Why do we add the iron (iii) chloride buffer to the salicylate solution?

Iron (III) chloride buffer is added to the salicyte solution in order to  qualitatively, or even quantitatively detect salicyclic acid (or salicylate salts) in solution.
The salicylic acid reacts with ferric chloride (FeCl3) to form iron (III) salicylate and hydrochloric acid.

Using a table of values, the outputs of f(x) for whole numbers are 0, 1, 4, 9, 16, 25, 36, and so on. For the same input values, g(x) has outputs of 1, 2, 4, 8, 16, 32, and 64. Continuing to double the output each time results in larger outputs than those of f(x). The exponential function, g(x), has a constant multiplicative rate of change and will increase at a faster rate than the quadratic function.

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