498 



[JtJNB, 1012. 



DYE STUFFS. 



NATURAL INDIGO AND SYNTHETIC 

 INDIGOTIN. 



(From the Indian Agriculturist, Vol. 

 XXXVII., No. 4, April 1, 1912.) 



Colonel Banking's Researches, 

 A Correspondent writes to the Indian 

 Planters' Gazette : — 



I have for a considerable time been 

 searching for a British subject, a man 

 of science, and a chemist, who could 

 give an impartial opinion about the re- 

 spective merits of Natural Indigo and 

 "Synthetic Indigotin," and I have found 

 him in Lieutenant-Colonel George Ran- 

 king, B.A., M.D., late professor of Chem- 

 istry at the Medical College, Calcutta ; 

 a man of undoubted capacity, and one 

 who had done a considerable amount of 

 research work in connection with the 

 chemistry of Indigo manufacture in 

 India. If this scientist who was on the 

 spot had been employed by the planters 

 in 1898 instead of a man from a Tech- 

 nical School, where Synthetic Indigotin 

 is driven into the very blood of the 

 pupils, the result would have been very 

 different from what it is, and the 

 indigo industry would have been saved 

 much grievous loss, and what is more 

 the planters would have been told the 

 truth long ago, which they can't discern 

 even yet, though it is staring them in 

 the face ! 



Colonel Ranking writes as follows :— 

 Dear Sir, — I have recently revived my 

 interest in the subject of Indigo manu- 

 facture, and have read some of the 

 correspondence, which has been passing, 

 on the comparative values of the natural 

 Indigo, and the synthetic products 

 which have been presented to the public 

 under the name of "Indigo." 



As some of the Behar planters will re- 

 member, it is very many years ago (1881) 

 that I first entered the field of research 

 into the chemistry of the manufacture of 

 Indigo from the plant. The process was 

 very imperfectly understood at that time 

 even by the leading chemists of the day, 



and, finding myself led to investigate the 

 process of Indian manufacture from the 

 point of view of the scientific chemist, to 

 make a long story short, I arrived at a 

 conclusive result, upon which I based 

 and patented a process for the improve- 

 ment of Indigo manufacture. That 

 patent was attacked under the provi- 

 sions of Act XV. of 1859 (which was the 

 Act by which patents were then regu- 

 lated) and was declared invalid, on the 

 ground that my specification was bad in 

 law, in that the substance which I 

 asserted to exist in the vat liquor of the 

 steeping vat (white Indigo), did not in 

 fact exist, and consequently that the re- 

 actions stated by me in my specification 

 to take place, the final result of which 

 reaction was Indigo-blue, could not 

 take place. 



The logic of this was unimpeachable 

 had the major premise been accurate — 

 which, as I propose to show, it was not, 



The Court gave its decision mainly 

 upon the evidence of two Calcutta 

 chemists, both of them Professors, whose 

 opinion rightly carried great weight. 

 Both these gentlemen swore affidavits 

 to the effect that the chemical reactions 

 stated by me to occur could not and did 

 not occur because the "Indigo white" 

 which I alleged to be present, and relied 

 upon as the essential starting point of 

 my reactions, had in point of fact, no 

 existence in the vat-liquor. 



As a result the patent was invalidated 

 at heavy pecuinary loss to me. I could 

 not afford to appeal, though I knew 

 perfectly well I was right, and the 

 learned Professors were wrong. I did 

 not blame them; they gave their opinion 

 in accordance with their knowledge. 



Now, mark the result. Within two 

 years my researches were confirmed by 

 Goppelsraeder, a German chemist; while 

 the highest authority on the Chemistry 

 of Dyestuffs to-day writes as follows, 

 speaking of the steeping vat : " The 

 liquid, now (i.e., after fermentation) con- 

 sisting of a solution of Indigo white." 

 Here, nearly thirty years later than my 



