COAL AND THE COAL-TAR COLORS. 207 



Not a fixation of oxygen, but a departure of hydrogen, takes place. 

 Then a phenomenon of condensation is exhibited ; a number of the 

 molecules unite to form a molecule of rosaniline. This wonderful col- 

 orant may be constituted by the action of almost any of the oxidizing 

 agents known in chemistry upon aniline. Curiously, rosaniline would 

 not be formed if the aniline were absolutely pure. Theoretically, 

 its molecule is formed by the union of a molecule of aniline and two 

 molecules of toluidine, with a loss between the two of six atoms of hy- 

 drogen. It can not be obtained by oxidizing either of these bases 

 separately. Rosaniline is solid at ordinary temperatures, and crys- 

 tallizes readily in lozenges or in fine needles, which are white when 

 protected from the air, but become rose and then red when brought in 

 contact with it. The nature of the change it undergoes is unknown. 

 It is not apparent in the composition. Rosaniline is soluble in water, 

 and more soluble in alcohol, and has basic qualities so strong as to dis- 

 place ammonia from its salts ; and it is most frequently employed as 

 a salt. It furnishes not red only, but all colors, according as it is 

 treated in the combinations into which it is made to enter. Violet 

 was first discovered by Mr. Perkins, in 1856, while trying to make ar- 

 tificial quinine by the action of bichromate of potash on sulphate of 

 aniline. He gave up the search for quinine, and turned his attention 

 to manufacturing the color. Three years afterward MM. Renard and 

 Verguin produced fuchsine, a purple salt of rosaniline, by treating 

 commercial aniline with a dehydrogenizing agent, bichloride of tin. 

 It is a mixture of hydrochl orate of rosaniline and salts of tin, and is 

 used by dyers and wine-merchants. Aniline is now oxidized by the ac- 

 tion of arsenic into crude red {rouge brut), a violet mixture, composed 

 principally of arsenite and arseniate of rosaniline, which is converted 

 into fuchsine by bringing about a substitution of hydrochloric for 

 arsenious or arsenic acid. This is done by boiling crude red with hy- 

 drochloric acid, or, more usually, with sea-salt. A double decompo- 

 sition takes place, and, when the liquor is cooled, crystals of fuchsine 

 are found in the bottom of the vessel, while the arsenites and arseni- 

 ates of soda are retained in the mother- water. INot all the coloring- 

 matter, however, is deposited in the crystals, and a good operator 

 loses nothing. Treated with carbonate of soda, the mother- water gives 

 a precipitate, from which is extracted a color known as aniline garnet 

 or yellow fuchsine. Nor is this all. The crude red has left a violet 

 deposit in the bottom of the boats in which it was cooled ; this is 

 washed in boiling water ; the water is colored red, and a blue dye- 

 stuff is collected from it. More is left still. The crude red has passed 

 through filters, and they have retained some insoluble substances. 

 These are carefully gathered up ; they form a paste which is boiled 

 with diluted hydrochloric acid and filtered over again to extract 

 what fuchsine is left. The insoluble residue furnishes aniline ma- 

 roon, a beautiful color readily applicable to wool. Thus a single 



