Naphtha, a term originally applied to a variety of pungent, volatile, inflammable liquids, chiefly belonging to the class of ethers; it was then extended to oils of natural origin, rock oil, petroleum, etc. Subsequently the light oil of coal tar, owing to its resemblance to mineral oil, was termed naphtha; more recently it has been again extended so as to include most of the inflammable liquids produced by the dry distillation of organic substances. In the United States it is applied to a series of hydrocarbons obtained from petroleum, and having specific gravities ranging from 0.625 (rhigolene) to 0.742, and boiling points varying with the densities from 65° to 300° F. The following are some of the naphthas known in commerce: 1, boghead naphtha, obtained by distilling the Torbane hill mineral or boghead coal at as low a temperature as possible; 2, bone naphtha, Dippel's animal oil; 3, coal naphtha, obtained by the distillation of coal tar, and often confounded with benzole; 4, mineral naphtha, from petroleum.
According to S. Dana Hayes, the petroleum naphthas have distinguishing characteristics by which they are easily recognized, and which place them in a class by themselves; and aside from their odors, densities, boiling points, volatilities, and solvent powers, a noticeable peculiarity is the absence of oily bodies; they do not leave any permanent stain on common writing paper, as do all the heavier oils obtained from petroleum. The commercial products are:
5. Wood naphtha, pyroligneous acid, pyroxylic spirit, or methylic alcohol, is a colorless, mobile, indifferent, inflammable liquid, which burns with a faintly illuminating, bluish flame; it is miscible in all proportions with water, alcohol, ether, and ethereal oils; specific gravity 0.796, boiling point 149° F. When pure it has been prescribed in medicine for diseases of the lungs, and owing to its cheapness it is often substituted for alcohol, and sometimes used to adulterate brandy. - As commonly described, naphtha is a very inflammable colorless liquid, of bituminous odor, tasteless, soluble in all proportions in absolute alcohol and in ether, insoluble in water, of specific gravity 0.700 to 0.847. It dissolves the fixed and essential oils in all proportions, and is hence advantageously used for removing grease from fabrics, and for the extraction of oils from seeds. It also dissolves sulphur, phosphorus, iodine, gum lac and copal, camphor, caoutchouc, the resins, etc.; a quality that adapts it for the preparation of varnishes, and for other similar uses in the arts.
In its preparation from artificial coal oils it is found that those which produce paraftine yield in general naphtha, while the product of those which contain naphthaline is rather limited to the hydrocarbons of the benzole series. It is manufactured into gas, is used to increase the illuminating power of coal gas in the place of benzole, and is sold for combustion in gas stoves and in lamps. There is probably no chemical product which has occasioned the loss of so many lives and the destruction of so much property as naphtha. Since its cheap manufacture as an incidental product in the distillation of petroleum, it has been thrown upon the market in enormous quantities, and owing to its cheapness has been mixed with petroleum or sold under a great variety of names for heating and illuminating purposes; and from its highly explosive and inflammable nature, it has proved little better in the hands of ignorant people than so much gunpowder. Its sale is now everywhere prohibited except for legitimate purposes.