Korosy1 has recently reported that copper formate decomposes when heated, evolving a small amount of a volatile copper compound. I encountered a similar phenomenon when gently igniting a deposit from a copper rectifying column, the deposit containing cupric acetate. According to Angel and Harcourt2 the formation of a white sublimate of cuprous acetate on heating cupric acetate was first observed so long ago as 1773 by Lassone3. The formation of such volatile compounds may result in low values for the copper content of such materials f as vinegar when dry-ashing methods are used in their analysis.