R. W. G. Wyckoff — Sodium Hydrogen Acetate. 193 



Art. XIX. — On the Symmetry and Crystal Structure of 

 Sodium Hydrogen Acetate, NaH(C 2 H 3 2 )2; by Ealph 

 W. G. Wyckoff. 1 



[Contribution from the Gates Chemical Laboratory of the California Insti- 

 tute of Technology, No. 17.] 



Introduction. 



This study of the structure of sodium hydrogen acetate 

 was undertaken in the attempt to find the arrangement 

 of the atoms in some organic compound. 



Sodium acid acetate was prepared by the long con- 

 tinued digestion of fused sodium acetate, glacial acetic 

 acid and acetic anhydride in sufficient quantity to remove 

 the small amounts of water which may be present. 2 It 

 was thus obtained in cubes which under the polarizing 

 microscope prove to be isotropic. Assignment to a par- 

 ticular class of symmetry on the basis of the ordinary 

 crystallographic evidence has never been made. 



The Study of the Structure of Sodium Hydrogen Acetate. 



Comparison reflection .spectra from the (100) face of 

 calcite and the (100) face of sodium acid acetate showed 

 three orders of reflection for the latter which stood in the 

 ratio of 2:3:4 (experimental conditions did not permit 

 of the first order registering itself). Measurements 

 upon these photographs combined with the density, p = 

 1.402, as determined by a flotation Westphal balance 

 method, gives the mean value 3.07 for the ratio m/n z ,m 

 being the number of chemical molecules within the unit 

 cube and n the order of the reflection. There are thus 

 either three or 24 chemical molecules of the composition 

 NaH(C 2 H 3 02)2 within the unit. The length of the side 

 of the cube having three molecules within it, as deter- 

 mined by these same measurements, is 7.98 9 A.U. (7.98 9 X 

 10- 8 cm.)! 



Several Laue photographs taken with the X-rays 

 nearly normal to the cube face of crystals from two dis- 



1 Member of the Staff of the Geophysical Laboratory of the Carnegie Insti- 

 tution of Washington. 



2 The writer is under obligation to Prof. H. J. Lucas and to L. M. Kirk- 

 patrick for some of these preparations. 



