HOW SMALL IS A MOLECULE? R E ROSE, E I. DU PONT DE NEMOWS & CO, INC, WUMINGTON, DELAWARE
If a human being could be reduced to the size of a molecule, and yet retain his faculties and senses, the world about him would look so different that i t would seem an entirely new universe, not one single thing would remain unaltered. No one can actually become the size of a molecule but many of us can train ourselves to see molecules with our mind's eye. This is what we do when we become chemists and physicists. How small is a molecule anyway? They are not all the same size, but even the largest is so much smaller than anything you can see that it is difficult to realize how minute they are. Of all the ways of defining the . size of molecules, I think this one appeals to me most: Suppose you draw a glass of water from the tap, and suppose that you are able in some miraculous manner to mark each molecule as a rancher brands his calves, and after having done this you empty the glass of water into the drain. Then you wait, and you wait long enough to allow that glass of water to mix uniformly with all the water in the world, in oceans, rivers, lakes, clouds, and animals and plants. You would have plenty of time to rest, because it would take a good many centuries. When the mixing is complete, if you draw a glass of water again and looking through pick out the molecules that you had marked you would find 2000 of them in the glass of water. You might think this just a chance, so you would draw another glass of w ~ t e r again , you would find 2000. Not believing this evidence you might gather rain water or go to the beach and take it from the ocean, or from a running brook. Always you would find 2000 of these original molecules in each glass of water, no matter where you get it from, whether in this country, or the arctic, or the tropics. In other words the concentration of marked molecules in all the waters of the world would become 2000 per glass, and all these molecules were actually in the original glass taken by you. If you could take the water out of your own body, you would find no less than 4S0,000 marked molecules in it, and if you could perform the same test on His Majesty, you would find the King of England had just as many. This in itself sounds more amusing than valuable, but it is because the chemist has found out just such things about molecules that he has been able to make cotton linters and wood pulp into rayon, coal tar into dyestuffs, steam and coke into wood alcohol, carbolic acid into resins, the casein of milk into billiard balls, and do hundreds of other things that make it easier for us to live in comfort. Because the chemist thinks in terms of these minute molecules he is always thinking of turning one thing into another, n i t as the engineer does by putting it in a machine but by taking the component molecules and rearranging them.
