An attempt has been made to find other crystalline compounds analogous to the mineral realgar, AsS. The recorded characteristics of NS, and NSe and NTe suggested that these might be realgar-like crystals. Nitrogen sulfide, the only one of this series to have received crystallographic attention, had previously been reported as monoclinic on the basis of a study of surface morphology, and orthorhombic on the basis of an x-ray study, the latter symmetry being made the groundwork for a proposed crystal structure. In the present paper, new and different x-ray results are reported, based upon an equi-inclination Weissenberg study. The correct characteristics are:

Crystal system: monoclinic  
Crystal class: 2/m = C2h  
Simplest cell:   
 a = 8.78 Å  
 b = 7.14  
 c = 8.645  
 β = 87°39′  
Formula weights NS per cell: 16 
Diffraction symbol: 2/mP21/n 
Space group: P21/n 
Crystal system: monoclinic  
Crystal class: 2/m = C2h  
Simplest cell:   
 a = 8.78 Å  
 b = 7.14  
 c = 8.645  
 β = 87°39′  
Formula weights NS per cell: 16 
Diffraction symbol: 2/mP21/n 
Space group: P21/n 

The general characteristics of this cell are identical with those of the realgar cell, but the cells of the two compounds differ markedly in dimensional aspects. This difference is attributed to the difference in radii of the N and As atoms, and the two compounds are believed to be isostructural. Jaeger and Zanstra’s crystal structure proposed for nitrogen sulfide must be incorrect because it is based upon an erroneous symmetry.

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