POPULAR MISCELLANY. 



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of civilization and of the cultivation of 

 plants kept pace with each other. This 

 does not prove that a meat diet is opposed 

 to civilization, but that the necessities of 

 people who are dependent on meat for food 

 hinder advance in civilization. They have 

 to be hunting, and wandering about from 

 place to place. It is when they have learned 

 to till fields and tame animals, and have be- 

 come fixed in homes, that they find time to 

 cultivate arts. The Arctic savages are fish- 

 hunters, the barbarians of the Asiatic 

 steppes depend on their herds, the meat- 

 eating Turks and Mongols were more bar- 

 barous than the vegetable-eating Hindoos 

 they conquered, and were the authors of the 

 woes of that suffering people, M. Beke- 

 toff's conclusion i3 that a vegetable diet 

 contributes more than any other to the in- 

 tellectual development of a people, while a 

 wholly animal diet determines a kind of life 

 incompatible with progress. A mixed diet 

 has not been the promoter of civilization, 

 for the most highly gifted authors have 

 often drawn their physical forces from a 

 wholly vegetable diet. Finally, " the great 

 thing is evidently not the kind of food, but 

 the kind of life that the food determines." 



Synthesis of Indigo. One of the most 

 important of the recent discoveries in 

 chemistry is that which Baeyer has made 

 of a practical process for the artificial pro- 

 duction of indigo. The successful experi- 

 ments of this chemist had been foreshad- 

 owed by the production of alizarene, the 

 coloring principle of the madder-root, from 

 the anthracene of coal-tar ; by the discover- 

 ies by Fritsche of the relations of indigo 

 with the benzene ring and the amido-group ; 

 by Erdmann and Laurent's discovery that 

 indigo on oxidation yields a crystalline body 

 possessing no coloring power, to which they 

 gave the name of isatin ; and by Baeyer and 

 Emmerling's accomplishment of the reverse 

 process of reducing isatin to indigo. Three 

 processes have been employed for the syn- 

 thesis of indigo, of which, however, only 

 one, by Baeyer, is of practical importance. 

 The three processes have in common that 

 they all proceed from some compound con- 

 taining the benzene nucleus ; that they all 

 start from compounds containing a nitrogen- 

 atom ; and that they all Commence with an 



ortho-compound. They difter from each 

 other in that Baeyer's process requires the 

 abstraction of an atom of carbon, while of 

 the others one requires the addition of an 

 atom of carbon, and the second starts with 

 the right number of atoms of carbon. Bae- 

 yer's successful process, which may be called 

 the manufacturing process, starts from cin- 

 namic acid, a substance which is contained 

 in gum-benzoin, balsam of Peru, and a few 

 other aromatic bodies, but which can be ob- 

 tained more cheaply by manufacturing it 

 artificially. Bertagnini has obtained it from 

 oil of bitter almonds ; and other processes 

 for the same purpose have been carried 

 out. One of the processes most likely to 

 be adopted is that of Dr. Caro, who con- 

 verts toluene, by adding chlorine, into ben- 

 zylene dichloride, and treating the latter sub- 

 stance with sodium acetate, forms cinnamic 

 acid and sodium chloride. The next steps 

 in the process are the formation from cin- 

 namic acid of ortho-nitro-cinnamic acid; the 

 conversion of this into its di-bromide ; the 

 separation from this of the two molecules 

 of hydrobromic acid, which gives rise to 

 ortho - nitro - phenyl - propriolic acid ; and, 

 lastly, the conversion of the latter product 

 into indigo by heating its alkaline solution 

 with grape-sugar, xanthate of soda, or some 

 other reducing agent. The actual yield of 

 indigo by the last reaction has not been 

 made equal to what is demanded by theory, 

 it being only 48 per cent, while the theoret- 

 ical yield would be 68 per cent. The artifi- 

 cial production of indigo by this process 

 may be considered as within reasonable dis- 

 tance of commercial success, for the ortho- 

 nitro-phenyl-propriolic acid, the colorless 

 substance which, on treatment with a re- 

 ducing agent, yields indigo-blue, is already 

 in the hands of the Manchester calico- 

 printers, and may be obtained at the price 

 of six shillings per pound of a paste con- 

 taining 25 per cent of the dry acid. Indigo 

 can not, however, be made profitably from 

 this product till the theoretical yield can be 

 obtained from it, and until the price of the 

 dry propriolic acid can be reduced to 20s. 

 per kilo, or 85. ($2.00) a pound. The proc- 

 ess may, however, be found applicable with 

 advantage even at present rates, for uses 

 for which natural indigo is unfitted. Of the 

 other processes for manufacturing indigo, 



