Carboxyl group content

Question 4. Why is the preliquefied insoluble product so easily liquefied The most probable answer. The preliquefaction product with the reduced carboxyl groups content is more easily liquefied than the parent coal. Based on the product distribution, solvent swelling data and the model simulation, this improvement results from a reduction in the CO2 associated crosslinks and from the bond breaking which produces the chloroform solubles. Both effects reduce the total number of bonds linking the network so that the coal can become fluid. If the chloroform soluble fraction is removed after preliquefaction and the residue liquefied, the drastic improvement in the liquefaction is not observed. The model simulation confirms that the residue alone will liquefy slightly better than the parent coal, but not nearly as well as the mixture. 

To show the effect of the percentage of dinitrogen tetroxide in the carbon tetrachloride solution on the nitrogen content and on the carboxyl group content of the reaction product, Kenyon reports the following data, collected in Table 84. 

Carboxyl group content of the substance o/ /o Nitrogen content 0/ /o i Solubility in acetone 1 0/... 

Empirical parameter describing how the Donnan volume varies with ionic strength. Carboxyl group content (mmolg 1 on moisture- and ash-free basis). 

The diethylene glycol and carboxyl group contents of the resin and its dispersity were used as a measure of the degree of side reactions taking place at the polycondensation stage. 

The carboxyl groups content is increased. The differential distribution curve (Fig.l) indicates a good polydispersity comparable with the one exhibited by the un-modified one. 

With the di-sodium salt of 1,2-dicarbomethoxyethylphosphonic acid as modifier the diethylene glycol content and the carboxyl group content is very low (Table III). These results indicate that the used modifier has also thermostabilizing properties. The integral and differential curves (Fig.2) of molecular mass distribution show that the polydispersity of modified resin is comparable to that of the un-modified. 

Graft onto 2,3-Dicarboxyl Cellulose. Cd-celluloses with different carboxyl group contents were grafted with methyl metha-... 

Figure 7. Effect of carboxyl group content on the yield of copolymer, molecular weight, and apparent number of grafted chains in the pMMA-grafted dicarboxyl-cellulose. Conditions cellulose, 0.3 g H O, 10 mL MMA, 2 mL. Key (reaction tube) open mark, quartz (50°C, 1 h) half closed mark, Pyrex (40°C, 1 h).

In addition, the decomposition of the carboxyl groups was studied by measuring the carboxylate concentrations in the chars after pyrolysis. The technique to determine the carboxyl group content is outlined in detail elsewhere (11), and is based on the work of Schafer (17). There are three basic steps involved acid washing, exchange with barium acetate and determination of the extent of exchange. 

These findings suggest that it may be possible to estimate lower bounds for the amount of C02 attainable from organic sources during pyrolysis, based on a knowledge of the carboxyl group content of the coal. Combination of this information with a determination of the carbonate content and appropriate thermodynamic equilibrium and kinetic calculations would allow estimates of the total amount of C02 evolution expected from pyrolysis. 

Recently, Hiller and Pacsu have shown that accurate results may be obtained in the absence of sodium chloride by a direct alkali titration of the carboxyl groups in purified cotton. The carboxyl group content found was 0.02%, but after oxidation with potassium permanganate solution, 0.126% was found. From these data it may be seen that both carboxyl and aldehydic groups are present in the original cellulosic... 

The affinity of variously oxidized cellulosic materials for certain basic dyes, notably methylene blue, has long been known. Kenyon and coworkers have recently shown that in the case of nitrogen dioxide oxycelluloses, the methylene blue absorption is a function of the carboxyl group content. Application of the reversible methylene blue method to the determination of carboxyl groups in purified cellulose has been made by Davidson and by Weber, who was able to show good agreement with the cation-exchange methods previously considered as well as with viscosity and osmotic pressure measurements. 

Linear regression analysis shows positive correlations (Table 6, Fig. 2) between residual free radical concentration percentages in the interaction- products (Table 5) and the carboxylic group contents of the HA s (Table 2). If we exclude the data relative to HA s from coal-2, soil-1, and possibly soil-3, much closer correlations are obtained for the residual spins/g percentages versus COOH contents and a positive trend (Table 6) is also shown between the former parameter and COOH/phenolic OH ratios (Table 2). Being assumed the residual free spin... 

The two reactions most commonly employed for the modification of protein carboxyl groups have been acid-catalyzed esterification (Wilcox 1967), and coupling with nucleophiles mediated by a water-soluble carbodiimide. The latter reaction has been exploited widely in the determination of the carboxyl group content of proteins as well as in studies of carboxyl group function, and would at present appear to be the reaction of choice for these purposes. 

De Nobih M., Contm M. (1994), Determination of carboxyl groups content in fulvic acids by the CTA (Cetyltrimethylammonium) method, Humic Substances in the Global Environment and ImpUcarions on Human Health, (Ed. N. Sene.si, T.M. Miano), Elsevier Science, 263-268. 

Table 13.4.3 shows the effect of solvent on the intrinsic viscosity, [tj], and carboxyl group content of PAIs. The carboxyl content was determined by potentiometric titration. It is interesting to note that intrinsic viscosity of PAI from PAAA prepared in DMAc is larger than that in MEK/water mixed solvent. This suggests that the polymerization degree decreases with decreasing activity of TMAH-Cl in MEK/water mixed solvent because of the hydrolysis of TMAH-Cl by water. 

The carboxyl group content of PAIs from PAAAs prepared in MEK/HjO mixed solvent was larger than that in DMAc. 

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