[Sis290025]

In the reaction of crystal violet (CV) with NaOH, the order of CV is 1 (first order). However, in an experiment that I did with a colorimeter, I did not entirely come up with this value. Graphical analysis was done to determine the best wavelength from the absorption spectrum and lambda_max = 590 nm.
After looking at the absorbance readings (or manipulations of A in relation to each order) vs. time at 0 order through 2nd order at 590 nm, it was concluded that 0 order (A vs t) gave the best line; this does not match the true value.

On the other hand, at 526 nm, which had a lower absorbance level than 590 nm, absorbance readings (and its manifestations) vs. time had the best line at first order (ln A vs t) than 0 and 2nd orders. Exactly why is the true value (first order) available at 526 nm but not at the lambda_max 590 nm?

Thanks.

[Sis290025]

Does it have to do with the amount of CV (perhaps less than the indicated mL was used or more)?  Any help would be appreciated! (I really don't know how to explain this or what could have possibly went wrong.)