1886.] on Recent Progress in the Coal-tar Industry. 455 



from anthracene at a rate of more tlian two millions sterling per 

 annum ; and it is stated that an offer was once made, in the earlier 

 stages of its history, by a manufacturer of anthracene to the Paris 

 authorities to take up the asphalt used in the streets for the purpose 

 of distilling it, in order to recover the crude anthracene. 



Again, we have in the azo-scarlets derived from naphthalene a 

 second remarkable instance of the replacement of a natural colouring 

 matter, that of the cochineal insect, by artificial tar-products, and the 

 naphthol-yellows are gradually driving out the dyes obtained from 

 wood extracts and berries. It is, how^ever, true that some of the natural 

 dye-stuffs appear to withstand the action of light better than their arti- 

 ficial substitutes, and our soldiers' red coats are still dyed with cochineal. 



The introduction of these artificial scarlets has, it is interesting 

 to note, greatly diminished the cultivation of cochineal in the Canaries, 

 where, in its place, tobacco and sugar are now being largely grown. 



Let us next turn to inquire as to the quantities of these various 

 products obtainable by the distillation of one ton of coal in a gas- 

 retort. The six most important materials found in gas-tar from which 

 coloui's can be prepared, are : — 



1. Benzene. 4. Metaxylene (from solvent naphtha). 



2. Toluene. 5. Naphthalene. 



3. Phenol. 6. Anthracene. 



The average quantity of each of these six raw materials obtainable 

 by the destructive distillation of one ton of Lancashire coal is seen 

 in Table I. Moreover, this table show^s the average amount of certain 

 colours which each of these raw materials yields, viz. :— - 



2:K-ta 0-623 lb. ^ V^S.' 'scL^i^ • U lbs. 

 3. Aurin 1-2 lb. 6. Alizarin 2-25 lbs. (20%). 



Further it shows the dyeing power of the above quantities of 

 each of these colours, all obtained from one ton of coal, viz. : — • 



1 and 2. Magenta, 500 yards of flannel. 



3. Aurin, 120 yards of flannel 27 in. wide. 



K* > Vermilline scarlet, 2560 yards of flannel. 



6. Alizarin, 255 yards Turkey red cloth. 



Lastly, to point out still more clearly these relationships, the 

 dyeing-power of one pound of coal is seen in the lowest horizontal 

 column, and here we have a particoloured flag, which exhibits the exact 

 amount of colour obtainable from one pound of Lancashire coal. 



Let us moreover remember, in this context, that no less than 

 ten million tons of coal are used for gas- making every year in 

 this country, and then let us form a notion of the vast colouring 

 power which this quantity of coal represents. 



