Denys Cochin

“ All of our products have been obtained from a vegetable or organic, not from the primary mineral, carbon; not from carbon either, but from compounds of carbon and hydrogen of a character which we have not yet been able to produce by synthesis of the primary mineral elements, but which the sun stored up for us ages ago, working through the agency of organic growth. ”

“ 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. ”

“ Anthracene is one of the most valuable of the hydrocarbon extracts of coal-tar. It evidently did not exist as anthracene in the coal, but has been formed during the distillation, a solid, crystalline body, by the combination and condensation of gases.
So, when coal is heated to a very high temperature, the substances that are disengaged in a gaseous form do not always remain in that state. Heat is not always a cause of the dissolution of bodies and of the dispersion of their elements. ”

“ Carbonic acid, one of the most common and stable compounds in the world, the final resultant of all combustion, loses its oxygen under excessive heat, and becomes an oxidizing agent. In this way good authorities explain the production of phenic, acetic, and cresylic acids, as hydrocarbons oxidized by the oxygen of carbonic acid. The hydrocarbons may also be dissociated. A liquid hydrocarbon analogous to benzine, toluene, takes hydrogen and leaves a deposit of anthracene. ”

“ But, if we work in a medium free from oxygen and all other foreign elements, they react upon one another, and a multitude of bodies are formed or decomposed by the interchange of elements, and the mixture we get when the heat is removed is a mixture of new elements. So, solid and dry coal gives the coal-tar liquids and illuminating gas, which did not exist in it, but were formed under the influence of heat. ”

“ Aniline exists already formed in coal-tar, but in very small quantity. Industry does not look after it, for the processes of extraction would be too costly. It is more convenient to make nitrobenzine and then reduce it, or deprive it of its oxygen by bringing it in contact with substances that will take that element from it. This may be effected by several processes. Sulphureted hydrogen, iron in fine particles, and acetic acid, are often employed as reducing agents. All the substances we have thus far derived from coal-tar are colorless. The moment has come for colors to appear. ”

“ No discovery of coal-tar products is more extraordinary or more fruitful in its bearings than that of the extraction of alizarine, or the artificial preparation of the coloring principle of madder, the effect of which has been to work a real economical revolution, and to destroy the most profitable agricultural industry of large districts of country. ”

“ The light oils of coal-tar are almost wholly composed of carburets of hydrogen; in the heavy oils bases and acids are also found with some very condensed carburets. They contain, for example, the ready-formed aniline, which it has not been found profitable to extract from them, and phenic acid, which, besides its valuable antiseptic properties, has been serviceable to the fabricants of coloring matters. ”

“ These are only a few of the examples of the reactions that take place when organic substances are raised to a high temperature. The four simple substances entering into the constitution of organic bodies form among one another more compounds than are furnished by all the minerals. If heating takes place in the open air, combustion ensues, and all these innumerable substances are oxidized and dissipated in the atmosphere as carbonic acid and aqueous vapor. ”

“ No; coal, as a whole, is a mass of substances composed of combinations of carbon with other bodies. These combinations are modified by heat. The tarry liquids and the gases do not exist in the coal, but are formed as the temperature rises in the retort. ”

“ When the heat is raised to a certain degree, one class of bodies, at a higher temperature another class of bodies, which had not reached their boiling-point at the former temperature, will be collected in the cold receiver. ”

“ Instead of acids uniting with bases to give rise to a third kind of bodies, salts, we have carburets, bases, uniting by twos or by threes, with or without the loss of one of their elements, and forming double or triple molecules of compounds, which may still be of the same chemical type. ”

“ That which passes at below 266° is mixed with light oils, while the products passing at above 392° are mingled with heavy oils. The light oils are next purified in a similar manner. The latter products are known in commerce as naphtha-oils, and are chiefly carburets of hydrogen. The eighteen or twenty of them which have been distinguished form a series, in which the proportion of carbon to hydrogen increases regularly. Those least rich in carbon are gaseous; then come the liquid hydrocarbons, and last the solid compounds. We select the liquid distillates for further operations. ”

“ All these bodies are formed during the preparation of fuchsine, and are separated by filtration or through their differences in solubility, or incapacity for crystallization. The separation of the substances which do not crystallize is difficult and incomplete. ”