Hydroformed naphtha is obtained by passing a petroleum distillate having a boiling-range up to 650-700 DEG F., or higher, in the vapour phase together with free hydrogen over a suitable catalyst under a pressure preferably between 50-200 atmospheres and a temperature preferably between 930-1050 DEG F., the amount of hydrogen being 1000-4000 c.ft. per barrel of oil and the amount of oil per volume of catalyst space per hour being 1,5-4 volumes. Thus, a sulphur dioxide extract of a burning oil, boiling from 300-550 DEG F., is hydroformed by passage over a molybdenum sulphide catalyst, under a pressure of 3000 lb./sq. inch and an average catalyst temperature of 984 DEG F., at a rate of 3 volumes of oil per volume of catalyst reaction space per hour and with 2000 c.ft. of hydrogen per 42-gallon barrel of oil. The hydroformed naphtha is separated, by distillation, into fractions of boiling ranges 200-275 DEG F., 275-365 DEG F. and 365-419 DEG F.ALSO:Synthetic resins are prepared by heating with strong condensing agents, such as the active halide condensing agents and sulphuric acid, hydroformed naphthas obtained by passing a petroleum distillate, having a boiling range extending up to 650-700 DEG F. or higher, in the vapour phase together with free hydrogen over a suitable catalyst under a pressure preferably between 50-200 atmospheres or higher and a temperature above 900 DEG F. and preferably between 930-1050 DEG F., the amount of hydrogen being preferably 1000-4000 c. ft. per barrel of oil and the amount of oil per volume of catalyst space per hour being 1,5-4 volumes. The hydroformed naphthas may be further condensed with olefins, diolefines, olefine dihalides or acetylene. Desirable products are obtained from hydroformed fractions separated from petroleum oils by selective solvents, e.g. sulphur dioxide, phenol, acetonitrile, furfurol, orthoanisidine, resorcinol diacetate, ethylene diacetate, tricresyl phosphate, triphenyl phophate, aniline, acetone. The hydroformed naphthas may be given a mild, preliminary treatment with a small amount, e.g. 1-5 per cent of sulphuric acid or aluminium chloride to obtain products of improved colour. In examples, a sulphur dioxide extract of a burning oil, boiling from 300-550 DEG F. is hydroformed by passage over a molybdenum sulphide catalyst, under a pressure of 3000lb./sq. inch and an average catalyst temperature of 984 DEG F., at a rate of 3 volumes of oil per volume of catalyst reaction space per hour, and with 2000 c. ft. of hydrogen per 42-gallon barrel of oil; the hydroformed naphtha thus obtained is separated by distillation into fractions of boiling-ranges 200-275 DEG F., 275-365 DEG F. and 365-419 DEG F. A residual brittle resin is obtained by heating such a fraction, under reflux with stirring, with an addition of 5 per cent aluminium chloride, removing about 50 per cent of the naphtha as distillate, cooling the residue, hydrolyzing the aluminium chloride by adding aqueous alcohol, allowing to settle, withdrawing the upper oil layer and distilling to 300 DEG F. under 4 mm. mercury. Products varying from a heavy oil to a hard, brittle resin are obtained by heating, under reflux, a hydroformed, sulphur dioxide extract with ethylene dichloride and aluminium chloride; such products are insoluble in water and alcohol but soluble in drying oils, hydrocarbon oils and chlorinated hydrocarbons. The hydroformed naphthas may also be condensed with aldhydes, e.g. a hydroformed sulphur dioxide extract is heated with formaldehyde, sulphuric and acetic acids, the reaction mixture diluted with water, the oily layer separated, combined with a benzene extract of the watery layer and evaporated to yield a transparent, soft, yellow resin. Resins may also be obtained by condensing hydroformed naphthas with olefins, diolefins and acetylenes, e.g. cracked petroleum gases, in the presence of strong condensing agents such as aluminium chloride, boron fluoride, sulphuric acid, &c. The Specification as open to inspection under Sect. 91 comprises the subject-matter of Specifications 477,014, 477,015, and 479,017, and also the following matters: (1) the preparation of resins from the phenolic products described in Specification 477,015 (a) by reaction with formaldehyde in the presence of ammonia, and (b) by condensation with ethylene dichloride in the presence of aluminium chloride; (2) the preparation of sulphonamides by treating a hydroformed, sulphur dioxide extract with chlorosulphonic acid and then with ammonia; and (3) the preparation of resins from such sulphonamides by dissolution in acetic acid together with trioxymethylene and subsequent heating with sulphuric acid. This subject-matter does not appear in the Specification as accepted.