Photochemical precipitation of Barium sulfate
Gelb, Carol K.
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A photolytic method is developed for the homogeneous precipitation of barium sulfate. The method involves the addition of excess barium, as the EDTA complex, to the sulfur sample. An ammonium slycinate buffer is used to control the pH value and ammonium chloroacetate is added as the photo-sensitizing reagent. Irradiation of the mixture with 2537 radiation results in hydrolysis of chloroacetate with subsequent pH lowering and slow generation of barium sulfate precipitate. Precipitations were essentially complete after five hours. Easily filtered precipitates were obtained after digestion with a larse portion of ammonium nitrate. Photo-micrographs of the undigested precipitate indicate crystallines five to ten microns in diameter. Digestion of the precipitate results in formation of crystalline aggregates up to one hundred microns in diameter. After ignition, the precipitate was suitable for direct weighing and could be used as a basis for gravimetric sulfate determination. Samples containing between 10 milligrams and 120 milligrams of sulfate could be determined with an accuracy of ±0.2% or better. The precision of individual analyses was ±1 milligram sulfate for large samples and ±0.4 milligrams sulfate for smaller samples.
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