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The procedures, as here prescribed, are applicable to iron ores in general, provided these ores contain no constituents which are reduced by zinc or stannous chloride and reoxidized by permanganates. Many iron ores contain titanium, and this element among others does interfere with the determination of iron by the process described.
Whatever other variations may occur in its composition, the ratio of 12 MoO :1 P seems to hold, and this fact is utilized in volumetric processes for the determination of phosphorus, in which the molybdenum is reduced to a lower oxide and reoxidized by a standard solution of potassium permanganate. The total volume of nitrate and washings should not much exceed 100 cc.
Lead glass is softer and more readily fusible than soda glass, but has the disagreeable property of growing black in a few seconds unless worked in a strong oxidizing flame. This may be prevented by using a "hissing" flame, with a large excess of air, and working in the extreme end of the flame; or the black lead formed may thus be reoxidized, and the glass restored to its original clearness.
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