CHEMISTRY. 279 



CHEMISTRY. 



Noyes, Arthur A., Massachusetts Institute of Technology, Cambridge, Massa- 

 chusetts. Researches upon (1) the properties of solutions in relation to the 

 ionic theory, and (2) the determination of the atomic structure of crystalline 

 substances by X rays. (For previous reports see Year Books Nos. 2-16.) 



The work described in last year's report on the potentials of the 

 copper cuprous-chloride and bismuth bismuth-oxychloride electrodes, 

 carried out with the assistance of Mr. Ming Chow, has been pubhshed. 



A thorough investigation has been made by Dr. C. L. Burdick and 

 Dr. E. S. Freed of the equilibrium conditions, at temperatures from 0° 

 to 75°, of the reaction 3 N02+H20 = 2 HNO3+NO, by determining 

 the pressures of the two nitrogen oxides which are in equilibrium with 

 nitric-acid solutions of various concentrations. This has thrown much 

 light on the problem of the absorption of nitrous vapors on a large 

 scale and the results are likely to be of importance in connection with 

 the war needs for manufacturing nitric acid. 



The research on the determination of crystal structure, referred to 

 in the last report, has been continued by Dr. Duncan A. Maclnnes 

 with the aid of Messrs. James A. Beattie and Arthur L. Davis. The 

 work has been directed mainly to developing a method by which the 

 intensities of the reflections can be accurately measured. In determin- 

 ing the structures of simpler crystals comparatively rough measure- 

 ments of the intensities suffice, but in studying the more complicated 

 atomic structures accurate determination of these intensities becomes 

 a matter of importance. Up to the present the intensities have been 

 assumed to be proportional to the deflections of the leaf in the elec- 

 troscope of the Bragg apparatus. This method can not give correct 

 results unless, among other things, the source of X rays is constant. 

 To eliminate this difficulty a modified Bragg apparatus has been 

 de\dsed, in which the X-ray beam strikes a second, reference, crystal, 

 and the reflected beam from this crj^stal affects a second electroscope. 

 The intensity of reflection of any order from any plane of a crystal can 

 thus be compared with that of the reference crystal. Provision is also 

 made for reproducing the deflections of the electroscope leaves by 

 applying measured electromotive forces, in terms of which the intensity 

 ratios can be expressed. 



Richards, Theodore W., Harvard University, Cambridge, Massachusetts. 

 Continuation of exact investigation of atomic weights and other physico- 

 chemical properties of elements and simple compounds. (For previous 

 reports see Year Books Nos. 2-16.) 



A part of the time and energy of the personnel of the Wolcott Gibbs 

 Memorial Laboratory was taken, during the earlier portion of the j^ear, 

 by important war work, which does not form a part of this report. 

 Throughout the year several army ofl[icers in the Sanitary Corps 



