October 19, 1906.] 



SCIENCE. 



487 



By means of coal tar colors even one of the 

 greatest of all problems— photography in 

 natural colors— has been realized. 



Curious to relate, with all these successes 

 to its credit, the problem which has oc- 

 cupied the attention of master minds now 

 for almost a century, and which was the 

 incentive of Perkin's research, so fruitful 

 in other fields— the artificial production of 

 quinine — remains unsolved up to the pres- 

 ent day. 



While thus new arts were constantly de- 

 veloped, the chemical industries, existing 

 at the time of Perkin 's discovery, were also 

 eminently benefited. The production of 

 aniline required at once large quantities of 

 sulfuric and nitric acids for the nitration 

 of benzol, and the demand of the new in- 

 dustry for highly concentrated sulfuric 

 acid gave to the world the contact process 

 in which the sulfurous acid gas, formed, 

 for example, in roasting zinc and iron 

 pyrites, which heretofore was allowed to 

 escape and then vitiated the atmosphere 

 and destroyed vegetation, is converted into 

 sulfuric acid by the oxygen of the air. 

 The manufacture of alizarin consumed 

 enormous quantities of caustic soda. 

 Bromine and iodine became staple articles 

 of commerce. The electrolysis of salt solu- 

 tion was economically perfected, and to- 

 gether with the contact process and the 

 liquefaction of chlorine is employed on an 

 immense scale for the synthesis of indigo. 

 The experience gained in electric methods 

 is being applied to the problem of utilizing 

 the nitrogen of the air, and to judge from 

 past successes, it will not be many years 

 before the Badische Anilin and Soda 

 Fabrik, in whose laboratories experiments 

 in this direction are being conducted, will 

 bring to the market nitrates, nitrites and 

 nitric acid made from atmospheric nitro- 

 gen, instead of Chile saltpeter, the supply 

 of which is calculated to last no longer 

 than about twenty years, and as Chile 



saltpeter is indispensable in agriculture, 

 especially in the raising of cereals, its arti- 

 ficial production in the manner indicated 

 will remove the anxiety expressed by wri- 

 ters on economics concerning the difficul- 

 ties of feeding an ever-increasing popula- 

 tion owing to the gradual exhaustion of 

 the soil. 



The distillation of coal tar itself was 

 changed in every respect to comply with 

 the new developments. All its by-products 

 are utilized, and one of them, sulfate of 

 ammonia, is produced so economically that 

 it is commonly employed as a fertilizer. 



In the cooking processes, of so great im- 

 portance in the manufacture of iron and 

 steel, the gaseous products are not allowed 

 to go to waste any more, but are recovered 

 and utilized to furnish benzol, etc., in ad- 

 dition to illuminating gas — in fact, the 

 United Coke and Gas Company operates 

 some of its plants in such a manner that 

 the gases are the principal products and 

 coke only a by-product. 



In the treatment of these gases, cyanide 

 of potassium is obtained at such low cost 

 that it is used for extracting low class 

 gold ores which hitherto were useless. 

 Hence this substance plays an important 

 part in the monetary system, as its cheap 

 production has disposed of the fear that 

 there would not be enough of the precious 

 metal to maintain the gold standard of the 

 civilized nations. 



The chemistry of benzol gave us our 

 modern theories, especially that of Kekule, 

 which in its application led to marvelous 

 prophesies of experimental results and is 

 recognized to be one of the most remark- 

 able achievements of the human mind. 



The coal-tar industry gave us our 

 modern chemical institutes, the wonderful 

 equipments of which were first utilized in 

 the laboratories of the factories, and above 

 all it gave us the intimate cooperation of 



