114 TRANSACTIONS OF THE [MAR. 21, 



for the snowy-white alkaloid of cinchona he was disgusted when 

 he obtained a dirty brown mass ; but the next moment he was filled 

 with joy when, on dissolving it in alcohol, he obtained that beauti- 

 ful coloi-ing-matter which he called mauve. From that simple ex- 

 periment there started an industry that to-day is probably worth 

 fifty millions of dollars to the world every year. 



Owing to the brilliancy of the results of the researches of Perkin 

 and Hofmann (w^ho, by the way, was a pupil of the great Leibig), 

 organic chemistry soon had an army of enthusiastic investigators 

 delving into its secrets and unearthing new substances almost daily. 

 The dyes and coloring-matters received a great deal of attention, 

 and after a time both alizarine and indigo yielded to synthetic 

 chemistry ; and to-day there is not an organic compound that we 

 can find the true constitution of that we cannot make in our labora- 

 tories. 



I have spoken of aniline. Like the oil of bitter almonds it is 

 derived from benzol, one of the products of coal-tar. 



The benzol is first treated with nitric acid, making what we call 

 nitrobenzol. 



This nitrobenzol is next mixed with iron filings and acetic acid, 

 when aniline oil, as it is called, is formed, and this is the basis of the 

 aniline colors ; think of the industry and wealth brought into the 

 world by such simple experiments. 



The first step in the successful imitation of a natural product is 

 to ascertain with certainty its constitution, into what products it is 

 most easily separated, and how these again break up into simpler 

 ones already known Kolbe knew that salicylic acid could be readily 

 converted into carbolic acid, carbonic acid being liberated. He rea- 

 soned, then, that if he could make carbonic acid act upon and com- 

 bine with carbolic acid, salicylic acid would probably result. By 

 the intervention of metallic sodium the reaction was accomplished ; 

 but sodium is too expensive a metal for such a purpose, hence he 

 sought and found a cheaper one in caustic soda. What the latter 

 lacked in energy was compensated for by simply raising the temper- 

 ature. 



Baeyer's recent synthesis of indigo is of no importance to the dyer 

 at present, because his method is too circuitous and expensive ; but 

 it is no less the great achievement of a master-mind. Another may 

 modify his method and make it profitable. 



Baeyer's synthesis of indigo-blue furnishes a most instructive ex- 

 ample of reversed operations. It had long been known that when 

 indigo is oxidized with nitric acid iaatine is formed ; so Baeyer 

 reasoned from this that he must be able to reduce isatine to indigo- 

 blue, and in this he succeeded by the aid of phosphorus and chlo- 

 ride of phosphorus. The next st(!p was to prepare the isatine. 

 Oxindole can be made from isatine ; therefore Baeyer thought he 

 could make isatine from oxindole, and after a few unsuccessful 

 efforts he finally succeeded in making isatine. This completed his 



