Rev. Rul. 54-185

Blends of two or more pure straight whiskies, aged in wood for a period of not less than 4 years, which are exempt from the rectification tax of 30 cents per proof gallon by section 2801 of the Internal Revenue Code and section 190.479 of Regulations 15, may have added thereto not more than 7 ounces of activated carbon for each 400 gallons of spirits for the purpose of clarification provided the character of the whisky is not changed thereby. Formulas on Form 27-B Supplemental, `Formula and Process for Rectified Spirits,' covering such blends of pure straight whiskies to which activated carbon is to be added should include a statement as to the amount to be used.