Biographical Account of the late John Dalton. 81 



His first important paper was published in 1802, in the fifth volume of 

 the first series of the Manchester Memoirs, and was entitled, On the Expan- 

 sion of the Elastic Fluids by Heat. At that time by far the greater number 

 of the gaseous bodies at present known had been discovered; many 

 experiments had been made on the expansion of these bodies by heat by 

 Deluc, General Roy, Saussure, and some other philosophers ; and in the 

 first volume of the Annales de Chimie, published in 1788, there appeared 

 an elaborate paper by M. M. de Morveau and du Vernois, showing that 

 every gas had a peculiar expansibility of its own, and that the same addition 

 of heat caused some gases to expand twelve times as much as others. 

 Mr. Dalton made a set of experiments to ascertain the accuracy of these 

 determinations. The result was, that all gases expand the same, or experi- 

 ence the same increase of volume, when the same quantity of heat is 

 added to them ; according to Dalton, 1000 volumes of air, or of any gas 

 when dry, becomes 1325 volumes when heated from 32° to 212°. 



The experiments of Dalton were read to the Philosophical Society of 

 Manchester in October, 1801. About six months after, a similar set of 

 experiments by Gay-Lussac was published in the Annales de Chimie 

 volume 43d. He obtained the same results as Mr. Dalton had done, — but 

 he found the expansion from 32° to 212° to be from 1000 to 1375 volumes. 

 Mr. Dalton afterwards in his system of chemistry adopted this number as 

 more accurate than his own. 



Many years after, Dr. Prout found the weight of 100 cubic inches of 

 air at 32° to be 32*79 grains, while at 60° they weighed only 31*0117 

 grains. Hence, 1000 volumes at 32° become, at 60°, 1057*34 volumes. 

 Hence, as the expansion is equable, 1000 volumes, if heated from 32° to 212°, 

 would become 1368*61 volumes. Still more lately, Rudberg, a Swedish 

 chemist, made a great number of experiments, being at great pains to dry 

 his gases. He found that 1000 volumes of air at 22° when heated to 

 212° became 1364*57 volumes. In 1842, a most elaborate set of experi- 

 ments was made by Regnault, on the expansibility of air and ten other 

 gases. He, like his predecessors, found the expansibility of all of them the 

 same, and that 1000 volumes, when heated to 212°, became 1366*5 

 volumes. Thus we have four determinations. 



By Dalton and Gay-Lussac 1000 at 32° become 1375 at 212°. 



Prout, 1000 1368*61 



Rudberg, 1000 1364*57 



Regnault, 1000 1366*5 



Mean, 1000 1368*67 



^ftSS*"} 100( > 136656 



According to Dalton and Gay-Lussac the expansion of air, or of any of 

 the gases, for 1° of Fahrenheit is ^ . But the mean of the expansion, for 1°, 

 according to the experiments of Prout, Rudberg, and Regnault, is ^j. 

 Thus 1 ) alt on's determinations, notwithstanding the simplicity of his method, 



