1825.] M, Berzelius's Hypothesis of the Atomic Theory. 187 



he also showed that when one metal is precipitated from its 

 solution by another, the neutrality of the liquid is not affected. 



The introduction of the antiphlogistic system by Lavoisier in 

 some measure interrupted the progress of the doctrine of chemi- 

 cal proportions ; and shortly after its establishment, BerthoUet, 

 in his celebrated Essai de Statique Chimique, endeavoured to 

 prove that the elements of bodies have certain fixed points, a 

 maximum and a minimum, beyond which they are incapable of 

 combining, but that between those limits they may unite in any 

 proportion. 



Proust combated this opinion, and demonstrated that the 

 combinations which metals form with oxygen and with sulphur 

 are in fixed and invariable proportions, and that the supposed 

 intermediate compounds between the highest and lowest degrees 

 of oxidation and sulphuration are, in fact, merely mixtures of 

 two definite oxides, or sulphurets. 



In 1789, Mr. Higgins published his "Comparative View of 

 the Phlogistic and Antiphlogistic Theories," in which he " con- 

 ceived that when gases combine in more than one proportion, 

 all the proportions of tlie same element are equal ; and he 

 founded this idea on the corpuscular hypothesis, that bodies 

 combine particle with particle, or one with two, or three, or a 

 greater number of particles." * He did not, however, follow the 

 clue he had thus happily hit upon, but left it to the genius of 

 Dalton, "apparently without the knowledge of what Mr. Higgins 

 had written "t to resume the subject, and give it a more 

 extended application. Dr. Thomson in 1807 published a sketch 

 of Mr. Dallon's hypothesis, in the tbjrd edition of his System of 

 Chemistry (vol. lii. p. 424), by permission of its sagacious 

 author; and in the following year, Mr. Dalton produced the 

 first volume of his " New System of Chemical Philosophy;" 

 and two years after, the second. 



Adopting views similar to those of Higgins, Dalton supposes 

 that bodies are composed of atoms, and that to form the simplest 

 or binary compounds, an atom of A unites to an atom of B. 

 A ternary compound results from the union of 2 atoms of A, 

 + 1 of B, or 2 B + A, iJcc, and generally the atom of one 

 element may combine with 1, 2, 3, or more atoms of another, but 

 not in any intermediate or fractional degree ; and an atom of a 

 compound Ijody may in like manner unite to 1, 2, 3, or more 

 inlegrnl atoms of another compound. This hypothesis was 

 afterwards confirmed by numerous experiments, amongst the 

 earliest and most important of which are those detailed by 

 Dr. Thomson in his paper on oxahc acid, and in Dr. WoUaston's 

 on super-acid and sub-acid salts. Both these interesting coni- 



* Davy's Element* of Chemical PliUosopliy, p. 107. + Ibid. 



