1825.] M. Berzelins's Hypothesis of the Aiomic Theori/. 34a 



the weight f>f the atom of lead in the table is just double that 

 number, viz. 2589. Again the composition per cent, of alumina 

 is aluminum 53-3, oxygen 46*7, and 46-7 : 63-3 :: 100 : 1 14*11 ; 

 which is just one-third of the tabular weight of the atom of 



aluminum, viz. 342-33.* Hence the expression C S- means the 

 neutral sulphate of lime, and not the bisulphate, which at first 

 view we should probably suppose it to represent, for as the lime 

 contains two hypothetical atoms of oxygen, the salt must also 

 contain two hypothetical atoms of acid, or the canon would be 

 violated which requires that the oxygen of the acid should be a 

 multiple by a whole number of the oxygen of the base. Hence 

 when we find such a symbol as the preceding, and wish to read 

 it correctly, we must remember that all the atoms are doubled, 

 and consequently represented by numbers, which, to reduce 

 them to those of English authors, must be divided by 2. In like 



manner in the expression Al S' (sulphate of alumina), all the 

 atoms are trebled. As three to one, according to Berzelius's 

 views, represents a neutral salt, so an equal number of atoms of 

 acid and base represents a salt loith excess of base ; and accord- 

 ingly we have Al S, signifying sulphas trialuminicus. 



We have not yet quite done with these simple views ; another 



formula remains to be noticed, namely, that of Al Si. After 

 what we have just shown respecting the sulphas trialuminicus, 

 the reader will probably suppose that this expression means 

 silicias trialuminicus. No such thing ; it is the neutral com- 

 pound, silicias aluniinicus. But with respect to this inconsist- 

 ency, hear Berzelius's own confession. 



" 1 must here point out a little inconsistency which I have 

 committed in the nomenclature of the silicates, by applying the 

 term silicias to combinations in which the oxygen of the base is 

 equal to that of the silica. The analogy of silica with acids con- 

 taining 3 atoms of oxygen would require that this appellation 

 should be given to those compounds in which the oxygen of the 

 sihca is three times that of the base. It is evident that these are 

 the true neutral silicates, and that the first are salts with excess 

 of base, since the alkalies, by decomposing a silicate with the 

 assistance of heat, always reduce it to that point at which the 

 silica and the base contain equal quantities of oxygen. However, 

 as the study of the silicates belongs principally to that branch 

 of chemistry which is chieHy applied to mineralogy, and as the 

 nomenclature of the numerous degrees of saturation of silica 



• To reduce Berzelius's numbers lo Thomson'!, divide by 100 ; and to reduce them 

 to Brande's, multiply by t*,. Berzelius's number for alumina accords pretty nearly 

 with Thomson's, l)ut not wi;h Brande's or Phillips's. I believe tiie former to be cor- 

 rect.— C. 



