PURPOSE: To obtain new various perfluorinated ethyldimethyl derivatives of cyclohexane valuable as inert stable boiling fluids required for the manufacture and examination of electronic parts in electronic secondary processing industry.

CONSTITUTION: The perfluorinated compound represented by formula I, in which carbons in the ring are completely fluorinated, e.g. the compound of formula II, formula III or formula IV, is obtained e.g. by gasifying a 1,1-di(orthoxylyl) ethane in a cobalt trifluoride reactor works at 230 to 350°C, subsequently collecting a fluorochemical product containing a perfluoro-1,1-di(orthoxylyl) methane and separating it from a hydrogen fluoride by-product. The compound of formula I has utilities as a vapor bath at the time of soldering and as a gas transporter for a fluid system. The compound of formula I is an inert fluid having an accurate boiling point and a accurate vapor pressure and a gas transporting ability.