methane is also given off by petroleum and it is the cause of the explosions in coal mines, being known to the miners as "firedamp." It is the first of a long series of substances which the chemist called paraffins. The first, as you see, consists of one of carbon and four of hydrogen. Add another of carbon and two more of hydrogen and you get the second "Ethane." Add the same again and you get the third, Propane, and so on until you can reach a substance consisting of thirty-five parts of carbon and seventy-two parts of hydrogen. All we need trouble about, however, is the first two, Methane and Ethane.

We have pictured to ourselves the molecule of methane: let us do the same with ethane. Imagine two carbon atoms side by side linked together or hand in hand. Each will be using one of its hooks to grasp one hook of its brother atom. Hence each will have three hooks to spare on to which we can hook a hydrogen atom. Thus we get two of carbon and six of hydrogen neatly and prettily linked up together. The atoms form an interesting little pattern and to build up the various paraffin molecules with a pencil and paper has all the attractions of a puzzle or game. All you have to do is to add a fresh atom of carbon alongside the others and then attach an atom of hydrogen to each available unused hook. If you care to try this you will get the whole series, each one having one atom of carbon and two of hydrogen more than its predecessor.

If you mix together a quantity of methane and an equal quantity of chlorine, which I have shown you in another chapter how to get from common salt, a change takes place, for in each molecule of methane one hydrogen atom becomes detached and an atom of chlorine takes its place. How or why this change occurs we do not know. It is a fact that the chlorine has this power to oust the hydrogen and there we must leave it, for the present at any rate. The substance so formed is called methyl chloride.

In another chapter reference has been made to that substance which is made from common salt and which is so important in so many manufactures called caustic soda. If we bring some of it into contact with the methyl chloride the chlorine is punished for its rudeness in displacing the hydrogen; it is paid back in its own coin, for it is in turn displaced not this time by a single atom but by a little partnership called "hydroxyl" one atom of hydrogen and one of oxygen acting together. We can again form a neat little picture of what happens. The oxygen atom has two hooks, one of which it gives to its friend the hydrogen atom and thus they go about hand-in-hand, the oxygen having one unused hook with which to hook on to something else. In this case it hooks on to that particular hook from which it pushes the chlorine.

We have thus seen two changes take place. First, the hydrogen is displaced by the chlorine: then the chlorine is turned out and its place taken by the hydroxyl. And during both these changes the central carbon atom and its three hydrogen partners have remained unaffected. Those four atoms are called the methyl group, and a methyl group combined with a hydroxyl group forms methyl alcohol.

Similar changes can be brought about with Ethane as with Methane, and in them the two carbon atoms and the five hydrogen remain unchanged, whence they too are regarded as a group, the Ethyl group, and an ethyl group hooked on to a hydroxyl group gives us a molecule of ethyl alcohol.

These groups of which we have been speaking never exist separately except at the moment of change, but in the wonderful changes which the chemist is able to bring about the atoms forming these groups seem to have a fondness for keeping together and moving together from one substance into another. In a word, they behave as if they were each a single atom and they are called by the name of Radicles; the word simply means a little root.

The methyl radicle and the ethyl radicle, since they form the basis of two of the paraffin series, are called paraffin radicles, so that we can describe this useful alcohol as a paraffin radicle with a hydroxyl radicle hooked on to it. If we use the methyl radicle we get methyl alcohol: if we use the ethyl radicle we get ethyl alcohol.

Now ethyl alcohol is the spirit which is contained in all strong drink. Whiskey has as much as 40 per cent and brandy and rum about the same, while ale has only about 6 per cent. All of them may be regarded as impure forms of ethyl alcohol, the various impurities giving to each its particular taste.

Ethyl alcohol, too, is what is sold at chemists' shops as "spirits of wine," where also we can purchase that which is familiar as "methylated spirits," whereby there hangs a tale.

All Governments regard alcohol for drinking as a fit subject for taxation. When anyone buys a drink with alcohol in it a part of what he pays goes to the Government in the form of duty. On the other hand, when alcohol is used for trade purposes, for making varnish or something like that, there is no reason whatever why it should be charged with duty. But if the varnish manufacturer is to have alcohol duty-free what is to prevent him from using some of it for drinking?

To get over the difficulty, that which is supplied to him or to anyone else for trade purposes is deliberately adulterated so as to make it so extremely nasty that no one is likely to want to put it in his mouth.

It so happens that methyl alcohol, while as good as the other for many purposes, is horrible to the taste and so it forms a very convenient adulterant for this purpose. Therefore, when methylated spirit is sold to you for drying your photographs, the chemist gives you ethyl alcohol with enough methyl alcohol in it to make sure that neither you nor anyone else will ever want to drink it.

That, then, is alcohol: a near relative of paraffin oil and also of coal gas, yet it is from neither of these that we get it. The changes described above enable you to realize what it is, but they do not tell how it is made in large quantities.

Ethyl alcohol is obtained from sugar by the employment of germs or microbes. Any sort of sugar will do: it need not be sugar such as we eat. In practice the sugar is usually obtained from starch, that very common substance which forms the material of potatoes, grain of all kinds, beans and so on. There is a kindly little germ which will quite readily turn starch into sugar for us if we give it the chance.

The maltster starts the process. He gets some grain, and spreading it out in a damp condition upon his floor sets it a-growing. As soon as it has just started to grow, however, he transfers it to his kiln, where by heating it he kills the young plants. As is well known, every seed contains the food to nourish the little growing plant until it is strong enough to draw its supplies from the soil and the food thus provided for the young wheat plant is starch, which, when it is ready for it, it turns into sugar. The little shoot lives on sugar and the maltster and distiller conspire to steal that sugar intended for the baby plants and turn it into alcohol.

So the little plant liberates by some wonderful means a material called diastase, which has the power of changing starch into sugar. It does it, of course, for the purpose of providing its own necessary food, but the maltster does not want the process to go too far: he only wants to produce the diastase, and that is why he kills the plants, after which he has finished with the matter and hands the "malted" grain or "malt" over to the distiller for the next process.

The distiller mixes the malt with warm water, whereupon the diastase commences the conversion of the starch of the grain. At this stage fresh grain may be added and potatoes, indeed almost anything composed largely of starch for the diastase to work upon. The process goes on until, in time, the liquid consists very largely of sugar dissolved in water, which is strained away from what is left of the grain, etc.

Malt sugar is very similar to, but not quite the same as, cane sugar. It consists of twelve parts of carbon, twenty-two of hydrogen and eleven of oxygen. It is an interesting little puzzle to sketch those atoms out on paper, each with its proper number of hooks, and see how they can be combined together. Malt sugar, milk sugar and cane sugar all consist of the same three elements in the same proportions and the difference between them is no doubt due to the different ways in which the atoms can be hooked up together.

Yeast is next added to the liquid, upon which the process of fermentation is set up, the tiny living cells of the yeast plant producing a substance which is able to change the sugar into alcohol.

The alcohol thus formed is, of course, combined with water, but it can be separated from it by gentle heating since it passes off into vapour at a lower temperature than does water. Thus the vapour first arising from the mixture is caught and cooled whereby the liquid alcohol is obtained. This operation, called fractional distillation, has to be repeated if alcohol quite free from water is required, in addition to which the attraction which quicklime has for water is called into play to coax the last remnant of water from the other.

And now, how about the methyl alcohol? That is obtained in quite a different way, by heating wood and collecting the vapours given off by it. Hence it is often called "wood spirit."

As a matter of fact, at least two very valuable substances are obtained by this operation, methyl alcohol and acetone.

The vapours given off by the wood are cooled, whereupon tar is formed while upon it there floats a dark liquid which contains the wood spirit, acetic acid and acetone.

To capture the acetic acid lime is added to the mixture, and since there is a natural affinity between them, the acetic acid and lime combine into a solid which remains behind when the whole mass is suitably heated. What comes over in the form of vapour is a mixture of water, acetone and wood spirit. The former is enticed away by the use of quicklime, while the other two are separated by the process of fractional distillation already referred to.

Now let me ask you to form another little picture, either in your mind or with paper and pencil. Imagine two methyl radicles, each, let me remind you, a carbon atom with three hydrogen atoms hooked on and one spare hook. Also imagine one atom of oxygen with its two hooks outstretched like two arms, and just link one radicle on to each. Then you have the picture of methyl ether. All the ethers are formed by taking two of the paraffin radicles and linking them together by means of the two hooks of an oxygen atom. The ether which is so largely used in hospitals for wounded soldiers is ethyl ether, consisting of two ethyl radicles joined by oxygen. How it is made we will come to in a moment, but as you see already it is a close relative of alcohol.

Now from methyl ether take away the central oxygen and in its place put carbon. This atom will have two hooks to spare which it can employ to hold on to the two hooks of the oxygen. The result is a molecule of acetone.

This is used as a solvent in a similar manner to alcohol for many purposes, and there was a great demand for it no doubt during the war.

One interesting use of acetone is in connection with the gas acetylene. Of great use both for lighting and also in conjunction with oxygen for welding and cutting metals, this gas suffers from the disadvantage that it cannot be compressed into cylinders and carried about as oxygen can. It can, however, be dissolved in acetone. The cylinders in which it is carried are therefore filled with coke saturated with acetone and then when the acetylene is pressed in it dissolves, coming out of solution again as soon as the pressure is released. In this dissolved condition it is quite safe to carry about.

For a moment let us turn back to the commencement of the chapter to the subject of methane. When mixed with chlorine, it will be remembered, one hydrogen atom gave place to a chlorine atom. If the process be repeated another hydrogen atom will be displaced in the same way, while a further repetition will result in the removal of a third, when there will be a carbon atom in the centre with three chlorine and one hydrogen hooked on to it. With that picture in your mind's eye you will be contemplating the molecule of that wonderful and beneficent substance, chloroform. When we think of the numberless operations which have been carried out by the surgeons in the course of this last war we realize a little how great is the total sum of pain and suffering which has been saved through the agency of this substance, this simple neat little arrangement of five tiny atoms.

Now that again is obtained in manufacture from alcohol. Alcohol, bleaching powder and water are mixed and then distilled, by which of course is meant that the mixture is evaporated by heat and the vapour collected and cooled back into liquid again. The liquid so obtained is chloroform.

Hardly less important than this, in our military hospitals, is ether, to which reference has already been made. It, too, is manufactured from alcohol. The alcohol, together with sulphuric acid, is placed in a still and heated, the vapour given off being led to another vessel and there condensed. The liquid thus obtained is ether and so long as the supply of fresh alcohol is kept up the production of ether goes on continuously.

The sulphuric acid does not disappear and so does not need to be replaced, from which it would appear as if it might just as well not be there, but that is not the case. It plays the part of what is called a "catalyst," one of the curiosities of chemistry. There are many instances in which two things will combine only in the presence of a third which appears to be itself unaffected. This third substance is a catalyst. It reminds one of the clergyman at a wedding who unites others but remains unchanged himself.

In conclusion, one may mention that many of the medicines with which our injured men were coaxed back to health and strength owe their existence to alcohol, for many drugs are obtained from vegetable substances by dissolving out a part of the herb with alcohol.

Thus, as a drink, it is unquestionably very harmful. Indeed, in that way it probably kills more people per year than its use in the manufacture of explosives caused in the worst year of the war. Yet it also furnishes chloroform, ether and medicinal drugs and performs a whole host of useful services to mankind. Finally, if oil and coal should ever run short it is quite prepared to run our engines for us. Truly it is a wonderful substance.