The Spectrophotometry II program calculates K_d for the dissociation of the thiocyanatoiron(III) complex ion from data collected in Experiment 7.¹ Highlight the default value (0.791) for the absorbance of Solution X in the column labeled "Absorbance" and enter your value. Highlight the default value (0.587) for the absorbance of Solution A and enter your value. Continue in this manner until you have entered the absorbances of all the solutions. Click the "Enter" button to obtain a plot. If you wish to correct the data or add new data, return to the Spectrophotometry II table, make the necessary changes, and again click the "Enter" button to update the plot.

    Click the "Linear Regression" button in the upper right-hand corner of the plot window to fit the data with the linear equation. The values for the K_d , the standard deviation of the K_d , the ab (eb), the standard deviation of ab (eb), and the correlation coefficient are displayed on the plot. The correlation coefficient is a measure of how closely the linear equation fits the data. Generally, the fit improves as the magnitude of the correlation coefficient approaches 1.000. To obtain a hard copy of the plot, press the "Print Screen" key on your keyboard (upper right). Open your favorite word processing program - WordPerfect, Word, WordPad - and "Paste" the plot to the blank page. Finally, print the page with the plot. A hard copy of the Spectrophotometry II table may be acquired in a similar manner. See the Tutorial for Spectrophotometry II for help.