1881. 



on Ind'ujo^ and its Artificial Production. 



m 



amount was seut out from the various chemical factories. So that in 

 len years the artilicial production liad oveitakcn tlie natural growth, 

 and the 300,000 or 400,000 acres of Lmd wliicli had hitherto been used 

 for the growth of madder, can henceforward be better cmi)loyed in 

 growing corn or other articles of food. According to returns, for 

 which the speaker had to thank Mr. Perkin, the estimated growth of 

 madder in the world previous to 18G9 was 90,000 tons, of the average 

 value of -45/. per ton, representing a total of 4,050,000/. 



Last year (1880) the estimated production of the artificial colouring 

 matter was 14,000 tons, but this contains only 10 per cent, of jniro 

 alizarin. Reckoning 1 ton of the artificial colouring matter as e(j[ual 

 to 9 tons of madder, the whole artificial product is equivalent to 

 120,000 tons of madder. The present value of these 14,000 tons of 

 alizarin paste, at 122Z. per ton, is 1,508,000/. That of 120,000 tons of 

 madder at 45/. is 5,070,000/., or a saving is cftected by the use of 

 alizarin of considerably over four millions sterling. In other words, 

 we get our alizarin dyeing done now for less than one-third of the 

 price which we had to pay to have it done with madder. 



Our knowledge concerning the chemistry of alizarin has also 

 proportionately increased since the above date. For whilst at that 

 time only one distinct body having the above composition was known, 

 we are now acquainted with no less than nine out of the ten di- 

 oxyanthraquinones whose existence is theoretically possible, according 

 as the positions of the two semi-molecules of hydroxyl are changed. 



t— CO — 



-co— 



Of the nine known di-oxyanthraquinoncs, only one, viz. alizarin, 

 or that in which the hydroxyls are contained in the positicm 1, 2, is 

 actually used as a colouring agent. Then again, three tri-oxyanthra- 

 quinones, 0411502(011)3, are known. One of these is contained in 

 madder-root, and has long been known as purpurin. Tlie other tri- 

 oxyanthroquinoncs can bo artificially prejiared. One termed anthra- 

 purpurin is an important colouring matter, especially valuable to 

 Turkey-red dyers, as giving a full or fiery red. The other, called 

 flavo-purpurin, gives an orange dye with alumina mordants. All 

 these various colouring matters can now be artificially produced, and 

 by mixing these in varying proportions a far greater variety of tints 

 can be obtained than was possible with madder alone, and thus the 

 power of diversifying the colour at will is placed in the hands of the 

 dyer and calico printer. 



