108 SIMPLER ORGANIC SUBSTANCES 



during the nineteenth and twentieth centuries accomplished 

 artificial syntheses of substances characteristic of living organ- 

 isms. Among these were the various sugars, amino acids, 

 lipids, numerous pigments derived from plants and animals 

 including alizarin, indigo and substances responsible for the 

 colours of flowers, fruits and berries, also substances respons- 

 ible for their flavours and scents, numerous acids, terpenes, 

 tanning substances, as well as alkaloids, resins, rubber and 

 many other substances. In recent times some very compli- 

 cated compounds, having intense biological activities, such 

 as vitamins, antibiotics and hormones, have also been syn- 

 thesised in the laboratory. 



At the same time the organic chemists also synthesised 

 substances which have never been found in any living organ- 

 ism, and thus have no direct relationship with living beings. 

 These, nevertheless, may be strikingly similar in their pro- 

 perties to substances originating from plants or animals. 

 Thus in many works of reference and text books^ ' organic 

 chemistry ' is defined as the chemistry of compounds of 

 carbon, since this element is present in all natural and arti- 

 ficial substances of this kind without exception. 



However, carbon is not only found in nature in the form 

 of its organic compounds. It also enters into the composition 

 of such substances as marble and metal carbides, that is, into 

 the composition of substances that have a manifestly inor- 

 ganic, mineral character. A much more accurate definition 

 of organic chemistry would appear to be that first given by 

 Carl Schorlemmer^ as ' the chemistry of hydrocarbons and 

 their derivatives '. This definition not only emphasises the 

 fact that any organic compound can be derived from some 

 hydrocarbon, but has another distinct advantage. It distin- 

 guishes the specific quality of organic chemistry, as a branch 

 of science concerned with investigating a higher stage in the 

 organisation of matter than that studied by inorganic chemis- 

 try.' 



From this point of view, organic chemistry is not simply 

 the chemistry of one of the elements from Mendeleev's 

 periodic table. It exhibits special, characteristic regularities 

 which first manifest themselves on passing from the inorganic 

 to the organic compounds of carbon. 



