At the second highest concentration of salicylic acid in Figure , the graph reaches a plateau. This disruption in the linear increase in absorption suggests that at that point, not all of the salicylic acid reacted with the iron (III) nitrate, or in other words, there was not enough iron (III) nitrate for all of the salicylic acid to react. The iron (III) nitrate solution used throughout the experiment was made by dissolving iron (III) nitrate powder in distilled water. It initially dissolved in the water easily, being an ionic compound, but after being left in the lab for a few days, there was precipitate observed at the bottom of the bottle holding the solution. It is likely that this occurred due to slow hydrolysis of the iron (III) in the solution, which produced iron (III) hydroxide, an orange precipitate . This would have reduced the concentration of iron (III) nitrate available in the solution for the salicylic acid to react with, explaining why despite iron (III) nitrate being in excess stoichiometrically, the salicylic acid did not fully react. This error can be prevented by the remaking of iron (III) nitrate solution in the beginning of every lab day, avoiding the slow formation of precipitate.