260 Wells £ Foote — One Hundred Years of Chemistry. 



gadro had understood it, however, and in 1811 had 

 reached the momentous conclusion that all gases and 

 vapors have equal numbers of molecules in equal volumes 

 at the same temperature and pressure. 



Davy in 1807 had isolated the alkali-metals, sodium 

 and potassium, by means of electrolysis, thus practically 

 dispelling the view that certain earthy substances might 

 be elementary ; and about four years later he had demon- 

 strated that chlorine was an element, not an oxide as had 

 been supposed previously, thus overthrowing Lavoisier's 

 view that oxygen was the characteristic constituent of all 

 acids. 



At the time that our period of history begins, the 

 atomic theory had been accepted generally, but in a some- 

 what indefinite form, since little attention had been paid 

 to Avogadro's principle, and since Dalton had used only 

 the principle of greatest simplicity in writing the formu- 

 las of compounds, considering water as HO and ammonia 

 NH, for example. At this time, however, Berzelius for 

 ten or fifteen years had been devoting tremendous energy 

 to the task of determining the atomic weights of nearly 

 all of the elements then known by analyzing their 

 compounds. He had confirmed the law of multiple pro- 

 portions, accepted the atomic theory, and utilized Avo- 

 gadro's principle, and it is an interesting coincidence 

 that his first table of atomic weights was published in the 

 year 1818. 



An interesting account of the views on chemistry held 

 at about that time was published in the Journal by Deni- 

 son Olmsted (11, 349, 1826; 12, 1, 1827), who had 

 recently become professor of natural philosophy in Yale 

 College. 



The most illustrious European chemists of that time 

 were Berzelius of Sweden, Davy of England, and Gay- 

 Lussac of France, and the curious circumstance may be 

 mentioned that all three of them and also Benjamin Silli- 

 man, the founder of the Journal, were born within a 

 period of eight months in 1778-1779. 



In this country Robert Hare of Philadelphia and Ben- 

 jamin Silliman were undoubtedly the most prominent 

 chemists of those days. Hare is best known for his 

 invention of the compound blowpipe, but his contribu- 

 tions to the Journal were very numerous, beginning 

 almost with the first volume and continuing for over 



