JUNE. 1950
AN IMPROVED QUALITATIVE TEST FOR CARBONATES RICHARD 8 . HAHN and RICHARD MULLINS Wayne University, Detroit, Michigan
THEapparatus shown in the illustration is an improvement over the usual methods of testing for carbonates. It yields results more reliable and more clearly visible than in the "hangingdrop" method. It avoids sucking back and eliminates false positive tests caused by decomposition of oxalates in the distillation method. Procedure. A small amount of unknown acidified with hydrochloric acid is introduced in the first tube; acidified dichromate in the second to react with such impurities as sulfur dioxide; barium hydroxide solution is put in the third tube. Suction or positive air pressure is then applied so a rapid but gently bubbling stream is observed in the tubes. If a carbonate is present a white precipitate will form in barium hydroxide within a minute or two. As little as 1 ma. COa- ion can be detected bv this method. One seGp $11 usually be sufficient 'for a class.
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