Molar water content

Molar Water Content, x Average Crystal Length L / pm Average Crystal Diameter D / pm Average Aspect Ratio L/D... 

Table 9-5 Molar water content of polymers related to structure groups at several relative humidities at 25 °C.

Looking at Table 9-5 it is obvious that one can ignore the water sorption capacity of the CH2 groups. Consequently, the two (CO)NH groups have a molar water content, at a relative humidity of 0.7, of ... 

Table 7.11 Maximum molar water content values per structural group at 20°C.

The maximum equilibrium water saturation of a cured epoxy system (resin system A/HHPA, see 7.2.3) was calculated succesfully using these new molar water content values. As repeating unit was recognised for this three dimensional network structure (see 7.2.4) ... 

Using the measured molar water content values from Table 7.11 results in ... 

The equilibrium water saturation measured of this epoxy resin casting sample was 0.90 %wt. Using the molar water content values reported by Van Krevelen ((1], Table 18.11 page 572), an equilibrium water concentration of 2.4 %wt. is calculated. 

This result seems to confirm these new, lower experimental molar water content values. But it will be clear that also the results calculated with this small number of new molar water content values can be only indicative ones. More experimental results like shown in Table 7.10 are necessary to obtain really firm molar water content group data. 

The calculated equilibrium water saturation of 1.23 %wt. holds for completely amorphous PK copolymer i.e. if x(c) > 0.63, the equilibrium water saturation value of the semi-crystalline polymer as such, becomes 0.50 %wt. The equilibrium water saturation, measured on sheet material in demineralised water at 20°C, was 2.55 %wt. The calculated water saturation depends in this case mainly on the molar water content value of the CO group used. The calculated value is about five times too low and this illustrates again the necessity of looking for better defined molar water content values. 

Nafion 117 in Hquid water takes up more water per sulfonic acid group than S-PEEKK of lEC values between 0.78mmol/g and 1.78mmol/g up to a certain temperature, which depends on the lEC value of the S-PEEKK. At this temperature, which is 65 °C for lEC = 1.78mmol/g, 80 °C for lEC = 1.4 mmol/g, 100 °C for lEC = 0.78 mmol/g, the water content of the S-PEEKK membranes increases tremendously. Nafion shows similar behavior only at a temperature of 140 °C. Until this temperature is reached, its molar water content is almost constant at A. = 20. The excess swelling of S-PEEKK at temperatures of 100 °C or less causes severe problems in using these materials as membranes in fuel cells. 

TABLE 4.15 Molar Water Content per Structural Group at Various Relative Humidities at 25 °C... 

The quahty of sulfonic acids produced as iatermediates on an iadustrial scale is important to detergent manufacturers. Parameters such as color, water, free oil (unsulfonated material), and acid value (actual sulfonic acid) are all factors that determine the quaUty of a sulfonic acid. The quaUty of the feedstock prior to sulfonation, such as iodine value, water content, and sulfonatabiUty, affects the quaUty of the sulfonic acid produced. Sulfonation conditions, such as temperature, molar ratio, rate, etc, also affect the quaUty of sulfonic acid. 

Molar excess of SMCA/NaOH to the nonionic Water content during the reaction... 

Good conversions are also obtained via a 80% solution of chloroacetic acid in water and a NaOH solution in water (about 50%) which at most a 1 M quantity of free monochloroacetic acid and a 2 M quantity of the aqueous NaOH solution (based on the molar quantity of the nonionic) distilling the water during the reaction, such that the water content of the reaction mixture during the addition of the reaction compounds amounts to 0.3-1.25 wt %. During the reaction there is always added some excess of NaOH with respect to the monochloroacetic acid. The reaction temperature is 70-90°C [15]. 

When the reaction was performed in the microreactor, the maximum conversion of 97.0 % was attained when the flow rate of Boc-AMP solution was 9 ml/min and the molar equivalents of KOH to Boc-AMP was 13 as shown in Fig. 1. Optimum operating conditions were obtained from a statistical method by using factorial design [6]. The yield decreased over the KOH equivalency of 13 in Fig. 1, since the phase separation between the t-Boc20 and the aqueous phase was observed due to the increased water content with increasing KOH equivalency. As the heat transfer performance of the microreactor was greatly improved compared with conventional reactors, higher reaction temperature could be admissible. 

Due to varying solvent systems, varying purities and water contents of purified pigments, different molar extinction coefficients have been reported." - - The most reliable ones commonly applied are 60,000 L/mol cm for betanin, 56,600 L/mol cm for amaranthin, and 48,000 L/mol cm for betaxanthins. ° Pigment contents may be calculated with the following formulae." - ... 

The relevance of Pt-OH formation to the change in the Tafel slope has been demonstrated by varying the content of water in the electrolyte [Murthi et al., 2004]. The experiments were performed in H20/trifluoromethanesulfonic acid (TFMSA) mixtures with several water/acid molar ratios. Whereas at high water contents the usual change in the Tafel slope from —112 to —59 mV/dec observed in aqueous solutions of H2SO4 and HCIO4 took place, at low water contents no change in the Tafel slope was observed. This corroborates the involvement of water in the formation... 

It was shown (1-3) that the silicon alkoxide solutions become spinnable when an acid is used as catalyst and the water content of the starting solution is small at less than 4 or 5 in the water to silicon alkoxide molar ratio. Recently, it has been found that this rule for the possibility of drawing fibers is only valid for the solutions reacted in the open system and no spinnability is found in the solutions reacted in the closed system (4). It has also been found that the addition of very large amounts of acid to the starting solution produces relatively large round-shaped particles, preventing the occurrence of spinnability (4). These will be discussed in the first half of this paper. 

The molar ellipticities are calculated for leucovorin free acid and have been corrected for water content. These values may be quite different from those of folinic acid. Although a single value is reported for each solvent, both spectra contain more than one absorption band. Whether the extraneous absorptions are due to impurities or are actually due to leucovorin s absorption behavior is not known at this time. 

Based on experimental results and a model describing the kinetics of the system, it has been found that the temperature has the strongest influence on the performance of the system as it affects both the kinetics of esterification and of pervaporation. The rate of reaction increases with temperature according to Arrhenius law, whereas an increased temperature accelerates the pervaporation process also. Consequently, the water content decreases much faster at a higher temperature. The second important parameter is the initial molar ratio of the reactants involved. It has to be noted, however, that a deviation in the initial molar ratio from the stoichiometric value requires a rather expensive separation step to recover the unreacted component afterwards. The third factor is the ratio of membrane area to reaction volume, at least in the case of a batch reactor. For continuous opera-... 

The magnitude of the CD has commonly been calibrated at 290 nm using ( + )-camphor-10-sulfonic acid as a standard. Because of its hygroscopic nature, the water content has led to some confusion. Tsujimura et al. have recommended to use a molar ellipticity of +7.78 x 103 for the compound in an aqueous solution 280). The concentration can be calibrated by the ORD of the same sample, which gave a molar rotation of +4.28 x 103 at 305 nm and of —5.44 x 103 at 270 nm. 

The phase transfer catalyzed alkylation reaction of dodecyl phenyl glycidyl ether (DPGE) with hydroxyethyl cellulose (HEC) was studied as a mechanistic model for the general PTC reaction with cellulose ethers. In this way, the most effective phase transfer catalysts and optimum reaction concentrations could be identified. As a model cellulose ether, CELLOSIZE HEC11 was chosen, and the phase transfer catalysts chosen for evaluation were aqueous solutions of choline hydroxide, tetramethyl-, tetrabutyl-, tetrahexyl-, and benzyltrimethylammonium hydroxides. The molar A/HEC ratio (molar ratio of alkali to HEC) used was 0.50, the diluent to HEC (D/HEC) weight ratio was 7.4, and the reaction diluent was aqueous /-butyl alcohol. Because some of the quaternary ammonium hydroxide charges would be accompanied by large additions of water, the initial water content of the diluent was adjusted so that the final diluent composition would be about 14.4% water in /-butyl alcohol. The results of these experiments are summarized in Table 2. 

The increase in alkylation efficiency of HEC with quaternary ammonium hydroxide is not limited to DPGE. Experiments were conducted in which HEC was alkylated with 1-bromohexadecane (cetyl bromide), 3-n-pentadecenyl phenyl glycidyl ether (PDPGE)14, or 1,2-epoxyhexadecane (C]6 a-olefin epoxide) in the presence of either sodium hydroxide or benzyltrimethylammonium hydroxide. As before, the molar A/HEC ratio was 0.50, and the water content of the diluent in the benzyltrimethylammonium hydroxide experiment was decreased to compensate for the higher water content of the base so that the final water content of both reactions was the same (14.4%). The hexadecyl content of the polymers was measured by gas chromatography. The sodium hydroxide mediated reaction of 1-bromohexadecane yielded a hexadecyl alkylation efficiency of 0.5%, while the benzyltrimethylammonium hydroxide reaction yielded a hexadecyl alkylation efficiency of 6.2%. A twelve-fold increase in the hexadecyl alkylation efficiency was observed in the reaction conducted with the quaternary ammonium hydroxide. 

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