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 wa-tery 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.
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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[52] 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 molasses, 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 put-
ting 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 circumstances 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 quantity 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[53] 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. After immersion the film is wet, not with water merely, but with a mixture of a lot of spirit and a little water. Hence the speed with which it evaporates. And the non-inflammability of the mixture is due to the presence of the water.
Methylated spirit only differs from the alcohol in alcoholic beverages in that something is added to make it undrinkable. Owing to the craving for it, which is so widespread, and the doubtful effect which it has on certain citizens, most states regard it as pre-emi- nently a subject for taxation, thereby on the one hand bringing in a good revenue, and on the other discouraging its too free use. But those considerations apply only to drinkable alcohol. That which is to be used for industrial purposes is not in any way a legitimate object for taxation. Hence the problem arises of making a form of alcohol which shall answer all the needs of the industries which use it, and at the same time be so repulsive to the senses that no one can possibly drink it. This result is achieved by adding some of the methyl alcohol derived from the vapour given off by wood when heated. Commonly known as "wood spirit," this is so unpleasant that it renders the mixture of no use for drinking, and so it can safely be freed from taxation.
Unfortunately this spirit has less heating value than petrol. That means that a given quantity of each liquid will produce more heat in the case of petrol than in the case of alcohol. Indeed the difference is about two to one. Hence an engine to give out a certain horse-power would need to have its cylinders twice as big if it were to use alcohol instead of the other fuel. There is a certain compensa-tion, however, in the fact that alcohol is very easily compressible.[54] In modern internal combustion-engines much of the efficiency is due to the explosive charge which is drawn into the cylinder being compressed into a small space before it is fired. It was the discovery of the value of compressing the gas which made the gas-engine so formidable a rival to the steam-engine, and the wonderful performances of the Diesel engines are due very largely to the fact that the air is compressed in the cylinder to a very high pressure. The jet of oil burns in highly compressed air. And because of the facility with which alcohol can be compressed it is said to be more effective as a source of motive power than would be expected from its comparatively feeble heat.
Thus we may sum up the possibilities of the future. Coal, petroleum and their derivatives exist in limited quantities in the world, and so far as we can see the vast drafts which we are taking from them are not being replaced, indeed at this stage of the earth's development cannot be replaced, by any more. Sooner or later we must come to an end of them. Is it not comforting, therefore, to know that there is another source of fuel at hand, inexhaustible, since it can be produced as needed. We have only to set the sun and the ground to work to produce grain, rice, potatoes, or any of the myriad substances which contain starch, and from that, by simple and well-known processes, we can obtain a cheap, safe and reliable fuel. Indeed there seems nothing but the ultimate loss of sunlight, countless millions of years hence, which can ever check the supply of this valuable commodity. What has doubtless, in many cases, been a curse in the past may turn out to be the great boon of the future.
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[55] CHAPTER IV
SOME VALUABLE ELECTRICAL PROCESSES
Students of that branch of science known as physics are coming to the conclusion that electricity plays a much more important part in the universe than was supposed. They are led to believe that electrical attraction is the cement which binds together those exceedingly minute particles out of which everything is built up. Whether electricity binds them together or not, it is certain that electrical action can in some cases separate those particles, and this process of separation provides a means of carrying on some very remarkable and useful industrial processes.
Let us imagine a vessel filled with water to which has been added a little sulphuric acid, while suspended in it are two strips of platinum. There is a space between the strips, so that when their upper ends are suitably connected to a source of electric current that current flows from one strip to the other through the liquid.
That is an example of the apparatus for carrying out this electrical separation in its simplest form, and it will facilitate the further description if the names of various parts are enumerated.
The process itself is electrolysis; the liquid is the electrolyte, while the strips are the electrodes. The individual electrodes, again, have special names, that by which the current enters being the anode and that by which it leaves the cathode. It is not difficult to remember which is which if we bear in mind that the current traverses them in alphabetical order. Since, however, it