CHEMISTRY OF THE NINETEENTH CENTURY. 625 



existing under pressure in a state in which it was neither a liquid nor 

 a gas, but something intermediate. Dr. Andrews found that other sub- 

 stances assumed the same condition, but each at a particular tem- 

 perature. 



The name of the eminent pupil of Liebig's, A. W. HOFMANN, now 

 Professor of Chemistry in the University of Berlin, whose words have 

 been quoted in a foregoing page, furnishes us with the opportunity of 

 illustrating the advantageous effects of scientific research on practical 

 industry, though this theme is well-nigh worn threadbare; and it has 

 become so much a truism, that successful manufacturers and traders 

 now vie with each other in encouraging " scientific research," presum- 

 ably for the prospect of having new fields for commercial operation, 

 rather than for any abstract love of science as such. Liebig, in a letter 

 to Faraday, says : " What struck me most in England was the percep- 

 tion that only those works which have a practical tendency awake 

 attention and command respect; while the purely scientific works, 

 which possess far greater merit, are almost unknown, and yet the 

 latter are the proper and true source from which the others flow. 

 Practice alone can never lead to the discovery of a truth or a principle. 

 In Germany it is quite the contrary. Here, in the eyes of scientific 

 men, 'no value, or at least but a trifling one, is placed on the practical 

 results. The enrichment of science is alone considered worthy of 

 attention. I do not mean to say that this is better : for both nations 

 the golden medium would certainly be a real good fortune." It may, 

 therefore, be not improbable that chemical symbols and chemical 

 theories may have greater interest for some readers, if it is shown that 

 by their aid discoveries creating entirely new branches of industry have 

 been effected. 



Faraday, engaged in a purely scientific research, discovered benzol 

 in 1825. In 1826 Unverdorben, by distilling indigo, obtained a sub- 

 stance he called crystalline, because its compounds readily crystallized. 

 In 1834 Runge found in coal-tar a substance he called cyanol, because 

 in certain reactions it yielded blue colorations. In 1841 Fritzsche, 

 by distilling indigo with potash, obtained a substance he called aniline, 

 from ajiil, the Portuguese name for indigo. About the same time 

 Zinin obtained from a derivative of benzol a liquid to which he gave 

 the name of benzidam. In the meantime, since Faraday's discovery 

 in 1825, something more had been found out about benzol. Mitscher- 

 lich in 1834 had obtained it by distilling bmzoicvjd& with lime hence 

 its present name. In 1843 Hofmann showed that crystalline, cyanol, 

 aniline, and benzidam are one and the same substance. A little later 

 he found that from coal-tar a considerable quantity of benzol may be 

 obtained. It followed, therefore, that coal-tar could readily be made 

 to furnish aniline. Aniline is a colourless oily-looking liquid ; but by 

 treating aniline with the proper chemical reagents, it is made to furnish 

 a series of colouring matters which are marvellous for their number 



40 



