Arthur John Hopkins

Name: The reaction between manganese dioxide and potassium permanganate
Author: Arthur John Hopkins

The reaction between manganese dioxide and potassium permanganate (1893)

Summary

“The reaction between manganese dioxide and potassium permanganate”, published in 1893, is a work by Arthur John Hopkins. It explores elements such as potassium permanganate, potassium and oxygen.

Quotes from The reaction between manganese dioxide and potassium permanganate (Arthur John Hopkins)

Arthur John Hopkins, The reaction between manganese dioxide and potassium permanganate (1893)

“ The conclusions to be drawn from the foregoing results are (1) that dilute solutions of potassium permanganate are more stable both in diffused light and in darkness than the more concentrated ones, and (2) that the presence of manganese oxides hasten to an enormous degree the reduction of potassium permanganate even at summer temperatures. It will also be observed that this reducing action of the manganese oxide is greater in the stronger than in the more dilute solutions. It should be remarked that the summer of 1892 in which these experiments were made, was one of unusual heat. ”

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Source: Gutenberg

Arthur John Hopkins, The reaction between manganese dioxide and potassium permanganate (1893)

“ The usual laboratory solution of potassium permanganate must be frequently restandardized. A slight loss in strength may be detected after standing even a few days and this change becomes more rapid as the decomposition proceeds. When one looks for the cause of this increase in the rate of the decomposition of the permanganate, the attention is naturally directed to the brown manganese oxide which [Pg 2] separates from the solution. A desire to ascertain whether the presence of this oxide influences the rate of the decomposition suggested the experiments here described. ”

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Source: Gutenberg

Arthur John Hopkins, The reaction between manganese dioxide and potassium permanganate (1893)

“ The light brown oxide which was used in the previous experiments had been prepared by adding a dilute solution of manganous sulphate to a hot [Pg 25] solution containing potassium permanganate in excess and dilute nitric acid. No analysis of the oxide thus prepared was made at the time of its preparation, but it has been shown by the work of others that the oxide must have had at that time a composition as regards the relation of manganese to oxygen, very nearly equivalent to that of MnO2. ”

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Source: Gutenberg

Arthur John Hopkins, The reaction between manganese dioxide and potassium permanganate (1893)

“ Potassium permanganate in weakly acid, in neutral, and in alkaline solutions, is reduced by manganese dioxide which has been prepared in the wet way, with evolution of one and one half atoms of oxygen for each molecule of the permanganate. ”

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Source: Gutenberg

Arthur John Hopkins, The reaction between manganese dioxide and potassium permanganate (1893)

“ The possibility of a reaction analogous to that between potassium permanganate and lead dioxide in the presence of strong nitric acid seems to be excluded by the fact that the higher oxides of manganese may be prepared in the presence of concentrated nitric acid. ”

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Source: Gutenberg

Arthur John Hopkins, The reaction between manganese dioxide and potassium permanganate (1893)

“ The foregoing results indicate (experiments III, IV, and V) that the oxygen lost spontaneously by manganese dioxide prepared in the wet way, is fully recovered when the reduced oxide is treated with excess of potassium permanganate.
The ratio of the manganese to the available oxygen was determined in the following manner. The contents of the flask were filtered through asbestos and the flask and the precipitate washed with cold water. The [Pg 54] contents of the filter were then returned to the flask and treated with an excess of a standard solution of oxalic acid and dilute sulphuric acid. ”

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Source: Gutenberg

Arthur John Hopkins, The reaction between manganese dioxide and potassium permanganate (1893)

“ The dilute nitric acid in which the oxide had been digested was found to contain manganous manganese, but analysis of the black product showed that the oxide had suffered a still further reduction. The ratio of manganese to available oxygen was found to have risen from 1.06: 1.00 to 1.157: 1.000. The analytical data are given below:— [Pg 27]
This ratio would correspond very nearly to a compound having the composition MnO·6MnO2 but it is by no means certain that the reducing action of nitric acid was finished. ”

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Source: Gutenberg

Arthur John Hopkins, The reaction between manganese dioxide and potassium permanganate (1893)

“ Acid neutralized = 38.10 percent.
XI. The flask contained black oxide 150 m.g. potassium permanganate 20 c.c. = 177.71 m.g., N/10 nitric acid 22.39 c.c. (= 2 molecules for each molecule of KMnO4) and was heated four and one half hours in the water bath.
Acid neutralized = 100.00 percent.
No definite conclusions can be drawn from these neutralization experiments since it is well known that manganese oxides prepared as were those used in these experiments always contain some, though probably not a constant quantity of alkali. ”

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Source: Gutenberg

Arthur John Hopkins, The reaction between manganese dioxide and potassium permanganate (1893)

“ He entered the Johns Hopkins University in 1890, was assistant in the quantitative laboratory of that university during the academic year of 1891-92, and the following year was appointed Fellow in Chemistry. ”

Arthur John Hopkins

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