The estimation of dinitro‐o‐cresol in winter washes consisting of petroleum oil, the cresol and emulsifier, must first involve the separation of the cresol from the other constituents present. A method applicable to the cases of emulsions compounded with various types of emulsiner failed when sulphite lye was present, and this was shown to be due to the action on the cresol of reducing sugars in alkaline solution. Avoiding an alkaline extraction until these interfering substances had been effectively removed led to an alternative method by which it was possible to separate D.N.C. in this type of emulsion.The results obtained demonstrate that the methods described are satisfactory for the routine estimation of D.N.C. in petroleum oil/D.N.C. emulsi