Council of Canada. Technical assistance was rendered by Mrs. B. Krizsan and Mrs. A. Salios. P. A. Y. gratefully acknowledges financial support of a MacMillan Family Foundation fellowship.

1 l-Tungstovanado(IV)phosphate Anion pentaborane(9), it was hoped that, in addition to obtaining a /BB value for l-CH(Br)(CH3)BsH8, dehydrohalogenation of this product would be a successful route to the unknown species l-vinylpentaborane(9). Instead, the product has been determined to be 2-bromo-l-ethylpentaborane(9) by infrared and mass spectral analysis and nB nmr spectra. This product would be expected from a free-radical bromination if halogenation of the basal position on B5H9 proceeds by a free-radical mechanism as proposed previously.37

Abstract.A characterization of meet-irreducible elements and atoms in an implicative lattice is obtained and used to derive the following theorems. A complete lattice is implicative and every element has a meet-irreducible decomposition if and only if there are enough principal prime relative annihilator ideals to separate distinct elements. The MacNeille completion of an implicative lattice is an implicative lattice; furthermore the embedding preserves relative pseudocomplements, meet-irreducible elements and atoms.

No abstract

A characterization of meet-irreducible elements and atoms in an implicative lattice is obtained and used to derive the following theorems. A complete lattice is implicative and every element has a meet-irreducible decomposition if and only if there are enough principal prime relative annihilator ideals to separate distinct elements. The MacNeille completion of an implicative lattice is an implicative lattice; furthermore the embedding preserves relative pseudocomplements, meet-irreducible elements and atoms.