Sediment volume determination

Demulsifier—A demulsifier should be used to promote the separation of water from the sample and to prevent its clinging to the walls of the centrifuge tube. The recommended stock solution is 25 % demulsifier to 75 % toluene. For some crude oils a different ratio of demulsifier to toluene may be required. Demulsifiers used in the concentration and quantity recommended will not add to the water and sediment volume determined. The solution must be stored in a dark bottle that is tightly closed. 

Miller CR (1953) Determination of the unit weight of sediment for use in sediment volume computations. US Bureau of Reclamation, Dept, of Interior, Denver, CO... 

Polymers may show an optimum flocculation concentration which depends on molecular weight and concentration of solids in suspension. Overdosing with flocculant may lead to restabilisation(44), as a consequence of particle surfaces becoming saturated with polymer. Optimum flocculant concentrations may be determined by a range of techniques including sedimentation rate, sedimentation volume, filtration rate and clarity of supernatant liquid. 

Sedimentation. The sedimentation experiments are tabulated in Tables I and II. In Table I typical sedimentation coefficients determined in H20 and D20 are in close agreement here and with previously reported values determined for both protio and deuterio phycocyanin from F. calothricoides (15,16). Each of the tabulated coefficients is for a single experiment at an approximate protein concentration of 15 mg. per ml. Lyophilizing a phycocyanin preparation twice had little effect on the observed sedimentation coefficients. In calculating the S values the same partial specific volume of the protein was used for both D20 and H20. This practice is consistent with the recent results of Edelstein and Schach-man (7). Small increases in sedimentation coefficients from H20 to D20 are to be expected because of deuterium substitution on exchangeable positions. The slope of an S vs. concentration plot for phycocyanin in H20 and D20 would also probably differ. Consequently, small changes in S from H20 to D20 would be expected at a constant protein concentration. 

Lovenberg, Buchanan, and Rabinowitz 65) showed that the molecular weight of C. pasteurianum ferredoxin is about 6000, based on sedimentation velocity and sedimentation equilibrium ultracentrifugation determinations and on amino acid analysis. The sedimentation coefficient, S2o,w was 1.4, and the partial specific volume, determined according to the method of Hvidt et al. 59) was 0.63, as compared to the value of 0.71 observed for most proteins. Similar investigations showed that ferredoxins from four other clostridia Lovenberg, Buchanan, and Rabinowitz 65)) and from a photosynthetic bacterium (Bachofen and Arnon 12)) also had a molecular weight of about 6000. 

Many methods are available for determining particle size in pharmaceutical practice, including microscopy, sieving, sedimentation, and determination of particle volume [19]. Sieve analysis with U.S. standard sieves is widely used to determine the particle size distribution based on powder weight. Sieves are classified according to the number of openings (Table 14) and are generally made of wire cloth woven from brass, bronze, or other suitable wire. 

In view of the possibility that the sedimentation volume of particles may show extrema when A = 0, such an extremum in the sedimentation volume may provide a means to determine the solid-vapor surface tension of the particles. The solid-vapor surface tension ysV of particles would be equal to yn. the surface tension of the suspending liquid at which the sedimentation volume extremum occurs. 

Therefore to determine the particle surface tension by using the sedimentation volume technique, the required basic procedures in the experiments can be summarized as follows ... 

Determine the liquid surface tension y % at which an extremum in the sedimentation volume occurs. 

The amount of deposited sediment is determined by its height and, since the settled volume is not independent of size, eirors are introduced. 

Mass median diameter (MMD) is the most common descriptor of primary particle size and may be determined by sieving or centrifugal sedimentation. Volume median diameter, as determined by laser diffraction, may be used as an approximation of MMD provided the particle density is known and does not vary with size and the particle shape is near spherical. The MMD of a powder can be used as a predictor of aerodynamic diameter by ... 

The optimum quantity of 6% crospovidone in the formulation in Table 143 was determined from the relative sediment volume. Figure 86 shows that, at this concentration, no further sedimentation takes place after 24 hours. With lower quantities of micronized crospovidone, a sediment was clearly visible. 

Again, the quantity of micronized crospovidone was determined from the relative sediment volume. As is evident from Fig. 87, no sedimentation was observed above a crospovidone concentration of 9% in the final suspension (= 29 g crospovidone in the sales product). After several weeks, it was still very easy to redisperse the suspension with a few rocking movements. 

The amount of carboxylic anhydride used for modification of A1(OH)3 determines the sedimentation rate of filler particles and the increase in water-based slurry viscosity. A limiting value of viscosity is attained at relatively low levels of modifier. This amount of modifier is sufficient to react with the available sites on the A1(OH)3 providing conditions for the breakdown of the aggregates and a separation of individual particles. Since the reaction decreases particle-particle interaction these processes are likely to occur. The sedimentation volume curve can be explained in the same way. 

In general, the volume received or delivered is calculated from the observed gauge readings. Corrections are made for any free water and sediment as determined by the gauge of the water level in the tank. The resultant volume is then corrected to the equivalent volume at 15.6°C (60°F) by use of the observed average temperature and the appropriate volume correction table (ASTM D-1250). When necessary, a further correction is made for any suspended water and sediment that may be present in materials such as crude petroleum and heavy fuel oils. 

HC hollow cathode HC-FANES hollow cathode - furnace atomic non-thermal excitation spectrometry hematocrit (centrifugation apparatus for) determination of the sedimentation volume of blood, i.e. the content of the cellular elements in blood in relation to the total volume... 

In order to understand the above observations, the settling rate and sediment volume of gypsum floes were determined. The filter medium resistance and filtrate viscosity were also measured. It was found that there was no change in viscosity with or without the polymers. The settling rates and sediment volumes are plotted in Figure 1 and Figure 2 respectively. The filter medium resistance data are summarized in Table II. 

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