The products thus obtained at the various stages of the process are themselves subjected to further distillation, and by the exercise of great care, requiring the most delicate and accurate treatment, a large variety of oils is obtained, and these are retailed under many and various fanciful names.

One of the most important and best known products of the fractional distillation of crude coal-naphtha is that known as benzene, or benzole, (C_{6}H_{6}).  This, in its unrefined condition, is a light spirit which distils over at a point somewhat below the boiling point of water, but a delicate process of rectification is necessary to produce the pure spirit.  Other products of the same light oils are toluene and xylene.

Benzene of a certain quality is of course a very familiar and useful household supplement.  It is sometimes known and sold as benzene collas, and is used for removing grease from clothing, cleaning kid gloves, &c.  If pure it is in reality a most dangerous spirit, being very inflammable; it is also extremely volatile, so much so that, if an uncorked bottle be left in a warm room where there is a fire or other light near, its vapour will probably ignite.  Should the vapour become mixed with air before ignition, it becomes a most dangerous explosive, and it will thus be seen how necessary it is to handle the article in household use in a most cautious manner.  Being highly volatile, a considerable degree of cold is experienced if a drop be placed on the hand and allowed to evaporate.

Benzene, which is only a compound of carbon and hydrogen, was first discovered by Faraday in 1825; it is now obtained in large quantities from coal-tar, not so much for use as benzene; is for its conversion, in the first place, by the action of nitric acid, into nitro-benzole, a liquid having an odour like the oil of bitter almonds, and which is much used by perfumers under the name of essence de mirbane; and, in the second place, for the production from this nitro-benzole of the far-famed aniline.  After the distillation of benzene from the crude coal-naphtha is completed, the chief impurities in the residue are charred and deposited by the action of strong sulphuric acid.  By further distillation a lighter oil is given off, often known as artificial turpentine oil, which is used as a solvent for varnishes and lackers.  This is very familiar to the costermonger fraternity as the oil which is burned in the flaring lamps which illuminate the New Cut or the Elephant and Castle on Saturday and other market nights.

By distillation of the heavy oils, carbolic acid and commercial anthracene are produced, and by a treatment of the residue, a white and crystalline substance known as naphthalin (C_{10}H_{8}) is finally obtained.

Thus, by the continued operation of the chemical process known as fractional distillation of the immediate products of coal-tar, these various series of useful oils are prepared.