I have supervised the advanced study and research work of Mr. Albrecht during the past three years. Mr. Albrecht has a thorough training in chemistry, and a good understanding also of physics and mathematics and related subjects. He has done satisfactory work in graduate courses at this Institute. As a research man he has mastered the difficult field of the x-ray study of the structure of crystals, and he is publishing in the May issue of the Journal of the American Chemical Society, in collaboration with Dr. R. B. Corey, a very important paper on the crystal structure of glycine.

Chairman, Division of Chemistry

California Institute of Technology Pasadena, California

April 4, 1934

April 12, 1934.

Dr. W.E. Bleick,

Institute for Advanced Study,

Princeton, New Jersey.

Dear Sir:

I wish to point out that you have overlooked Sherman's treatment of the proton affinity of ammonia in his extensive discussion of crystal energy (Chem. Rev. 11, 94-170 (1932), especially pp. 150-152). Using the same method as yours, except for the small van der Waals term, he obtained 206.8 kcal/mole, in nearly exact agreement with your 206.4. Of course there is considerable cancellation of errors in any such treatment.

I know of no justification for your statement that one of the four neighbors of an ion in NH₄F is closer to it than the other three. The only structure investigations with which I am familiar place the value of the parameter at 3/8. Have you done some unpublished x-ray work, causing you to disagree with my explanation of the 14 kcal excess crystal energy of the substance (published by Sherman on p. 152) ?

Very truly yours

[handwritten] LP