482 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



oxygen as obtained above is just 16 times that of hydrogen 

 as now ascertained, and the specific gravity of azote just 

 14 times" 1 (loc. cit. p. 322). 



Hydrogen as "protyl" (Prout 1816). This correct 

 determination of the density of hydrogen 2 was essential for 

 the development of the stimulating and suggestive hypothesis 

 of integral 3 atomic weights, which led Prout to conclude 

 that : 



"If the views we have ventured to advance be correct, we 

 may almost consider the Trpwrrj vXrj of the ancients to be 

 realised in hydrogen ; an opinion, by the by, not altogether 

 new. If we consider this to be the case. . . the specific 

 gravities, or absolute weights of all bodies in the gaseous 

 state, must be multiples of the specific gravity or absolute 

 weight of the first matter (TT/OWTT? vXy), because all bodies in 

 a gaseous state which unite with one another unite with 

 reference to their volume" (Annals of Philosophy, 1816, 7, 

 US)- 



Atomic weights in relation to oxygen. Two years 

 before Prout's paper appeared, Thomas Thomson pointed 

 out (Annals of Philosophy, 1813, 2, 114) that if oxygen be 

 taken as unity "there are eight atoms of simple bodies 

 whose weights are denoted by whole numbers ; namely 



Oxygen i Sulphur 2 Potassium 5 Arsenic 6 

 Copper 8 Tungsten 8 Uranium 12 Mercury 25." 



The first of these ratios was confirmed by Dumas, but most 

 of the others are obviously incorrect. Dumas concluded 

 that : 



" If oxygen be represented by 8, sulphur must be repre- 

 sented by 1 6. There exists then between these equivalents 

 the simple ratio i : 2, of which organic chemistry presents 

 so many examples" (loc. cit. p. 148). 



1 " i 'II in -f- -0694=16 and -9722^-0694-14." 



2 Thomson in 1813 using an earlier value for the density of hydrogen, 

 had only been able to find one integral multiple. 



3 No longer even numbers in the second (1816) paper. 



