Solid determination, percentage

Scrape off fhe camphor onto a piece of weighing paper. Camphor is a white solid. Determine the weight of fhe purified camphor and determine the percentage yield. 

Crystallize your entire sample from hot 95% ethanol. You will have to use the crystallization techniques introduced in Experiment 3 to crystallize the chalcone. Once the crystals have been allowed to dry thoroughly, weigh the solid, determine the percentage yield, and determine the melting point. 

Titration can also be used to determine percentage composition of samples. For example, consider that a 1.136 g sample containing solid NaOH and inert material was weighed out, dissolved and titrated with 0.1036 M standard HCl, of which 48.61 mL was required. What was the percentage of NaOH, molar mass 40.0, in the sample At the end point, the number of moles of NaOH in the sample exactly equals the number of moles of HCl added. But, because the NaOH is in a solid and the mass of NaOH is needed to calculate the percentage of it in the sample, the following equation can be used ... 

Solid-phase microextraction (SPME) consists of dipping a fiber into an aqueous sample to adsorb the analytes followed by thermal desorption into the carrier stream for GC, or, if the analytes are thermally labile, they can be desorbed into the mobile phase for LC. Examples of commercially available fibers include 100-qm PDMS, 65-qm Carbowax-divinylbenzene (CW-DVB), 75-qm Carboxen-polydimethylsiloxane (CX-PDMS), and 85-qm polyacrylate, the last being more suitable for the determination of triazines. The LCDs can be as low as 0.1 qgL Since the quantity of analyte adsorbed on the fiber is based on equilibrium rather than extraction, procedural recovery cannot be assessed on the basis of percentage extraction. The robustness and sensitivity of the technique were demonstrated in an inter-laboratory validation study for several parent triazines and DEA and DIA. A 65-qm CW-DVB fiber was employed for analyte adsorption followed by desorption into the injection port (split/splitless) of a gas chromatograph. The sample was adjusted to neutral pH, and sodium chloride was added to obtain a concentration of 0.3 g During continuous... 

This information is reported as the percentage that each of the clay mineral type contributes to total identifiable clay mineral content of the noncarbonate clay-sized fraction of the surface sediments. These percentages were determined by x-ray diffraction, which is luiable to identify noncrystalline solids. Using this technique, clay minerals were found to comprise about 60% of the mass of carbonate-free fine-grained fraction. Most of the noncrystalline soUds are probably mixed-layer clay minerals. Carbonate was removed to facilitate the x-ray diffraction characterization of the clay minerals. In some cases, roimd off errors cause the sum of the percentages of kaolinite, illite, montmorillonite, and chlorite to deviate slightly from 100%. 

Quantitative FT-IR Analysis. Selected samples of the liquefaction products, total product, the chloroform extracts, the asphaltenes, and the solid residues were analyzed as KBr pellets by FT-IR. The methods employed for quantitative analysis have been described previously (14-17). Measured amounts of sample are mixed with measured amounts of KBr, so that spectra are reported in absorbance units/mg of sample in a 1.33 cm pellet. A spectral thesis routine was used to obtain peak areas for individual functional groups and previously determined absorbtivities (17) were employed to obtain the reported percentages of each functional group. 

The solid provides an extended surface to the reaction or adsorption to take place. The area provided by the solid is the sum of the exterior and interior ones. Consequently, the solid surface includes not only the geometrical one as determined from the solid s shape but also the interior surface that is the result of its porous structure. The surface area is expressed as specific surface area in units of m2/g. Its value may be from a few m2/g up to hundreds of m2/g. In the case of a porous solid, the interior surface constitutes the greatest percentage of the total surface, and high values of specific surface area may be achieved. Specifically, the specific area of an activated carbon can reach the value of 1500 m2/g. So, the available area for a hydrocarbon to react on 4 g of activated carbon is equal to that of a football field. 

Refractive Index. The refractometric value of sugar solutions is used as a rapid method for the approximate determination of the solids content (also known as dry substance), because it is assumed that the nonsugars present have a similar influence on the refractive index as sucrose. Measurement is usually carried out on a Brix refractometer, which is graduated in percentage of sucrose on a wt/wt basis (g sucrose/100 g solution) according to ICUMSA tables of refractive index at 20.0°C and 589 nm. Tables are available that give mass fraction corrections to refractometric values at temperatures different from 20°C. 

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