1Japan Special Steel Co., Ltd., Research Laboratory, Tokyo
An experiment was carried out to establish a simple and accurate method for the determination of microamounts of bismuth in high alloy steel.
The bismuth was separated as a thionalide complex from iron and other elements in an ammoniacal solution in which were masked these elements by the use of ammonium tartarate, sodium cyanide and sodium sulfite. By means of the separation method with thionalide, the microamounts of bismuth can be separated easily and accuratlly from large amounts of various elements. Niobium and tantalum were coprecipitated as pentaoxides with tungstic acid by the hydrolysis method with sodium sulfite in a perchloric acid medium to which was added 5 mL of sodium tungstate solution (1 mL=1 mg W) as coprecipitating reagent and were separated beforehand from other elements.
The separated bismuth was determined by the spectrophotometric method with dithizone.
In this dithizone method, the formation and extraction of the bismuth dithizonate complex were done in a perchloric acid medium containing ascorbic acid, and in this way the most suitable pH is found to be 2.0 ± 0.2.
This dithizonate complex is extracted with benzene quantitatively and readily.
The absorption maximum of this dithizonate complex is at 510 mill microns when the absorption is measured against a dithizone benzene solution reference. At this wavelength, the relation between the amounts of bismuth and the absorption follows Beer's law in the range from 0 to 25γ/10 mL of bismuth.
As a result of the experiment, the author succeeded to establish a method in which less than 0.005% of bismuth in high alloy steel can precisely be measured without difficulty.
The bismuth contents in synthetic samples were measured by this method with satisfactory results.
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