Abstract
Comparing with other methods of determination of Mn in iron and steel, the estimation by measn of As2O3 solution is not only, quicker and economical, but also yields rather good results, so it is widely adopted as routine analysis in numerous plants. Though rapid and simple, it has, on the other hand, several defects as causing analytical errors, and there remain many points still to be cleared, in consequence of incompleteness in the theoretical explanation and the method of confirming the mechanism of reaction. In the present investigation, therefore, every condition of operation is carefully studied, and the best ones found are as follows.(1) The time of boiling after adding (NH4)2S2O6 shall be limited to a minute. (2) The temperature of the solution at the time of titration shall be below 30°C. (3) The shorter the time required for titration is, the better is the result, but ordinary titrating velocity will do too. (4) AS regards the concentration of acid for dissolution, 30 c.c. of HNO3(1:1) will do as shown in Gakushin Method, but the use of H2SO4 at the same time in more rational for certain kinds bf samples in view of the sluggishness of dissolution velocity thereof. (5) The most suitable amount of AgNO3 to be added is 10 c.c. of 1% solution, and (6) that of (NH4)2S2O3 is 10c.c. of 25% solution just as in customary practice.
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