ALCOHOL DILUTION PRACTICES
FOR DISTILLERS W R I T T E N B Y G A R Y S P E D D I N G , P h . D . , A M B E R W E Y G A N D T, B . S c . , & M A T T H E W L I N S K E , B . S c .
istillers and those dealing with industrial ethanol in large quantities are often required to make dilutions to lower the alcoholic strength of their products. Many solutions can simply be mixed in appropriate volumes to yield the desired ending concentration. However, some chemicals exhibit a contraction effect when mixed with other aqueous solvents, resulting in a final solution of lower volume than would be expected theoretically. Alcohol water mixtures are a prime example of this relationship at work. Many chemists, mathematicians and distillers still use the algebraic formula V1C1 = V2C2 for ethanol water solutions. (V = volume in any unit and C = concentration, often % v/v for alcohol solutions.) However, due to the contraction effect of water and alcohols, the above formula is inadequate for accurate mixing purposes with respect to ethanol and water mixtures. The magnitude of this physical effect (often seen as 3% in the literature) is actually from 0 to 4% and can be illustrated as a curve across the full range of water – ethanol volume permutations. (See Addendum for comments and terms used.) Distilled spirits are known to contain many congeners besides ethanol. These congeners are generally insignificant in their weight and volume contribution in terms of the contraction effect and are not considered further in this current discussion. Tables that give water volumes to add to a defined volume of alcohol exist often in discrete increments, which leaves the chemist or distiller to interpolate data for actual or desired conditions. Algorithms and other data tables also supply information enabling certain mixtures to be made, but are also either difficult to find, use or adopt by the distiller or are unknown to many (or may not be appropriate to task or accepted by regulatory bodies). Failure to understand hydroalcoholic dilutions can lead to label errors and rejection of product for sale by regulatory authorities. WWW.ARTISANSPIRITMAG.COM
Recently, Dr. Travagli, a professor of Pharmacy, presented an online paper dealing with applications of mixing ethanol solutions for drug delivery. The paper turns out to be a boon to the distilling industry in that it provides both the theory and the equations that may make it easier to attain accurate volumetric dilutions, ideally by first going through the mass relationship properties of alcohol. This prevents some possible errors for spirit dilution and proofing for bottling. An interpretation and extension of the paper is presented to broaden its acceptance and application to and for distillers (Travagli – see Reference citation at the end of this article). It, at the very least, provides us with a much-needed talking point for the new age distilling industry folks, though it is noted that the U.S. TTB regulatory agency would likely rely upon methods using the Gauging manual tables. Distillers should be aware of this latter approach and be clear on how to do proofing dilutions when bottling their spirits (see Addendum for more on this). The equations and approaches here may well be useful for double-checking proofing calculations and confirming the accuracy of dilutions.
INTRODUCTION Many years back, several publications (early treatises) discussed alcohol blending and alcohol dilution issues, especially for distillers, and presented some data in tabulated form. The available tables, although limited in scope, showed a few data points for specific volumes of water to add to various strengths of alcohol to lead to correct dilutions of distilled spirits. Distillers and regulatory agencies provided details dealing with Proofing, Proof Gallon equations etc., to adequately report alcohol content for excise purposes. Such instructions can be found on the TTB website, and require some practice. (See: U.S. Govt. Gauging Manual table 6 - “Respective