222 On some Coal-tar Products. 



a result they obtained alizarine, or the colouring principle of the 

 madder plant. This treatment by bromine, however, proved too 

 expensive, and soon two patents, one by Perkin in England, and 

 the other by Caro Grsebe and Lieberman, were brought out, 

 heated sulphuric acid being thereby substituted for bromine. 

 These patents were subsequently combined. The production of 

 artificial ahzarine has now almost superseded the natural pro- 

 duct, and the growth of the plant has almost ceased. 



Of late years many other important discoveries have been 

 made, including one described by Sir Henry Eoscoe as "the 

 most remarkable of all the marvellous products of the Coal-tar 

 Industry." I allude to Saccharine, the discovery of which is due 

 to Dr. Constantin Fahlberg. He was engaged in studying the 

 oxidation products of the toluene sulphamides, and found that 

 by oxidising pure ortho-toluene sulphamide he obtained a re- 

 markably sweet compound. By much further study and research, 

 extending over several years, he succeeded in producing sac- 

 charine on a practical scale ; its starting-point is toluene, which 

 in the first place is heated with sulphouic acid, forming toluene 

 sulphonic acid ; the succeeding treatments, six in number, are 

 somewhat complicated, and it is hardly advisable for me to enu- 

 merate them, the final one, however, is the oxidation of the 

 ortho-toluene sulphonic-amide by potassic permanganate in the 

 presence of an alkali, and the precipitation of the resulting 

 product with a dilute mineral acid, when Benzoyl-sulphonic-imide, 

 or saccharine, separates out. 



I have here a sample of the pure product, which is some 800 

 times sweeter than cane sugar, and also a sample in its commer- . 

 cial and soluble form. On account of its great sweetening 

 power it is claimed that it is as cheap as sugar at 8d. per pound. 



It is of great value in medical cases, being powerfully anti- 

 septic and non-fermenting, and can be given to persons who are 

 forbidden the use of sugar. 



I would also mention a substance, a derivative of Coal-tar, 

 which is greatly used in pharmacy, viz., Antipyiin, a febrifuge of 

 certain action ; it is also claimed to be of great value in the 

 treatment of sea-sickness, and, in fact, in various other ailments. 

 I fear I have already taken up more of yom- time than is usual on 

 these occasions, and must therefore content myself with having 

 given you but a slight insight into the productive properties 

 of Coal-tar. 



