GAY-LUSSAC 179 



Gay-Lussac stated in the Memoires de la Societe 

 d'Arcueil, tome ii., p. 207, that "lorsque deux gaz se 

 combinent, leurs volumes mesure"s a la meme temperature 

 et a la meme pression sont dans des rapports simples." 

 It will be seen that Gay-Lussac anticipated the great law 

 of Avogadro, although it was left to the Italian physicist 

 to distinguish between the ultimate particles of compounds 

 and elements between molecule and atom. As Roscoe 

 and Schorlemmer say : " The discovery by Gay-Lussac of 

 the law of volume combination, together with Avogadro 's 

 explanation of the law served no doubt as most valuable 

 supports of Dalton's atomic theory ; but the truth of this 

 latter theory was still further asserted by a discovery made 

 by Dulong and Petit in 1819. These French chemists 

 determined the specific heat of thirteen elementary bodies, 

 and found that the numbers thus obtained, when compared 

 with the atomic weights of the same bodies, showed that 

 the specific heats of the several elements are inversely 

 proportional to their atomic weights ; or, in other words, 

 the atom of each of these elements possesses the same 

 capacity for heat. Although subsequent research has 

 shown that this law does not apply in every case, it still 

 remains a valuable means of controlling the atomic-weight 

 determinations of many elements." 



Gay-Lussac was the inventor of the tower, known by 

 his name, in the manufacture of sulphuric acid. Formerly 

 the nitrous fumes were allowed to escape into the air, but 



