Formocresol is a solution of 19% formaldehyde, 35% cresol in a vehicle of 15% glycerine and water. To prepare a 1:5 concentration of this formula, first thoroughly mix 3 parts of glycerin with 1 part of distilled waler, then add 4 parts of this preparation to 1 part Buckley’s formocresol, and thoroughly mix again. Key Concept In formocresol, we use 19% formaldehyde and 35% cresol i.e. ratio of 1:2.