September 5, 1919] 



SCIENCE 



219 



is, they were working in the organic division 

 of chemistry. As you know, chemistry is serv- 

 iceably, even though crudely, grouped under 

 two grand divisions, organic and inorganic, 

 and for many years these were treated quite 

 separately from each other ; I know " organic " 

 chemists who look with mild indulgence upon 

 the " inorganic " chemists and I also know 

 inorganic chemists who return the compliment 

 — ^with interest. In 1901, however, one of 

 these so-called " inorganic " chemists, in 

 searching for new worlds to conquer, hit upon 

 an idea which he thought would make one of 

 the discarded and discredited methods of 

 making indigo a worthy rival of the only com- 

 mercially successful indigo method of that 

 day. And he was right! The owners of the 

 1897 method were forced to look to their 

 laurels. 



The history of the synthetic production 

 of indigo is filled with many different dis- 

 coveries of how indigo may be made in the 

 laboratory, most of them wholly unrelated to 

 the methods of 1882, 1897 and 1901. Two. at 

 least, of them have made an unsuccessful and 

 short-lived attempt to grow into an invention 

 capable of meeting competitive conditions. 

 Now, it is curious to note that the 1901 

 method was an offspring of the cyanide 

 method of extracting gold which in turn is 

 the gold-extraction method that made the 

 South African gold fields so valuable. Im- 

 mense amounts of that deadly poison, sodium 

 cyanide, were needed in preparation for this 

 gold extraction; that, in turn, called for un- 

 usually large amounts of other things and 

 among these was that particular inorganic 

 material that gave competitive ability in the 

 world's markets to one of the theretofore dis- 

 carded indigo methods. From the gold fields 

 of South Africa to synthetic indigo is, indeed, 

 a long cry. Is it, therefore, not wholly reason- 

 able to expect that from some other equally 

 far-off branch of chemical industry or of 

 chemical research may come the proper stim- 

 ulus to bring to active competitive life some 

 of these other discarded indigo methods or 

 even to create new methods superior to any 

 we know of to-day? Among chemists we also 

 distinguish physical chemists who are curious 



about subjects in that great twilight zone be- 

 tween the field of chemistry on the one hand 

 and^of physics on the other; also we have the 

 electrochemist who is always searching for 

 more or less direct chemical applications of 

 the electric current. Just as the inorganic 

 chemist in 1901 taught the organic chemist 

 the secret of endowing a discarded indigo 

 method with competitive life, may we not 

 reasonably expect that some day the physical 

 chemist and the electrochemist may, one or 

 both, in the course of wholly unrelated chem- 

 ical research work, come across facts which 

 when intelligently applied to the indigo prob- 

 lem may still further advance it? 



The chemical knowledge and research that 

 enter into the synthetic production of indigo, 

 as we know it to-day, come from over three 

 generations of chemists, scattered all over the 

 globe, speaking many languages, researching 

 on many different and separate problems 

 which touch almost every phase of human 

 endeavor, and the end is not yet. 



For centuries indigo has been the undis- 

 puted king among dyes. Chemists have made 

 many attempts to displace it by other dyes, 

 but it has so far successfully withstood all 

 such attacks upon it — except as to its source 

 or origin. Indigo is still the king, but its 

 supremacy is thi'eatened and threatened seri- 

 ously and its undoing, if that should ensue, 

 is traceable directly to itself. Chemists have 

 long felt sure that the true reason for the 

 supremacy of indigo lay in the manner in 

 which it dyes fabric. It possesses the unique 

 faculty of being, what you have all so often 

 read of in the daily papers, a " vat " dye. It 

 is the pioneer vat^ye and imtil comparatively 

 recently it was the only vat-dye. Vain at- 

 tempts to create or imitate this vat-dyeing 

 property in other dyes are recorded by the 

 score in the history of coal tar dyes. But, 

 about twenty years ago, a real vat-dye was 

 constructed in a research laboratory which 

 ultimately turned out to have an entirely 

 different constitution from indigo. This sup- 

 plied the key to an entirely new class of dyes. 

 Although among the multitudes of " vat " dyes 

 constructed along these new lines many are 

 wholly worthless, there are, nevertheless, a 



