Density sink-float method

Density Sink-float method Corn husk 7... 

Birefringence measurements were obtained by the Becke line method, and density measurements were obtained by the sink-float method (26). 

Balog P. S., Secco R. A., and Rubie D. C. (2001) Density measurements of liquids at high pressure modifications to the sink/float method by using composite spheres, and application to Fe-10 wt.%S. High Press. Res. 21, 237-261. 

The sink-float method requires a beaker, pipette, burette and two liquids. The liquids must be miscible and inert to the fiber being tested. One liquid must be less dense than the fiber and the other liquid must be more dense. A known volume of liquid A is pipetted into a beaker and the fiber is immersed in the liquid. The second liquid, B, is then added dropwise from a burette to the beaker with constant stirring. As the density of the liquid solution in the beaker changes, a point is reached where the density of the liquid precisely equals that of the fiber and the fiber will neither sink nor float but will remain suspended in the liquids. The volume of the second liquid added to the beaker is recorded and the density of the fiber is calculated ... 

There exist a number of familiar procedures for effecting mineral separations, including sink-float methods based on density differences and froth flotation based on wettability. Because of the tendency of kerogen to swell and soften in the presence of organic liquids and thus possibly to mobilize trapped mineral particles, and because most minerals are water-wetted and thus extractable with water, we investigated a liquid-liquid (oil-water) pelletization method. 

TABLE 6.12 Density (specific gravity) of some commercial deck boards. Data were obtained using sink/float method (see below)... 

DETERMINATION OF DENSITY OF WOOD-PLASTIC COMPOSITES USING A SINK/FLOAT METHOD... 

Analysis and spectroscopic study. The elemental analysis was performed with anICP-6000 spectrometer. The precursors crystallization was studied by thermal analysis methods (TG85). The samples were analysed by IR spectroscopy (Nicollet, FTIR-7500) and powder X-ray diffraction (PXRD, DRON-3). The morphology of surface was studied by scanning electron microscopy (SEM) (JEOL, JSM-6100). The density of KTP particles was determined by a sink-float method. Local x-ray analysis was performed using Link ISIS microanalysis system (Si Li detector) mounted on Jeol 2000 FX microscope. Bruker-400 apparatus was used for P, C and H NMR study of precursor solution. The YAG Nd SHG was measured on LS-10 device. 

Three methods are common, viz, the liquid displacement method, the sink-float method and the density gradient column method. Each of these is a common, standard technique and is fully described in ISO 10119, 1992 (for the determination of the density of carbon fiber), and also in ASTM D 276-87 (reapproved in 1993), which in fact also refers to ASTM D 1505, ASTM D 792, and AATCC, Method 20 (1990) (Fiber identification), each of which deals with the above techniques. ISO 10119 is a very good and concise description of the techniques. However the measurement liquids specified in ISO 10119 of ethanol, methanol, acetone, tricloroethane, and carbon tetrachloride, although suitable for carbon fibers, are not at all suitable for the general range of textile polymers, with the exception perhaps of ethanol and methanol. ASTM D 276 87 recommends the use of / -Heptane for universal application, except, of course for the olefins, such as polyethylene. A range of typical fiber densities is given in Table 4. 

Sink-float methods are commonly used for quality control measurements for glasses. A sample is placed into a test tube containing an organic liquid which is slightly more dense than the sample. The tube is heated until the density of the liquid becomes less than that of the sample, whereupon the sample will begin to sink. If the test tube also contains a standard of known density, the difference in temperature at which the sample and standard sink can be used to calculate the difference in their densities, provided the temperature dependence of the density of the liquid is known. This method is capable of detecting differences in density of as little as 20 ppm. 

Although more labor-intensive and less efficient, information on the densification kinetics and densification can also be obtained from density measurements on different individual samples as a function of time for otherwise identical sintering conditions. Bulk density measurements on <92% dense sintered samples containing open porosity can be determined from the measured mass and dimensions of the compact, while Archimedes method works well for closed pore, >92% dense bodies. The density of closed pore samples can also be determined by pycnome-try (e.g., helium pycnometry),, 37 mercury porosimetry, and by the sink-float method (i.e., whereby the buoyancy of the sample is assessed and compared in different density liquids). Density can also be estimated from micrographs using quantitative stereology. 

Float-Sink or Suspension Method This method involves placing a solid sample into a liquid with known and adjustable density. The density of liquid is incrementally adjusted until the sample begins to sink-float (ASTM C729-75 [25]), or is suspended at neutral density in the liquid (ASTM C693-93 [26]). At the point of equilibrium the density of the sample is equal to the density of the liquid. 

ASTM C729-75 el (1995), Standard Test Method for Density of Glass by the Sink-Float Comparator, American Society for Testing and Materials, Philadelphia, PA. 

The method is based on the creation of a heavy medium suspension of intermediate density between that of heavy and light fraction. The desired density is accomplished by mixing proper quantities of finely ground materials (e.g., magnetite, ferrosilicon, galena, etc.) and water. Shredded materials feed the heavy medium bath. The particles with a lower density than that of the suspension float (light product), while those with higher density sink (heavy product). 

The density of any material is defined as its weight per unit volume. Textile fiber density is more conveniently determined indirectly by comparing the sample with standards of known density. The two conunonly used techniques are the sink-float and gradient density methods. 

A quick and reliable method for density determination of WPC materials is a sink/float procedure. It is readily applicable in a laboratory as well as at a plant LDl Composites routinely uses this procedure for regular QC of GeoDeck deck boards at manufacturing sites. 

Sink-and-float methods. A sink-and-float method uses a liquid sorting medium, the density of which is intermediate between that of the light material and that of the heavy. Then the heavy particles settle through the medium, and the lighter ones float, and a separation is thus obtained. This method has the advantage that, in principle, the separation depends only on the difference in the densities of the two substances and is independent of the particle size. This method is also called heavy-fluid separation. 

There are several separation methods to accomplish this by sink-and-float and differential settling. In the sink-and-float method, a liquid is used whose density is intermediate between that of the heavy or high-density material and the light-density material. In this method the heavy particles will not float but settle from the medium, and the light particles float. 

Since it is a quantitative property, it is often more useful for identification than a qualitative property like color or smell. Moreover, density determines whether an object will float in a given liquid. If the object is less dense than the liquid, it will float if it is more dense, it will sink. It is also useful to discuss density here for practice with the factor-label method of solving problems, and as such, it is often emphasized on early quizzes and examinations. 

The sample is placed in each solution in series. When the sample sinks, the density of the sample is said to lie between a range of densities corresponding to the one it sank in and the closest solution in which it floated. The precision of this method may be improved by increasing the number of solutions within a given density range. 

In plasma, Lp(a) moves with a pre-beta-1 mobility (B8, B9) and has been referred to as the sinking pre-beta fraction, as it shares the mobility of VLDL yet does not float at the same density in the ultracentrifuge. Serum electrophoresis followed by a lipid staining with Oil Red O or Fat Red should be a convenient method for detection of elevated Lp(a) levels. Sample collection and preservation are, however, critical parameters in this assay (B26, K9). 

An iron deficiency could be accommodated by a defect structure in two ways either iron vacancies, giving the formula Fe] /D, or alternatively, there could be an excess of oxygen in interstitial positions, with the formula FeOi+ f. A comparison of the theoretical and measured densities of the crystal distinguishes between the alternatives. The easiest method of measuring the density of a crystal is the flotation method. Liquids of differing densities which dissolve in each other, are mixed together until a mixture is found that will just suspend the crystal so that it neither floats nor sinks. The density of that liquid mixture must then be the same as that of the crystal, and it can be found by weighing an accurately measured volume. 

Another common method is sorting by density in a float-sink tank or hydrocyclone. This method is, however, difficult for polyolefins as these have very similar density. Air classification uses a combination of density and shape to achieve the separation, e.g. for separating plastic films and paper residues. 

Separation Method. Trial experiments with small portions of the coked catalyst in progressively more dense mixtures of carbon tetrachloride (d - 1.594 g/cc) and 1,1,2,2- tetrabromoethane (d - 2.967 g/cc) showed that the lightest catalyst fractions exhibited a density of about 2.3 g/cc. A solvent mixture with d - 2.33 g/cc was prepared from a mixture of 46.4 ml of carbon tetrachloride and 53.6 ml of tetrabromoethane. A 20 g portion of coked catalyst was placed in a 120 ml quantity of this solvent mixture in a 250 ml Teflon centrifuge bottle. The mixture was thoroughly agitated for several minutes and then placed in a centrifuge at 3,600 rpm for 30 minutes. Upon removal from the centrifuge, the mixture was allowed to stand for several hours in order to obtain well-defined float and sink fractions. 

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