556 SPECIAL METHODS OF DISCOVERY. 



other substance under suitable conditions of pressure 

 temperature, electrolysis, &c., an almost infinite series, o 

 ever-increasing extent, of new compounds is continually 

 expanding before us in our views of the chemistry of th 

 future. 1 



During the ninth century, Greber discovered, by mix 

 ing together nitric acid and salammoniac, that a liquic 

 was formed which was capable of dissolving gold. Sylvius 

 a medical man of Amsterdam (born in 1614), by employ 

 ing this method, was one of the first to discover that tw< 

 substances, which by mutual contact acted violently upon 

 each other, by their union lost their violence ; and this 

 discovery has ever since constituted a fundamental part of 

 the idea and definition of chemical energy. 



By examining the contact action of substances upon 

 each other, Boyle, about the year 1670, and Bergman n 

 (about the year 1770) made many chemical discoveries. 2 

 The great value of this method of discovery, especially 

 in the science of chemistry, is well illustrated by the fact, 

 that Scheele, one of the most successful chemical disco- 

 verers, largely employed it, and made nearly the whole of 

 his numerous discoveries by its means. When investigating 

 the properties of black oxide of manganese, ' Scheele's 

 method of proceeding was to try the effect of all the 

 different reagents on it. It dissolved in sulphurous and 

 nitrous acids, and the solution was colourless. Dilute sul- 

 phuric acid did not act upon it, nor nitric acid ; but con- 

 centrated sulphuric acid dissolved it by the assistance of 

 heat.' ' Muriatic acid effervesced with it, when assisted 

 by heat, and the elastic fluid that passed off had a yel- 

 lowish colour, and the smell of aqua-regia. He collected 

 quantities of this elastic fluid (chlorine) in bladders, and 

 determined some of its most remarkable properties ; it 



1 Compare pages 30, 31. 2 See pages 538-540. 



