A quantitative chemical distribution of five elements in several undecalcified sections of teeth was determined by the electron microprobe method. The calcium (Ca)! phosphorus (P) weight percent ratios were determined in scans through the enamel and dentin, and characteristic curves for the concentration of the trace elements magnesium (Mg), sodium (Na), and chlorine (Cl) were obtained.The electron microprobe permits the qualitative and quantitative analysis of elements in a continuing or spot scan of an extremely smooth dental or other mineralized surface. This instrument has been widely and successfully used in the fields of metallurgy and geology and in the study of semiconductors. Smith and co-workers'-5 have developed correction formulae for quantitative analyses of chemically complex systems and have shown that values obtained are accurate within 1-5%.Several laboratories have been doing biological analyses using the microprobe from the time it was first marketed in this country. The earlier work was primarily on samples that could be analyzed for elements heavier than sodium and was generally limited to biologically hard parts such as bone.6 Hoerman et a17 have reported the uptake of tin and fluorine in human enamel in situ by the topical applications of stannous fluoride. Tin concentrations were determined by the electron microprobe, and fluorine (F) determinations were made chemically. Their report demonstrates the use of the electron probe for the analysis of certain elements in calcified tooth sections.Frank, Capitant and Gonis reported electron microprobe analyses of Ca, P, and Cl in anorganic tooth tissues impregnated with KI to establish uniformity in density, espe-
SYNOPSIS IN INTERLINGUA TRANSPORTO MOLECULAR IN MICRO-VOLUMINES SIMULANTE AREAS DE RETENTION SALIVARI.In spatios restringite, solutiones es retenite e protegite contra displaciamento per capillaritate. Le transport in tal areas es multo lente quando le solution del area de retention e le medio circumjacente es iso-osmotic. Differentias del concentration osmotic inter solutiones interne e externe esseva utilisate pro determiner le velocitates del transport. Esseva constatate que tal differentias osmotic es multo efficace in le transport de massa. In un micre compartimento le proportion del existente grande superficie con le micre volumine pare esser un obstaculo pro le alteration o le protection del parietes continent si un transport de massa non occurre frequentemente.Molecules and ions in solution diffuse very slowly, without aid from physical forces other than random molecular motion even in large vessels. Reported data' reveal the diffusion of a 53 mM aqueous solution of KCl into pure water at 100 C. to be 1.27 cm.'/day and a 2.9 mM solution of sucrose at 120 C. to be 0.254 cm.2/day. It appears as though these rates of diffusion for such low concentrations of the compounds are influenced very little, if any, by osmotic or other physical forces.Such slow transport of molecules and ions by diffusion alone was demonstrated by Besic2 in narrow space arrangements. In each experiment two similar steel spheres were immersed in a HCl solution and immediately brought into contact with each other for the duration of the experiment. As the spheres were brought into contact in this manner, the solution trapped in the narrow space surrounding the contact point was similar to the bulk of the exterior solution. The amount of the solution within the narrow area between the spheres was so small compared with the great area of the surfaces of the spheres bounding this region (large S/V ratio) that the HCl it contained was rapidly consumed without producing a grossly visible corrosion of the steel surfaces similar to the corrosion seen outside the contact point areas. Eventual visible corrosion occurred after sufficient acid had
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