Page:Popular Science Monthly Volume 25.djvu/218

208 operation has given us the violet red of fuchsine, garnet, blue, and maroon.

Whence come all of these colors? And how does chemistry explain the provision of so various hues by the same body? The differences do not arise solely from the fact that the same base, rosaniline, is found associated with different acids. We must not forget that we had at first, notwithstanding the separations effected by fractional distillations, a mixture of substances. These substances react upon one another; and the theory of their reactions, of which we have already given some idea, appears so ingenious and interesting that we must say a few words more about it.

Benzine and toluene, mixed, furnished, after some reactions, a mixture of aniline and toluidine. Two molecules of toluidine and one molecule of aniline united, with a loss of hydrogen, to form a molecule of rosaniline. Now, two molecules of aniline and one molecule of toluidine, also losing hydrogen, might also unite in a similar manner; or three molecules of aniline, or three molecules of toluidine, might be introduced in the process, with analogous results. Here we have four distinct arrangements, four possible cases, conceived in theory and realized in practice. In the first case we had rosaniline; in the second, we have mauvaniline; in the third, violaniline; and, in the fourth, chrysotoluidine. We have described the first of these substances. The second forms light-brown crystals, that become darker on heating, while the liquids in which they are dissolved take a violet tinge. Violaniline is hardly soluble, and difficult to get crystallized; it is a very dark—nearly black—brown powder. Its salts, when a few drops of concentrated sulphuric acid are added to the solution, give a dark blue. Chrysotoluidine is yellow. 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. The red continues united with the yellow in greater or less proportion, and gives maroon or garnet.

Through all these processes, in which we have observed the hydrocarbons decomposing one another, and forming new compounds, we have found that the chemistry of coal does not always have to borrow its powerful reagents, its acids and alkalies, from mineral chemistry; but that the compounds of carbon themselves, closely allied in constitution and properties, are very frequently capable of reacting upon and transforming one another, without the intervention of foreign agents. 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. The first experiments in the practical