Dissolution patterns of polydisperse powders: oxalic acid dihydrate

The dissolution of oxalic acid dihydrate crystals of log-normal particle-size distribution in 0.1 N HC1 was studied. A biphasic cube root dependence was found; the slopes of the initial cube root plots were consistent with theory based on dissolution of isometric, isotropic particles where assumptions were made of: (a) sink conditions, (b) particle-size-independent solubility, and (c) particle-size-independent film thickness of adsorbed liquid layers.

Nonsink dissolution rate equations

In spite of the fact that film theory is based on severe assumptionss, it is shown to be a good working model. The Niebergall-Goyan equation, the Short-Sharkey-Rhodes equation, and the Pothisiri-Carstensen equation-all based on simple film theory-are shown to hold through 80-90% of the dissolutin process for p-hydroxybenzoic acid and sodium chloride, both at values below and above the amount necessary to saturate the dissolution medium. Deviations are attributed to experimental difficulties and to improper definition of monodisperseness rather than to the assumptions made in the theory.

New polyene antifungal antibiotic produced by a species of Actinoplanes

A new species of Actinoplanes, which has been deposited with the designation NRRL 5325 at the Northern Utilization Research and Development Division of the U. S. Department of Agriculture, produces a polyene antifungal complex designated as Sch 16656. The complex, consisting of one major and three minor components, is isolated from the fermentation broth by a solvent extraction procedure and purified by precipitation methods. The major component is a heptaene and is highly active in vitro and in vivo against Candida albicans. It is active also against strains of Torulopsis and is significantly more potent orally than candicidin in mice against Candida infections.