Showing papers by "Takeru Higuchi published in 1960"

Theoretical analysis of diffusional movement through heterogeneous barriers

Abstract: A number of theoretical relations dealing with diffusion through heterogeneous barriers are presented and discussed. These are expected to be useful in predicting barrier behavior in formulations such as pharmaceutical and particularly protective ointments and films. A relationship has been derived which expresses the effective permeability constant, Pm, of a two phase mixture as a function of the volume fraction and the permeability of each phase. The effect of the shape of the particles on Pm is also considered. Where data are available, agreement with theory is satisfactory. The nonstationary state behavior of a two phase heterogeneous barrier is discussed in relation to the diffusion coefficient, partition coefficient, the volume fraction, and the particle size associated with each phase. It is shown that the effectiveness of one heterogeneous barrier may be greater than another for a given time of exposure while for a longer time of exposure the reverse may be the case. The effect of a “skin” or a coat of a third phase on the internal phase particle has also been examined. Finally, the situation in which simultaneous diffusion and absorption occur is discussed and an expression for the lag time has been derived for this case.

A general method for the chromatographic analysis of mono‐, di‐, and triglycerides and the mono‐ and diesters of ethylene glycol and polyethylene glycol

Abstract: A procedure for the chromatographic separation and determination of the ester mixtures of glycerin, ethylene glycol, and polyethylene glycol is presented. The adsorbent is silea gel, and the mobile phase is a series of solvents with increasing polarity. A procedure for quantitative determination of small amounts of monoglyceride present in a glyceryl ester mixture is presented. A solvent system different from that used for glyceryl and ethylene glycol ester mixtures was developed for ester mixtures of polyethylene glycols. The esters of polyethylene glycols with average molecular weights of 300–600 were shown to give the same chromatogram.

Investigation and Development of Protective Ointments IV.: The influence of active fillers on the permeability of semisolids

Abstract: The permeability of protective barriers containing adsorbent type fillers has been studied. It has been shown that the time for the nonstationary state permeation of these barriers can be significantly increased by the incorporation of small quantities of an active filler into the ointment base. The theoretical considerations of permeation through filled ointments have been presented with particular emphasis placed on the theory pertaining to barriers containing a filler with a high affinity for the penetrant. An equation relating the lag time to the concentration and maximum adsorptive capacity of this type filler and to the initial concentration of the chemical agent has been derived and verified by experimental procedures.

Investigation and Development of Protective Ointments III*: Adsorption characteristics of sarin from solutions

Abstract: The adsorption of sarin from n -heptane solutions by silica gels, alumina, bentonite, and certain carbonaceous adsorbents was studied. The results obtained have been interpreted according to the Langmuir adsorption isotherm. Of the various adsorbents tested, those of a silicaceous nature were found to be superior, exhibiting very strong adsorptive tendencies toward the fluorophosphate ester. A linear relationship was found to exist between the limiting adsorptive capacity and the specific surface area of the adsorbents. The average area occupied by a sarin molecule, furthermore, was found to be approximately 80 A 2 , irrespective of the adsorbent, a value in reasonable agreement with that suggested by a molecular model. Both of these relationships indicate that sarin is adsorbed primarily as a unimolecular layer.

The Physics of Tablet Compression XII*: Extrusion and Flow Studies on Tablet Ingredients

Abstract: A method for determining the force required to extrude materials through a hole in a tablet die by means of a high force hydraulic press is presented. Extrusion forces are given for various simple inorganic electrolytes and common tablet lubricants. Extrusion of organic tablet constituents was impossible with two exceptions. Either no extrusion could be obtained at the maximum force of the press, or implosion occurred. Mixtures of sodium chloride and potassium chloride, and sodium chloride and magnesium stearate were extruded and semiempirical equations expressing behavior were evolved. Resistance to extrusion seems to correlate with the hardness of the materials under test.

The complexing tendencies of cyanocobalamin with inorganic compounds. Heteromolybdates and heavy metal chlorides

Abstract: The interactions of vitamin B 12 with numerous inorganic compounds have been investigated. Nine of the compounds studied yielded slightly soluble adducts with cyanocobalamin. These were phosphotungstic and pnosphomolybdic acid, the sodium, nickel, and manganese salts of phospho-12-molybdic acid, and the chlorides of gold, platinum, and palladium. Several of the reagents caused a change in the absorption spectrum of the vitamin in the system. This effect was found to be a function of the concentration of the reagent, but independent of hydrogen ion concentration.