Linus Pauling: I can tell an anecdote, something that happened to me when I was about 13 years old
and had just developed an interest in chemistry. I already had an interest in physics,
and geology, mineralogy before then. In Portland, I was walking along one evening
in the rain, holding an umbrella. The street lights were arc lights so that the light
came from a rather small source, a quarter of an inch in diameter perhaps, the arc
between the two carbon electrodes. And I was 150 feet away, saw the arc light through
the fabric of the umbrella. I noticed that there was a rainbow, a spectrum of light,
violet, indigo, blue, green, yellow, orange, red, out to one side of this light and
also on the opposite side and above and below and four others at 45-degree angles.
And I wondered "what is it that causes that?" It took me a couple of years to learn.
I, I wasn't in the habit yet of trying to find out things by reading, I waited until
I had the course in physics and then learned that as the rays of light come through
and go through the different holes in the fabric they're separated a little from one
another so that the path length is a little different. And for some differences in
path length, equal to the wavelength of the light, you get a strengthening of the
color. And for other colors, slightly different wavelengths, these waves interfere,
they balance one another out. Consequently you get the different colors showing up
at different angles off from the central beam.
Now, x-rays it turned out, have about the same wavelength as the distances between
the atoms in the crystal. Consequently if you shine a beam of x-rays at the crystal
you get this sort of spectrum of x-rays caused by the three-dimensional lattice of
the atoms, which is similar to the two-dimensional crossed grating of the fibers in
the fabric of the umbrella. And the theory is quite straight-forward, sometimes difficult
to apply if you have a complicated crystal. Well this is really wonderful. I had been
interested in the question of why different chemical compounds, or even elements,
have different properties. What is it about them that causes sugar to be sweet and
salt to be salty? Well that's a rather complicated problem and we don't know the complete
answer now because it involves the structures on the tongue, the tastes buds, that
we're still somewhat ignorant about. But I could ask, why is it that steel is strong?
Or, I was interested in metallurgy. I, in fact, my first year had a course in forging,
made a horse shoe and a miner's hammer or pick, with which, a geologist's hammer they're
called and made various other chisels and even a knife for myself, a butcher knife.
I was interested in the phenomena associated with metallurgy. Why is it that pure
iron is rather soft? Why, a wire of pure iron can be bent very easily. If you put
in a little carbon, just one-percent of carbon, then you can get a very hard steel
that approaches diamond in hardness. Or at least approaches one of the somewhat less-hard,
but still hard metals such as, minerals, such as ruby or sapphire.
So, I was very much interested in these questions and I wanted to know what the structures
of crystals were. In the first three months, two months, that I was a graduate student
I prepared a dozen crystals. I read the crystallographic literature, which was quite
extensive, and selected out various substances that formed crystals that experience
had shown might be amenable to successful attack by the x-ray diffraction method.
And with Professor Dickinson supervising me when it came to the x-ray part I, in my
little laboratory, would synthesize and crystallize one substance after another and
then using the methods that he showed me, start to determine the structure. And I
was disappointed twelve times. The first twelve substances that appealed to me, whose
structures I wanted to determine, turned out to be more complicated than the existing
techniques could encompass. Then we succeeded. Professor Dickinson got a mineral,
molybdenite, and we made the x-ray pictures and analyzed them. I had soon started
making some other substances whose structures I could determine. Then I was off, I
made I don't know how many, I counted them up once.