Date of Award


Degree Type

Bachelors Essay

Degree Name

Bachelor of Science (BS)




In the Journal of Industrial and Engineering Chemistry for November, 1913, J.W. Ellms and S.J. Hauser introduced the ortho-tolidine test for the detection of minute quantities of free chlorine in water. Antecedant to the experimentation of the above men with ortho-tolidine, the starch-iodide test ·was universally used for the· detection of free chlorine. In this test, the chlorine is calculated by liberating iodine from potassium iodide by the available chlorine, and the iodine being titrated with sodium thio sulfate. starch solution is used as the indicator. However, this particular method offers difficulties in the presence of minute quantities of chlorine because both the sodium thio sulfate and the potassium iodide solutions deteriorate on standing. Thus, for scientifically accurate results, it would be necessary to prepare fresh standard solutions of thiosulfate, or else keep re-standardizing the already prepared standards. This element is an inconvenience, and a needless expenditure of time. On the other hand, the ortho-tolidine solution used in the test can be kept for a relatively long period of time without a change in its strength. In conjunction with its permanence, the ortho-tolidine is very sensitive to chlorine...


A Thesis submitted partially to fulfill the requirement for The Degree of Bachelor of Science

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