1 1 On the Daltonian Theory of [Ace. 



particular points, which I shall notice as I proceed. I shall give in 

 the form of a table the atoms whose weights seem to require alte- 

 ration, together with a few bodies respecting the weight of the atom 

 of which I differ in opinion from other chemists. 



Weight nf an 



atom. 



Oxygen 1 -000 



Hydrogen 0-132 a 



Azote 1 -803 b 



Phosphorus 12-618 c 



■2^-1 Boron 0733 d 



284 Chlorine 4-408 f 



285 Iodine 11-160 f 



a This weight is founded on the result of my own experiments to 

 determine the specific gravity of hydrogen. Biot's experiments 

 make the weight 0133, a difference too inconsiderable to require 

 correction. I still consider water as a compound of one atom 

 hydrogen and one atom oxygen, for reasons formerly assigned. 

 Davy, Wollaston, Berzelius, consider water as composed of one 

 atom oxygen and t.vo atoms hydrogen. This would reduce the 

 weight of an atom of hydrogen to 0-066. 



b I have given my reasons for this change in the Annals of Philo- 

 sophy, vol. iii. p. 135. Dr. Wollaston makes it 1'754. 



L Rose found phosphoric acid a compound of 100 phosphorus + 

 114*7 oxygen. I have repeated this experiment several times, and 

 have obtained results that approach sufficiently near to satisfy myself 

 that Rose's numbers are very near the truth. Davy informs us that 

 lie found phosphorous acid a compound of 100 base + 77 oxygen. 

 'Xow 77 is to 1 14*7 very nearly as two to three. Hence 1 think we 

 can scarcely hesitate to consider phosphorous acid as a compound of 

 1 atom phosphorus + 2 atoms oxygen, and phosphoric acid of 1 

 atom phosphorus + 3 atoms oxygen. Hence the weight of an 

 atom of phosphorus given in the text. 



d This number is the result of the experiments of Davy and 

 Berzelius {Annals of Philosophy, vol. iii. p. 56), and supposes 

 boraeic acid to be a compound of 1 atom boron + 2 atoms oxygen. 

 This is analogous to the composition of carbonic acid, an analogy 

 likely to hold good on account of the close resemblance between 

 charcoal and boron. 



The reasons which induced me to che number for the 



weight of an atom of chlorine have been assigned in the Annals of 

 Philosophy, vol. iv. p. 18. 



' This is the number which results from the experiments of Davy. 

 I shall very soon give an account of my own experiments to deter- 

 mine the weight of an atom of iodine. 



