USP Arsanilic Acid assay

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poorpatti
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USP Arsanilic Acid assay

Hello, I am doing the USP assay for arsanilic acid over again and getting results out of specification.  Has anyone done this test?  How about on a non-USP grade arsanilic acid?  I end up having to transfer the test solution from a 125-mL Erlenmeyer into a 250-mL Erlenmeyer to finish and am getting way too much 0.1 N potassium permanganate added.  This is occurring over a number of samples. 

Thanks!