Revisiting the Determination of Percent Aspirin Lab: Using a Limiting Reactant Approach for Students To Also Determine the Amount of Iron(III) Chloride

Abstract

The spectrophotometric determination of the percent composition of an aspirin tablet is a common first-year, general chemistry undergraduate laboratory procedure. The experiment requires that a known amount of pure acetylsalicylic acid be quantitatively converted into the soluble disodium salicylic acid that is further reacted with excess iron­(III) chloride solution to form a deep blue tetraaqua-octahedral complex. This complex, through serial dilutions, is used to construct a Beer’s law plot that may be used to determine the concentration of aspirin. In a novel twist, this paper describes how the same Beer’s law plot can be used to determine the concentration of iron in the iron­(III) complex, which is then used to determine the concentration of the original iron­(III) chloride solution used to make the aspirin–iron­(III) complex. The method has been adapted by high school students in determining iron concentrations in stream waters.

Iron Quantification in Dietary Supplements using Four Colorimetric Assays

“…In the pH range 0.7–2.5, the salicylic acid assay has been used to quantify salicylic acid in liquid facewash , and acetylsalicylic acid hydrolyzed samples. , …”

“…In the pH range 0.7−2.5, the salicylic acid assay has been used to quantify salicylic acid in liquid facewash 82,83 and acetylsalicylic acid hydrolyzed samples. 84,85 Here, the salicylic assay was carried at a pH close to 5, where Fe 3+ and salicylate form a red complex like in the KSCN assay, and its λ max value was also close to that of the FeSCN 2+ complex. The value of 480 nm corresponds to the B channel, and the G channel gave the highest calibration sensitivity (Figure 6).…”

Colorimetric Detection of Salicylic Acid in Aspirin Using MIL-53(Fe) Nanozyme

“…To illuminate the mechanism of inhibitory effects of SA on the MIL-53(Fe) activity, the purple complex of SA-Fe(III) was characterized by UV-Vis absorbance spectroscopy. As revealed by Figure 3 , a conspicuous absorption peak at ~520 nm appears when FeCl 3 is used as the standard sample to incubate with SA (Chang et al, 2017 ; Bodek et al, 2020 ), and the color of the solution changes to purple. Likewise, the same absorption peak at 520 nm occurs when MIL-53(Fe) and SA are incubated together.…”

All Roads Lead to Rome: Triple Stoichiometry with a Lithium Battery

“…To reinforce its concepts, experiments are continuously designed so that students can better understand molar ratios from a practical standpoint. For example, in the past decade, the Journal of Chemical Education published papers on the subject whereby the favorite techniques to ascertain stoichiometric relationships included mainly colorimetry/spectrophotometry, − conductivity, , electrochemistry, − gravimetry, − titrimetry, , gas generation, − thermochemistry/thermal analysis, , − and catalysis …”