Manganese Interference in the o–Tolidine Test for Available Chlorine<sup>1</sup>

Hopkins, Edward S.

doi:10.1021/ie50210a034

Cited by 10 publications

(5 citation statements)

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“…More recent suggestions are the use of dimethylp-phenylenediamine hydrochloride as a reagent for chlorine (3) and methyl orange for the estimation of chlorine in the absence of chloramine.The chief interfering substances in the accurate determination of chlorine by o-tolidine have been found to be manganese, nitrites and iron (1,5,6,7,8). Phelps suggested the use of 0tolidine in acetic acid (1) and Ellms and Hauser devised a method for estimation of chlorine based upon the use of o-tolidine in hydrochloric acid (2).…”

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The Determination of Free Chlorine

1934

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A number of reagents have been proposed for determination of free chlorine or chloramine in water. Phelps suggested the use of 0tolidine in acetic acid (1) and Ellms and Hauser devised a method for estimation of chlorine based upon the use of o-tolidine in hydrochloric acid (2). The starch iodide test has been used for some time by certain workers. More recent suggestions are the use of dimethylp-phenylenediamine hydrochloride as a reagent for chlorine (3) and methyl orange for the estimation of chlorine in the absence of chloramine.The chief interfering substances in the accurate determination of chlorine by o-tolidine have been found to be manganese, nitrites and iron (1,5,6,7,8). At an earlier date Boruff and Buswell showed that there was no interference from nitrites and iron under the conditions necessary for making the o-tolidine test for free chlorine (9). But with the present general use of chloramine instead of chlorine longer reaction time must be allowed for the development of full color. Where this long reaction time is used, nitrites and iron, as well as manganese, interfere in the test. Obviously, the o-tolidine reagent is not entirely satisfactory and attempts have been made to adapt the reagent to the purpose by making corrections or eliminating the cause of interference either mechanically or chemically (4).In the o-tolidine test, each of the following would exert an effect: concentration of chlorine, oxidation potential of the chlorine or chloramine, pH and HCl concentration, concentrations of manganese and iron and the degree of oxidation of each, concentration of nitrite, concentration of the reagent and reaction time. With these things in mind work has been carried on in an attempt to find a reagent which would eliminate part of the difficulties experienced with 0tolidine. This investigation has been divided into three parts, involving (I) the application of the principle of oxidation-reduction potentials to the problem (II) nitrite interference in the o-tolidine test and (III) the nature of o-tolidine reactions. 1645

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“…The chief interfering substances in the accurate determination of chlorine by o-tolidine have been found to be manganese, nitrites and iron (1,5,6,7,8). At an earlier date Boruff and Buswell showed that there was no interference from nitrites and iron under the conditions necessary for making the o-tolidine test for free chlorine (9).…”

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The Determination of Free Chlorine

1934

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“…Ellms and Hauser (1, 2) and Forsberg (8) report that iron interferes with the determination of oxidizing agents using o-tolidine. Hopkins (4) found that manganese interferes and Mellan (8) reported that copper reacts with otolidine. The interference of iron and manganese was found to be proportional to the amount present and copper did not interfere under the authors' conditions.…”

Section: A Colorimetric Methods Dwight Williams and George S Hainesmentioning

confidence: 99%

Colorimetric Method

Williams¹,

Haines²

1945

Ind. Eng. Chem. Anal. Ed.

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“…Monfort (5) presented experimental evidence favoring the belief that the color production is essentially due to oxidation and lists a number of oxidizing agents including manganic and permanganate salts which are capable of producing the coloration when treated with orthotolidine. Hopkins (6) points out that such salts produce coloration with the reagent in proportion to their states of oxidation and that the reaction is not fundamentally a chlorination since he could produce the coloration in the absence of hydrochloric acid and chlorides. Apparently the above mentioned workers investigated only the qualitative character of the reaction.…”

Section: Nature Of the Ortho-tolidine Reactionmentioning

confidence: 99%