RESULTS:
The oxidation was first studied qualitatively, various amounts of acid,
indicator and dichromate being mixed at different temperatures, and the
time noted at which the color first became perceptible. The results were
not very exact since it was hard to perceive the first tinge of violet, due to a
green which often accompanied it. The hue is somewhat dependent upon
the acidity, being violet at low hydrogen-ion concentrations, and more blue
in acid concentrations higher than 4 N.
The speed of oxidation is approximately proportional to the amount of
dichromate added for a given amount of indicator, and to the amount of
indicator used for a given amount of dichromate. Furthermore, the reaction
velocity increases rapidly with the temperature, being about four
times as great at 55 as at 25'.