Aluminum aluminon color development

Analysis of Sample. Fifty ml. of the sample aliquot was centrifuged with an International Centrifuge Size 2 at 2000 r.p.m. (approximately 1000 G) for 20 minutes. The centrifugates were analyzed for their pH, concentrations of aluminum and phosphate, and the rate of aluminum-aluminon color development. The precipitates were washed with 30 ml. of water four times, dissolved in 10 ml. of N HCl, and analyzed for their concentrations of aluminum, phosphate, and sodium. 

Rate of Aluminum-Aluminon Color Development. The preparation of color solution for rate measurement was similar to the procedure for aluminum determination (9), but the following remarks are important ... 

The rate of aluminum-aluminon color development is shown in Figure 3. In this experiment, aluminon was added to aluminum solutions and the color intensity measured at various intervals. It was found that free AF reacted with aluminon very rapidly, the color intensity reaching 75% of its maximum intensity in two minutes, and 95% in about 20 minutes. The rate of color development was considerably lowered when phosphate was present in the original solutions (Figure 3), whereas the final color intensity was not aflFected. The absorption spectra in the... 

Figure 3. Rate of aluminum-aluminon color development. The color intensity is converted to % A1 found for plotting. All solutions are O.OIM in Al...

Aluminum was quantitatively determined by spectrophotometry (Amax 540 nm) after extracting from silica layer with double-distilled water and developing the color with 0.1% aqueous aluminon. 

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