Specific Turbidity Research Articles

Influence of polydispersity and assumed distribution on functional dependences of light scattering transmission methods

In the study of the effect of polydispersity and assumed distribution on functional dependence of light scattering transmission methods the principal inconvenience in application of Stevenson-Heller-Wallach distribution was found. But logarithmic distribution of negative order gave logically running system of working curves characteristic for the specific turbidity and turbidity ratio methods. The conditions were pointed out, under which the working relationships valid for monodisperse system in particle size determination can be used.

Radiolytic Reduction of Colloidal Silver Bromide

Colloidal silver bromide, in aqueous suspensions containing ethanol, i-propanol or acetone, is reduced to the metal and HBr upon absorption of ionizing radiation. The reaction has been studied by measurement of electrical conductivity in suspensions of particles of mean radius, r, as characterized by specific turbidity measurements. Electron microscopy showed a close correlation between particle population and surface area in a real suspension of primarily cubic particles and those in the suspension described in terms of spherical particles of radius r. The reaction rate is proportional to the surface area. For a suspension containing 10/sup 10/ particle per ml with an apparent mean radius of 54 nm and at pH 3.5 in 0.15 M ethanol, the G value is 1.1. The magnitude of the rate is consistent with either a homogeneous reaction of Ag/sup +/ and molecular AgBr or a heterogeneous reaction at the particle surface. Pulsed radiolysis experiments suggest the latter mechanism.

A simple method for determination of the average particle size of coarse suspensions from measurements of apparent specific turbidity

If the turbidity of a suspension of large spherical polydisperse particles is independent of the wavelength of light, the apparent specific turbidity, as measured by an inexpensive commercially available spectrophotometer, is inversely proportional to the average radius of the particle size distribution. It is shown experimentally that this relation holds for suspensions of monomodal polydisperse styrenedivinylbenzene copolymer latices of average radius from 12 to 50 μm. This observation permits development of a quick method for determination of the various average particle sizes of coarse monomodally polydisperse suspensions from apparent specific turbidity measurements using a simple spectrophotometer such as the Spectronic-20. Attempts to verify similar relations for the determination of the average floc size of suspensions of silica and carbon black were unsuccessful, since it was not possible to obtain comparison values of the floc size distributions by the Coulter Counter because of extensive deflocculation of the aggregates on passage through the aperture.

Clogging in Surface Spreading Operations for Artificial Ground‐Water Recharge

Clogging is a complex phenomenon dependent upon many variables. For the conditions studied it is essentially a surface‐sealing process. When turbid water contains a range of grain sizes, clogging is initiated by the deposition of a surface layer that is graded because of the gravitational segregation of heavier particles. Most of the clogging results from the straining of finer particles from the flowing water by the graded depositional layer. An equation was developed which predicts accumulated water quantity versus time relationships for several concentrations of a specific turbidity. Even coarse‐grained porous media clogged at turbid water concentrations as low as 50 ppm.

Studies on the Proteolytic Action of Dairy Lactic Acid Bacteria

Intracellular protease (IPLB) of Streptococcus cremoris was extracted from the cells, which were cultivated in liquid media, by momentarily disrupting between two disks by high pressure.The hydrolyzing modes of αs-, crude k-, β-, and whole casein by IPLB of Str. cremoris or rennet were observed through the released amounts of tyrosine, sialic acid, NPN, and calcium insensitive substance. Relative specific turbidity of casein solution and dissymmetry coefficient of casein were measured. Particle weight and UV absorption spectrum of each high molecular hydrolyzate of whole casein were also determined.Among four kinds of casein fractions, αs- or crude k-casein was most easily hydrolyzed by IPLB of Str. cremoris or rennet. Relative specific turbidity of crude k-casein solution was remarkably, but those of αs-, β-, and whole casein slightly increased by the action of IPLB of Str. cremoris or of rennet. Changes of dissymmetry coefficients were negligibly induced by these two enzymes. Absorption spectrum of IPLB...

The stability of acid-soluble chromosomal proteins from avian erythrocytes

The stability of avian erythrocyte histones was examined under the conditions of extraction, chromatography, electrophoresis, and storage, in order to avoid degradation during these operations. Since turbidity in trichloroacetic acid (TCA) was used as a measure of histone integrity, optimal conditions for quantitative assay were established as follows. One volume of histone sample was mixed with five volumes of 1.1 M TCA at room temperature, and the optical density at 400 mμ was measured after 25 min. The relation between turbidity and protein concentration was linear from 0.03 to at least 0.3 mg histone per milliliter and was not related to the kind of histone, except for the lysine-rich fraction which showed slightly less specific turbidity. Under these conditions turbidity was not sensitive to concomitant solutes such as guanidinium chloride, acetic acid, and dilute buffers and acids.With turbidity as the criterion of protein integrity, it was confirmed that brief manipulation in the cold is desirable in most media, including the dilute acids used for extraction. Nevertheless, chromatography at room temperature in concentrated solutions of guanidinium chloride or acetic acid appears to be tolerably safe. The effect of these conditions of manipulation and storage on histone fractions was substantiated by chromatography and starch-gel electrophoresis. Prolonged extraction of avian erythrocyte nuclei at acid pH released additional non-histone basic protein without alteration of authentic histone fractions.

Estimating globule-size distribution of oil-in-water emulsions by spectroturbidimetry

The specific turbidity of highly diluted emulsions is determined as a function of wavelength, and the results are matched with spectra theoretically computed for various globule-size distributions. Features of this method are the use of a wide range of wavelengths (1:4.5), constant compensation for variations in refractive index, and the simplicity of the technique, once the preliminary computations are performed. Some characteristics of the size distribution are found with accuracy, namely the volume—surface average diameter d vs (which gives directly the total dispersed surface area) and the extent of polydispersity; often a third parameter has to be introduced, such as an upper size limit. Fine details of the distribution are not revealed. The results agree well with those of other methods (Coulter counter, microscope), and the reproducibility is very good. The method is applicable to emulsions with d vs between about 0.2 and 15 μ, for any polydispersity. Coarse emulsions can be analyzed after increasing the refractive index of the continuous phase.

Physicochemical differences between fragments of plasma membrane and endoplasmic reticulum.

Specific turbidities, densities, and refractive indices of fragments of plasma membrane (PM) and endoplasmic reticulum (ER) from Ehrlich ascites carcinoma have been measured. A spherical shell model of specified dimensions and refractive index was established for PM fragments. The ionic composition of the dispersion medium was varied systematically. Increases in Gamma/2 caused increases in the turbidity of both PM and ER suspensions, the greatest effects being observed with Ca(2+) and Mg(2+). In the case of PM this effect is attributable mainly to aggregation, whereas "structural" changes account for most of the turbidity increase with ER. The pH was also varied systematically to obtain pH- density and turbidity profiles and to establish the isoelectric pH of the two membrane types (PM-3.6; ER-4.35). Turbidity was maximum at "isoelectric" pH, which corresponds in each case to the region of minimum charge on the particle surfaces. Both PM and ER show large increases of density at the "isoelectric" pH, but only ER shows substantial structurally based turbidity increase under these conditions. Both PM and ER show operation of electrostatic attractions near "isoelectric" pH. PM has been shown to have ionically distinctive inner and outer surfaces while ER shows no such dissymmetry. The necessary theoretical background for interpretation of turbidity and density measurements is included, as well as a discussion of the limitations of our conclusions and the biological importance of our results.

Theoretical Studies of the Use of the Double Extrapolation Method to Determine the Forward Scattering of Light by Spherical Colloidal Particles

Abstract An application of the double extrapolation method (the Zimm-plot method) for the reduced intensity of light scattered by colloidal dispersions, instead of polymer solutions, is discussed theoretically on the basis of the Mie theory. The correction factor, F, required to recalculate the experimental value of the molecular weight, MR, to the true value, M (M=FMR), is equal to unity in the case of the Rayleigh scattering (α→0) and the Rayleigh-Gans-Debye (R-G-D) scattering (|m–1|→0, where m is the relative refractive index of the sphere to the medium). Usually, however, the value of F is not equal to unity, but is found to be given by an empirical equation F=1–0.155Q+bQ1.5, where Q is a quantity proportional to the reduced specific scattering intensity at θ→0. For the determination of the radius of gyration from the “initial slope,” the R-G-D equation is applicable even in cases where |m–1| is not small. In order to determine the true molecular weight from the molecular weight, Mτ, obtained from the specific turbidity at the infinite dilution, the factor Φ is needed (M=ΦMτ). The factor Φ is considered to be a product; that is, Φ=F\varphi, where the factor \varphi seems to be independent of the m value. The empirical equation obtained was \varphi=1+0.537α2.08

Theoretical Investigations on the Light Scattering of Colloidal Spheres. IV. Specific Turbidities in the Lower Microscopic Range and Fine Structure Phenomena

Additional calculations were carried out on the scattering cross sections of spheres and the specific turbidities of their dispersed systems using again the Mie theory. The parameters considered were α=7.0 (0.2) 25.6 and m=1.05 (0.05) 1.30. The close spacing of the α values allowed the detection of a fine structure of regular period in the (τ/c)0(α) curves and related curves. The fine structure is explained as the result of interferences of secondary magnitude.

Theoretical Investigations on the Light Scattering of Colloidal Spheres. III. Analytical Expressions for Turbidity Approximating the Performance of the Mie Equations Prior to the First Maximum

Analytical expressions are developed for the specific turbidity in dispersed systems of light scattering spheres. They yield particle diameters approximating over an appreciable range of α and m values and within better than 5% those obtained from the Mie-equations. The m range encompassed satisfactorily by the equations exceeds appreciably the range of validity of the Rayleigh-Gans and Debye equations. The limiting lower and upper values of α and m to which the equations are applicable, are defined quantitatively.

Theoretical Investigations on the Light Scattering of Colloidal Spheres. I. The Specific Turbidity

Scattering cross sections, scattering coefficients and specific turbidities are calculated from the Mie equations for α = 0.2(0.2)7.0(1)15 and m = 1.05(0.05)1.30; and, in addition, for α = 22(2)32; 39(1)41 and m = 1.05, for α = 16(1)21 and m = 1.10, for α = 7.2(0.2)15.2 and m = 1.20. Thus, the calculations cover virtually all dispersed systems of ultramicroscopic or small microscopic nonabsorbing spherical particles dispersed in a liquid. The effect of α and m upon these functions is discussed and a few approximating equations are given and tested for the limit of α→∞. The most important features of the Mie theory are briefly discussed and compared with those of alternate approximating theories.

Experimental investigations on the light scattering of colloidal spheres: I. The specific turbidity

Specific turbidities were measured on 23 nearly monodisperse polystyrene and polyvinyltoluene latices containing rigid spherical particles. The uniform diameters varied systematically from 45 to 824 millimicrons. The particle diameters calculated from the turbidity data by means of the Mie theory agreed so well with electron microscopic diameters that the results can be regarded as a conclusive proof of the Mie theory. A precision apparatus and the general experimental technique are described which allow one to determine particle diameters with a precision of better than 0.33%, which far exceeds the precision obtainable with the electron microscope. It is shown that the refractive index of the scattering spheres must be determined very exactly in order to obtain, in addition, highly accurate particle diameters. Evaluation of the turbidity data by means of the Rayleigh-Gans theory shows that it can give quantitatively significant particle diameters only for a very limited size range if the relative refractive index is near 1.2.

Experimental investigations on the light scattering of colloidal spheres *1I. The specific turbidity

Specific turbidities were measured on 23 nearly monodisperse polystyrene and polyvinyltoluene latices containing rigid spherical particles. The uniform diameters varied systematically from 45 to 824 millimicrons. The particle diameters calculated from the turbidity data by means of the Mie theory agreed so well with electron microscopic diameters that the results can be regarded as a conclusive proof of the Mie theory. A precision apparatus and the general experimental technique are described which allow one to determine particle diameters with a precision of better than 0.33%, which far exceeds the precision obtainable with the electron microscope. It is shown that the refractive index of the scattering spheres must be determined very exactly in order to obtain, in addition, highly accurate particle diameters. Evaluation of the turbidity data by means of the Rayleigh-Gans theory shows that it can give quantitatively significant particle diameters only for a very limited size range if the relative refractive index is near 1.2.

Light scattering investigation of potato amylopectin

AbstractLight scattering measurements were made on amylopectin prepared from potato starch by two procedures. Potato starch dispersed in water at 90° and fractionated with mixed pentanols gave an amylopectin I having a weight‐average molecular weight of 36 million. Dispersion of starch by autoclaving at 120°, followed by nitrobenzene precipitation of amylose, yielded an amylopectin II with weight‐average molecular weight of 14 million. No evidence was found for dissociation of these amylopectins into smaller units in aqueous solution at concentrations as low as 10−6 g./ml., at elevated temperatures, or in sodium hydroxide solutions. Aggregation of amylopectin II occurred at potassium chloride concentrations above 5 × 10−4 molar. Marked reduction of molecular weight of amylopectin II resulted from treatment under a high rate of shear in a Waring Blendor. Acetylated II (40% acetyl content) was soluble in nitromethane, chloroform, acetone, dioxane, and acetonitrile. In all these solvents the molecular weight, corrected for acetyl, was close to 10 million. No evidence was found for an increase in reciprocal specific turbidity at low concentration which would parallel reported osmotic pressure results. Polydispersity was demonstrated by ultracentrifugal sedimentation patterns of amylopectin II, and by separation of amylopectin I into a series of fractions ranging from 7 to 73 million in molecular weight.

The Determination of Particle Size and Refractive Index Near the Turbidity Maximum in Monodisperse Suspensions of Spherical Particles

Theoretical values on the specific turbidity of colloidal spheres within the range of diameters of 1 to 2 microns are given. It is shown how an unambiguous particle size can be determined within this range in spite of a turbidity maximum. The latter can be determined for almost any refractive index by means of an empirical equation. An alternate turbidity maximum can be used for determining the refractive index of the light scattering material provided the diameter is known.

Size and shape of blood group A-substance.

Kekwick has recently presented data on the size and shape of an A-substance preparation from pseudomucinous ovarian cyst fluid1. He obtained a molecular weight of 260000 and an axial ratio of 60/1 from ultracentrifuge and diffusion measurements. For comparison it seems worthwhile to present briefly data obtained on other preparations of A-substance2.Materials. The closely related preparations R18-F10, R19-F1A, and R19-F2A of A-substance from hog gastric mucin were used (3,4).‡ This material is known to be chemically and immunologically inhomogeneous (3,4). The solvent used in all experiments was 0.02 M phosphate buffer at pH 7.1 with sufficient sodium chloride to give an ionic strength of 0.15.Light scattering. Measurements were made at concentrations between 1.0 and 0.1%. Values of the reciprocal of specific turbidity were plotted against concentration and extrapolated to zero concentration. The molecular weights of R19-F1A and R19-F2A calculated from the values of (C/τ) c=o were 900,000 and 1,100,000 re...