ANNALS 



or 



PHILOSOPHY- 



JANUARY, 1821 



Article I. 



Experiments to determine the true Atomic Weight of StrontiaUy 

 Limey Magnesia, Phosphoric Acid, and Arsenic Acid, By- 

 Thomas Thomson, M.D. F.R.S. 



In two papers published in the preceding volume of the J-wwa/so/* 

 Fhilosophy, I have endeavoured to determine the real weight of 

 the atom of 13 simple bodies, and a considerable number of 

 compounds formed by the union of these bodies with each 

 other. In every one of these cases we found reason to conclude 

 that the atomic weight of every body is a multiple of the weight 

 •of an atom of hydrogen. I showed that the determinations of 

 Dr. Wollaston and Prof. Berzelius, though in most cases consti- 

 tuting very good approximations, are never rigidly exact, the 

 true weights of the atoms of bodies constituting much simpler 

 numbers than they have supposed. I have shown, I trust to the 

 satisfaction of all practical chemists, that the mode of experi- 

 menting adopted by Berzelius is not precise enough for the 

 determination of the weights of the atoms of bodies. I ought 

 to observe, however, that Berzelius is undoubtedly a very great 

 master of the analytical art ; that his analyses approach upon 

 the whole exceedingly near the truth ; and exhibit a consistency 

 which is highly satisfactory, and does a great deal of credit to 

 the industry and sagacity of their author. But unfortunately 

 his mode of experimenting admits of no criterion by which the 

 experimenter can determine whether the results be accurate or 

 not ; so that he has no means of checking himself, and of taking 



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