Effect of ethanol strength on the volatility of higher alcohols and aldehydes

Activity coefficients of selected higher alcohols and aldehydes from the ho mologous series C6 to C12 (even carbon number), dissolved in aqueous soluti ons at different ethanol strengths, were obtained using headspace analysis by Gas Chromatography with Flame Ionisation Detection. Determinations from 5 to 25% ethanol showed a log-linear decrease from 17% ethanol for octanal, while for octanol the behaviour approximated more a log linear decrease ov er the whole range of ethanol concentrations. Reductions in activity coeffi cients were significant between 10 and 15% ethanol for decanol, dodecanol a nd dodecanal, and between 10 and 20% ethanol for all the other compounds. C hanges in the proportion of ethanol-water mixtures had the same effect for aldehydes as previously found for ethyl esters, presumed to be related to c lustering of ethanol molecules at >15% ethanol. The behaviour of higher alc ohols showed no clear relation with the structural changes in the solution.