Grans

For volumes of titrant before the equivalence point, a plot of Vb X [H3O+] versus Vb is a straight line with an x-intercept equal to the volume of titrant at the end point and a slope equal to Results for the data in Table 9.5 are shown in Table 9.6 and plotted in Figure 9.13d. Plots such as this, which convert a portion of a titration curve into a straight line, are called Gran plots. 

A second approach for determining the piQ of an acid is to replot the titration curve in a linear form as a Gran plot. For example, earlier we learned that the titration of a weak acid with a strong base can be plotted in a linear form using the following equation... 

This short paper describes a modification to the traditional Gran plot for determining the concentration of a weak acid in the presence of a strong acid. 

Directions are provided in this experiment for determining the dissociation constant for a weak acid. Potentiometric titration data are analyzed by a modified Gran plot. The experiment is carried out at a variety of ionic strengths and the thermodynamic dissociation constant determined by extrapolating to zero ionic strength. 

The following data were collected with an automatic titrator during the titration of a monoprotic weak acid with a strong base. Prepare normal, first-derivative, second-derivative, and Gran plot titration curves for this data, and locate the equivalence point for each. 

Schwartz has published some hypothetical data for the titration of a 1.02 X ICr" M solution of a monoprotic weak acid (pXa = 8.16) with 1.004 X ICr M NaOH. " A 50-mL pipet is used to transfer a portion of the weak acid solution to the titration vessel. Calibration of the pipet, however, shows that it delivers a volume of only 49.94 ml. Prepare normal, first-derivative, second-derivative, and Gran plot titration curves for these data, and determine the equivalence point for each. How do these equivalence points compare with the expected equivalence point Comment on the utility of each titration curve for the analysis of very dilute solutions of very weak acids. 

Meloun, M. Havel, J. Hogfeldt, E. Computation of Solution Equilibria. Ellis Horwood Limited Chichester, England, 1988. The following paper provides additional information about the use of Gran plots. 

Schwartz, L. M. Advances in Acid-Base Gran Plot Methodology, /. Chem. Educ. 1987, 64, 947-950. 

Gran plot a linearized form of a titration curve, (p. 293) graphite furnace an electrothermal atomizer that relies on resistive heating to atomize samples, (p. 414) gravimetry any method in which the signal is a mass or change in mass. (p. 233)... 

Table 9-43 is based on the method suggested by J. Gran [Eng. Process Econ., 2, 89-90 (1977)]. He showed that reasonably accurate plant-cost indices for various countries could be derived by using two component indices in the equation... 

General References Ennis Litster, The Science Engineeiing of Gran-... 

Mass and Energy Balances Due to the good mixing and heat-transfer properties of fluidized beds, the exit-gas temperature is assumed to be the same as the bed temperature. Fluidized bed gran-... 

A variation of the classical reductive fflnination procedure uses sodium cyanoboro-hydride (NaBH3CN) instead of hydrogen as the reducing agent and is better suited to fflnine syntheses in which only a few grans of material ae needed. All that is required is to add sodium cyanoborohydride to an alcohol solution of the ca bonyl compound and an anine. 

Gran-plot (multiple standard addition with 10iE/s vs. concentration) 0.1-3% 0-1-3% less accurate if interfering ions are present best results if many points between 30 and 80% of a titration curve are evaluated and discordant points are eliminated... 

A number of commercial titrators are available in which the electrical measuring unit is coupled to a chart recorder to produce directly a titration curve, and by linking the delivery of titrant from the burette to the movement of the recorder chart, an auto-titrator is produced. It is possible to stop the delivery of the titrant when the indicator electrode attains the potential corresponding to the equivalence point of the particular titration this is a feature of some importance when a number of repetitive titrations have to be performed. Many such instruments are controlled by a microprocessor so that the whole titration procedure is, to a large extent, automated. In addition to the normal titration curve, such instruments will also plot the first-derivative curve (AE/AV), the second-derivative curve (A2 E/AV2), and will provide a Gran s plot (Section 15.18). 

The success of the Keck telescopes led to a Spanish project Gran Telescopic Canarias (GTC) to build a 10-m telescope on the Canary Islands in La Palma. This telescope is similar to the Keck, and should be operational in 2006. 

Formulation(s) gran. 250 mg syrup 250 mg tabl. 750 mg (as sodium salt)... 

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