Final answer:
The ascorbic acid was added drop by drop during titration to control the reaction's progress and ensure an accurate measurement of the endpoint, minimizing the risk of inaccuracies.
Step-by-step explanation:
During a titration assay, it is important to add the ascorbic acid drop by drop to achieve a precise endpoint. In the context of the titration assay described, ascorbic acid was oxidized with I3- and the excess I3- was back titrated with Na2S2O3.
A controlled addition ensures that the reaction between the reagents proceeds steadily and allows for accurate detection of the endpoint, often indicated by a color change with an added indicator. This gradual approach minimizes the risk of overshooting the endpoint, which would result in an inaccurate measurement of the ascorbic acid concentration.