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He then proceeded to consider the manufacture of alizarine purpurine, and divided its manufacture into four stages: 1, the purification of crude anthracine; 2, the conversion of the purified anthracine into anthraquinone; and 3, the production of sulpho acid of anthraquinone and the conversion of this sulpho-acid into alizarine and purpurine.
The lecturer then reviewed, in case of an increased demand for anthracine, the probable new sources of obtaining increased supplies of coal tar: The destructive distillation of petroleum; coke ovens and blast furnaces; the carbonization of coal for general manufacturing purposes, using the coal and gas as fuel, and giving tar, benzine, and ammonia as residues; and distillation of coal with the object of obtaining the principal products, tar and benzine, and as the residual product, gas.
The German chemists found that alizarine produced from madder in undergoing certain treatment gave a substance identical with anthracine, one of the constituents of coal tar, and in 1869 the same chemists announced to the world that they had accomplished the synthesis of alizarine from anthracine. The effect of this discovery was to throw madder out of cultivation. Mr.
In the course of the lecture many interesting specimens of various products were produced and dilated upon, the lecturer fully describing the process of purifying the crude anthracine and of the conversion of the purified anthracine into anthraquinone.
"Anthracine," obtained from coal tar, has been manufactured largely for the purpose of producing the various brilliant dyes now so common.
Alizarine manufacturers originally found scarcity of anthracine; at present the supply is in excess of the demand, and the price during the last 18 months has fallen from 3s. 6d. to 1s. per unit, and the probabilities are that the supply will increase. The quantity of gas tar now obtained the lecturer estimated at 500,000 tons per annum, and the coal carbonized for gas making, 10,000,000 tons.
He also stated that alizarine, 20 per cent. quality, is sold to-day at 2s 6d. per lb., but that if the price were reduced by one-half there will still be a handsome profit to makers, and that the United Kingdom is the largest consumer, absorbing one-third of the entire production, and that England possesses advantages over all other countries for manufacturing alizarine first, by having a splendid supply of the raw material, anthracine; secondly, cheaper caustic soda in England than in Germany by fully L4 per ton; thirdly, cheaper fuel; fourthly, large consumption at our own doors; and, fifthly, special facilities for exporting.
He then proceeded to explain the source from which nearly all the artificial coloring matters are derived, viz., gas tar; showing the principal products of this wonderful, complex mixture, of which one is anthracine.
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