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increasing as the interatomic distances decrease, hence, as the density increases. The coulombic energies between nonclosest neighbors would be expected to be fairly large in substakces such as the borates. They are both attractions and repulsions, and both types increase as the density increases. It seems impossible to evaluate the net effect in any simple way and it will not now be attempted.Neglecting the possible effect of differences in the density dependence of the nonclosest-neighbor coulombic energy, increasing pressure should favor class C structures, with higher coordination numbers and higher densities, over class A structures of the same chemical composition. This is in line with the fact that the stable structure for boric oxide a t normal pressures is class A, while a high-pressure phase has a class C structure. NOBORU OHKAKU AND KAZUO NAKAMOTO ConclusionThe types of structons in known structures of anhydrous boric oxide and borates have been listed and compared. Certain regularities have been noted and related to stability factors. It has been found that the arrangements of boron and oxygen atoms almost invariably conform to a few "minimum sets" of structon types. The relative stabilities of different sets, as affected by overall composition and by the cation-oxygen arrangements, have been discussed in some detail. Factors affecting the stability of nonbridging oxygens (0') and oxygens with three boron neighbors (0'") have been especially considered. I t is hoped that this paper will serve as a basis for prediction of the structon types (and relative numbers of each) in crystals that have not yet been analyzed and in borate glasses. CONTRIBUTION FROM THE TODD WEHR CHEMISTRY BVILDIKG,Low-frequency infrared spectra (650-100 cm-l) have been obtained for isotopic pairs of some first-row transition metal oxinates (8-hydroxyquinolinates) of the types MQ2 (M = asa6ZNi, 6r,*5Cu, and64@Zn), MQ2.2H20 (M = 5 4 67Fe, 5s162Ni, and 64,68Zn), C U Q~.~H~O -C U Q Z .~D~O , and MQa (M = a4,57Fe) where Q denotes an oxinate anion Based on the observed isotopic shifts, the metal-oxygen and metal-nitrogen stretching bands have been assigned in the regions of 332-210 and 300-190 cm-1, respectively Structures of several metal oxinates have been elucidated from the number of isotope-sensitive bands and the general pattern of the spectra. The spectra of CoQ2 and its dihydrated derivative have been studied The spectra of a and p forms of anhydrous CuQp have been compared and discussed.

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