Sulfur plot, concentration versus time

In industrial production of acid-modified starches, a 40% slurry of normal com starch or waxy maize starch is acidified with hydrochloric or sulfuric acid at 25—55°C. Reaction time is controlled by measuring loss of viscosity and may vary from 6 to 24 hs. For product reproducibiUty, it is necessary to strictly control the type of starch, its concentration, the type of acid and its concentration, the temperature, and time of reaction. Viscosity is plotted versus time, and when the desired amount of thinning is attained the mixture is neutralized with soda ash or dilute sodium hydroxide. The acid-modified starch is then filtered and dried. If the starch is washed with a nonaqueous solvent (89), gelling time is reduced, but such drying is seldom used. Acid treatment may be used in conjunction with preparation of starch ethers (90), cationic starches, or cross-linked starches. Acid treatment of 34 different rice starches has been reported (91), as well as acidic hydrolysis of wheat and com starches followed by hydroxypropylation for the purpose of preparing thin-hoiling and nongelling adhesives (92). 

The kinetics of the polymerization of pyrrole can be followed by measuring the disappearance of the reactants. Pyrrole concentrations can be determined by gas chromatography [10]. The depletion of iron can be followed by the titration of the iron(III) chloride with a complexing agent, and the disappearance of the sulfur-containing doping agents can be determined by inductively coupled plasma (ICP) [47]. Experiments reveal that the reaction follows second-order autocatalytic kinetics [ 10]. A plot of the concentrations of pyrrole monomer (surface and no surface) versus time at room temperature is shown in Fig. 35.5. The surface resistance of the polypyrrole-coated textiles can be controlled by... 

Figure 20 Progress of intramolecular sulfurization of malabaricatriene (I) with depth in anoxic Cariaco basin sediments. Plot of the ratio of the concentrations of I to the sum of the concentrations of I + V (see Figure 19 for structures) as a function of sediment depth. The progress of transformation of I-V with increasing sediment depth is indicated by the steady decrease in the relative abundance of the precursor lipid (I). Inset plot of In ([ ]/([ ] + [V])) versus sediment age (= time), used to empirically determine the first-order rate constant for sulfur incorporation...

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