The most effective catalyst to use in the process of producing adhesives using formaldehyde and urea is an acidic catalyst. Commonly used acidic catalysts for this reaction include ammonium chloride NH4Cl and ammonium sulfate NH4 2SO4 . These catalysts help to promote the condensation reaction between formaldehyde and urea, leading to the formation of urea-formaldehyde resins, which are widely used in the adhesive industry.