MOLECULES IN MOTION
September 17, 1944
I would like to take away some of the mystery that surrounds chemistry. Most people think of it only in terms of a laboratory and are impressed and perhaps awed by the test tubes, chemical balances, peculiar smells and numerous bottles with their mysterious labels. Chemistry is everywhere and everything: it is the air we breathe, the water we drink, the food we eat -- it is the mountains, the trees and our own selves. And every home has a chemical laboratory -- the kitchen!
Chemistry is really the science of molecule building. Perhaps there is no other science or industry in the world where there are so many promising frontiers. Our synthetic rubber program is a great tribute to both the science and the industry. When we speak of a “molecule,” we are referring to groups of atoms -- such as hydrogen, oxygen, carbon etc. Water is made up of two hydrogen and one oxygen, table salt is one sodium and one chlorine, and sugar is formed from atoms of carbon, hydrogen and oxygen. But the majority of us haven’t a very good mental picture of a “molecule,” so let’s look at it this way. Suppose we were in an airplane three or four thousand feet in the air looking down on a parade of soldiers going down a street. From that height, we would get an impression of a solid mass moving along. But if we came down to about 100 feet, we would see this mass is simply groups of individuals walking along in military order. And the analogy holds true with any substance -- normally we view a substance as though from a great distance. Most molecules are too small to ever be seen as individuals.
When a gun is fired, the molecules of the powder are changed to other forms with the sudden release of energy. It is important in this case that this change called explosion take place very quickly. The greatest distance we could shoot in the last war was about 80 miles. Now we can take projectiles much farther but in a different way -- an internal combustion engine can drive an airplane over great distances and then drop bombs. The fuel we use to propel the plane is a chemical substance made up of atoms of hydrogen and carbon. The only difference, as contrasted to the explosive used in a gun, is that the combustion of fuel in an airplane engine should be much slower. In our studies, we found many years ago that by adding very small amounts of compounds such as tetraethyl lead to the fuel, we could slow down the rate of combustion, thereby opening the way to increasing engine power and improving economy.
At the same time, our investigations took us into the study of the specific structure of fuel molecules. We found that when the carbons and hydrogens are hooked together as long chain molecules, they “knock” very badly -- that is they burn too fast; while the more compact form of the same number of atoms burns slower and “knocks” very little.
In the course of these investigations in 1926, we tried a very compact compound known later as Triptane which was made for the first time in 1922 by a Belgian, Chavanne. The results of the tests were outstanding and we put it at the top of our list for further study. After years of research, our chemists have developed a method of making this material quite pure, but the process must remain secret until after the war.
In order to evaluate just what has resulted from this investigation of such a special fuel molecule, let us look at the performance of an aviation engine using different fuels. Suppose the engine is our 12 cylinder Allison. If we were to use ordinary automobile gasoline, this engine could develop about 500 horsepower. If we used the best automobile fuel, we could increase this to nearly a thousand horsepower, and using 100 octane or better aviation gasoline, the power might be increased to fifteen hundred. But when using only a 60% Triptane blend, the horsepower is raised to over 2500. In other words, by just rearranging the position of the hydrogen and carbon atoms in the molecule, great gains are made both in power and economy. The production of power is the combination of engine and fuel and not either one alone. It may be a disappointment to some to learn that you won’t be able to get this new fuel tomorrow, but someday, perhaps ten years from now, it may be available in the filling station pumps to match new high efficiency engines, which can be designed after the war.
We study fuels from the standpoint of the engine builder and not as fuel producers. We consider fuel as much a part of the engine as the pistons or crank shaft. This point of view helps us determine the road which our future researches should take, because what may be technically and commercially impractical today, may be easily made an everyday product in the not too distant future.