590 Professor H. E. Boscoe [May 27, •'- 



colouring matter may also be printed on the cloth and the colour 

 fixed by moderate steaming without damage to the indigo-blue. This > 



process is now in actual use by printers both in England and on the 

 Continent, so that, thanks especially to the talent and energy of Dr. 

 Caro, Baeyer's discovery has been practically applied within the short 

 space of twelve months of its conception. Operations on a manu- 

 facturing scale have been successfully carried on in the Baden Soda 

 and Aniline Works at Ludwigshafen for the last two months, and 

 the directors see no reason why they should not be able to supply any 

 demand, however great, which may be made for ortho-nitro-phenyl- 

 propiolic acid. 



The proper way of looking at this question at present is, therefore, 

 to consider ortho-nitro-phenyl-propiolic acid and indigo as two distinct 

 products not comparable with each other, inasmuch as the one can be 

 put to uses for which the other is unfitted, and there is surely scope 

 enough for both. Still, looking at the improvements which will every 

 day be made in the manufacturing details, he must be a bold man who 

 would assert the impossibility of competition with indigo in all its 

 applications. For we must remember that we are only at the be- 

 ginning of these researches in the indigo field. Baeyer and other 

 workers will not stay their hands, and possibly other colouring 

 matters of equal intensity and of equal stability to indigo may be 

 obtained from other as yet unknown or unrecognised sources, and 

 it is not improbable that these may turn out to be more formidable 

 competitors in the race with natural indigo than ortho-nitro-phenyl- 

 propiolic acid. 



Looking at this question of the possible competition of artificial 

 with the natural indigo from another point of view, it must, on the 

 other hand, be borne in mind that the present mode of manufacturing 

 indigo from the plant is extremely rude and imperfect, and that by 

 an improved and more careful carrying out of the process, great 

 saving in colouring matter may be effected, so that it may prove 

 possible to produce a purer article at a lower price, and thus to 

 counterbalance the production of the artificial material. 



The following are the directions issued by the patentees to calico 

 printers for using the new colour : — 



PRINTING WITH ARTIFICIAL INDIGO. 



No. I. — On Unprepared Cloth. 

 Standard. 



Take 4 lb. propiolic acid paste (equal to 1 lb. dry acid), and 1 lb. 

 borax finely powdered ; mix well. The mixture first becomes fluid 

 and at last turns stiff. Then add 3 quarts white starch thickening 

 (wheat starch), mix well, and strain. 



