Verley and Meerwein and Schmidt discovered independently that an aldehyde can be reduced to the primary alcohol by treatment with aluminum ethoxide in the presence of ethanol. The reduction of the aldehyde occurs at the expense of an equivalent amount of ethanol which is oxidized to acetaldehyde. The reaction is reversible, but the equilibrium can be shifted to the point of complete reduction by removal of the acetaldehyde with a stream of hydrogen or nitrogen. This has the additional advantage of preventing side reactions such as aldol condensation between the original aldehyde and acetaldehyde. This method of reduction with aluminum chloride was found applicable to several aldehydes, but to only a few ketones of special types. This mild and specific method of reducing carbonyl compounds became know as the Meerwein-Ponndorf-Verley reduction Lund later studied the scope and limitations of the reaction.