Conversion gravimetric determination

This procedure is based on the measurement of the contraction of volume that results from the different densities of the monomer and polymer. The conversion of the volume contraction to the yield of polymer can be made by means of a gravimetrically determined calibration curve or by calculation from the specific volumes (see Example 3-6). 

Comprehensive accounts of the various gravimetric, polarographic, spectrophotometric, and neutron activation analytical methods have been published (1,2,5,17,19,65—67). Sampling and analysis of biological materials and oiganic compounds is treated in References 60 and 68. Many analytical methods depend on the conversion of selenium in the sample to selenous acid, H SeO and reduction to elemental selenium when a gravimetric determination is desired. 

In the present work, twenty-seven of these oils were separately analyzed for sulfur content and sulfur isotope ratio (Parr Instrument Company bomb. Sulfate in washings from the bomb were precipitated with Ba2+. The BaSOA precipitate served for gravimetric determination of the S-content conversion to S02 for mass spectrometry (4). The 3AS/32S abundance ratios are presented in the usual 63AS notation. 

The polymerization kinetics were studied via time-conversion relationships at different dose rates (Figures 6-9). The radiation curing was carried out at room temperature in closed aluminum capsules. Percent monomer conversion was determined gravimetrically for N-vinylpyrrolidone. Evaporation was accomplished under vacuum in a ventilated oven at 50 °C until the weight was constant. For butyl methacrylate and polyester resins, the residual monomer content was determined by gas chromatographic analysis after immersion of the cured products in acetone. 

When conversion is determined gravimetrically. Interval I may be completed before the first sample is taken. When rates of emulsion polymerization are discussed it is the constant rate fi-equently observed during Interval II which is meant. Most commonly, practically all the emulsifier is adsorbed on the surface of the latex particles at the end of Interval I then the surface concentration of adsorbed emulsifier decreases as the latex particles grow. Soap titration [67], in which the volume of a standard emulsifier solution required to reduce the surface tension of the latex to the value characterizing the presence of micellar soap is determined can be used to determine the final surface concentration of emulsifier. The surface-average particle size can be calculated from a knowledge of the amount of surfactant adsorbed at this point and the area occupied at the interface by a surfactant molecule in a saturated monolayer. This area should... 

Cationic latex particles with surface amino groups were prepared by a multi-step batch emulsion polymerisation. Monodisperse cationic latex particles to be used as the seed were synthesised first. Then the amino-functionalised monomer, aminoethylmethacrylate hydrochloride, was used to synthesise the final functionalised latex particles. Three different azo initiators were used 2,2 -azobisisobutyramidine dihydrochloride, 2,2 -azobisdimethyleneisobutyramidine dihydrochloride, and 2,2 -azobisisobutyronitrile. Hexadecyltrimethylammonium bromide was used as the emulsifier. The latices were characterised by photon correlation spectroscopy to study the mean particle diameters, transmission electron microscopy to deteimine the particle size distributions, and hence the number- and weight-average diameters and the polydispersity index. The conversion was determined gravimetrically, the surface density of the amino groups was detemiined by conductimetric titrations, and the... 

At room temperature and atmospheric pressure, vinyl chloride is a gas, albeit a readily condensable one. At ambient temperatures, the solubility of PVC in the monomer (by direct gravimetric determination) is 0.03% [37], although the literature states elsewhere that at about 0.5% conversion of vinyl chloride, precipitation of the polymer is noted [36]. 

Directly after irradiation, the polymerization cell was opened and the contents were mixed with a tiny amount of inhibitor ( 500 ppm, hydroquinone, Merck, fotopur) to prevent further polymerization. Samples were dried in the dark at reduced pressure (< 10 Pa) for at least 72 hours. The conversion was determined gravimetrically and was typically 1 to 2 %. 

SO that the ester which is always present even in freshly-prepared alcoholic solutions of mustard oil does not decompose quantitatively with ammonia- cal silver solution, with formation of sulphide of silver, but is partly pre- cipitated as a silver salt of the above-mentioned ester. Whilst this admixture, owing to its molecular weight 252, which differs but little from that of silver sulphide 248, cannot cause an appreciable error in the gravimetric determination, it cans s a considerable difference in the volumetric estimation, because in the formation of this ester salt only 1 atom of silver corresponds to 1 molecule of mustard oil, whereas for the conversion into silver sulphide, 2 atoms of silver are required, so that the titration results are obviously too low. 

The same equation applies in a 3-component system containing diluent at constant mole fraction of diluent. Therefore, pressure drop can be related to conversion, if data on the partial molal properties of monomer and polymer and the compressibility of the mixture axe available. Since such data are unavailable, conversion must be obtained by sampling and gravimetric determinations of yield or by means of a previously established calibration of 3deld vs. pressure drop 34). 

The rate-limiting step in Reaction Scheme 10 was determined to be conversion of trans- Ir(N02)4Cl2]3 to [Ir(N02)6]3. The kinetics were studied gravimetrically between 80 °C and... 

Table 10.4 Substances Determined Gravimetrically by Conversion to Free Base...

Procedures. A standard recipe for the latex preparation is shown below (St + M2) 20 g, (water + buffer) 160 g, and initiator 5 mmole/1. The weight fraction of M2 in monomer charge (f) was varied from 0.01 to 0.50. Polymerizations were carried out at 55°C or 70°C and pH 2.5 or 9.0 under nitrogen. Samples were withdrawn from the reaction mixture at various time intervals and the polymer was precipitated in an excess of acetone. The conversion and polymer composition were determined by gravimetric means and by elemental analysis, respectively. The M2 fraction in instantaneously-formed copolymer ( Fi ) was calculated from eq. 1 ... 

Cumene Cracking Reactions on Separated Fractions. Cumene cracking reactions were tested on a gravimetric setup the basic flow diagram for the reactor system is shown in Figure 1. The reactor determines both the activity of the catalyst (cracking of cumene to benzene and propylene) and the instantaneous rate at which coke is deposited on the catalyst (polymerization of the propylene). Conversion of the cumene is adjusted to exclude the amount of cumene disproportionation which yields benzene and diisopropyl benzene. 

As alluded to earlier, in a conventional gravimetric microbalance, it is not possible to determine the true space velocity since an undeterminable, but a large amount of the feed bypasses the catalyst bed. Therefore, the conversion observed in the exit gas cannot be related to the true activity of the catalyst. To demonstrate that the plug-flow-vibration microbalance has overcome this problem we have carried out an experiment in the microbalance and in a conventional fixed bed reactor using 0.3wt%Pt-0.3wt%Re/Al203 under the same conditions 210 kPa, 750 K, = 3 and liquid-weight-hourly space... 

Method III (Sample Preparation) Proceed as directed for Method III in Total Color under Colors, Appendix IIIC. The gravimetric conversion factor (F) for Erythrosine is 1.074. Arsenic Determine as directed under Arsenic Limit Test, Appendix IIIB, using a Sample Solution prepared as directed for organic compounds. 

The polymer was isolated by evaporation of the unconverted monomer and the conversion determined gravimetrically. 

Conversion and coke formation during catalytic ethene oligomerization catalyzed by HZSM-5 have been investigated in the TEOM and in a conventional gravimetric microbalance under similar conditions (2). The results show that the TEOM is a powerful tool for determination of the kinetics of deactivation of catalysts, with a design that makes determination of the true space velocity (or space time) easy. The TEOM combines the advantages of the conventional microbalance with those of a fixed-bed reactor, and the same criteria can be used to check for plug flow and differential operation. 

Conversion of the as-deposited film into the crystalline state has been carried out by a variety of methods. The most typical approach is a two-step heat treatment process involving separate low-temperature pyrolysis ( 300 to 350°C) and high-temperature ( 550 to 750°C) crystallization anneals. The times and temperatures utilized depend upon precursor chemistry, film composition, and layer thickness. At the laboratory scale, the pyrolysis step is most often carried out by simply placing the film on a hot plate that has been preset to the desired temperature. Nearly always, pyrolysis conditions are chosen based on the thermal decomposition behavior of powders derived from the same solution chemistry. Thermal gravimetric analysis (TGA) is normally employed for these studies, and while this approach seems less than ideal, it has proved reasonably effective. A few investigators have studied organic pyrolysis in thin films by Fourier transform infrared spectroscopy (FTIR) using reflectance techniques. - This approach allows for an in situ determination of film pyrolysis behavior. 

In the atmospheric experiments an "SDT 2960, TA-instruments simultaneous differential and thermal gravimetric analyser" were used to determine the COr gasification reactivity under isothermal conditions. The samples were kept isothermal for 10 minutes in N2 at 150 C, before the sample temperature was increased (heating rate 30°C/min) to the defined reaction temperature and switching to the N2ICO2 mixture. The gas flow used was 400 ml/min. Ash was determined by increasing the temperature to 1000 C for complete conversion. 

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