The 12 gallons of tar yield 1-1/10 lb. of benzene, 9/10 lb. of toluene, 1½ lb. of carbolic acid, between 1/10 and 2/10 lb. of xylene, 6½ lb. of naphthalene, and ½ lb. of anthracene, whilst the quantity of pitch left behind is 69½ lb. But our table shows us more; it indicates to us what the steps are from each raw material to each colouring matter, as well as showing us each colouring matter. We see here that our benzene yields us an equal weight of aniline, and the toluene (9/10 lb.) about 3/4 lb. of toluidine, the mixture giving, on oxidation, between ½ and 3/4 lb of Magenta. From carbolic acid are obtained both Aurin and picric acid, and here is the actual quantity of Aurin obtainable (1-1/4 lb.). From naphthalene, either naphthylamine (a body like aniline) or naphthol (resembling phenol) may be prepared. The amounts obtainable you see in the table. There are two varieties of naphthol, called alpha- and beta-naphthol, but only one phenol, namely, carbolic acid. Naphthol Yellow is of course a naphthol colour, whilst Vermilline Scarlet is a dye containing both naphthylamine and naphthol. You see the quantities of these dyes, namely 7 lb. of Scarlet and 9½ lb. of the Naphthol Yellow. The amount of pure anthracene obtained is ½ lb. This pure anthracene exhibits the phenomenon of fluorescence, that is, it not only looks white, but when the light falls on it, it seems to reflect a delicate violet or blue light. Our table shows us that from the 12 gallons of tar from 1 ton of coal we may gain 2-1/4 lb. of 20 per cent. Alizarin paste. Chemically pure Alizarin crystallises in bright-red needles; it is the colouring principle of madder, and also of Alizarin paste. But the most wonderful thing about substantive coal-tar colours is their immense tinctorial power, i.e. the very little quantity of each required compared with the immense superficies of cloth it will dye to a full shade.
TABLE A.[1]
Twelve Gallons of Gas-Tar (average of Manchester and Salford Tar) yield:—
| Benzene. | Toluene. | Phenol. | Solvent Naphtha for India rubber, containing the three Xylenes. | Heavy Naphtha. | Naphthalene. | Creosote. | Heavy Oil | Anthracene. | Pitch. |
| 1·10 lb.= 1·10 lb. of Aniline | 0·90 lb.= 0·77 lb. of Toluidine. | 1·5 lb. = 1·2 lb. of Aurin. | 2·44 lb., yielding 0·12 lb. of Xylene = 0·07 lb. of Xylidine. | 2·40 lb. | 6·30 lb. = 5·25 lb. of α-Naphthylamine= 7·11 lb. of Vermilline Scarlet RRR; or 4·75 lb. of α- or β- Naphthol = 9·50 lb. of Naphthol Yellow. | 17 lb. | 14 lb. | 0·46 lb. = 2·25 lb. of Alizarin (20%). | 69·6 lb. |
| \_____________ | ___/ | ||||||||
| = 0·623 lb of | Magenta. | ||||||||
| or 1·10 lb. of Aniline yields 1·23 lb. of Methyl Violet. |
[1] This table was compiled by Mr. Ivan Levinstein, of Manchester.
The next table (see Table B) shows you the dyeing power of the colouring matters derived from 1 ton of Lancashire coal, which will astonish any thoughtful mind, for the Magenta will dye 500 yards of flannel, the Aurin 120 yards, the Vermilline Scarlet 2560 yards, and the Alizarin 255 yards (Turkey-red cotton cloth).
The next table (Table C) shows the latent dyeing power resident, so to speak, in 1 lb. of coal.
By a very simple experiment a little of a very fine violet dye can be made from mere traces of the materials. One of the raw materials for preparing this violet dye is a substance with a long name, which itself was prepared from aniline. This substance is tetramethyldiamidobenzophenone, and a little bit of it is placed in a small glass test-tube, just moistened with a couple of drops of another aniline derivative called dimethylaniline, and then two drops of a fuming liquid, trichloride of phosphorus, added. On simply warming this mixture, the violet dyestuff is produced in about a minute. Two drops of the mixture will colour a large cylinder of water a beautiful violet. The remainder (perhaps two drops more) will dye a skein of silk a bright full shade of violet. Here, then, is a magnificent example of enormous tinctorial power. I must now draw the rein, or I shall simply transport you through a perfect wonderland of magic, bright colours and apparent chemical conjuring, without, however, an adequate return of solid instruction that you can carry usefully with you into every-day life and practice.