Professor Henry K. Benson, Chairman,

Division of Chemistry,

National Research Council,

Washington, D. C.

Dear Professor Bensen:

I have received two grants, of $900 and $1000 respectively, from the National Research Council. This money has been used in paying half the salary of an assistant, Dr. J. H. Sturdivant, working with me on the experimental determination of the electron distribution in crystals. The work done in this direction follows:

July 1930 to June 1931. An Astbury integrating X-ray photometer was designed and constructed, and calibrated for measuring the intensities of Laue photographs, and an apparatus for preparing Laue photographs at liquid air temperatures was constructed. A study of the theory of the reflection of X-rays was made to obtain an expression suitable for the Laue technique. It was then found that the available spectrometrically-measured intensities of reflection from simple planes reported in the literature are not sufficiently accurate, and Dr. Sturdivant, who had previously spent one month in Berkeley with Professor Allison studying ionization spectrometers, designed one especially adapted to our needs. This has not yet been constructed.

July 1931 to November 1931. One of the troublesome factors in the interpretation of intensity measurements is the correction for extinction. The discovery by Fox and Carr that a piezo-electrically oscillating quartz crystal reflects more strongly than a non-oscillating one suggested that sending supersonic waves through crystals might do away with primary extinction. Hence we have constructed an oscillating circuit, and are preparing Laue photographs of various crystals attached to the oscillating quartz crystal.

We are accordingly still rather far from the goal of accurate electron distributions. The preliminary investigations are, however, nearly complete, and after the construction of the spectrometer rapid progress is expected.

In addition, Dr. Sturdivant has devoted some time to another investigation, dealing with aluminum phosphate. He found aluminum phosphate, AlPO₄, be closely similar to quartz, SIO₂, having two forms, with a transition only 6˚ above that of quartz. This work will soon be published.

I hope that this report is satisfactory.

With best wishes, I am

Very sincerely yours,

Linus Pauling

LP:M