6 Biographical Memoir of Sir Humphry Davy. 



evaporate at a red heat*. Klaproth, the first individual in our 

 days who discovered a new metal, wished to question their metal- 

 lic quality on the ground of their specific lightness ; and in fact 

 all the known metals are heavy, but in very different degrees. 

 Tellurium, for example, is four times lighter than platina, and 

 there is no reason why sodium and potassium, (the names by 

 which Mr Davy distinguished the new substances) although six 

 times lighter than tellurium, should be excluded from that class 

 of substances to which they belong by all their other attributes. 



This grand discovery was made in 1807, and formed the 

 subject of the Bakerian Lecture for the month of November of 

 the same yearf. It could not fail to lead a mind like Davy's to 

 new researches and new ideas ; he tried the same process on 

 many other earths, and Berzelius did the same, proving.that they 

 must all be regarded as oxides. 



The great Swedish chemist, having electrified negatively some 

 mercury in contact with a solution of ammonia, succeeded in 

 producing an amalgam ; and Mr Davy, who had arrived^at the 

 same result by more simple means |, observed the mercury be- 

 come solid, and lose three-fourths of its specific gravity, by the 

 addition of a quantity of gas, scarcely equivalent to ^^^^ of its 

 weight ; he was led, therefore, to think that the ammonia had 

 likewise a base, and that perhaps the azote and hydrogen, of 

 which it is composed, are themselves metallic oxides §. Rising 



" The more correct statement is this : — Potassium at 50" Fahr. is soft and 

 malleable, but melts at 1 364° ; sodium is soft and malleable at the common 

 temperature of the atmosphere, and melts at 194° F. 



•j- On some new phenomena of chemical changes produced by electricity, 

 particularly the decomposition of fixed alkalies, and the exhibition of the new- 

 substances which constitute their bases, and on the general nature of alkaline 

 bodies. — Roy. Soc. Lond. 12th and 19th November 1807. Phil. Trans, of Lon- 

 don, vol. xcviii. p. 1. Ann. de Chimie. Ixviii. p. 203-225. Biblioth. Brit. 

 vol. xxxviiL p. 3. 



+ An account of some analytical researches on the nature of certain bodies, 

 particularly the alkalies, phosphorus, sulphur, carbonaceous matter, and the' 

 acids hitherto undecompounded ; with some general observations on chemical 

 theory. Roy. Soc. Lond. 15th December 1808. Phil. Trans, vol. xcix. p. 39; 

 Ann. de Chim. tom Ixxii. p. 244, and Ixxiii. p. 5. Biblioth. Brit. vol. xlii 

 p. 27. Joum. de Phys. tom. Ixix. p. 360. 



§ New analytical researches on the nature of certain bodies. 1st, Further 

 inquiries on the action of potassium or ammonia, and on the analvsis of am- 



