Oct. 4, 1921 abstracts: inorganic chemistry 391 



the mineral is found in quartz veins in some of the California locali- 

 ties, but its occurrence at Mono Lake in quartzite is similar to that 

 in the southeast Atlantic states. Fewer minerals are associated with 

 lazulite in the California localities, but those noted are also found 

 in the southeast Atlantic states. In Green Lake Canyon, i- near 

 Bodie, lazulite is developed in deep blue anhedra associated with quartz 

 and muscovite in a quartz vein; and in Breyfogle Canyon, ^^ Death 

 Valley, it is distributed as crystals and crystal aggregates of pale to 

 fairly deep azure blue in patches through a white quartz vein cutting 

 schist. At Mono Lake ^^ it is associated with rutile in bands in a white 

 quartzite. 



ABSTRACTS 



Authors of scientific papers are requested to see tbat abstracts, preferably prepared and 

 signed by themselves, are forwarded promptly to the editors. The abstracts should con- 

 form in length and general style to those appearing in this issue. 



INORGANIC CHEMISTRY. — The crystal structure of some carbonates of 

 the calcite group. Ralph W. G. Wyckoff. Amer. Journ. Sci. 50: 

 317-360. 1920. 



By the same general method that has been employed in studying caesium 

 dichloriodide and sodium nitrate, a unique solution has been obtained for the 

 crystal structures of calcite and rhodochrosite. Of the assumptions commonly 

 made in crystal-structure study, the only one required in this determination 

 was that the atoms reflect X-rays in an amount roughly proportional to 

 their atomic numbers. The structure of siderite was shown to be so nearly 

 the same as that of rhodochrosite as to be indistinguishable by the means at 

 hand. Magnesite was also found to give the same sort of pattern and hence 

 to have the same general arrangement of atoms as the other members of the 

 group. 



The positions of the oxygen atoms, as determined by the present method and 

 by the spectrometer results, are compared. In this particular case, the "nor- 

 mal" decline of intensities is in surprising agreement with the reflections. 

 Evidence is obtained from these crystal structures to show the existence of 

 groups of atoms, as carbonate groups, in the crystal. It is also pointed out 

 that unless every atom in the crystal is electrostatically charged, the outside 

 electrons of the atoms making up these crystals cannot be arranged at the cor- 

 ners of cubes. 



Some connections are pointed out between the development of faces on cal- 

 cite and its crystal structure, and a way is indicated of deciding the most prob- 

 able indices of a plane when they are in doubt. The bearing of these struc- 

 tures upon the question of what constitutes a series of isomorphous substances 

 is mentioned. 



A criterion is suggested for determining, in the case of an hexagonal crystal, 

 whether the fundamental unit is a rhombohedron or an hexagonal prism. 



" A. F. Rogers. Op. cit., p. 375. 



»» D. B. Sterrett. Op. cit., p. 1060. 



1* A. S. EaklE. Op. cit., p. 162. 



