SCIENCE 



[N. S. Vol. XL VI. No. 1175 



sible point of view for fifteen years. The 

 various steps in the process were greatly 

 improved and more than a hundred patents 

 were taken out, but it was never possible to 

 convert Baeyer 's synthesis into a successful 

 manufacture of indigo on a large scale. 

 The original material required for that 

 sjrnthesis is the toluene of coal tar and the 

 annual production of this substance would 

 be sufficient to produce only about one 

 fourth of the indigo required in the world. 

 As toluene is used in the manufacture of a 

 great variety of other dyes and compounds 

 it is evident that any considerable use for 

 the manufacture of indigo would cause 

 such an increase in price as automatically 

 to stop the manufacture. No manufacture 

 of indigo could succeed unless the dye were 

 made at a price to compete with the agri- 

 cultural production in India. 



The factory found its way out of this cul- 

 de-sac by means of a discovery made by 

 Professor Heumann in the chemical labora- 

 tory of the Polytechnic at Zurich, Switzer- 

 land — a laboratory which has given us 

 many brilliant discoveries in chemistry and 

 which is conducted on a high scientific 

 plane, not on the theory that it must devote 

 itself to so-called practical problems. By 

 combining Heumann 's discovery with 

 another made by Hoogewerf and van Dorp 

 in a laboratory in Holland it became pos- 

 sible to manufacture indigo with naphtha- 

 lene of coal tar as the starting-point. 

 Naphthalene, known to us all in the fa- 

 miliar moth balls, is abundant and cheap. 



Even with the aid of these fundamental 

 discoveries from the university laboratories 

 the chemists of the factory worked inces- 

 santly upon the problem for seven years 

 before they felt sufficiently sure of their 

 ground to recommend the building of a 

 plant for the manufacture on a large scale. 

 Two incidents of the development are of 

 sufficient interest to deserve mention. The 

 first step in the process is the oxidation of 



naphthalene to phthalic acid. The proc- 

 esses which had been used before that were 

 too tedious and expensive. In the course 

 of a systematic examination of aU possible 

 methods for cheapening the process a chem- 

 ist accidentally broke a thermometer in a 

 mixture of naphthalene and sulfuric acid 

 which he was heating. The mercuric sul- 

 fate which was formed proved to be the 

 needed catalyst to hasten the reaction and 

 the details of a successful process for the 

 oxidation were soon developed. But, as is 

 so often the case, the solution of one prob- 

 lem brought out a second difficulty. 

 Strong sulfuric acid is required for the 

 oxidation and this is reduced to sulfur di- 

 oxide, which it is necessary to recover and 

 convert back into the strong acid by oxida- 

 tion with air. This led to the transforma- 

 tion of the old and well-known contact 

 process for the manufacture of sulfuric 

 acid into a new and radically changed form. 

 Incidentally it may be remarked that the 

 new contact process soon found its way to 

 America and has been used to convert to 

 sulfuric acid the sulfur dioxide obtained as 

 the first step in the reduction of zinc ores. 

 The strong sulfuric acid has been used, in 

 turn, in making dynamite. 



Finally, in July, 1897, the preliminary 

 work was completed and the Badische Ani- 

 lin Soda Fabrik was ready to begin the 

 construction of the necessary factories. In 

 October, 1900, Dr. Brunck reported that 

 the firm had spent about eighteen million 

 marks or four and a half million dollars 

 upon their plant and that the production 

 had already attained a proportion which 

 corresponded with the natural production 

 from 100,000 hectares or nearly 250,000 

 acres of land. In reply to the suggestion 

 that the competition might prove disastrous 

 to the farmers of India he expressed the 

 hope that the land now used for the pro- 

 duction of indigo may be released for rais- 



