   Ask the Expert Question-and-Answer Archive by Ron Joseph January, 2007 Calculating VOC from an MSDS That Provides Specific Gravity Q: Please provide me a tip to calculate a VOC pd/gal if the MSDS only has a Specific Gravity. Ex. 1.5  A:  To calculate the VOC of a coating from a Material Safety Data Sheet (MSDS) one needs to multiply the percent weight (organic) solvent (% Wt. solvents), or (% Wt. volatiles) by the density of the coating.  Density is sometimes given as WPG (weight per gallon). For instance, if the % Wt. (organic) volatiles = 48% and the WPG = 9.4 lbs/gal, the VOC content = 0.48 * 9.4 lbs/gal = 4.51 lbs/gal. If the density is not given in lbs/gal but as specific gravity (S.G), such as S.G. = 1.5 you need to multiply by 8.33 lbs/gal. Specific gravity is the ratio of the density of a compound to the density of water, which is 8.33 lbs/gal. (Some references give the density of water as 8.34 lbs/gal). In the calculation given above the density of the coating is 9.4 lbs/gal, therefore its S.G. = 9.4lbs/gal / 8.33 lbs/gal = 1.13 If the S.G. of the coating had been given in the above example, the calculation would have been: VOC (lbs/gal) = 0.48 * 1.13 * 8.33 lbs/gal = 4.51 lbs/gal Regards, Ron Joseph

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