of the cleansing agents. They are then put into the market as illuminating oils. They may also be used for solutions of India-rubber, but sulphuret of carbon is preferred for that purpose.
Faraday discovered benzine in 1825 among the products arising in the manufacture of oil-gas, and called it bicarbureted hydrogen. Mitscherlich, in 1825, in treating benzoic acid with soda, obtained a volatile liquid which he called benzine. Hofmann, in 1825, demonstrated that these two substances were the same. Berthelot explained the formation of the substance, and made a synthesis of it by heating acetylene, its molecule being composed of three molecules of that gas united, or of twelve atoms of carbon and six of hydrogen. Benzine is a type of a class of organic bodies that furnish, by substitution, innumerable series of derivatives. They are like buildings from which we can take the stones one at a time and replace them with others. They are the organic radicals, in which a number of atoms of carbon and hydrogen are associated in such a way that the energy of one atom of hydrogen is left free. In benzine, for instance, we may substitute for each atom of hydrogen an atom of chlorine and get benzine monochloride, benzine dichloride, etc., or an atom of bromine or iodine and get benzine bromide and benzine iodide; or another radical, such as methyl or ethyl, and get methylbenzine or ethylbenzine, dimethylbenzine, trimethylbenzine, and so on. These theories permit us to account for the long series of bodies which organic chemistry has revealed, many of which are now employed in industry.
Benzine, as everybody knows, is a light liquid, perfectly colorless, and having a nauseous odor. It nevertheless furnishes perfumes and dyes. Charles Mansfield, who was the first person to utilize benzine, and make it on a large scale, announced in 1847 that he had found among the derivatives of stone-coal an oil that might take the place of the oil of bitter-almonds. It was nitrobenzine. Mitscherlich had previously produced, by the lively reaction of nitric acid on benzine, a colorless liquid, in which a compound molecule of nitrogen and oxygen was substituted for one of the six atoms of hydrogen in benzine, but his experiment never got beyond the laboratories. It was attended by too great dangers. Nevertheless, Mansfield ventured to repeat it in his shop, and succeeded in basing an industrial operation upon it. Nitrobenzine can not be pure unless the benzine was pure, and that is rarely the case with the commercial article. In the mixture of hydrocarbons, of which naphtha is constituted, are some very nearly alike in composition and in respect to their boiling-point, and it is difficult, even with the best distilling apparatus, to arrest the passage of some of them. Toluene, for example, nearly always comes over with benzine. Like it, it is attacked by nitric acid and then yields a nitrotoluene. There has also been found, associated with nitrobenzine, a peculiar yellowish-colored acid, endowed with the smell and taste of the pineapple; and its ethers taste like the strawberry or the rasp-
