344 Mr. Childrev's Summary View of [MaV, 



greater proportion than that of a single atom ; soda, oxide of 

 lead, carbonic acid, sulphuric acid, 8cc. may be quoted as fami- 

 liar instances. This is still more ol3servable in the combinations 

 of compound atoms, as in the salts, where several atoms of the 

 electro-negative oxide are commonly found united to a single 

 atom of the electro-positive. On the other hand there is every 

 reason to believe that the atoms are only united one to one in 

 those bodies which manifest weak affinities, as the gaseous 

 oxide of carbon, the oxidules of copper, mercury, gold, tkc. ; so 

 that we may presume that all bodies composed of an atom of 

 bade and an atom of oxygen have more or less the characters 

 of sub-oxides. It appears, moreover, certain, that the atoms of 

 the stronger acids and bases contain more than one atom of 

 oxygen. Since the number of simple atoms in a compound 

 atom must necessarily influence the form, and consequently the 

 properties of the latter, we have a right to suppose that oxides 

 which contaifi the same number of atoms of oxygen, have at 

 least some general properties in common which distinguish them 

 from those that have either a greater or a less number. Thus, 

 as we have reason to presume that the oxides which contain 

 only 1 atom of oxygen have the weakest affinities, we find a 

 whole series of more strongly marked salifiable bases, in which 

 the number of the atoms of oxygen must be twice as great as in 

 the former, and therefore it is probable that all the stronger 

 bases contain tw o atoms of oxygen. Those which contain three 

 atoms of oxygen, on the contrary, are weaker, and many of them 

 may even be electro-negative with respect to some of the electro- 

 positive oxides ; "* that is, act as acids. 



Amongst the stronger bases, Berzelius includes all the alka- 

 lies and alkaline earths, the protoxides of lead, silver, cadmium, 

 iron, copper, tin, zinc, &.c. but alumina, silica, and some others, 

 as may be seen in the table at the end of this abstract, he consi- 

 ders as containing 3 atoms of oxygen. Now, having laid down 

 this arbitrary law, two consequences follow, which the student 

 must keep in mind, or he will be liable to fall into error when he 

 endeavours to translate the formulae into common language, or 

 compares Berzelius's atomic weights with those of English 

 authors. The first is, that to preserve the proportion between 

 the weight of the oxygen and that of the base, as found by analy- 

 sis, Berzelius has been obliged to double the weights of the atoms 

 of all those elementary substances whose protoxides he consi- 

 ders as containing two atoms of oxygen, and to treble those 

 which contain three. Thus the protoxide of lead, according to 

 the table (see oxidum plumbicum), contains percent. 92-83 lead, 

 ■and 7-171 oxygen, and 7-171 : 92-83 :: lOOf : 1294-5; but 



• Essai, p. 1 1 4, et seq. 



f The weight of an atom of oxygen. 



