2o8 THE POPULAR SCIENCE MONTHLY, 



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

 maroon. 



Whence come all of these colors ? And how does chemistry ex- 

 plain the provision of so various hues by the same body ? The differ- 

 ences 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 dis- 

 tillations, 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 mixt- 

 ure of aniline and toluidine. Two molecules of toluidine and one 

 molecule of aniline united, with a loss of hydrogen, to form a mole- 

 cule of rosaniline. Now, two molecules of aniline and one molecule 

 of toluidine, also losing hydrogen, might also unite in a similar man- 

 ner ; 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 crys- 

 tallized ; 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 sepa- 

 rated by filtration or through their differences in solubility, or inca- 

 pacity 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 hydro- 

 carbons 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 consti- 

 tution 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 applica- 



