LECTURE XIV.] HISTORY OF CHEMISTRY. 289 



method is not sufficient for establishing the chemical nature of 

 a compound, and that the synthetical method constitutes a 

 necessary complement. The first method usually precedes the 

 second ; but, in the history of a substance, its synthesis, with 

 rare exceptions, marks a period, and, with it, the interest which 

 the scientific investigation of the substance presents, is usually 

 at an end. 



From this point of view, the syntheses of specially important 

 substances are worthy of mention here. Thus alanine was 

 prepared, in 1850, by Strecker, from aldehyde ammonia, hydro- 

 cyanic acid, and hydrochloric acid. 104 Five years later, Zinin 

 obtained mustard oil from allyl iodide and potassium thio- 

 cyanate, 105 its connection with garlic oil having already been 

 established much earlier by Wertheim. 106 Glycocoll was pre- 

 pared synthetically by Perkin and Duppa 107 from bromacetic 

 acid and ammonia, and Hiifner afterwards obtained leucine 108 

 in an analogous manner. Racemic acid was prepared syntheti- 

 cally by Perkin and Duppa 109 from dibromsuccinic acid, and 

 malic acid by Kekule no from monobromsuccinic acid. We 

 are indebted to Kolbe for the synthesis of taurine, 111 a substance 

 which he prepared from isethionic acid. Anthracene was first 

 prepared artificially by Limpricht, by boiling benzyl chloride 

 with water; 112 and guanidine was prepared by Hofmann, 113 

 who obtained it from chlorpicrin, and by Erlenmeyer, 114 who 

 obtained it from cyanamide by the action of ammonia. 

 Volhard prepared creatine synthetically from chloracetic acid, 115 

 by converting the latter into sarcosine by the action of methyl- 

 amine and then converting the sarcosine into creatine by means 

 of cyanamide. Picoline and collidine were prepared syntheti- 

 cally by Baeyer 116 from aldehyde ammonias; crotonic acid, 

 by Kekule, from aldehyde; 117 and glycerine by Friedel and 



104 Annalen. 75, 29. 10S Ibid. 95, 128. 106 Ibid. 55, 297- 



107 Ibid. 108, 112. 108 Hiifner, J. pr. Chem. [2] I, 6. 109 Journ. 

 Chem. Soc. 13, 102 ; Annalen. 117, 130. no Ibid. 117, 120. ln Kolbe, 

 ibid. 122, 33. 112 Ibid. 139, 308. 113 Berichte. I, 145. m Annalen. 

 146, 259. 115 Zeitschrift fur Chemie. 12, 318. 116 Annalen. 155, 283. 

 117 Ibid. 162, 92. 



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