106 CHEMICAL DISCOVERY AND INVENTION 



chemical decomposition, or electrolysis, may be the object on 

 one occasion, while on another a high tension discharge through 

 a so-called vacuum tube may be wanted or the production of an 

 arc for experiments at high temperatures. Machines for the 

 liquefaction of air and other gases afford, on the other hand, the 

 means of producing great cold, and much has been learned 

 during the last twenty years about the properties of matter at 

 low temperatures, and the influence of temperature on chemical 

 action. The range of temperatures thus attainable in the labora- 

 tory stretches from approximately that of interplanetary space 

 to near the central heat of the sun. Many manufacturing 

 operations are now conducted at the temperature of the electric 

 arc, such as the production of calcium carbide, the manufacture 

 of phosphorus and carborundum, the fusion of quartz for making 

 silica vessels, and the reduction of several metals from their 

 oxides. 



Among the most remarkable results of the application of 

 modern theoretical ideas should be remembered the success 

 which has attended the production of organic compounds, 

 many of which had been previously known only as naturally 

 occurring constituents of the tissues of animals or plants. The 

 synthesis of alizarin, the red colouring matter of madder, has 

 for many years been conducted on a large scale for industrial 

 purposes, and the synthesis of indigo bids fair to result before 

 long in the almost total extinction of the cultivation of the 

 indigo plant. 



Some of the sugars, fats, and proteins or albuminoid con- 

 stituents of animal matters have in like manner been built up 

 by chemical operations from purely inorganic materials. And 

 it is a matter of common knowledge that many of the drugs 

 employed in modern medical practice, saccharin, aspirin, 

 phenacetin, antipyrin, sulphonal, etc. are artificial products 

 of the chemical laboratory. 



In theoretical chemistry electrical ideas are predominant. 

 Chemical combination or decomposition is attributed to ex- 

 changes of electrical units, and the decomposition of fluid 

 bodies by the electric current is almost universally attributed to 

 the presence of " ions," wandering free fragments of molecules 

 carrying electric charges. From the discoveries which have 

 been made during the last thirty years by Sir William Crookes, 

 and especially more recently by Sir Joseph J. Thomson and his 



