334 CHEMICAL DISCOVERY AND INVENTION 



whereby it loses the elements of water in two stages and leaves 

 a residue which is urea. Here again a rearrangement takes place, 

 but it is accompanied by elimination of hydrogen and oxygen 

 in the form of water. 



O . r ONH 4 O . r ONH 4 



<ONH 4 <NH 2 NH 2 



ammonium ammonium carbamide 



carbonate. carbamate. or urea. 



The production of urea in the animal body is, apparently, 

 closely related to this change, the primary materials being the 

 ammonia and carbonic acid of the blood which unite to form 

 ammonium carbonate or carbamate. 



Another organic compound produced from inorganic sub- 

 stances in the chemical laboratory was acetic acid, which was 

 synthesised by Kolbe in 1845. Again very little attention was 

 given to the discovery owing to the state of ignorance then 

 prevalent in the domain of organic chemistry. 



It was only some years later that a systematic study of syn- 

 thetical processes was undertaken by Berthelot the famous 

 French chemist. He showed how, by starting from the elements 

 and from mineral substances, carbon can be combined step by 

 step with hydrogen, then with oxygen, and again with nitrogen, 

 producing thereby organic compounds, some identical with 

 certain products of nature, others only analogous thereto, but 

 at the same time serving as starting points for the formation of 

 natural organic compounds. A single example taken from 

 Berthelot's work will suffice by way of illustration. By heating 

 carbon (coke or charcoal) in the electric arc surrounded by an 

 atmosphere of hydrogen acetylene C 2 H 2 is formed. By an easy 

 process acetylene can be made to combine with more hydrogen 

 so as to produce ethylene, C 2 H 4 . Ethylene dissolves in concen- 

 trated sulphuric acid, and the compound thus formed when 

 mixed with water unites with the elements of water and, distilled, 

 yields alcohol, C 2 H 6 0. The alcohol thus formed is identical in 

 every respect with alcohol produced by fermentation of sugar. 

 The synthetic process is so practicable that a company was at 

 one time actually formed with the object of manufacturing 

 alcohol from common coal-gas, of which ethylene is a constituent. 

 This was fifty years ago, but the development of the same idea 

 as that which was the basis of Berthelot's experiments has led 



