{HEAD ~ Method} of treating maleic anhydride to remove color therefrom comprising passing {TAIL ~ molten or dissolved maleic anhydride} through an acidic cation exchange column to remove cations therefrom, and thereafter adding to the maleic anhydride thus treated from about 1 to about 1000 ppm of 3,3 thiodipropionitrile 
comprising passing
{ HEAD ~ Method } of treating maleic anhydride to remove color therefrom comprising passing { TAIL ~ molten or dissolved maleic anhydride } through an acidic cation exchange column to remove cations therefrom , and thereafter adding to the maleic anhydride thus treated from about 1 to about 1000 ppm of 3,3 thiodipropionitrile
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