428 



INDIGO, ARTIFICIAL PRODUCTION OF. 



County gives the best return, the cost being 

 but $1 for every $48 worth of production. It 

 is followed by Tippecanoe County, with $1 

 to $43. Several others are nearly even, and 

 raise the average of the State to $1 to $27. 

 There is much difference in the conditions of 

 the counties. For instance, in some the wear 

 of machinery by the nature of the soil, etc., is 

 much greater than in others; the market for 

 purchasing implements is often so convenient 

 as to materially increase their cost by frequent 



and unnecessary purchases; and the market 

 for the sale of products is extremely variable. 

 In considering the table, all these conditions 

 are to be taken into account, as it is probable 

 that, if the same status existed throughout 

 the State, the table might be very materially 

 changed. 



Following is the population of the State by 

 counties, as finally returned by the census of 

 1880, and as compared with the population of 

 1870: 



INDIGO, AETIFICIAL PRODUCTION OF. The 

 industrial reproduction of the most valuable 

 coloring matter derived from organic nature is 

 the latest and the crowning achievement of the 

 coal-tar industry. This great industry affords 

 a striking argument in favor of the practical 

 utility of the cultivation of science for purely 

 scientific objects; since here, as in many other 

 cases, the study of the deeper problems of nat- 

 ure has led incidentally to great improvements 

 in the arts of life. The inventor of the artifi- 

 cial process of preparing indigo is a distin- 

 guished German chemist, Professor Bayer. 

 His discovery was published in 1880. Bayer 

 set out with the definite object of discovering 

 the synthesis of indigo. His study of its com- 

 position in the light of the modern theory of 

 atom-linking or molecular arrangement led him 

 to the conclusion that it is built up of one 

 molecule of benzole, containing a side chain of 

 two carbon-atoms, and on this latter a nitro- 

 gen-atom in the ortho-position. In search- 

 ing for bodies whose transformation products 

 showed a similar arrangement of atoms, he 

 discovered derivatives of cinnamic acid which 

 seemed to present the same molecular group- 

 ing. Cinnamic acid was formerly obtained 

 only from certain costly resins, as storax, tolu, 



and Peru balsams. It has, however, recently 

 been produced synthetically by the action 

 of acetyl chloride on benzaldehyde ; and a 

 cheaper process has been found in which ben- 

 zole chloride is treated with acetate of soda. 

 The chloride of benzole with its derivative al- 

 dehyde are produced from toluole, one of the 

 waste products of coal-tar distillation. Bayer's 

 discovery of the synthesis of indigo led to ex- 

 tensive experiments with derivatives of cin- 

 namic acid, to find a process of conversion ca- 

 pable of industrial utilization. The derivative 

 best adapted for the purpose was found to be 

 ortho-nitro-phenyl-propriolic acid, which, when 

 treated with alkaline reducing agents, produces 

 indigo directly. Nitro-phenyl-propryolic acid 

 is a yellowish-white powder in the dry state. 

 It is obtained in the following manner: Cin- 

 namic acid is first nitrified with nitric acid, the 

 product being a mixture of ortho-, meta-, and 

 para-nitro-cinnamic acids. To separate the 

 ortho acid, which is the one used in indigo 

 manufacture, they are converted into methylic 

 ethers by the aid of hydrochloric acid and 

 wood spirits, and the ethers are separated by 

 fractional distillation. From the para acid, 

 which is the most abundant by-product, a 

 beautiful red dye has been obtained. The me- 



